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Flashcards in Genome Organisation Deck (45)
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1

What is positive super coiling?

DNA overrotated
Helix twists on itself

2

What are the four possible nitrogenous bases for DNA?

Adenine
Thymine
Cytosine
Guanine

3

What are the four possible nitrogenous bases for DNA?

Adenine
Thymine
Cytosine
Guanine

4

Why are Adenine and Guanine called purines?

have double rings

5

Why are Thymine and Cytosine called pyrimidines?

Only one ring

6

What is the approximate amount of base pairs for each turn in the helix of DNA?

10

7

What does the major groove contain?

base pair specific information

8

What does the minor groove contain?

base pair non specific information

9

What are the two main ways for viral genome packaging?

Many viruses assemble their capsids around the viral genomes

form protein capsid shells first and then package their genomes into the procapsids

10

How does ssRNA helical tobacco mosaic virus package its genome?

assemble capsid around genome

11

How do some dsRNA and dsDNA viruses package their genome?

some dsDNA viruses (like herpesviruses) and dsRNA viruses (e.g. φ6 and φ12 bacteriophages) form protein capsid shells first and then package their genomes into the procapsids. These viruses use a packaging motor protein that is driven by the hydrolysis of ATP to condense the nucleic acids into a confined space.

12

What is the typical bacterial genome like?

typically comprised one circular chromosome but often harbored extrachromosomal elements in the form of plasmids or phages

13

How does the bacterial genome form nucleoids?

genome interacts with proteins (nucleoid-associated proteins H-NS and HU) and is tightly negatively supercoiled

14

What is Topoisomerase?

The enzyme responsible for adding and removing turns in the coil

15

When does positive supercoiling occur?

DNA overrotated so it twists on itself

16

When does negative supercoiling occur?

DNA underrotated
twists on itself in the opposite direction

17

How does topoisomerase I catalyse relaxation of negative supercoils

(1) cleavage of one DNA strand;
(2) passage of a segment of DNA through the break, and
(3) resealing the break. No ATP energy required for this reaction.

18

How does topoisomerase I catalyse relaxation of negative supercoils

(1) cleavage of one DNA strand;
(2) passage of a segment of DNA through the break, and
(3) resealing the break. No ATP energy required for this reaction.

19

What is the Hierarchical organization of the eukaryotic genomic DNA

double stranded DNA helix
nucleosome
30nm chromatin fiber

20

What is the subunit of chromosomes?

chromatin

21

What is chromatin made of?

nucleosome

22

What is euchromatin?

undergo condensation and decondensation in the cell cycle

23

What is heterochromatin?

remains tightly condensed throughout the cell cycle

24

What is a nucleosomes?

The nucleosome is a cylinder with DNA organized into ~1.7 turns around the surface.

Nucleosome looks like beads on a string in the chromatin

Nucleosomes contain an octamer of histones around which DNA winds up

Makes chromatin

25

What is the length of DNA in a nucleosome (in base pairs and histones)?

146bp - 260bp
histones

26

In base pairs how long is the core DNA?

146bp

27

What is Histone H1 for?

H1 is associated with linker DNA and can lie at the point where DNA enters or exits the nucleosome.

28

What Histones is a nucleosome made of?

2 x H2A
2 x H2B
2 x H3
2 x H4

29

What does the linker DNA region disfavour?

nucleosome formation
by
exhibiting a strong preference for sequences that resisting DNA bending

30

What does the linker DNA region disfavour?

nucleosome formation
by
exhibiting a strong preference for sequences that resisting DNA bending