Molecular genetics Flashcards
What are somatic cells
- opposite from germ cells, they carry a full copy of the genome. All cells except germ cells.
What happens globally during mitosis
- replication of the genome by chromosome replication -> chromatids. 2n -> 4n
- the analogous chromatids get pulled apart, forming 2 cells with both the exact same 2n genome.
What happens globally during meiosis
meiosis I: replication of 2n into 4n chromatids.
Lining up of the different alleles of the chromosome pairs. Recombination and seperation of the alleles in a pair. 2 x 2n
Meiosis II: pulling apart of the chromatids -> 4 x 1n
What are the 2 functions of genotype
- replication (growth by mitosis, reproduction by meiosis)
2. protein synthesis
What are some of the ways the human genome makes sure it’s robust to errors?
- mutations don’t always lead to different amino acids
- different amino acids don’t always lead to different function
- DNA polymerase checks for errors
- redundancy but not ambiguity: different triplets code for same amino acid but no triplets code for different amino acids.
- segmental duplication (mutations): allows room for evolved mutated DNA functions without damaging original function
- introns and exons
DNA structure
Backbone of sugar and phosphates, base pairs of purines ( A and G) and pyrimidines ( C and T ) that make for a constant diameter.
The 3’ and 5’ end make for directionality.
The genetic code is
What amino acids are translated from the triplets, the rules for translation
DNA is
the molecule that contains the genotype, the information necessary for coding the phenotype. Determined by the type, order and reading frame of nucleotide bases.
Why do prairie voles show more pair bonding than other rodents?
The rodents all have the V1a gene that codes for the receptor for arginine vasopressin hormone that increases pair bonding. But the prairie voles have different microsatellites that regulate the expression (how much transcription happens) of this gene. Overexpression = more receptors made.
What happens during replication
- helicase unwinds, a replication bubble forms
- RNA primase lays down a few nucleotides on a template strand as a primer for DNA polymerase
- a) DNA polymerase does its thing laying down nucleotides from 5’ to 3’ on the leading strand.
b) Lagging strand: RNA primase lays down multiple primers. DNA polymerase copies the strand from 5’ to 3’ until it hits a ‘wall’, then jumps backwards (direction of replication fork/helicase) to continue with the other Okozaki fragments.
What is transcription
A general term for the synthesis of RNA on a DNA template
What happens during transcription
- helicase unwinds?
- RNA Polymerase lands at a promoter site.
- Pre mRNA is created: a single strand of primary transcript that is then processed: deletion of introns, splicing together of exons, transported outside of nucleus towards ribosomes
What happens during translation
In the ribosome, the coding strand of RNA is translated, starting at the 5’ end and moving towards the 3’ end. tRNA is bound and forms a polypeptide chain.
What is the reading frame and why is it important
The organisation of the order in which you read the nucleotides. Because the order of the nucleotides determines which amino acid is coded for.
If it shifts like during frameshift mutations (insertion, deletion of anything that isn’t a multitude of 3) this has bad consequences.
Forms of mutation
- Point mutations: nucleotide pair substitutions
Silent mutation: synonymous
Nonsynomous: missense (codes different amino acid) and nonsense (codes stop) - Frameshift: insertion/deletion
- Simple sequence repetitions (microsatellites): some natural variation in this, very common form. Happens bc of slippage. AKA repeat expansion like in Huntingtons
- Segmental duplications
- Structural changes
