Lecture 5

Question 1

What are the four main differences between prokaryotes and eukaryotes?

Answer 1

1. ) Pro: No membrane bound nucleus or organelles, single and circular chromosome, single cell organisms
2. ) Eu: All have membrane bound nucleus, number of chromosomes varies by species (humans have 23 pairs of chromosome but chicken may have different), membrane-bound organelles. can be single or multi-celled organisms

Question 2

What determines the sex of cells?

Answer 2

X and Y are sex chromosomes (22 pairs of autosomal chromosomal and 1 pair of sex chromosomes)
XX= Female
XY= Male

Question 3

After S phase how many alleles are there after S phase? and before S phase?

Answer 3

After S phase = 4 Alleles

ANY other times is ONLY 2 allele

Question 4

True/False: Eu and Pro have the same reasons for wanting to undergo cell division

Answer 4

Largely False: But do share one similarity- REPRODUCTION

Eukaryote: Also go through cell division for tissue growth and to repair damaged tissues

Question 5

What are the two main stages of mitosis?

Answer 5

Inter[hase (DAND replication happens in the S phase)

Mitosis and cytokinesis (nuclear division and the production of two identical daughter cells)

Question 6

What stage does a cell spend most of its life?

Answer 6

Interphase

Question 7

What stage in interphase does the replication of organelles happen?

Answer 7

G1 Phase

Question 8

True/False: The growth of RNA and protein stops after S phase ?

Answer 8

FALSE

Question 9

Which stage in interphase is the longest?

Answer 9

G1 phase

Question 10

What are the stages in mitosis?

Answer 10

Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis

Question 11

At which part during mitosis are sister chromatids classified as chromosomes?

Answer 11

During Anaphase as the sister chromatids are pulled apart

Question 12

How many chromosomes and chromatids are there at the beginning of mitosis?

Answer 12

Chromosomes: 46
Chromatids: 92

Question 13

How many chromosomes and chromatids are there at the end of anaphase?

Answer 13

Chromosomes: 92
Chromatids: 92

Question 14

How many chromosomes and chromatids are there during telophase of mitosis?

Answer 14

Chromosomes: 92
Chromatids: 92

Question 15

How many chromosomes and chromatids are there after cytokinesis of mitosis?

Answer 15

Chromosomes: 46
Chromatids: 46

Question 16

How many chromosomes and kinetochores are there on a chromosome in mitosis?

Answer 16

2 kinetochores and 2 chromosomes

Question 17

True/ False: The frequency of cell division varies with cell type

Answer 17

True

Question 18

What happens when a checkpoint requirement is not met?

Answer 18

If there is something wrong, the cell waits till the error is corrected and if can’t be corrected, the cell undergoes apoptosis *programmed cell death)

Question 19

What are the four main checkpoints during cell division?

Answer 19

G1 (Cell growth, and env), S (DNA replication), G2 (Cell growth and env), and metaphase (chromosome alignment on spindle)

Question 20

What are the three main reasons for a checkpoint?

Answer 20

The checkpoints are programmed BUT can also be triggered. Save energy and resources that does not need to be wasted. Looking at internal env (kinetochores and microtubules formation), and external factors (such as hormones, and growth factors)

Question 21

What two things does a successful cell division require?

Answer 21

DNA replicating only once - must not try to divide until replication is complete
Cell mass must increase- must not be able to replicate until cell mass is sufficient as have to make two daughter cells

Question 22

What happens when one of two factors is wrong?

Answer 22

The cell undergoes cardiac arrest

Question 23

What is the solution to preserving information while making it variable at the same time?

Answer 23

Sexual reproduction (fusion of gametes) and meiosis (production of gametes)

Question 24

What happens during anaphase I?

Answer 24

Separation homologous chromosomes

Question 25

How many chromosomes and chromatids are there during anaphase I?

Answer 25

Chromosomes: 46
Chromatids: 92

Question 26

How many chromosomes and chromatids are there during Telophase I?

Answer 26

Chromosomes: 23
Chromatids: 46

Question 27

How is variability created?

Answer 27

1. ) Independent assortment of homologous chromosomes in meiosis - 2*n
2. )Crossing ober during prophase I

Question 28

How many chromosomes and chromatids are there during Anaphase II?

Answer 28

Chromosomes: 46
Chromatids: 46

Question 29

How many chromosomes and chromatids are there during Telophase II?

Answer 29

Chromosomes: 23
Chromatids: 23

Question 30

What is the difference between non-disjunction and aneuploidy?

Answer 30

Non-disjunction: Failure of linked homologs or chromatids to separate during anaphase of mitosis or meiosis
Aneuploidy is often as a result of non-disjunction- a state where a cell has an abnormal number of chromosomes

Question 31

What are three instances where non-disjunction can occur?

Answer 31

Mitotic divisions of the primordial germ cells from which the gametes form
Mitotic divisions of the embryo following fertilization
Meiotic divisions of an oocyte or sperm (most times maternal meiosis)

Question 32

What are the two important factors that affects non-disjunction?

Answer 32

Metaphase checkpoint, cohesins

Size and shape of chromosomes, acrocentric chromosomes more prone to forming vulnerable bivalent