Theme 1B Structure of DNA and Genomes

Question 1

Name the components of DNA.

Answer 1

1. Pentose sugar: RNA/DNA
2. nitrogenous bases
3. Phospate

Question 2

What’s the difference between RNA and DNA?

Answer 2

DNA does not have an oxygen attached to the second carbon, RNA does.

Question 3

What are the components of a nucleoside (subdivision of DNA)?

Answer 3

A sugar and a base (no phosphate).

Question 4

Name the deoxyribonucleosides.

Answer 4

Deoxyguanosine, Deoxythymidine, Deoxycytidine, deoxyadenosine.

Question 5

What is a nucleotide?

Answer 5

Nucleoside and phosphate.

Question 6

Which carbon does phosphate attach to? What carbon does the nitrogenous base attach to?

Answer 6

5’ and 1’.

Question 7

How do mononucleotides join together?

Answer 7

Through phosphodiester bond.

Question 8

How is their polarity in DNA?

Answer 8

The 5’ end has free phosphates, which is a negative charge, and the 3’ end is just hydroxyl group.

Question 9

How is nucleotide formed?

Answer 9

By removing 2 waters, sugar can form phosphodiester bond with phosphate, and glycosidic bond with base.

Question 10

What is the orientation of the base pairs?

Answer 10

Stacked flat lying perpendicular to the axis.

Question 11

How many hydrogen bonds are between A-T, C-G?

Answer 11

A-T: 2

C-G: 3

Question 12

What causes renaturation of single strands?

Answer 12

Temperature driven, highly specific and concentration dependent (competitive hybridization) (check ppt)

Question 13

Why is replication called semi-conservative?

Answer 13

Double helix will have a parental strand and a newly synthesized strand.

Question 14

What is a chromatin?

Answer 14

A given region of DNA with associated proteins on a chromosome.

Question 15

What is the shape of a chromosome in prokaryotes?

Answer 15

Circular for one chromosome, and other small circular DNA called plasmids.

Question 16

What is the shape of a chromosome in eukaryotes?

Answer 16

Linear and enclosed in nucleus.

Question 17

What are the three essential components of eukaryotic chromosomes?

Answer 17

1. Origins of replication: DNA sequences along chromosomes which initiate DNA replication.
2. Centromeres: Allow correct segregation of chromosomes.
3. Telomeres: Prevent degradation and allow proper replications of chromosome ends.

Question 18

What is homologous chromosomes?

Answer 18

two copies of each chromosome.

Question 19

Why is DNA organized as chromosomes? (3)

Answer 19

1. Chromosomes compact DNA.
2. Chromosome structure protect DNA from damage, more stable than naked DNA.
3. Easily separated and transmitted to each daughter cell during cell division.

Question 20

What are histones and their role?

Answer 20

A positively charged protein that DNA wind around, are involved with DNA packaging.

Question 21

Name the types of chromatin proteins.

Answer 21

1. Histones (nucleosome)
2. Chromatin remodelling enzymes.
3. Transcription factors and RNA polymerase.