Nucleic acids and chromosomes

Question 1

What is the difference between a nucleotide and nucleoside?

Answer 1

Nucleotide= base, a sugar, and a phosphate

Nucleoside=base and a sugar

Question 2

Which bases are pyrimidines and which are purines?

Answer 2

Pyrimidines: CUT
Purines: A, G

Question 3

what is the secondary structure of DNA?

Answer 3

right-handed double helix

Question 4

What causes the bases to melt or dissociate/ and then reanneal?

Answer 4

High temperature or low salt concentration.

Low temp, high salt causes re-annealing

Question 5

What is hybridisation

Answer 5

In a mixture of DNA with different sequences, the complementary strands will find each other in the mixture.

Question 6

How are eukaryotic DNA packed?

Answer 6

-DNA is packed into chromatin
-chromatin consists of DNA and protein
-

Question 7

What’s the difference between deoxyribose and ribose

Answer 7

Deoxyribose lacks an oxygen but ribose contains it.

Question 8

What is the lowest level of packaging and what is structure of it

Answer 8

Nucleosome, which consists of DNA wrapped around a histone protein.
The nucleosomes form a chain which pack into a helical array
Nucleosome:
-Histones are positively charged so interact with negatively charged sugar phosphate backbone.
-There’s 8 histones around which DNA is wrapped
nucleosome causes 7 fold condensing

Question 9

What is the next level of packing of DNA?

Answer 9

30 nm fibre

Question 10

On which carbon does the base and phosphate attach to?

Answer 10

1’ carbon attaches to the base

5’ attaches to the phosphate

Question 11

Describe the structure of the DNA?

Answer 11

-The first nucleotide has a free 5’ phosphate and the last nucleotide has a free 3’ hydroxyl group.

Question 12

What is the name of the complex of DNA, histones, and non-histone proteins found in the nucleus of eukaryotic cells?

Answer 12

Chromatin

Question 13

A nucleosome is best described as:

Answer 13

A short length of DNA wrapped around a core of histone protein.

Question 14

What is Double stranded DNAs structure and Double stranded RNA

Answer 14

Always double helix : 3D for DNA - 10 base pairs per helical turn ( 1 minor groove and 1 major groove)
Double stranded RNAs, 3D structure is variable: so it is termed dsRNA

Question 15

How many base pairs are there per helical turn and how wide is the double helix?

Answer 15

10 bp per helical turn 2nm