Lecture 8 - Genetic Variation, Genomes And Mutation Flashcards
What is the arrangement of eukaryotic genomes?
Linear chromosomes
How many somatic chromosomes are in the main genome of the nucleus?
22 somatic chromosomes
What is the size of the human mitochondrial genome?
16,500 bp
What are the key components of chromosome 22?
- Centromere
- 2 telomeres
- Origins of replication
- Heterochromatin
- Intergenic regions
- UTRs
- Promoters
- Introns
- Protein coding regions
What percentage of the human genome is made up of protein-coding exons?
1.5%
Define LINEs in the context of genetics.
Long interspersed nuclear elements
Define SINEs in the context of genetics.
Short interspersed nuclear elements
What are transposons often referred to as?
Jumping genes
What are the two categories of transposition?
- Cut and paste transposition: gone from donor DNA
- Replicative transposition: still in donor DNA
What is the role of retrotransposons?
Transpose via mRNA
What is reverse transcription?
mRNA to DNA
What is the definition of an allele?
Alternative forms of a heritable trait
What is the definition of polymorphism?
Variation within a population of a given trait
Name the types of variation in genetics.
- Single nucleotide polymorphisms (SNPs)
- Indels (insertions or deletions)
How many SNPs are approximately found in humans?
About 10 million SNPs
What are the effects of base substitutions?
- Silent: doesn’t change amino acid
- Missense: changes amino acid
- Nonsense: changes amino acid to stop codon
What is a phenotypic effect of sickle cell anemia?
Single nucleotide polymorphism of adenine to thymine in beta-haemoglobin gene
What happens to coding regions after a base insertion?
Frameshift mutation occurs
What is an example of a disease caused by an indel?
- Cystic fibrosis
- Albinism
What are Mendelian diseases?
Disorders caused by variation in a single gene
What technology is used in Oxford Nanopore sequencing?
Small flow cell with nanopores that a DNA strand passes through then the signal is decoded to discover the sequence (each base gives a different signal)
What mechanisms do cells have to prevent mutations?
- Proofreading DNA polymerase
- Post-replication mismatch repair
- DNA repair by homologous recombination
- Cell cycle checkpoints
What are somatic cell mutations primarily associated with?
Cancers
What is a mutagen?
Substance that causes mutations
What type of damage does UV light cause?
Point mutations
What are intercalating agents?
Flat molecules that insert between base pairs causing frame shift mutations
What is the effect of base analogues?
Incorporated into DNA in place of normal base due to their similar molecular structure to the bases
What are base modifying agents?
Covalently alter bases causing mispairing such as deaminating (removes amino group), hydroxylating (add hydroxyl group) and alkylating (add alkyl groups)
What are the 6 ways that genomes can be altered?
- Mutations within a gene
- Mutations within regulatory DNA - repressor
- Gene duplication and divergence
- Exon shuffling (swapping genes)
- Transposition
- Horizontal transfer from other organisms
Why does most genetic variation have no phenotypic effect?
Falls in intergenic or non-codon region
What mechanisms do cells have to prevent and correct mutations?
Proofreading by DNA polymerase
Post replication mismatch repair
DNA repair by homologous recombination
Cell cycle checkpoints
