Intro To Molecular Biology 1

Question 1

Difference between RNA and DNA:

Answer 1

RNA has extra component on sugar (oxygen and hydrogen)

Question 2

What linkage is present in the DNA and RNA polymers?

Answer 2

5-3 Phosphodiester Linkage

Phosphorus between oxygens

Question 3

What are purines?

Answer 3

2 rings

Adenine and Guadine

Question 4

What are pyramidines?

Answer 4

Single ring

Thymine and Cytoseine

Question 5

Bases in RNA:

Answer 5

Uracil instead of Thymine

Question 6

How is uracil different to thymine?

Answer 6

Uracil misses the methyl group

Question 7

Strands in DNA:

Answer 7

Two complementary strands of DNA bind together - held by hydrogen bonds

Question 8

Hydrogen bonds between bases:

Answer 8

A-T = 2 H bonds

C-G = 3 H bonds (more energy to break)

Question 9

Structure of Double Helix:

Answer 9

Sugar-phosphate backbone

Bases on inside

Major and minor groove formed

Question 10

Properties of DNA strands in double helix:

Answer 10

Polar

Antiparallel

Question 11

How can chromosomes be distinguished?

Answer 11

Size

G-banding

Question 12

How is DNA organised?

Answer 12

Into chromosomes

Question 13

What happens to chromosomes when cells divide?

Answer 13

Condense

Question 14

What is a nucleosome?

Answer 14

147 base pairs of DNA

Wrapped around histone proteins

1.7 left-handed turns

Question 15

What are histone proteins?

Answer 15

Positively charged

Long N-termini

Question 16

How are histone proteins arranged in nucleosome?

Answer 16

Histone proteins in centre but with amino-terminal tails protruding

DNA strands on outside

Question 17

What does histone H1 help form?

Answer 17

30nm fibre

Fits inside groove to allow DNA to keep folding and staying in place around core histones

Question 18

How is DNA packaged?

Answer 18

As ‘beads on string’

Into 30nm fibre and further condensed

Question 19

Does chromosome compaction vary?

Answer 19

During cell cycle

Question 20

Why do chromosomes need to be remodelled?

Answer 20

Chromatin can decondense to allow protein access

Question 21

What’s included in repetitive DNA?

Answer 21

Interspersed repeats - repeat sequences are dispersed throughout genome

Tandem repeats - short series of bases repeated multiple times after one another (satellites, minisatellites and microsatellites)

Question 22

What is repetive DNA important in?

Answer 22

Forensics

Question 23

What is mitochondrial DNA like?

Answer 23

Circular

Maternally inherited - implications for disease

Used for forensics