Ch 4 4.3

Question 1

Stages of DNA replication

Answer 1

1. Unwinding
2. Unzipping
3. Synthesis

Question 2

What happens in the unwinding stage of DNA replication?

Answer 2

DNA unwinds from histones

Question 3

What happens in the unzipping stage of DNA replication?

Answer 3

DNA helicase breaks hydrogen bonds and makes replication fork (each strand runs in a different direction because of phosphodiester backbone)

Question 4

Five prime end of DNA strand is which group?

Answer 4

Phosphate

Question 5

Three prime end of DNA strand is which group?

Answer 5

Sugar group

Question 6

What happens during Synthesis stage of DNA replication?

Answer 6

DNA polymerase uses template strand to synthesize new strand via complementary base pairing.

Question 7

In which direction does the DNA polymerase add bases on a new strand?

Answer 7

5’ to 3’

Question 8

In which direction does DNA polymerase move down the old DNA strand (template)?

Answer 8

3’ to 5’

Question 9

What is the continuous strand during DNA replication?

Answer 9

The strand on which DNA polymerase can continuously synthesize because it is in the correct orientation

Question 10

What is the lagging strand in DNA replication?

Answer 10

The strand on which DNA polymerase Hass to keep jumping around because it is in the opposite direction; has gaps in the strand. Each fragment called Okazaki fragment

Question 11

Okazaki fragments

Answer 11

The fragments which DNA polymerase synthesizes on the lagging strand

Question 12

What does DNA ligase do in DNA replication?

Answer 12

Repairs and seals gaps between Okazaki fragments on lagging strand

Question 13

DNA polymerase synthesizes the new strand by adding bases in which direction?

Answer 13

Five prime to three prime

Question 14

What is a semi conservative method of DNA replication?

Answer 14

Breaking apart the parental strand using each individual strand as template and then copying it to make two new molecules

Question 15

Mutations in DNA replication

Answer 15

DNA polymerase can make mistakes which can lead to mutations; can correct itself

Question 16

Why are some mutations in DNA replication not bad?

Answer 16

Proteins Come from a three base pair sequence of amino acids; there are a variety of combos for each amino acid so sometimes it doesn’t change the sequence and don’t see the error but it’s still a mutation

Question 17

When is a DNA replication Mutation a bad thing?

Answer 17

When a different amino acid is placed, it can change the protein in structure which changes its function and synthesis ex: cancer cells

Question 18

Phases of the cell cycle

Answer 18

Interphase
G1
S
G2
Mitosis
Prophase
Metaphase
Anaphase
Telophase and Cytokinesis

Question 19

What happens during interphase G1?

Answer 19

 normal growth and metabolism of cell; Checkpoint one: moves to S or goes to G0

Question 20

What happens during synthesis?

Answer 20

DNA replication; divide or apoptosis

Question 21

What happens during G2?

Answer 21

Prep for mitosis
Repair DNA mutations (or apoptosis)
Synthesize needed enzymes

Question 22

How many DNA molecules are there in G1 phase? After S phase? How many chromosomes?

Answer 22

G1:46 DNA molecules, 23 different kinds, 46 chromosomes
S: 92 DNA molecules, 23 different kinds, 46 chromosomes (sister chromatids)

Question 23

Three functions of mitosis:

Answer 23

1. Growth of all tissues and organs after birth
2. Replacement of cells that die
   3. Repair damaged tissues

Question 24

What happens during prophase?

Answer 24

-Densely coiled chromosomes (46 chromosomes, 92 DNA molecules)
– nuclear envelope disintegrates
– centrioles move to different poles
– development of spindle fibers

Question 25

What happens during metaphase?

Answer 25

-Chromosomes align on metaphase plate
-Spindle fibers complete mitotic spindles, attach to kinetochores

Question 26

Asters

Answer 26

Starlight projection made of centriole in spindle fibers extending

Question 27

What happens during anaphase?

Answer 27

-Sister chromatids split
-Single stranded daughter chromosomes migrate to each pole from spindle fibers for track

Question 28

What happens during telophase?

Answer 28

-Chromosomes cluster on opposite sides and uncoil into chromatin
-rough ER makes new nuclear envelope around Cummington
– mitotic spindles disintegrate
-Nucleus forms

Question 29

When does cytokinesis happen? What happens during cytokinesis?

Answer 29

Telophase;
– division of cytoplasm
– cleavage furrow

Question 30

When does cell division occur?

Answer 30

1. Enough cytoplasm for two cells
   2. DNA replicated
2. Adequate supply of nutrients
3. Stimulated by growth factors
   5. Neighboring cells die opening up space

Question 31

When do cells stop dividing?

Answer 31

1. Snuggly contact neighboring cells
2. Nutrients or growth factors are withdrawn
   3. Contact inhibition

Question 32

What is contact inhibition?

Answer 32

When a cell contacts with neighboring cells and has a plethora of cells= stop dividing

Question 33

What are cyclins and when do they form?

Answer 33

Regulatory proteins for cell division that form during interphase

Question 34

Cyclin–dependent kinases (CDK’s)

Answer 34

Enzymes activated by cyclins that allow cell to move from one checkpoint to another

Question 35

G1 checkpoint Kolin when and what?

Answer 35

Between G1 and S phases; commitment stage: G0 ( don’t divide) or Synthesis. Apoptosis can happen at this point

Question 36

G2/M checkpoint

Answer 36

Mitosis or apoptosis

Question 37

What is meiosis? How is it different from mitosis?

Answer 37

-Division of sex cells (sperm and egg).
-Mitosis: two genetically identical daughter cells
-Meiosis: four or two genetically DIFFERENT Daughter cells (Only have one of each chromosome instead of two like in mitosis)