L2 Genome Anatomy

Question 1

What is the structural difference between DNA and RNA?

Answer 1

RNA has a hydroxyl group on carbon 2’. DNA doesn’t have this -OH group.

DNA is much more stable.

Question 2

DNA sequences are written in a _____ direction

Answer 2

5’ to 3’

This is also the direction of DNA/RNA synthesis

Question 3

What are Okazaki fragments?

Answer 3

short fragments of DNA formed on the lagging strand during DNA replication.

On the leading strand, replication occurs in a single strand that follows the splitting fork. But on the lagging strand, it cannot replicate continuously as it has to replicate from the point of the fork and work away (5-3) so forms in fragments – Okazaki fragments

Question 4

The genome is wound up in nucleosomes around a ____ core

Answer 4

histone

Question 5

A chromosome has consists of two short arms (the ___1___ arms) and two long arms (the ___2___ arms). They are bound in the middle by the ___3___.

Answer 5

1. p
2. q
3. centromere

Remember p is for petite = short arm

Question 6

At either end of a chromatid is a ___1___. These structures are made up of repeating ___2___ sequences

Answer 6

1. telomere

2. TTAGGG

Question 7

True or false: Telomeres determines how many divisions can occur from each somatic cell

Answer 7

True.

Telomeres shorten with each somatic cell division, meaning there is a finite number of divisions that can take place. Cancer can reactivate telomerase and prevent these chains from shortening, thus allowing for uncontrolled division.

Question 8

Why is it important for geneticists to specify the version of the reference genome database they used to compile a report?

Answer 8

The database is being updated regularly, so locations change with each release.

Question 9

Define haploinsufficiency

Answer 9

Haploinsufficient = only 1 copy of the gene (haploid) is not enough to bring about it’s action/presentation.

Question 10

Which gene is responsible for making a foetus develop into a male?

Answer 10

Sex-determining Region Y (SRY) gene.

Only found on a Y chromosome, triggers to testis formation. The testis then produce the other male traits.

Question 11

Large blocks of repetitive DNA sequence, commonly found at centromeres, are termed __?__ DNA (e.g. alphoid DNA)

Answer 11

satellite

Question 12

Smaller repetitive DNA sequences that are scattered around the genome are termed __?__ repeats (e.g. Alu repeats)

Answer 12

Interspersed

Question 13

What is the functional purpose of alphoid satellite DNA?

Answer 13

Alphoid DNA is required for assembly of the centromere

Question 14

Alu repeats are dispersed throughout the genome by __?__

Answer 14

retrotransposition