Study sets, textbooks, questions
Upgrade to remove ads
Gene Mutation and DNA Repair
Terms in this set (32)
2. Occurs in what cells? (2 types)
1. heritable alteration or change in genetic material
2. Can occur in somatic cells or germ cells
Base Substitution or Point Mutation
Change of one base pair in DNA sequence
- most common!
- missense, nonsense, silent, transition, transversion
Change in a nitrogenous base leads to a change in the amino acid
DNA sequence changes --> RNA sequence changes --> Early stop codon introduced
- translation stops and protein is incomplete
Change in a single codon but the amino acid it codes for remains the same
Transition vs. Transversion
Transition: pyrimidine to pyrimidine or purine to purine
- C to T or A to G
Transversion: Pyrimidine to purine or vice versa
- T to A or G
- C to A or G
- A to T or C
- G to T or C
Insertions and deletions - they shift the reading frame of a genetic message
- can change every amino acid that follows!
- can end up drastically altering a protein
Examples of expansion of trinucleotide repeats that can be devastating
- Fragile X syndrome (too many CGG)
- Huntington disease (too many CAG)
-- Huntington's occurs on Chromosome 4
1. Normally how many repeats are present?
2. How many repeats in those with Huntington's disease?
3. Those with 36-39 repeats?
4. Effects on the protein
1. 10-35 CAG repeats
2. 36-120+ CAG repeats
3. Those with 36-39 repeats may or may not develop symptoms of the disease
- those with 40+ usually always have symptoms
4. Production of abnormally long version of the huntington protein
- elongated protein is cut into smaller, toxic fragments that clump together in neurons and disrupt the normal function of neurons
-- neurons end up dying!
1. Description of what it is?
2. When do affected individuals develop symptoms
1. Causes progressive breakdown of nerve cells in brain
2. Develop symptoms in 30's/40's
- Juvenile form can show up in someone's 20's
3. Movement/cognitive/psychiatric disorders
- jerking, writhing, abnormal eye movements, balance problems
- inability to focus, inflexible behaviors, lack of impulse control
- social withdrawal, insomnia, sadness, irritability, thoughts of suicide
Mutations in non-coding DNA (Can occur in what 3 areas?)
1. Promoter regions
2. Enhancer/regulatory regions
3. Inside introns (at splicing junctions)
What do you usually see at the beginning and end of introns?
GU at beginning and AG at end
Two ways in which mutations can exert their phenotypic effect?
1. Loss of function
2. Gain of function
Loss of Function Mutation
1. What happens to the gene product?
2. What is it called if the function is totally lost?
3. Dominant or recessive mutations?
4. Description of person if they have a phenotype
5. Example of #4 that leads to monocyte and B cell deficiency?
1. Reduces/eliminates function of gene product
2. Null mutation
4. Often heterozygotes appear normal but if there is a phenotype then they are said to suffer from "haplo-insufficiency"
- occurs when 50% of normal active form of a protein is expressed in a cell
*sometimes it's not even enough to have 50% of a functioning gene
5. occurs in hets for transcription factor GATA2
Gain of Function Mutation
1. What does it result in?
2. Dominant or recessive?
3. Example: RAS Protein
1. New gene product with new function
3. Protein that functions in the cell's "grow" signaling pathway but it's under strict control
- causes RAS to give the "grow" signal all the time!
- associated with poor prognosis and eventually cancer
Dominant Negative Mutation
1. What does the mutant allele in heterozygotes result in?
2. Marfan's Syndrome
1. Results in loss of protein activity/function because mutant protein interferes with functioning of the normal wild type protein
2. Mutant fibrillin protein interferes with functioning of the normal fibrillin in the heterozygote
- Abraham Lincoln had this?
1. Spontaneous mutations
2. Induced mutations
1. They just happen; error during replication, or some other cellular process
2. Have outside source, either natural or artificial
- aflatoxins (peanut butter), charred meats, x-rays
2012 Study in Iceland
Scientists sequenced SNP's throughout the genomes of 78 parent/offspring sets
- newborn baby's genome has 60 new mutations compared with the parent's genome
- older the father = more mutations in the newborn
- mom contributes about 15 regardless of age
Radiation as Source of Induced Mutation: Ionizing Radiation
X-rays, gamma rays, high-energy a and b particles
- X-ray and gamma rays penetrate deep into tissues and eject electrons from atoms they encounter - cause point mutations
- a and b high energy particles don't penetrate soft tissue beyond a few mm or even less
- genetic effects are cumulative
Average U.S. Doses and Sources
1. Natural sources
2. Man-made sources
3. Average annual radiation dose
6. Head CT
7. Full body CT
8. Living in Denver
1. Minerals in the ground
3. 620 millirem **
4. 10 millirem
5. 42 millirem
6. 200 millirem **
7. 1000 millirem
8. 80 millirem/year
- alkylating agents
- some dyes
- some food additives
- chargrilled meat (HCAs can intercalate in DNA and hinder replication)
- ethidium bromide
INFO FOR EXAM #2
Three repair mechanisms?
1. Nucleotide excision repair
2. Post-replication repair
3. Mismatch repair
1. Function of DNA polymerases during normal replication
2. What does this repair correct?
3. How does it work?
1. DNA polymerases "catch" almost all of their mistakes made during replication and immediately correct them
2. Mistakes that are not caught are corrected with this method
3. Enzymes recognize and "nick" the strand with the mistake
- the mistake and a few nucleotides on either side are removed
- DNA polymerase synthesizes new DNA in the gap and ligase forms a phosphodiester bond between the old and new DNA
Nucleotide Excision Repair
1. What does it remove?
2. How many proteins are involved?
3. Understanding of this type of repair has been furthered by studying what condition?
4. Similar to mismatch repair how?
5. Similar to base excision repair how?
1. Thymine dimers and large chemical adducts
2. More than 30 proteins
3. Xeroderma Pigmentosum
4. Nucleotides are removed at the site of the mutation and DNA polymerase and ligase finish the repair
5. Repairs uracil in DNA
2. How many genes involved?
3. Common or rare?
4. What must the sufferers avoid?
5. If they don't avoid the above, what could they get?
1. Autosomal recessive
2. At least 7 genes involved
4. Avoid sunlight!
5. Basal cell tumors, squamous cell tumors, melanoma
Base Excision Repair
- fixes incorrect bases
- minor lesions that don't stop replication
1. What is it?
2. Two types
1. Can repair double strand breaks caused by ionizing radiation and reactive oxygen species
2. Homologous recombination repair and non-homologous end joining
Homologous Recombination Repair
1. What is it?
2. Two important genes involved?
3. Is it error-prone?
1. Broken chromosome ends "invade" a sister chromosome and use it as a template to make the repair
2. BRCA1 and BRCA2
3. Not error prone!
Overhangs at the break ("staggered ends") are trimmed and the ends are ligated together
- it is error prone!!
Translesional DNA Synthesis
If some types of mutation are not repaired by other methods then the cell can do this method
- enzymes involved in replication "jump over" the site of the mistake and continue replication farther down from the mutation
- may comprise up to half of our genome (SINEs and LINEs)
- documented cases of disease due to insertion of SINEs and LINEs into essential genes
Recommended textbook explanations
Fundamentals of Biochemistry
Charlotte W. Pratt, Donald Voet, Judith G. Voet
Lehninger Principles of Biochemistry
David L Nelson, Michael M. Cox
Biocalculus: Calculus for the Life Sciences
Biocalculus: Calculus, Probability, and Statistics for the Life Sciences
Sets found in the same folder
Mendelian Genetics: Chapter 1
DNA Chromosome Structure & Replication: Chapter 2
The Genetic Code, Transcription, and Translation
Sets with similar terms
SHORTER -> CH7 Genomic Variation Producing Disease…
Bio Final Guide
Bio 001 final
CH 8 - types of mutations
Other sets by this creator
GT: Chronic Kidney Disease
Pharmacology: GU Infections
SS: Non-Glomerular Diseases
SS: Glomerular Diseases
Other Quizlet sets
Instruments Exam 2
D501 TopHat Questions- Block 1