Chromosomes, Genes And DNA Flashcards Preview

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Flashcards in Chromosomes, Genes And DNA Deck (18):
0

What charge does DNA have?

Negative

1

In an electron micrograph, what appears darker - heterochromatin or euchromatin?

Heterochromatin

2

What is the difference between the pentose sugars in DNA and RNA?

RNA - pentose sugar has an OH group
DNA just has an H on its own

3

What is the difference between a purine and a pyrimidine?

Purine has 2 rings
Pyrimidine has 1 ring

4

Name the purine bases

Guanine and adenine

5

Name the pyrimidine bases

Thymine, cytosine and uracil

6

Which bonds are found between nucleotides?

Phosphodiester

7

What is a nucleoside?

A nitrogenous base and a pentose sugar (found in RNA)

8

What is found at the 5' end and at the 3' end in DNA?

5' - a free phosphate group
3' - an -OH group

12

Give some key features of the DNA double helix

Double stranded
Strands run anti-parallel
One complete turn is 10 base pairs
Purines and pyrimidines are planar and unsaturated
Space between base pairs is 0.34 nm
Within sugar-phosphate backbone, major and minor grooves exist

13

In DNA replication, what does helicase do?

It uses ATP to unravel the DNA double helix
Helicases also reform the DNA helix around the replication fork

14

What occurs in initiation of DNA replication?

Recognition of origin of replication
Helicase unravels the DNA double helix
DNA polymerase is recruited. This can only start from 3' end so PRIMASE is needed to initiate each strand

15

What occurs during DNA elongation?

Leading strand is replicated from 5' to 3'
Lagging strand is replicated discontinuously as Okazaki fragments
Fragments are joined by DNA ligase from OH to phosphate group

16

What does DNA ligase do?

Joins Okazaki fragments together

17

Describe the process of termination in DNA replication

Replication forms move from the ends of the DNA strands towards eachother
Lead strands move towards lagging strands and vice versa

24

How many bonds are between the base pairs GC?

3

25

Describe how DNA is packaged into chromosomes

DNA wrapped around histones to form nucleosomes - beads on a string
These pack tightly together to form solenoid structures
These fibres are compacted into several hierarchical loops
These create chromosomes

26

In which phase of the cell cycle does DNA replication occur?

The S phase