Lecture 8 - Genetic Variation, Genomes And Mutation

Question 1

What is the arrangement of eukaryotic genomes?

Answer 1

Linear chromosomes

Question 2

How many somatic chromosomes are in the main genome of the nucleus?

Answer 2

22 somatic chromosomes

Question 3

What is the size of the human mitochondrial genome?

Answer 3

16,500 bp

Question 4

What are the key components of chromosome 22?

Answer 4

• Centromere
• 2 telomeres
• Origins of replication
• Heterochromatin
• Intergenic regions
• UTRs
• Promoters
• Introns
• Protein coding regions

Question 5

What percentage of the human genome is made up of protein-coding exons?

Answer 5

1.5%

Question 6

Define LINEs in the context of genetics.

Answer 6

Long interspersed nuclear elements

Question 7

Define SINEs in the context of genetics.

Answer 7

Short interspersed nuclear elements

Question 8

What are transposons often referred to as?

Answer 8

Jumping genes

Question 9

What are the two categories of transposition?

Answer 9

• Cut and paste transposition: gone from donor DNA
• Replicative transposition: still in donor DNA

Question 10

What is the role of retrotransposons?

Answer 10

Transpose via mRNA

Question 11

What is reverse transcription?

Answer 11

mRNA to DNA

Question 12

What is the definition of an allele?

Answer 12

Alternative forms of a heritable trait

Question 13

What is the definition of polymorphism?

Answer 13

Variation within a population of a given trait

Question 14

Name the types of variation in genetics.

Answer 14

• Single nucleotide polymorphisms (SNPs)
• Indels (insertions or deletions)

Question 15

How many SNPs are approximately found in humans?

Answer 15

About 10 million SNPs

Question 16

What are the effects of base substitutions?

Answer 16

• Silent: doesn’t change amino acid
• Missense: changes amino acid
• Nonsense: changes amino acid to stop codon

Question 17

What is a phenotypic effect of sickle cell anemia?

Answer 17

Single nucleotide polymorphism of adenine to thymine in beta-haemoglobin gene

Question 18

What happens to coding regions after a base insertion?

Answer 18

Frameshift mutation occurs

Question 19

What is an example of a disease caused by an indel?

Answer 19

• Cystic fibrosis
• Albinism

Question 20

What are Mendelian diseases?

Answer 20

Disorders caused by variation in a single gene

Question 21

What technology is used in Oxford Nanopore sequencing?

Answer 21

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)

Question 22

What mechanisms do cells have to prevent mutations?

Answer 22

• Proofreading DNA polymerase
• Post-replication mismatch repair
• DNA repair by homologous recombination
• Cell cycle checkpoints

Question 23

What are somatic cell mutations primarily associated with?

Answer 23

Cancers

Question 24

What is a mutagen?

Answer 24

Substance that causes mutations

Question 25

What type of damage does UV light cause?

Answer 25

Point mutations

Question 26

What are intercalating agents?

Answer 26

Flat molecules that insert between base pairs causing frame shift mutations

Question 27

What is the effect of base analogues?

Answer 27

Incorporated into DNA in place of normal base due to their similar molecular structure to the bases

Question 28

What are base modifying agents?

Answer 28

Covalently alter bases causing mispairing such as deaminating (removes amino group), hydroxylating (add hydroxyl group) and alkylating (add alkyl groups)

Question 29

What are the 6 ways that genomes can be altered?

Answer 29

1. Mutations within a gene 2. Mutations within regulatory DNA - repressor 3. Gene duplication and divergence 4. Exon shuffling (swapping genes) 5. Transposition 6. Horizontal transfer from other organisms

Question 30

Why does most genetic variation have no phenotypic effect?

Answer 30

Falls in intergenic or non-codon region

Question 31

What mechanisms do cells have to prevent and correct mutations?

Answer 31

Proofreading by DNA polymerase Post replication mismatch repair DNA repair by homologous recombination Cell cycle checkpoints