Nucleic acids and chromosomes

Question 1

Nucleic acids

Answer 1

linear polymers of nucleotides

Question 2

Nucleotide

Answer 2

Nitrogenous base + Sugar + Phosphate group

Question 3

Nucleoside

Answer 3

Nitrogenous base + Sugar

Question 4

How does deoxyribose differ to ribose?

Answer 4

Deoxyribose, lacks an oxygen atom on C2 that is present in ribose, the parent compound

Question 5

Which nucleotide bases are purines?

Answer 5

Adenine

Guanine

Question 6

Which nucleotide bases are pyrimidines?

Answer 6

Cytosine

Thymine

Question 7

How many rings in a purine?

Answer 7

2

Question 8

How many rings in a pyrimidine?

Answer 8

1

Question 9

4 nucleotide bases in DNA

Answer 9

A T C G

Question 10

4 nucleotide bases in RNA

Answer 10

A U C G

Question 11

What are the complementary base pairs?

Answer 11

A + T

C + G

Question 12

How many hydrogen bonds between each base pair?

Answer 12

A-T = 2 Hydrogen bonds
C-G = 3 Hydrogen bonds, more stable

Question 13

Structure of DNA

Answer 13

Double helix
Antiparallel strands
Major groove and minor groove

Question 14

How many bps per helical turn in DNA?

Answer 14

10bp

Question 15

How wide is DNA strand?

Answer 15

2nm

Question 16

Phosphodiester link

Answer 16

The 3’-OH of sugar of one nucleotide is linked to phosphate group, which in turn is joined to 5’-OH of adjacent sugar

Question 17

How is a strand in DNA not symmetrical?

Answer 17

Chain has 2 ends

5’ and 3’ ends

Question 18

1st nucleotide in a sequence has a free

Answer 18

5’ phosphate

Question 19

last nucleotide in the sequence has a free

Answer 19

3’ hydroxyl group

Question 20

In which direction do you write the sequence?

Answer 20

5’ to 3’

Question 21

What are the 2 chains held together by?

Answer 21

Hydrogen bonds between the bases

Question 22

How are the groups arranged in a DNA helix?

Answer 22

Deoxyribose and phosphate groups run along the outside with the negative charges outside
Bases point inwards and the flat planes are perpendicular to the helix

Question 23

What shape is RNA?

Answer 23

Can assume a variety of shapes

Question 24

Separate DNA strand

Answer 24

Heat or Low Salt

= Melting or Denaturing

Question 25

Anneal DNA strand

Answer 25

Cool or High Salt

= Re-anneal or Hybridise

Question 26

Primary structure of DNA

Answer 26

Sequence of bases

Question 27

Secondary structure of DNA

Answer 27

Double helix resulting from complementary base pairing (A+T, C+G)

Question 28

When are chromosomes visible?

Answer 28

Just before cell divides

Question 29

What form are chromosomes in at miotic stage?

Answer 29

Highly condensed

Question 30

What form are chromosomes in at interphase?

Answer 30

Extended form

Question 31

Karyotype

Answer 31

An organised profile of someones chromosomes

Question 32

How many chromosomes in a diploid human cell?

Answer 32

46

Question 33

What do the 46 chromosomes in a human diploid cell comprise of?

Answer 33

22 autosomal pairs

2 sex chromosomes

Question 34

Female sex chromosomes

Answer 34

XX

Question 35

Male sex chromosomes

Answer 35

XY

Question 36

How can karyotypes be useful?

Answer 36

An abnormal Karyotype can be used as a diagnostic tool

Question 37

Chromatin

Answer 37

DNA tightly packaged, forming a complex with proteins
During interphase chromatin is more extended.
Further condensation during mitosis produces chromosomes

Question 38

Nucleosomes

Answer 38

DNA wrapped around positively charged histone proteins with linker DNA between histones

Question 39

What is the lowest level of packaging?

Answer 39

Nucleosomes

Question 40

How many bp’s of DNA per nucleosome?

Answer 40

200 bp’s

Question 41

30nm Fiber

Answer 41

chain of nucleosomes further packed to generate a more compact structure, giving ~40-fold condensation

Question 42

What is the net result of condensing packing DNA?

Answer 42

each DNA molecule has been packaged into a mitotic chromosome that is 10 000 fold shorter than its fully extended length.