Tuesday, February 25, 2014
Interesting Facts about Rett Syndrome
-Rett syndrome is a debilitating neurological disorder that predominantly affects females.
-Female children with Rett syndrome are born normal until about the age of one-three years old.
-Rett syndrome is caused by a single gene mutation that leads to underproduction of an important brain protein.
-Rett syndrome is considered the most severe form of autism.
-Rett syndrome is the leading genetic cause of severe impairment in females-most women cannot speak, walk, or use their hands,
-Despite their physical disabilities, women with Rett syndrome are now believed to be functioning mentally at a much higher level than previously thought.
-Rett syndrome is as prevalent as Cystic Fibrosis, ALS, and Huntington's Disease.
-Every 90 minutes, another child is born with Rett syndrome.
-RESEARCH HAS PROVEN THAT ONCE PROTEIN LEVEL ARE RETURNED TO NORMAL LEVELS, RETT SYNDROME IS POTENTIALLY REVERSIBLE.
For more information on Rett syndrome, please visit:
-http:www.girlpower2cure.org/who-we-are/rett-syndrome.aspx
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-Female children with Rett syndrome are born normal until about the age of one-three years old.
-Rett syndrome is caused by a single gene mutation that leads to underproduction of an important brain protein.
-Rett syndrome is considered the most severe form of autism.
-Rett syndrome is the leading genetic cause of severe impairment in females-most women cannot speak, walk, or use their hands,
-Despite their physical disabilities, women with Rett syndrome are now believed to be functioning mentally at a much higher level than previously thought.
-Rett syndrome is as prevalent as Cystic Fibrosis, ALS, and Huntington's Disease.
-Every 90 minutes, another child is born with Rett syndrome.
-RESEARCH HAS PROVEN THAT ONCE PROTEIN LEVEL ARE RETURNED TO NORMAL LEVELS, RETT SYNDROME IS POTENTIALLY REVERSIBLE.
For more information on Rett syndrome, please visit:
-http:www.girlpower2cure.org/who-we-are/rett-syndrome.aspx
Statistics and Everyday Life
Statistics
It is estimated that 1/10,000 females in the US will be born with Rett syndrome, so about 16,000 women in the US have Rett syndrome. Rett syndrome has been classified as a rare disease by the Office of Rare Diseases of the National Institutes of Health.
Everyday Life
Families have reported that life surrounding a child afflicted with Rett syndrome is usually a constant state of challenging emotional conflict because of the overwhelming responsibility of the family to care for the child. Families are advised to seek therapists for themselves and their family, and support groups are also advised.
For more information, please visit:
-http://www.rsrt.org/rett-and-mecp2-disorders/rett-syndrome/
It is estimated that 1/10,000 females in the US will be born with Rett syndrome, so about 16,000 women in the US have Rett syndrome. Rett syndrome has been classified as a rare disease by the Office of Rare Diseases of the National Institutes of Health.
Everyday Life
Families have reported that life surrounding a child afflicted with Rett syndrome is usually a constant state of challenging emotional conflict because of the overwhelming responsibility of the family to care for the child. Families are advised to seek therapists for themselves and their family, and support groups are also advised.
For more information, please visit:
-http://www.rsrt.org/rett-and-mecp2-disorders/rett-syndrome/
Life Expectancy and Treatment
Life Expectancy
The average lifespan of someone afflicted with Rett syndrome is 50 years, although sudden deaths may occur.
Treatment
After an experiment using mice was conducted, scientists concluded that there are potential therapies for Rett syndrome, such as insulin-like growth factor, disabling GABAergic neuron function, and stem cell transplantation. There is no cure for Rett syndrome.
For more information of the life expectancy and treatment of people suffering with Rett syndrome, please visit:
-http://www.mayoclinic.org/diseases-conditions/rett-syndrome/basics/symptoms/con-200208086
-http://www.sciencemag.org/content/342/6156/318.summary
The average lifespan of someone afflicted with Rett syndrome is 50 years, although sudden deaths may occur.
Treatment
After an experiment using mice was conducted, scientists concluded that there are potential therapies for Rett syndrome, such as insulin-like growth factor, disabling GABAergic neuron function, and stem cell transplantation. There is no cure for Rett syndrome.
For more information of the life expectancy and treatment of people suffering with Rett syndrome, please visit:
-http://www.mayoclinic.org/diseases-conditions/rett-syndrome/basics/symptoms/con-200208086
-http://www.sciencemag.org/content/342/6156/318.summary
How Does Someone Get Rett Syndrome?
How Do People Get Rett Syndrome?
More than 99% of people with Rett syndrome have no family history of the disorder and the condition is not inherited because Rett syndrome results from a genetic mutation of the MECP2 gene, but there have been cases in which there has been a history of Rett syndrome within the family. Cases in which there has been a history of Rett syndrome within the family has helped researchers of the disorder discover that the cause of the disorder and its variants have an X-linked dominant pattern of inheritance. A genetic condition is considered X-linked if the mutated gene that caused the disorder is located on the X chromosome, and the inheritance occurs, if it is dominant, when one copy of the altered gene in each cell is sufficient enough to cause the condition.
Males with mutations in the MECP2 gene usually die in infancy because the Y chromosome is too small to support life with a dysfunctional partner chromosome, but a small portion of males with a genetic mutation Involving MECP2 have exhibited signs of Rett syndrome, such as intellectual' disability, seizures, and movement dysfunctions, which is known as neonatal encephalopathy.
Genotypes of Parents Whose Offspring had Rett Syndrome
DNA extracted from patients who had Rett syndrome and DNA extracted from the parents showed that the patient had one paternal and one maternal allele, which is normal, so researchers delved deeper in to the mystery. Single nucleotide polymorphisms (SNPs) are variations in the DNA code that are unique to individuals, much like finger prints, so if the patient had only one copy of an SNP within the MECP2 gene, then researchers could look at the parents' DNA to discover the same SNP present within their genes also present n their child's, thus allowing scientists to find the origin of the patient's alleles and thus the origin of the mutation. After all of the data, researchers concluded that, although Rett syndrome only affects women, parental genes are at the origin of Rett syndrome IN MOST CASES.
Chances of Rett Syndrome Being Passed Down to Offspring
A parent with a small portion of mutated cells with a Rett syndrome mutation, while not exhibiting Rett syndrome, will pass these genes to their child and all of the child's cells will be mutated, resulting in Rett syndrome. People who have a small portion of their cells mutated while not exhibiting a genetic disorder or abnormality are called "mosaicism". People who have Rett syndrome and have children do not always produce children with Rett syndrome, but there is a 50% chance to pass the disorder on to the child during pregnancy. If the child is male, the Rett syndrome exhibited in the male will ne extreme. Most people-women-with Rett syndrome do not have children.
For more information, please visit:
- http://www.ghr.nlm.nih.gov/condition/rett-syndrome
- http://www.rett.childhealthresearch.org.au/our-research/research-snapshots/zhang-parental-origin-of-mutations.aspx
-http://www.elcaminogmi.dnadirect.com/gcr/patient-site/rett-syndrome-diagnosis/genetics-of-rett-syndrome.html
More than 99% of people with Rett syndrome have no family history of the disorder and the condition is not inherited because Rett syndrome results from a genetic mutation of the MECP2 gene, but there have been cases in which there has been a history of Rett syndrome within the family. Cases in which there has been a history of Rett syndrome within the family has helped researchers of the disorder discover that the cause of the disorder and its variants have an X-linked dominant pattern of inheritance. A genetic condition is considered X-linked if the mutated gene that caused the disorder is located on the X chromosome, and the inheritance occurs, if it is dominant, when one copy of the altered gene in each cell is sufficient enough to cause the condition.
Males with mutations in the MECP2 gene usually die in infancy because the Y chromosome is too small to support life with a dysfunctional partner chromosome, but a small portion of males with a genetic mutation Involving MECP2 have exhibited signs of Rett syndrome, such as intellectual' disability, seizures, and movement dysfunctions, which is known as neonatal encephalopathy.
Genotypes of Parents Whose Offspring had Rett Syndrome
DNA extracted from patients who had Rett syndrome and DNA extracted from the parents showed that the patient had one paternal and one maternal allele, which is normal, so researchers delved deeper in to the mystery. Single nucleotide polymorphisms (SNPs) are variations in the DNA code that are unique to individuals, much like finger prints, so if the patient had only one copy of an SNP within the MECP2 gene, then researchers could look at the parents' DNA to discover the same SNP present within their genes also present n their child's, thus allowing scientists to find the origin of the patient's alleles and thus the origin of the mutation. After all of the data, researchers concluded that, although Rett syndrome only affects women, parental genes are at the origin of Rett syndrome IN MOST CASES.
Chances of Rett Syndrome Being Passed Down to Offspring
A parent with a small portion of mutated cells with a Rett syndrome mutation, while not exhibiting Rett syndrome, will pass these genes to their child and all of the child's cells will be mutated, resulting in Rett syndrome. People who have a small portion of their cells mutated while not exhibiting a genetic disorder or abnormality are called "mosaicism". People who have Rett syndrome and have children do not always produce children with Rett syndrome, but there is a 50% chance to pass the disorder on to the child during pregnancy. If the child is male, the Rett syndrome exhibited in the male will ne extreme. Most people-women-with Rett syndrome do not have children.
For more information, please visit:
- http://www.ghr.nlm.nih.gov/condition/rett-syndrome
- http://www.rett.childhealthresearch.org.au/our-research/research-snapshots/zhang-parental-origin-of-mutations.aspx
-http://www.elcaminogmi.dnadirect.com/gcr/patient-site/rett-syndrome-diagnosis/genetics-of-rett-syndrome.html
Symptoms and Diagnosis of Rett Syndrome
Symptoms of Rett Syndrome
6-18 Months
At first, children with Rett syndrome develop normally and then:
-Neurological development slows down or the child does not gain any new skills (this can continue to age four)
-In some cases, usually after 9 months, there is a regression of skills the children already had been exhibiting
- Regular speech is gone, but sounds, such as laughing and crying, remain intact
-The wringing or flapping of hands begins
-Loss of fine motor coordination
19 Months-15 Years
-Walking may become unsteady or the ability can be lost all together
-Children will hyperventilate or develop breathing problems, such as holding one's breath for long periods of time
-Panic attacks
-Screaming fits/tantrums
-Crying fits
-Laughing fits/hysterics
-Increased fear, stress, and easily over-excited, which results in the children often being very shaky
15 Years+
-People experience little to no interest in the outside world
-Avoid eye contact/social interactions
-Seizures
-Scoliosis
Diagnosis of Rett Syndrome
A genetic test is performed upon the child to confirm the diagnosis of Rett syndrome. The test detects the MECP2 mutation located on the child's X chromosome, and the test is usually 80% correct. Unfortunately, some children with an MECP2 genetic mutation do not always have Rett syndrome, resulting in false positives. Because of this, an MECP2 genetic test is performed as well as careful observation of the child's behavior in early childhood.
Other disorders associated with an MECP2 genetic mutation are cerebral palsy, autism, or other non-specific developmental delays.
For more information about the symptoms and diagnosis of Rett syndrome, please visit:
- http://www.webmd.com/brain/autism/rett-syndrome
-http://www.childrenshospital.org/health-topics/conditions/rett-syndrome
6-18 Months
At first, children with Rett syndrome develop normally and then:
-Neurological development slows down or the child does not gain any new skills (this can continue to age four)
-In some cases, usually after 9 months, there is a regression of skills the children already had been exhibiting
- Regular speech is gone, but sounds, such as laughing and crying, remain intact
-The wringing or flapping of hands begins
-Loss of fine motor coordination
19 Months-15 Years
-Walking may become unsteady or the ability can be lost all together
-Children will hyperventilate or develop breathing problems, such as holding one's breath for long periods of time
-Panic attacks
-Screaming fits/tantrums
-Crying fits
-Laughing fits/hysterics
-Increased fear, stress, and easily over-excited, which results in the children often being very shaky
15 Years+
-People experience little to no interest in the outside world
-Avoid eye contact/social interactions
-Seizures
-Scoliosis
Diagnosis of Rett Syndrome
A genetic test is performed upon the child to confirm the diagnosis of Rett syndrome. The test detects the MECP2 mutation located on the child's X chromosome, and the test is usually 80% correct. Unfortunately, some children with an MECP2 genetic mutation do not always have Rett syndrome, resulting in false positives. Because of this, an MECP2 genetic test is performed as well as careful observation of the child's behavior in early childhood.
Other disorders associated with an MECP2 genetic mutation are cerebral palsy, autism, or other non-specific developmental delays.
For more information about the symptoms and diagnosis of Rett syndrome, please visit:
- http://www.webmd.com/brain/autism/rett-syndrome
-http://www.childrenshospital.org/health-topics/conditions/rett-syndrome
The History of Rett Sydnrome
Year Discovered
Rett syndrome was discovered by Dr. Andreas Rett, an Austrian physician who documented the disorder in a journal artcile in 1966. Unfortunately, not until 1983, after another article on Rett syndrome was published by Swedish physician Dr. Bengt Hagberg, that the disorder was officially recognized by the public and physicians.
How Rett Syndrome was Discovered
-Andreas Rett
In 1954, pediatrician Dr. Andreas Rett of Vienna, Austria, noticed two girls who sat with their mothers in the waiting room who exhibited similar hand-washing motions. In 1966, Rett published his findings (a film he made of women all experiencing the same symptoms) in several German medical journals, but the magazines in which his articles were published were not main-streamed enough in to the world-wide medical community for the disorder to be widely known.
-Bengt Hagberg
Although Rett published an article on his self-named disorder, Rett syndrome, in 1966, a paper published by Dr. Bengt Hagberg in 1983 resulted in Rett syndrome becoming widely known in the medical world.
Please visit the following for more information on the history of Rett syndrome and lther useful information about the disorder:
- http://www.ninds.nih.gov/disorders/rett/detail_rett.htm
- http://www.rettsyndrome.org/understandimg-rett-syndrome/about-rett-syndrome/history
- http://www.bundlings.com/irsg.htm
Rett syndrome was discovered by Dr. Andreas Rett, an Austrian physician who documented the disorder in a journal artcile in 1966. Unfortunately, not until 1983, after another article on Rett syndrome was published by Swedish physician Dr. Bengt Hagberg, that the disorder was officially recognized by the public and physicians.
How Rett Syndrome was Discovered
-Andreas Rett
In 1954, pediatrician Dr. Andreas Rett of Vienna, Austria, noticed two girls who sat with their mothers in the waiting room who exhibited similar hand-washing motions. In 1966, Rett published his findings (a film he made of women all experiencing the same symptoms) in several German medical journals, but the magazines in which his articles were published were not main-streamed enough in to the world-wide medical community for the disorder to be widely known.
-Bengt Hagberg
Although Rett published an article on his self-named disorder, Rett syndrome, in 1966, a paper published by Dr. Bengt Hagberg in 1983 resulted in Rett syndrome becoming widely known in the medical world.
Please visit the following for more information on the history of Rett syndrome and lther useful information about the disorder:
- http://www.ninds.nih.gov/disorders/rett/detail_rett.htm
- http://www.rettsyndrome.org/understandimg-rett-syndrome/about-rett-syndrome/history
- http://www.bundlings.com/irsg.htm
All About DNA (cont.)
WHAT IS GENETICS?
Genetics are the scientific study of heredity, which is the passing of traits from parents to offspring, such as hair color, eye color, or number of fingers or toes.
WHO WAS GREGOR MENDEL?
Gregor Mendel was a monk who lived over 100 years in a monestary in Vienna, Italy, and he discovered the basic principles of heredity by breeding garden peas in carefully planned experiments. He was the first to develop rules that accurately predict patterns in heredity. In conducting his experiment, Mendell chose to study pea plants because they reproduce and grow quickly, so he could study many generations of pea plants within a short amount of time. Pea plants were the ideal plant to study for this type of experiment because they are considered very "simple" organsims since they express few genes.
WHAT IS MENDELIAN GENETICS?
(Vocab)
-Trait: heritable
•feature: petal color
-Allele: variant for a characteristic
•purple (red and blue)
-P generation: parents
-F1 generation: first filial generation
The firs experiments Mendel conducted were monohybrid crosses, which involved one trait (flower color or seed shape).
SO WHAT IS MENDEL'S THEORY
1) For each inherited trait, an individual has two copies, one from each parent (the traits come in pairs. This became the Law of Segregation, which means one trait from each parent.
2) There are alternative versions of traits. These become known as "alleles".
3) When two different alleles occur together, one trait may be expressed while the other is not expressed.
4)Alleles for each trait separate independently when forming gametes (which are sex cells, such as eggs or sperm). Gametes only carry one allele for each trait. This became known as the Law of Independent Assortment, which means traits are inherited independently.
DOMINANT V RECESSIVE
A dominant trait is expressed if 1/2 of the alleles are present, while a recessive trait is expressed if two alleles are present.
HOMOZYGOUS V HETEROZYGOUS
"Homozygous" means having a pair of identical alleles for a trait. (Think: "homo"=same) "Heterozygous" means hving two different alleles for a trait.
WHAT IF THERE ARE EXTRA OR MISSING CHROMOSOMES?
If humans are missing one chromosome, making 45 of the regular 46 chromosomes, the human usually does not survive. The mother's body will usually reject the embryo as it grows in her womb through the gestation period, resulting in a miscarriage. If the child is born, then they will usually pass away soon after birth.
If there are extra copies of chromosomes, the result will be abnormal growth and disabilities or nondisfunction, which is when homologous chromosomes fail to separate.
Mutations occur if there are changes in chromosomal structures (or the DNA codes).
GENOTYPE V PHENOTYPE
A genotype is the genetic make-up of an organism, and they are genes that are expeessed. A phenotype is the physical appearance of an organism; the result of genotypes.
WHAT IS INCOMPLETE DOMINANCE?
Incomplete dominance is a condition in which neither of the two traits in a pair masks the other, result in the blend of the traits. For example, if a blue and red flow had an offspring with incomplete dominance for petal color, the flower's color would be purple. In humans, the best known example of incomplete dominance are hazel eyes, which are the mixture (or separation) of light brown and extremely dark green.
HOW DO CHROMOSOMES DETERMINE GENDER?
There are things called autosomes, which are the 22 pairs of chromosomes that are not involved in determining a person's gender. The one chromosome that is involved in determining someone's gender is called the sex chromosome. Women have a matching set of X ( so XX) while men hav a set of XY (the Y makes the person of male gender).
WHAT ARE SEX-LINKED TRAITS?
Sex-linked traits are usually carried on the X chromosome, so, as a result, females are less likely than males to inherit sex-linked traits, such as color blindness, because they have a second countering X. Males are XY so if the sex-linked trait is carried on the X chromosome, then they woll either have the trait or not because they can only have one X chromosome.
Tuesday, February 18, 2014
ALL ABOUT DNA
Discovery of the Structure of DNA
In 1928, Frederick Griffith discovered that a factor (which would later become DNA) in diseased bacteria could transform harmless bacteria into deadly bacteria. He conducted his experiment using mice. The DNA in the harmless bacteria would become lethal because both bacteria had the same DNA, so, when exposed to each other, the lethal DNA turned on genes in the harmless DNA that made it lethal, thus altering its DNA to be similar to the deadly bacteria. In 1952, Rosalind Franklin took the very first picture of DNA, and she would not share her findings with any other scientists. In 1953, two scientists, Watson and Crick, needed Franklin's photo of DNA to prove that DNA was a double helix, but, since Franklin would not show her picture of the DNA, the men stole it. To get the picture of the DNA, Franklin used x-rays, and, unfortunately, there was not enough information about the consequences of standing in front of an x-ray without lead protection, so she developed cervical cancer. Before Franklin died of cancer, Watson and Crick published their findings of DNA, giving little credit to Rosalind Franklin, and they received the Pulitzer Prize. Because of prevalent sexism in America in the mid-20th century, Franklin received no compensation for her photograph and died before she, too, was awarded the Pulitzer Prize.
Structure of DNA
-Double Helix: The shape of DNA, which appears to be a winding (or spiral) staircase.
-Deoxyribose: The five carbon sugar found in DNA.
-Nucleotides: The subunits of DNA that is made up of three parts; phosphate, five carbon sugars (aka Deoxyribose), and the base.
-Nucleic acids: Genes or specific traits.
DNA is made up of repeating molecules called nucleotides. Three nucleotides create a codon, which codes for a specific amino acid. (Amino acids are the building blocks of DNA.) There are four types of nitrogen bases that make up nucleotides: Adenine (A); Guanine (G, not to be confused with guano!); Thymine (T); and Cytosine (C). With these nitrogen bases is the Base-Pairing Rule, which states that Adenine always pairs up with Thymine (which are called Purines) and Cytosine and Guanine always pair up (which are called Pyrimidines). When A and T bond and C and G bond, the two strands are called complimentary bonds. Between the complimentary bonds, hydrogen bonds form, weak bonds, which easily separate for reproduction. The genetic information in the DNA is stored as a sequence of bases (nucleotides), and the order of the bases determines the genetic information.
How Does DNA Replicate?
Replication is used to make a copy, occurs in the nucleus of cells, and is used to prepare for cell division. The complimentary structure of DNA helps it to make copies of itself. Replication occurs in three steps:
1) DNA helicase unzips:
-Helicase, an enzyme, splits the complimentary strands by breaking the hydrogen bonds that linked the nitrogen bases.
2) DNA polymerase:
-Polymerase, also an enzyme, adds new nucleotides to the exposed nitrogen bases.
3) The two new molecules separate when both are complete.
As a result of Replication, the DNA molecules produce two identical new complimentary strands. Each strand of the original DNA serves as a template for the new strand.
What's RNA?
RNA is similar to DNA because it has a single strand of nucleotides and also has complimentary strands, but it has ribose instead of Deoxyribose and uses Uracil (U) instead of Thymine (T). Although U is used instead of T, Uracil will still pair with Adenine.
How Does DNA "Make" Protein?
In its simplest sense, expressing a gene means manufacturing its corresponding proteins, and it's a multilayered process between Transcription and Translation. Transcription is the creation of RNA, which is the message from the DNA created during Transcription. Transcription occurs in the nucleus and is used because it is the process involving the transcribing of genetic information from DNA to RNA. When a gene is activated, the DNA strands separate and one of them serves as a template for copying a messenger RNA (which is called mRNA). Transcription occurs in three steps:
1) RNA polymerase binds to DNA.
2)Elongation:
-DNA strand unwinds and polymerase allows RNA to transcribe only a single strand.
3)Termination:
-RNA releases and detaches from the DNA strand
Translation is the actual creation of a protein (called polypeptide) under the direction of RNA. The mRNA is "read" according to the genetic code. Translation occurs in the cytoplasm with the ribosomes of cells, and it is used to put the amino acids together to make proteins (mRNA-tRNA-amino acids). Each group of three base pairs in mRNA makes a codon, and each codon specifies for a particular amino acid. The mRNA sequence is used as a template to assemble (in order) the chain of amino acids that form a protein. Transfer RNA (called tRNA) attaches and transports amino acids nto growing chains to form proteins. Basically, the tRNA is already present in the ribosome and attaches free amino acids into one growing structure. TRNA functions as an interpreter for nucleic acid and peptide sequences, and tRNA picks up amino acids and matches them to the proper codons in mRNA. TRNA is complimentary to mRNA.
What Are Genetic Mutations?
Mutations are permanent changes in the DNA sequence, and mutations can occur in two ways:
1) Mistakes that occur when a cell copies its DNA:
-such as in cellular division
2) Acquired during a person's lifetime:
-ex: environmental factors (UV light, chemicals, radiation)
Mutations generally occur in somatic cells, but can not be passed on to the next generations. The actual number of mistakes that remain incorporated into the DNA is low, because cells contain special DNA repair proteins that fix many of the mistakes in the DNA that care caused by mutagens (aka mutation-causing agents). There are eight types of genetic mutations:
1) Base-Pair Substitutions (genes):
-known as "silent mutations"
-they have no effect on proteins
2)Missense/Substitution:
-substitutes a different amino acid for the correct amino acid
-it results in a different protein
3)Nonsense:
-substitutes to a stop codon
-results in a nonfunctional protein
4) Deletion:
-changes the number of DNA bases by removing a segment of DNA
(The following are chromosomal genetic mutations)
5) Duplication:
-multiple copies of all chromosomal regions are created
6) Inversion:
-reverses the orientation of a chromosomal segment
7) Insertion:
-changes the number of DNA bases by inserting a segment of DNA
-can disrupt the grouping of codons
•resulting m a completely different translation from the original
•the earlier in the sequence the deletion/Insertion occurs, the more altered the produced protein is
8) Translocation:
-interchange of genetic parts from nonhomologus chromosomes
•chromosomes occur in pairs (one from each parent)
•nonhomologus would be Chromosome Four exchanging a DNA segment with Chromosome Twenty.
In 1928, Frederick Griffith discovered that a factor (which would later become DNA) in diseased bacteria could transform harmless bacteria into deadly bacteria. He conducted his experiment using mice. The DNA in the harmless bacteria would become lethal because both bacteria had the same DNA, so, when exposed to each other, the lethal DNA turned on genes in the harmless DNA that made it lethal, thus altering its DNA to be similar to the deadly bacteria. In 1952, Rosalind Franklin took the very first picture of DNA, and she would not share her findings with any other scientists. In 1953, two scientists, Watson and Crick, needed Franklin's photo of DNA to prove that DNA was a double helix, but, since Franklin would not show her picture of the DNA, the men stole it. To get the picture of the DNA, Franklin used x-rays, and, unfortunately, there was not enough information about the consequences of standing in front of an x-ray without lead protection, so she developed cervical cancer. Before Franklin died of cancer, Watson and Crick published their findings of DNA, giving little credit to Rosalind Franklin, and they received the Pulitzer Prize. Because of prevalent sexism in America in the mid-20th century, Franklin received no compensation for her photograph and died before she, too, was awarded the Pulitzer Prize.
Structure of DNA
-Double Helix: The shape of DNA, which appears to be a winding (or spiral) staircase.
-Deoxyribose: The five carbon sugar found in DNA.
-Nucleotides: The subunits of DNA that is made up of three parts; phosphate, five carbon sugars (aka Deoxyribose), and the base.
-Nucleic acids: Genes or specific traits.
DNA is made up of repeating molecules called nucleotides. Three nucleotides create a codon, which codes for a specific amino acid. (Amino acids are the building blocks of DNA.) There are four types of nitrogen bases that make up nucleotides: Adenine (A); Guanine (G, not to be confused with guano!); Thymine (T); and Cytosine (C). With these nitrogen bases is the Base-Pairing Rule, which states that Adenine always pairs up with Thymine (which are called Purines) and Cytosine and Guanine always pair up (which are called Pyrimidines). When A and T bond and C and G bond, the two strands are called complimentary bonds. Between the complimentary bonds, hydrogen bonds form, weak bonds, which easily separate for reproduction. The genetic information in the DNA is stored as a sequence of bases (nucleotides), and the order of the bases determines the genetic information.
How Does DNA Replicate?
Replication is used to make a copy, occurs in the nucleus of cells, and is used to prepare for cell division. The complimentary structure of DNA helps it to make copies of itself. Replication occurs in three steps:
1) DNA helicase unzips:
-Helicase, an enzyme, splits the complimentary strands by breaking the hydrogen bonds that linked the nitrogen bases.
2) DNA polymerase:
-Polymerase, also an enzyme, adds new nucleotides to the exposed nitrogen bases.
3) The two new molecules separate when both are complete.
As a result of Replication, the DNA molecules produce two identical new complimentary strands. Each strand of the original DNA serves as a template for the new strand.
What's RNA?
RNA is similar to DNA because it has a single strand of nucleotides and also has complimentary strands, but it has ribose instead of Deoxyribose and uses Uracil (U) instead of Thymine (T). Although U is used instead of T, Uracil will still pair with Adenine.
How Does DNA "Make" Protein?
In its simplest sense, expressing a gene means manufacturing its corresponding proteins, and it's a multilayered process between Transcription and Translation. Transcription is the creation of RNA, which is the message from the DNA created during Transcription. Transcription occurs in the nucleus and is used because it is the process involving the transcribing of genetic information from DNA to RNA. When a gene is activated, the DNA strands separate and one of them serves as a template for copying a messenger RNA (which is called mRNA). Transcription occurs in three steps:
1) RNA polymerase binds to DNA.
2)Elongation:
-DNA strand unwinds and polymerase allows RNA to transcribe only a single strand.
3)Termination:
-RNA releases and detaches from the DNA strand
Translation is the actual creation of a protein (called polypeptide) under the direction of RNA. The mRNA is "read" according to the genetic code. Translation occurs in the cytoplasm with the ribosomes of cells, and it is used to put the amino acids together to make proteins (mRNA-tRNA-amino acids). Each group of three base pairs in mRNA makes a codon, and each codon specifies for a particular amino acid. The mRNA sequence is used as a template to assemble (in order) the chain of amino acids that form a protein. Transfer RNA (called tRNA) attaches and transports amino acids nto growing chains to form proteins. Basically, the tRNA is already present in the ribosome and attaches free amino acids into one growing structure. TRNA functions as an interpreter for nucleic acid and peptide sequences, and tRNA picks up amino acids and matches them to the proper codons in mRNA. TRNA is complimentary to mRNA.
What Are Genetic Mutations?
Mutations are permanent changes in the DNA sequence, and mutations can occur in two ways:
1) Mistakes that occur when a cell copies its DNA:
-such as in cellular division
2) Acquired during a person's lifetime:
-ex: environmental factors (UV light, chemicals, radiation)
Mutations generally occur in somatic cells, but can not be passed on to the next generations. The actual number of mistakes that remain incorporated into the DNA is low, because cells contain special DNA repair proteins that fix many of the mistakes in the DNA that care caused by mutagens (aka mutation-causing agents). There are eight types of genetic mutations:
1) Base-Pair Substitutions (genes):
-known as "silent mutations"
-they have no effect on proteins
2)Missense/Substitution:
-substitutes a different amino acid for the correct amino acid
-it results in a different protein
3)Nonsense:
-substitutes to a stop codon
-results in a nonfunctional protein
4) Deletion:
-changes the number of DNA bases by removing a segment of DNA
(The following are chromosomal genetic mutations)
5) Duplication:
-multiple copies of all chromosomal regions are created
6) Inversion:
-reverses the orientation of a chromosomal segment
7) Insertion:
-changes the number of DNA bases by inserting a segment of DNA
-can disrupt the grouping of codons
•resulting m a completely different translation from the original
•the earlier in the sequence the deletion/Insertion occurs, the more altered the produced protein is
8) Translocation:
-interchange of genetic parts from nonhomologus chromosomes
•chromosomes occur in pairs (one from each parent)
•nonhomologus would be Chromosome Four exchanging a DNA segment with Chromosome Twenty.
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