Genomic Structure

Question 1

What is DNA?

Answer 1

• DNA is deoxyribonucleic acid.
• It is a macromolecule consisting of a linear strand of nucleotides.

Question 2

In what direction is the sequence of single stranded DNA read from?

Answer 2

5’ to 3’

Question 3

Describe the DNA three dimensional structure.

Answer 3

• two antiparallel strands of DNA
• bases “stacked”
  Two grooves [Major + minor]

Question 4

Does genome size reflect the complexity of a organism?

Answer 4

There is a trend for simpler organisms to have fever genes.

However genome size is not strongly related to complexity of an organism.

Question 5

Define the genome packing problem.

Answer 5

2m of DNA in a nucleatid cell
7.44 x 10^13 DNA in the body
How do we fit 2m of DNA in a cell?

Question 6

What are histones?

Answer 6

Basic (+vely charged) proteins that bind DNA

Question 7

How are histones a solution to the genome packing problem?

Answer 7

• Eight histones 2x(H2A+H2B+H3+H4) form the nucleosome
• Histone 1 binds the linker DNA

Question 8

Describe the order of the structures involved in DNA Packing.

Answer 8

DNA double helix > Neucleosomes > chromatin fibre > Extended section of chromosome > Loops of chromatin fibre > metaphase chromosome

Question 9

What is the exome?

Answer 9

All of the coding gene sequences in DNA

Question 10

What is a Gene?

Answer 10

All of the DNA that is transcribed into RNA plus all of the cis-linked (local) control regions that are required to ensure quantitatively appropriate tissue-specific expression of the final protein

Question 11

Describe the structure of a metaphase chromosome?

Answer 11

• Made up of 98% intergenic region
• And genes

Question 12

What are integenic regions?

Answer 12

• Contain sequences of no known function, such as repetitive DNA, endogenous retroviruses, pseudogenes.
• They may contain many regulatory elements.

Question 13

Describe the structure of a gene from 5’ to 3’

Answer 13

At the 5’ end there’s the CAAT box
The TATA box is located after the CAAT box
Then there’s the transcription initiation site
Then the translation initiation site (ATG) is located after it.
Then we have our exons and introns
Then the translation termination site
Then the transcription termination site at the 3’ end.

Question 14

What is in the promoter region made of?

Answer 14

The regulatory element and the TATA box.

Question 15

What the function of the regulatory element of the promoter?

Answer 15

needed to regulate recruitment of RNA polymerase

Question 16

What is the function of the TATA box?

Answer 16

needed to recruit general transcription factors and RNA polymerase.

Question 17

What’s the function of the promoter

Answer 17

• Promoters recruit RNA polymerase to a DNA template
• RNA polymerase binds asymmetrically and can only move 5’ to 3’
• Regulation occurs via transcription factors

Question 18

What are enhancers? What are they’re function?

Answer 18

• they are short sequences that can be in the gene or many kilobases distant
• They are targets for transcription factors (activators)

Question 19

What is the function of silencers?

Answer 19

They are position - independent and are also targets for transcription factors (repressors).

Question 20

What are insulators? What are they’re function?

Answer 20

• short sequences
• act to prevent enhancers/silencers influencing other genes