Nucleic Acids and Chromosomes

Question 1

What is the difference between a Nucleotide and a Nucleoside?

Answer 1

A nucleotide is Sugar + Base + Phosphate

A nucleoside is Sugar + Base

Question 2

Which carbon is the Base attached to on (deoxy)ribose

Answer 2

1’

Question 3

Which carbon is the phosphate attached to on (deoxy)ribose

Answer 3

5’

Question 4

Which bases are purines?

Answer 4

Adenine and Guanine (PAG)

Question 5

Which bases are pyrimidines?

Answer 5

Cytosine, Thymine and Uracil

Question 6

What type of bond joins bases?

Answer 6

Hydrogen bond

Question 7

How many hydrogen bonds are there between A-T

Answer 7

2

Question 8

How many hydrogen bonds are there between C-G

Answer 8

3

Question 9

Whats the difference between Deoxyribose and Ribose?

Answer 9

The -OH group on C2 in ribose is -H in Deoxyribose

Question 10

What is the bond that holds 2 Nucleotides together in DNA?

Answer 10

Phosphodiester bond

Question 11

Which carbon is the Phosphate group attached to in a nucleotide, and which carbon does it bond to in polymerisation?

Answer 11

5’

3’

Question 12

How many base pairs are there per helical turn?

Answer 12

10bp

Question 13

How wide is a strand of DNA?

Answer 13

2nm

Question 14

How would you separate a DNA strand?

Answer 14

Heat it or place it in a low concentration salt solution

Question 15

How would you anneal two DNA strands?

Answer 15

Cool them, or place them in a high salt solution

Question 16

What is a karyotype?

Answer 16

Organised profile of Chromosomes

Question 17

How many chromosomes would a normal human karyotype have?

Answer 17

22 pairs of Autosomal Chromosomes

1 pair of Sex chromosomes

Question 18

Roughly how long is the human genome?

Answer 18

3x10^9 bp

Question 19

What is the protein DNA wraps around, and why is it specialised for this function?

Answer 19

Histones

Positively charged, so interact closely with the negative sugar phosphate backbone

Question 20

What is chromatin?

Answer 20

The histone-DNA complex

Question 21

What is a nucleosome?

Answer 21

The lowest level of DNA packing; DNA wrapped around histones with linker DNA.

Question 22

Roughly how long is a nucleosome?

Answer 22

~200bp

Question 23

What is the next level of DNA packing after Nucleosomes?

Answer 23

30nm Chromatin Fiber arrangement; further packing leading to 40 fold condensation.

Question 24

How many folds of condensation is a nucleosome?

Answer 24

7

Question 25

What are the 30nm Chromatin fibres arranged to, and how thick is this?

Answer 25

Folded loops of chromatin

700nm

Question 26

What is the final condensation of DNA?

How thick is this?

Answer 26

A Chromosome

1400nm (2x700nm)