Lecture 7

Question 1

How many chromosomes do most Eukaryotes have in their body cells?

Answer 1

10-50.

Question 2

How many chromosomes do humans have?

Answer 2

46 chromosomes in 23 almost identical pairs.

Question 3

What is a karyotype?

Answer 3

A particular array of chromosomes in an individual organism.

Question 4

What is diploid?

Answer 4

2 complete sets of chromosomes.

Question 5

What is Haploid?

Answer 5

One set of chromosomes.

Question 6

What are chromosomes made of?

Answer 6

Chromatin.

Question 7

What makes up chromatin?

Answer 7

DNA and protein.

Question 8

What else is associated with chromosomes?

Answer 8

RNA during RNA synthesis.

Question 9

What are 2 types of chromosomes?

Answer 9

1. Heterochromatin
2. Euchromatin

Question 10

What are heterochromatin chromosomes?

Answer 10

Ones that are compressed and not expressed (turned off, not accessible)

Question 11

What are euchromatin chromosomes?

Answer 11

Chromosomes that are loose and expressed (turned on, accessible).

Question 12

What is a nucleosome?

Answer 12

A complex of DNA and histone proteins.

Question 13

What do histone proteins do?

Answer 13

Promote and guide coiling of DNA

Question 14

What are histone core proteins?

Answer 14

Proteins that act as a bobbin for the DNA to wrap around.

Question 15

What are histone link proteins?

Answer 15

It holds the DNA on the core protein (kind of like a crimp bead).

Question 16

What is the most compact form of DNA?

Answer 16

Chromosomes.

Question 17

How are chromosomes organized for replication?

Answer 17

Each sister chromatid is held together by proteins in an x shape to keep them organized before they are moved to the new cell.

Question 18

What do chromosomes look like before and after replication?

Answer 18

Before each chromosome is composed of a single DNA molecule and after each is composed of 2 identical DNA molecules.

Question 19

What 3 things are required for DNA replication?

Answer 19

1. Something to copy
2. Something to do the copying
3. Building blocks to make copy

Question 20

What are the three things that are used for DNA replication?

Answer 20

1. Parental DNA molecule
2. Enzymes
3. Nucleotide triphosphates

Question 21

What are 3 stages of DNA replication?

Answer 21

1. Initiation - replication begins
2. Elongation - new strands of DNA are synthesized by DNA polymerase
3. Termination - replication is terminated

Question 22

What nucleotide bases are linked in DNA double helix?

Answer 22

CG and AT

Question 23

What is a DNA polymerase?

Answer 23

A protein that matches existing DNA bases with complementary nucleotides and links them.

Question 24

What are common features of polymerase?

Answer 24

1. Adds new bases to 3 prime end of existing strands
2. Synthesizes in 5’-3’ direction
3. Requires a primer of RNA

Question 25

How do DNA polymerase and RNA polymerase work together?

Answer 25

The RNA polymerase makes the primer and the DNA polymerase extends the primer.

Question 26

What model does Prokaryotic replication use?

Answer 26

E. coli model.

Question 27

What is the E. coli model of replication?

Answer 27

Starts with a single circular molecule of DNA. Replication begins at the origin of replication and proceeds in both directions around the chromosome.

Question 28

What are the 3 DNA polymerases in E. coli?

Answer 28

1. DNA polymerase 1 2. DNA polymerase 2 3. DNA polymerase 3

Question 29

What is DNA polymerase 1?

Answer 29

Acts on lagging strand to remove primers and replace them with DNA.

Question 30

What is DNA polymerase 2?

Answer 30

Involved in DNA repair processes.

Question 31

What is DNA polymerase 3?

Answer 31

Main replication enzyme.

Question 32

What do all three polymerase have?

Answer 32

3'-5' exonuclease activity.

Question 33

What is 3'-5' exonuclease activity?

Answer 33

Proofreading oved the DNA.

Question 34

What does DNA polymerase 1 also have?

Answer 34

5'-3' exonuclease activity.

Question 35

What is 5'-3' exonuclease activity?

Answer 35

It goes back and removes the RNA primers.

Question 36

What are helicases?

Answer 36

Enzymes that use energy from ATP to unwind DNA.

Question 37

What are Single-stand-binding (SSBs) proteins?

Answer 37

Enzymes that coat DNA strands to keep them apart. (keeps the DNA from going back to the double helix form.)

Question 38

What are topoisomerases?

Answer 38

Enzymes that prevent supercoiling (gets rid of knots and twists in the DNA).

Question 39

What is DNA gyrase?

Answer 39

The topoisomerase involved in DNA replication.

Question 40

What is a replication fork?

Answer 40

The partial opening of the DNA helix.

Question 41

What is DNA primase?

Answer 41

The RNA polymerase that makes RNA primer.

Question 42

How many directions can DNA polymerase synthesize in?

Answer 42

1.

Question 43

What is the leading strand in DNA replication?

Answer 43

The strand that synthesizes continuously from an initial primer.

Question 44

What is the lagging strand in DNA replication?

Answer 44

The strand that synthesizes discontinuously with multiple priming events.

Question 45

What are Okazaki fragments?

Answer 45

DNA fragments on the lagging strand.