DNA and Genetics Flashcards
What is the correct name for an unmutated gene
The wild type gene
Why is one allele dominant to another
Both genes are expressed (one producing an enzyme and the other not for example) however if only 1 genes worth of enzyme is required then that allele is dominant to the other if both genes would be required to produce enough then that is recessive
What are the names for the hidden gene and controlling gene in epistasis
Hidden = Hydrostatic
Controlling = epostatic
What do core nucleosomes contain
2 copies of different histones wrapping around the outside of the core nucleosome
What is a solenoid
When a nuclesome string wraps around itself
What is the role of the mRNA cap
- The cap protects the 5’ end of the mRNA from degradation
- The cap recruits translation factors which can recruit ribosomes
- The cap interacts with the cap binding complex involved in the export of mRNA out of the nucleus
- The cap is important for splicing of introns near to the 5’ end
Approximately how many genes does a human being have
20,000
When do mendals laws of genetics not apply
- Mitochondrial DNA
- Linkage (when 2 genes are physically very close together)
- Linkage disequilibrium (2 alleles that are not inherited separately)
Why is mRNA slightly longer then DNA
Untranslated DNA regions
What are the 2 different terminators in prokaryotes
- Intrinsic terminator - the RNA folds on to itself and when it reaches a weaker region it breaks of its own accord
- Rho terminator - areas are rich in C but have very little G slowing down the polymerase so that the Rho factor can catch up and inhibit the polymerase
What is unusual about tRNA base pairing and why
It has been modified from standard Watson and crick rules this is to help strengthen codon anticodon interactions
What are the names and function of the 3 ribosomal binding sites
- A (aminoacyl) site - accommodates the tRNA incoming aminoacyl-tRNA
- P (peptidyl) site - accommodates the tRNA attached to the growing chain
- E (exit) site - accommodates the tRNA without an amino acid ready for ejection
Which bond is weaker A too T or C too G and why
A too T is considerably weaker because it only has 2 H bonds instead of 3
What are the 3 different forms of DNA
- A DNA - squashed
- B DNA - regular
- Z DNA - stretched
Which end does DNA polymerase act on in DNA replication
The 3’ end only
What are the differences between the leading and lagging strand in DNA replication and why is the lagging strand different
The leading strand is made continuously whereas the lagging strand is made discontinously because it has to wait for more DNA to become exposed for it to replicate
What is an issue with replicating linear chromosomes and how is it resolved in some cells
The last RNA primer on the lagging strand is removed but cannot be replaced so the lagging strand gets shorter with each replication.
This is resolved by telomerase which adds a new section onto the DNA which is sacrificed instead of the chromosomal DNA (telomerase is only present in sperm and egg cells)
What do 3’-5’ exonucleotides do
They proofread nucleotides to check that polynucleotides have been formed correctly
What does genic mean
Something in genes
What is the ratio of genic too intergenic in humans
1:3
When are introns removed from DNA
As the RNA polymerase moves down the gene co-transcriptually
Can DNA be formed from RNA
it is not believed so
What is a missense mutation
A substitution mutation that slightly changes the structure of the polypeptide
What are 4 of they types of DNA damage
- Adduct (something is added)
- Nick (a small cut)
- Mismatch
- Replicated adduct (top and bottom)
- Chromosomal break
- Cross link
