Lecture 3 Meiosis & Mitosis

Question 1

In Mitosis - What phase follows the G2 phase and what are the 4 sub-phases called

Answer 1

Mitotic Phase

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

Question 2

What phases of Mitosis are the organelles copied?

Answer 2

G2 Phase

Question 3

How many chromosomes/ pieces of DNA are in a cell during Interphase

Answer 3

Depends on the stage
46 in G1
92 by end of S phase

Question 4

Why does a cell phave 92 pieces of DNA

Answer 4

Because it is going to divide into 2 daughter cells that will have 46 each

Question 5

What are the phases of interphase

Answer 5

G1
S
G2

Question 6

What is the non-dividing portion of the cell life

Answer 6

Interphase

Question 7

What happens during Prophase

Answer 7

Nuclear envelope dissolves
Centrosomes push each other to opposite ends of cell
Chromatin condenses to form chromosomes
Identical copies of DNA - known as Sister Chromatids pair up

Question 8

What is Chromatin

Answer 8

DNA that is loose and uncoiled - accessible for ribosomes to read

Question 9

What are Chromosomes

Answer 9

Coiled version of chromatin - tightly coiled DNA

Question 10

What are Sister Chromatids

Answer 10

identical copies of DNA that pair up and are connected with a centromere

Question 11

What events happen during Metaphase

Answer 11

DNA are lined up on mid-line called metaphase plate

Micro tubules connect to centromere

Question 12

What events happen during Anaphase

Answer 12

Micro-tubules pull DNA to opposite ends of cell

Centromere breaks

Question 13

What events happen during Telopphase

Answer 13

New nuclear enveloped form around DNA

Cleavage furrow formed by micro-tubules and deepens from tightening of micro-tubules eventually causing cytokineses

Question 14

Through what cell cycle are gametes formed - what are gametes

Answer 14

Meiosis

Sex cells - sperm & egg cells

Question 15

How many pieces of DNA in the primary sex cell

Answer 15

46

Question 16

How many pieces of DNA in the secondary sex cells

Answer 16

23

Question 17

What is Meiosis part 1 in the male sex cell life cycle

Answer 17

The reduction division when the Primary sex cells divides into 2 secondary sex cells that each have 23 pieces of DNA each

Question 18

What happens in Meiosis 2 in the male sex cell life cycle

Answer 18

Both priimary sex cells duplicate into 2 indentical cells known as Spermatids each have 23 pieces of DNA

Question 19

What is the female Primary sex cell known as

Answer 19

Oocyte - has 46 pieces of DNA

Question 20

What happens in Meiosis 1 in a female cell cycle

Answer 20

Primary Oocyte divides into a Secondary Oocyte and a 1st polar body - takes on average 14 days

Question 21

What is a 1st polar body

Answer 21

The secondary oocyte that has too small of a cytoplasm to survive and therefore does not mature

Question 22

What happens to the Secondary Oocyte that does mature

Answer 22

Ovulated in response to the Lutinizing Hormone - typically does not go through Meiosis 2, but if fertilization happens it will go through Meiosis 2

Question 23

Meiosis 2 in a Secondary Oocyte only occurs when

Answer 23

If fertilization happens with a sperm

Question 24

What are the products of Meiosis 2 in the female cell cycle

Answer 24

2nd polar body - has too small of cytoplasm and dies
&
Ovum are created
Ovum then goes through Mitosis and a Zygote with 46 pieces of DNA is created which then continues to replicate becoming an embryo with stem cells

Question 25

What is Nondisjunction

Answer 25

Failure of one pair of chromosomes to split during Meiosis 1 causing a Trisomy such as Trisomy #21 or a Monosomy

Question 26

Trisomy #21 has how many pieces of DNA

Answer 26

47 pieces total
3 copies of chromosome #21
Down Syndrome

Question 27

How many pieces of DNA does someone with Monosomy 21 have

Answer 27

45 pieces total

1 copy of chromosome #21

Question 28

How many autosomes would be found in a cell from a person with Trisomy #12 during anaphase

Answer 28

90 autosomes
45 at G1
90 at end of S phase and throughout