Ch. 7: DNA

Question 1

What is the unwinding process of DNA replication?

Answer 1

Unwinding DNA:

1. Begins at start codon
2. Helicase unzips DNA by breaking the hydrogen bonds
3. Opening = replication fork
4. Primase now has access to build primers (short rna) for DNA polymerase to be added to.

Question 2

What is the DNA synthesis process of DNA replication?

Answer 2

1. DNA polymerase builds from primers.
2. Leading strand only needs one single primer so the DNA synthesis is continuous.
3. Lagging strand needs many primers. There are breaks and the fragments of primers are known as okazaki fragments.
4. Okazaki fragments are combined by replacing RNA primers with DNA polymerase III then joined by ligase.

Question 3

Why is DNA semiconservative?

Answer 3

DNA replicates into two molecules with one old strand and one new strand.

Question 4

Why is salt present in protease?

Answer 4

Salt helps DNA stabalize

Question 5

What is the process of transcription?

Answer 5

1. Proteins with RNA polymerase assemble on DNA = transc. initiation complex
2. Activator proteins touch complex to start process
3. RNA polymerase runs down DNA strand

Question 6

What is the process of translation?

Answer 6

Used to build proteins.

1. Ribosome begins process at start codon of mRNA.
2. Amino acids are added until stop codon
3. Engage, elongate, terminate.

Question 7

How is a chromosome made?

Answer 7

Formation of nucleosome (histone wrapped by DNA), nucleosomes pack together to create chromatin, these further fold to create tightly packed DNA aka chromosomes

Question 8

What is the purpose of topisomerase?

Answer 8

Loosens DNA for replication fork.

Question 9

5’ vs 3’ ?

Answer 9

The position of sugar of nucleotide.

Question 10

What direction does DNA polymerase work?

Answer 10

5 - 3

Question 11

Purpose of Ligase?

Answer 11

Creates hydrogen bonds between new and original strands.

Question 12

Okazaki fragments

Answer 12

Regions of formed DNA by RNA primers, replaced by DNA polymerase III, then joined together by ligase.

Question 13

Mitochondrial DNA vs. Chloroplast DNA

Answer 13

Both: 
1. Function = energy transformation 
2. Structure : multiple layers 
3. Eukaryotic cells 
Mitochondria 
1. 
Chloroplast

Question 14

What is the purpose of lysis buffer?

Answer 14

Break open cells to expose DNA

Question 15

What is the function of protease?

Answer 15

Degrades histones to expose DNA.

Question 16

Why put tube in 50 deg. C waterbath?

Answer 16

Protease functions at this temperature

Question 17

Why is cold ethanol added to tube?

Answer 17

Precipitates DNA from solution.