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Flashcards in DNA Deck (264)
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1

How do you prove that DNA is the genetic material

Take a pathogenic bacterium (S strain) which undergoes a random mutation forming R strain (non-pathogenic).
Grow R cells in presence of heat killed S cells
R strain cells are transformed to S strain whose daughters are pathogenic
Test each molecule for transformation: only DNA results in S strain

2

What do S strain cells cause

Pneumonia

3

3 things DNA needs to do

Be stored

Be propagated

Be read

4

What are nucleic acids made of

Sugar
Phosphate
Aromatic Bases

5

How remember purine from Pyrimidine

Purine: 2 rings
Pyrimidine: 1 rings

6

Which bases are purines and Pyrimidines

Purine:
A
G

Pyrimidine
T
C
U

7

Is DNA branched

No it is a linear chain of nucleotides

5’ to 3’ polarity

8

Which is the 5’ end

Where phosphate bonds to CH2

9

Which is the 3’ end

Where phosphate group binds directly to C in ring

10

Give 6 types of nucleic acid polymers

DNA
mRNA
tRNA
rRNA
miRNA
IncRNA

11

What is chargaff’s rule

%A=%T
%C=%G

12

What does it mean to say DNA is an anti parallel double helix

One strand is 3’ to 5’ and the other is 5’ to 3’

13

How many base pairs per turn

Why is it not an integer

10.5

It is an average

14

How are the planes of bases related to the helix axis

Perpendicular

15

What basic fact about sequence specific recognition by transcription factors is important

The edges of bases are exposed to solvent

16

Give and briefly describe the 3 types of DNA

Which is most common

A-DNA - squashed, right handed
B-DNA - most common
Z- DNA - left handed, less regular, less stable and therefore transient

17

How much DNA must be packed into a cell?

What is the average cell size?

How is this done

2m

10μm

Supercoiling

18

What is supercoiling

The coiling of a coil

In DNA it’s when the axis of the double helix is wound upon itself

19

Is the supercoiled state relaxed

No it is high energy and generates structural strain

20

How is DNA usually wound

Why

Underwound

Facilitates compaction and strand separation

21

How can supercoiling be measured

Topology

22

How can supercoiling be controlled

Enzymes can change the degree of cooling. These are called topoisomerases

23

How do topoisomerases work briefly

Cleaning and rejoining DNA strands

24

What is a nucleoid

A rosette model of DNA organisation

25

What is the basic unit of eukaryote chromosome structure

The nucleosome

26

What is a nucleosome

where DNA is wrapped around a protein barrel made of a Histone octamer

DNA wraps 2x around the barrel

27

Are histones charged

Yes they are positive

28

What histones do nucleosomes contain

How much DNA is there

2 copies of H2A, H2B, H3 and H4 and one copy of H1

200 nucleotides worth

29

What does H1 do

It is a linker histone, linking the entry and exit points of DNA as well as binding DNA between nucleosomes

30

What is a chromatin

Chromosomal DNA packaged with histones. It’s simplest form is the 10nm fibre