1 - Nucleic Acids and Chromosomes

Question 1

Chromosomes are made of what?

Answer 1

DNA plus proteins

Question 2

What are nucleic acids?

Answer 2

Linear polymers of nucleotides

Question 3

What nucleotides are in DNA?

Answer 3

ATCG

Question 4

What nucleotides are in RNA?

Answer 4

AUCG

Question 5

Structure of DNA?

Answer 5

Double helix, antiparallel strands

Question 6

Structure of RNA?

Answer 6

Depends on type of RNA

Question 7

Nucteotides are made of…

Answer 7

Sugar, phosphate, nitrogenous base

Question 8

Sugar found in DNA?

Answer 8

Deoxyribose

Question 9

Sugar found in RNA?

Answer 9

Ribose

Question 10

Which number carbon in the sugar is linked to a) the phosphate and b) the base?

Answer 10

a) 5

b) 1

Question 11

Purines

Answer 11

Double - A, G

Question 12

Pyrimidines

Answer 12

Single - T, U, C

Question 13

What chemical feature does Adenine have?

Answer 13

Amino group (NH2) on C6 of left ring

Question 14

What chemical feature(s) does Guanine have?

Answer 14

Carbonyl group (=O) on C6 of left ring.
Amino group (NH2) on C2 of left ring.

Question 15

What chemical features does Thymine have?

Answer 15

Carbonyl group (=O) on C4.
Methyl group (CH3) on C5.

Question 16

What chemical features does Uracil have?

Answer 16

Carbonyl group (=O) on C4.

Question 17

What chemical features does Cytosine have?

Answer 17

Amino group (NH2) on C4.

Question 18

What is a nucleoside? What is the name of the linkage?

Answer 18

Base + Sugar (glycosidic linkage)

Question 19

What is the name of the nucleotide with adenine, ribose and one phosphate?

Answer 19

Adenosine monophosphate (AMP)

Question 20

What is the name of the nucleotide with cytosine, deoxyribose and 3 phosphates?

Answer 20

Deoxycytidine triphosphate (dCTP)

Question 21

How are deoxyribonucleotide units linked?

Answer 21

Phosphodiester bonds

Question 22

How are nucleotides linked? (Numbers)

Answer 22

3’ - OH of sugar is linked to the phosphate.

Phosphate joins to the 5’ - OH of the next sugar.

Question 23

DNA Primary structure?

Answer 23

Sugar phosphate backbone with bases.
Bases carry genetic info.
Sequence is specified from 5’ end to 3’ end.

Question 24

DNA Secondary structure?

Answer 24

Right-handed double helix. The two chains in the helix run in opposite directions.

Question 25

What charge is on the outside of the helix?

Answer 25

Negative, due to sugar phosphate backbone.

Question 26

How are the 2 chains held together?

Answer 26

Hydrogen bonds

Question 27

The bases point inwards and are...

Answer 27

The FLAT planes are PERPENDICULAR to the helix.

Question 28

Watson-Crick base pairs?

Answer 28

A- -T =2 H bonds so less stable | G- - -C =3 H bonds so more stable

Question 29

What is melting (denature) caused by?

Answer 29

High temp | Low salt conc.

Question 30

What is re-annealing (hybridise) caused by?

Answer 30

Cool temp. | High salt conc.

Question 31

Hybridisation definition

Answer 31

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

Question 32

How many base pairs in human (haploid) genome?

Answer 32

3x10^9

Question 33

How many base pairs in E.coli genome?

Answer 33

4.7x10^6 in a single circular double stranded molecule. The length of the E.coli DNA is 1.4 mm.

Question 34

What is a genome?

Answer 34

The entire DNA coding for an organism.

Question 35

What is a karyotype?

Answer 35

The organised profile of chromosomes in an organism.

Question 36

How many chromosomes in a diploid human cell?

Answer 36

46 (22 pairs of autosomes and 2 sex chromosomes).

Question 37

Translocation definition

Answer 37

2 bits of the same chromosome with 1 bit of another

Question 38

Aneuploidy definition

Answer 38

Wrong no. of chromosomes.

Question 39

Stages of packaging in eukaryotic DNA?

Answer 39

1. Nucleosome 2. Nucleosome causes 7 fold condensation of DNA 3. Chain of nucleosomes packed to make 30nm fiber = 40 fold condensation. 4. Chromatin fibre folded to loops = 700nm. 5. Entire mitotic chromosome 1400nm. 10,000 times shorter than original length.

Question 40

What is chromatin?

Answer 40

DNA and proteins

Question 41

What is the nucleosome?

Answer 41

DNA (200bp) wrapped round histone proteins (2x 2a, 2b, 3, 4) Linker and core DNA. Histones have +ve charge.