Genome Structure and Function

Question 1

How are viruses genetically classified?

Answer 1

Based on their nucleic acid structure

Question 2

What are the 4 genomic classifications of viruses?

Answer 2

• ssDNA
• dsDNA
• positive sense ssRNA
• negative sense ssRNA
• dsRNA

Question 3

What does ss stand for?

Answer 3

Single stranded

Question 4

What does ds stand for?

Answer 4

Double stranded

Question 5

Can positive sense ssRNA be directly translated?

Answer 5

Yes

Question 6

Can negative sense ssRNA be directly translated?

Answer 6

No

- it must be copied producing a positive sense complementary strand which can be translated

Question 7

What is the most widely used method for sequencing genomes?

Answer 7

Whole genome sequencing (WGS)

Question 8

What type of sequencing WGS?

Answer 8

Shotgun sequencing

Question 9

How does WGS work?

Answer 9

1. DNA cut into overlapping fragments by restriction enzymes, creating a series of contiguous fragments (‘contigs’)
2. Overlapping sequenced fragments aligned using computer programming, assembling an entire chromosomes

Question 10

What are the characteristics of prokaryotic genetic material?

Answer 10

• genes are tightly packed
• coding sequences on both strands
• coding sequences may overlap
• positive correlation between genome size and number of genes
• supercoiling leads to compaction of chromosomes

Question 11

What is eukaryotic genetic material organised into?

Answer 11

• circular mitochondrial chromosomes

- linear nuclear chromosomes

Question 12

What is a telomere?

Answer 12

The ends of each chromosome

Question 13

Which arm is shorter, q or p?

Answer 13

p

Question 14

Which arm is the top arm, p or q

Answer 14

p

Question 15

Describe a metacentric chromosome

Answer 15

Both arms are equal in length

Question 16

Describe a sub-metacentric chromosome

Answer 16

The p arm is slightly shorter than the q arm

Question 17

Describe an acrocentric chromosome

Answer 17

The p arm is much shorter than the q arm

Question 18

Describe a telocentric chromosome

Answer 18

There is no p arm just the q arm

Question 19

What are the two types of chromosomes present in humans and some other eukaryotes?

Answer 19

• autosomes

- sex determining chromosomes

Question 20

What is C value?

Answer 20

Amount of DNA in the haploid nuclear genome

Question 21

What is satellite DNA?

Answer 21

Non-coding DNA present as multiple tandem repeats.

- the main component of centromeres and other heterochromatic regions

Question 22

What is a tandem repeat?

Answer 22

A sequence of two or more DNA base pairs that is repeated that the repeats lie adjacent to each other on the chromosome

Question 23

Name 4 repetitive elements of the genome

Answer 23

• multiple copy genes
• retrotransposons
• mini-satellites (VNTRs)
• micro-satellites (STRs)

Question 24

What are the two types of retrotransposons?

Answer 24

• Short interspersed nuclear elements (SINES)

- Long interspersed nuclear elements (LINES)

Question 25

Define autopolyploidy

Answer 25

Multiples of the same genome

Question 26

Define allopoyploidy/amphidiploidy

Answer 26

Multiples of different genomes

Question 27

How is sex determined in humans?

Answer 27

By the presence (male) or absence (female) of SRY

Question 28

What are the two types of possible DNA damage?

Answer 28

- exogenous | - endogenous

Question 29

What is exogenous DNA damage?

Answer 29

Damage from outside cell

Question 30

What is endogenous DNA damage?

Answer 30

Damage from inside cell

Question 31

Give 3 examples of exogenous DNA damage

Answer 31

- ionising radiation - UV radiation - chemicals in environment

Question 32

Give 2 examples of endogenous DNA damage

Answer 32

- chemicals produced in the cell (e.g. oxygen free radicals) | - errors during DNA metabolism

Question 33

Name the 5 types of oxidative DNA damage

Answer 33

- base modification - depurination - deamidation - single strand break - double strand break

Question 34

Name the 4 types of DNA repair mechanisms

Answer 34

- direct reversal - excision repair - mismatch repair (MMR) - double-strand break repair

Question 35

What type of DNA repair mechanism is photoreactivation (PR)?

Answer 35

Direct reversal

Question 36

What does PR do?

Answer 36

Repairs pyrimidine dimers

Question 37

Name the 2 types of excision repair

Answer 37

- base excision repair (BER) | - nucleotide excision repair (NER)

Question 38

What do mismatch repair, base excision repair, and nucleotide excision repair do?

Answer 38

Remove damaged nucleotides and replace them using the undamaged strand as a template

Question 39

Name the 3 types of double-strand break repair

Answer 39

- homologous recombination (HR) - non-homologous DNA end joint (NHEJ) - microhomology-mediated end joining (MMEJ)

Question 40

How does homologous repair work?

Answer 40

Repairs strand breaks using the homologous chromosome as a template