BGM1004/L15 Genome Evolution

Question 1

How well is gene order on chromosomes conserved?

Answer 1

Very highly over wide evolutionary distances

Question 2

How are sentencing genes grouped on chromosomes of different species?

Answer 2

Grouped in the same way

Question 3

What are synteny blocks?

Answer 3

Regions containing homologous genes

Question 4

How can chromosomal rearrangements be identified?

Answer 4

By looking for blocks of synteny between chromosomes of different organisms

Question 5

What is reciprocal translocation?

Answer 5

Where 2 non-homologous chromosomes break and exchange fragments

Question 6

What can result from meiosis after translocation?

Answer 6

Trisomy

Question 7

What is centric fusion?

Answer 7

2 telocentric chromosomes fuse to generate one new chromosome

Question 8

What is Robertsonian translocation?

Answer 8

Short arms of two acrocentric chromosomes lost

Question 9

What can result from Robertsonian translocation after meiosis?

Answer 9

Trisomy or Monopsony

Question 10

Give the 2 types of inversion.

Answer 10

Paracentric (one arm)
Pericentric (two arms or around centromere)

Question 11

What can increase the complexity of the genome? (2)

Answer 11

Small scale gene duplications
Large scale gene/genome duplications followed by loss of superfluous genes and divergence of retained homologues

Question 12

What leads to unequal crossover?

Answer 12

Repetitive region of one chromatid does not line up with corresponding region in others
Different repeat numbers result

Question 13

What is sister chromatid exchange?

Answer 13

Strands breaking on sister chromatids producing different repeat numbers

Question 14

Give an example of an organism that has undergone a relatively recent genome duplication.

Answer 14

Saccharomyces cerevisae

Question 15

Why is genome duplication evolutionary advantageous?

Answer 15

‘Extra set’ does not have the same restriction on mutation rate as a single copy (selective pressure to retain function)

Question 16

How do multigene families arise?

Answer 16

After duplication events

Question 17

What follows multigene families?

Answer 17

Mutations to generate alterations in expression/function

Question 18

How do 2 specialised genes arise from one precursor?

Answer 18

Gene duplication
Mutation so elements promote expression in specific tissues

Question 19

What is the correlation between gene position in a hox cluster and its expression?

Answer 19

First on the chromosome = expressed earlier/towards anterior of species

Question 20

How does mutation of a hox gene lead to changes in segmental identity?

Answer 20

Altered expression of downstream targets i.e. genes for which the hox protein is a transcription factor

Question 21

What is a pseudogene?

Answer 21

A identifiable non-functional gene

Question 22

What is thalessemia?

Answer 22

Unbalanced production of globins resulting in abnormal haemoglobin

Question 23

What is exon shuffling?

Answer 23

Exons corresponding to discrete domains can be moved around the chromosome and retain function

Question 24

What is de novo generation of genes?

Answer 24

Transcription of genome can lead to protein formation
Retained function if the protein is neutral or advantageous