Genome Evolution

Question 1

What is the genome?

Answer 1

Complete set of genes or genetic material present in a cell or organism

Question 2

What is evolution?

Answer 2

Change in heritable characteristics of biological populations over successive generations (i.e., change over time)!

Question 3

What does it mean that “Most traits are polygenic”

Answer 3

Controlled by multiple genes

Question 4

What is polyploidy?

Answer 4

Condition where an organism has more than 2 complete sets of chromosomes

Answer 5

Plants, wheats, strawberries, bananas

Question 6

What is autopolyploidy?

Answer 6

Multiple chromosome sets from one species (within species)

Question 7

What causes autopolyploidy?

Answer 7

Errors in cell division

Question 8

What is allopolyploidy? What are some examples?

Answer 8

Chromosome sets from two or more different species (hybrid)

Ex: wheat (hexaploid from three species) and tobacco

Question 9

What are the reasons that drive the rates of genome evolution?

Answer 9

1. Generation time
2. Polymerase repair efficiency
3. DNA repair mechanisms
4. Cancer
5. tp53

Question 10

Cancer is the accumulation of mutations in ________.

Answer 10

Oncogenes

Question 11

What is tp53? What is its role? Compare the amount of copies in humans vs elephants.

Answer 11

• Gatekeeper of cell cycle
• Stops cell cycle if there is DNA damage
• 2 copies in humans
• 43 copies in elephants

Question 12

Why do elephants have much more copies of tp53 than other organisms like humans?

Answer 12

Elephants:
* As many cells as 100 people
Many more rounds of mitosis

• Each round of mitosis is a risk of developing a mutation in genome
• More chances to develop mutation in p53 gene that might lead to cancer
• Other copies evolved to counteract this

Question 13

Only 1/3 of highly conserved residues in human code for proteins. What are the rest for?

Answer 13

1. Regulatory sequences
2. Noncoding RNAs (e.g., miRNAs), etc. (things that control gene expression)

Question 14

What is one contributing factor to why genome size and gene number vary greatly among eukaryote species? What does it result in?

Answer 14

Whole-genome duplication

Results in polyploidy (more than two complete sets of chromosomes in cells)

Question 15

Whole-genome duplication occurs more commonly in _________.

Answer 15

Plants

Question 16

Polyploidy in plants

Question 17

Genome

Question 18

What are the fates of duplication gene?

Answer 18

1. Losing function through subsequent mutation (fate of most duplicated genes)
2. Gaining a novel function through subsequent mutation
3. Having total function partitioned into two duplicates

Question 19

Which types of human genes are more likely to be duplicated (have higher rates of duplication)?

Answer 19

1. Growth and development genes
2. Immune system genes
3. Cell-surface receptors

Question 20

Compare and contrast karyotypes of orangutan, gorilla, chimp, and human

Answer 20

Humans have 1 fewer chromosome than chimps, gorillas and orangutans –> Fusion of two chromosomes into one chromosome (chromosome 2 in humans)

Question 21

What is synteny? Why is it important?

Answer 21

Conservation of large blocks of DNA

Allows researchers to locate a gene in a different species using information about synteny (identify markers traveling together)

Question 22

Explain the FOXP2 gene. What role does it play? What happens when there is a mutation? Compare it in different animals.

Answer 22

Single point mutations –> impaired speech and grammar but not in language comrephension

Found in chimps, goraillas, orangutans, rhesus macaques, and mice

FOXP2 protein in mice and humans differs by only 3 aa; 2 aa in other primates

Question 23

What is the significance of the NOVA1 gene? What did it do to mice?

Answer 23

Human version of gene in mouse

Speech pattern changed

Human variation changed vocal pattern of mouse

Question 24

As we sequence more genomes, we can compare genomic level differences and:

Answer 24

• understand workings of evolution
• improve crops
• identify genetic basis of disease

Question 25

What is the relationship between complexity of an organism and genome size?

Answer 25

Multicellular organisms with multiple tissues generally have more genes

Question 26

More complex organism = ________ genome

Answer 26

Larger

Question 27

To examine relationships between similar organisms, it is better to focus on more _______ mutations.

Answer 27

Neutral

Question 28

Since each organism changes independently, divergence between 2 organisms will be twice as much as between an organism and its ancestor. This is related to what concept?

Answer 28

Molecular clock

Question 29

What proportion of human genomes contain protein coding sequences? Plants?

Question 30

Describe gene duplication in humans.

Answer 30

Most likely to occur in three most gene-rich chromosomes Least amount of duplication in seven chromosomes with least genes

Question 31

Majority of genome is _______.

Answer 31

Non-protein encoded

Question 32

Give three examples of genomes evolving at different rates.

Answer 32

1. Viral and bacterial genomes evolve in a matter of days 2. Insect genomes evolve more rapidly than mammalian genomes 3. Plant genomes change much more rapidly than animal genomes, especially in noncoding DNA

Question 33

How much of human genome is functionally active and how much encodes? What does the functionally active segments of genome do?

Answer 33

80% functionally active; 2% encodes 80% active - create promoters, enhancers; tells gene when to turn on