lecture 3 Flashcards
define ‘gene’
a region of DNA that can be expressed to produce a final functional product that is either a polypeptide or RNA molecule
what is meant by: copy number variation?
sections of the genome are repeated, the number of repeats in the genome varies between individuals
what type of trait does achondroplasia result from? what is the impact of this on a cellular level?
autosomal dominant trait
mutation in the fibroblast growth factor receptor 3 gene
what is an anonymous SNP?
a single nucleotide polymorphism which has no known effect on gene function
what is a synonymous coding SNP?
encodes the same amino acid as the original
where are CNVs found and what causes them?
repetitive sequences caused by replication slippage
what is the genetic basis for Huntington’s disease?
triplet expansion of CAG caused by replication slippage
how many CAG repeats are found in the normal gene and huntington’s diseased gene?
normal: 6-39
diseased: 35-121
what is the molecular basis for DNA fingerprinting?
- very high mutation rate per locus per generation
- very high levels of polymorphism in a population
- very low probability of finding the same length variant in unrelated individuals
- by analysis of a sufficient number of loci, we can make a ‘unique’ DNA profile
what is the ames test? how does it work?
a screening for potential mutagens
assays the ability of chemicals to revert mutant strains of salmonella typhimurium
outline the procedure for the ames test
1) 10^8 cells of bacteria auxotrophic for histidine (His-) are spread with liver enzymes on a plate lacking histidine
2) to grow, the His- must revert to His+
which mutations are most and least likely to cause His- to revert to His+?
most likely: base substitutions
less likely: frameshift mutations
least likely: deletions
how is reversion frequency calculated?
number of revertant colonies/total number of cells plated
outline the DNA damage response
sensor proteins -> signalling cascade -> transducer proteins -> mediator proteins/effector proteins -> apoptosis or senescence
how do the cell cycle checkpoints prevent error?
G1, G2 and M cause senescence until DNA damage is repaired
