Lecture 14 - Lifecycle of a Gene

Question 1

Which organisms generally have the smallest genome sizes?

Answer 1

Prokaryotes.

Question 2

Which groups show the largest genome sizes?

Answer 2

Birds, mammals, and reptiles.

Question 3

What are the three main categories of genome composition?

Answer 3

Coding DNA, non-coding DNA, and repeats.

Question 4

How does genome composition differ between S. cerevisiae and H. sapiens?

Answer 4

S. cerevisiae: Mostly coding DNA (~75%).

H. sapiens: Large amounts of non-coding DNA and repeats, with less coding DNA.

Question 5

What are the three primary sources of new genes?

Answer 5

Horizontal gene transfer.

Duplication of an existing gene.

De novo creation from non-coding DNA.

Question 6

What is horizontal gene transfer (HGT)?

Answer 6

The exchange of genetic material between different organisms, not involving parent-offspring inheritance (asexual species).

Question 7

Name the three mechanisms of horizontal gene transfer in bacteria.

Answer 7

Transformation, conjugation, and transduction.

Question 8

How does transformation work?

Answer 8

DNA from the environment is incorporated into the bacterial genome.

Question 9

What is conjugation?

Answer 9

Direct transfer of DNA between bacteria using a sex pilus.

Question 10

How does transduction occur?

Answer 10

Viruses transfer bacterial DNA to another host during infection.

Question 11

What are the main types of gene duplication in eukaryotes?

Answer 11

Whole genome duplication, whole chromosome duplication, and DNA segment duplication.

Question 12

What is polyploidisation?

Answer 12

An increase in the number of chromosome sets within an organism.

Question 13

How can polyploidisation lead to a new species?

Answer 13

Through allopolyploidy, combining genomes of different species.

Question 14

What are the possible fates of new genes?

Answer 14

Loss or preservation.

Question 15

What is pseudogenisation?

Answer 15

The loss of gene function through mutation.

Question 16

What are the three types of preservation mechanisms?

Answer 16

Compensation, neofunctionalisation, and subfunctionalisation.

Question 17

What is neofunctionalisation?

Answer 17

A duplicated gene acquires a completely new function.

Question 18

What is subfunctionalisation?

Answer 18

Gene copies specialise in specific functions or timings, e.g., globin gene family in humans.

Question 19

Give an example of adaptation through gene duplication in humans.

Answer 19

High-starch diets selected for more copies of the AMY1 gene in some populations.

Question 20

How do transposable elements (TEs) contribute to genome adaptation?

Answer 20

They can duplicate and spread advantageous traits.

Question 21

What are transposable elements (TEs)?

Answer 21

Genetic sequences that can move within the genome.

Question 22

What are the two classes of TEs?

Answer 22

Class 1 (retrotransposons): Copy-and-paste mechanism.

Class 2 (DNA transposons): Cut-and-paste mechanism.

Question 23

What can cause genome instability?

Answer 23

Replication errors, unequal crossover, retrotransposition, and aneuploidy.

Question 24

What are telomeres, and why are they important?

Answer 24

Telomeres are repetitive DNA sequences at chromosome ends that protect against deterioration during replication.

Question 25

How does telomere shortening contribute to disease?

Answer 25

It is linked to ageing, cancer, and various metabolic and psychiatric disorders.

Question 26

What is the role of transposable elements in fruit flies?

Answer 26

They extend telomeres, protecting DNA from shortening.

Question 27

What are the three main sources of new genes?

Answer 27

Horizontal gene transfer, duplication, and de novo creation.

Question 28

What are examples of adaptation via genome evolution?

Answer 28

Antibiotic resistance in bacteria.
Starch digestion in humans.
Electric organs in fish.