Chapter 20 & 21

Question 1

What two steps occur when a cell with a distinct nucleus divides?

Answer 1

1. Mitosis

2. Cytokinesis

Question 2

What is mitosis?

Answer 2

When the nucleus divides to form two nuclei
Hereditary material in parent cell duplicates and then divides into two identical sets
2n -> 2n 2n

Question 3

What is cytokinesis?

Answer 3

When the cytoplasm divides into two parts, each contains one of the newly formed nuclei

Question 4

How does DNA exist in the nucleus in a cell that is not dividing?

Answer 4

It exists in a mass of thin twisted threads called chromatin

Question 5

What does DNA do when a cell is about to split?

Answer 5

They like into chromosomes then make duplicates to make double chromosomes (or a chromatid)

Question 6

How many different chromosomes do humans have?

Answer 6

23 pairs

46 chromosomes

Question 7

What does a centromere do?

Answer 7

The double chromosome attaches to the centromere in the middle and the spindles reach out and connect to the centromere

Question 8

What are the centrioles?

Answer 8

The ends of the cell during cell division that the spindles spring out of

Question 9

When does cytokinesis take place?

Answer 9

Inbetween anaphase and telophase

Question 10

What causes cell division to stop and start?

Answer 10

It is not known yet

Question 11

What is it called when a group of cells begin to divide in an uncontrolled fashion?

Answer 11

Cancer

Question 12

What causes cancer?

Answer 12

Genetic changes (mutations) in the DNA of somatic cells

Question 13

What is asexual reproduction in multicellular organisms?

Answer 13

The offspring develop from undifferentiated, unspecialized cells of the parent organism
Has exactly same hereditary information as parents

Question 14

Examples of asexual reproduction?

Answer 14

Binary fission
Budding
Regeneration
Spore formation

Question 15

What is Vegetative reproduction?

Answer 15

When undifferentiated cells divide miotically and then differentiate to produce an independent plant
Has same hereditary characteristic as parents

Question 16

What are gametes?

Answer 16

Sex cells (male or female) 
Haploid cells

Question 17

What is fertilization?

Answer 17

The fusion of the nuclei or the male and female gametes

Question 18

What is a zygote?

Answer 18

The single cell formed from the fusion of fertilization

Question 19

How are gametes formed?

Answer 19

Meiosis

Question 20

What are somatic cells?

Answer 20

The cells of an organism except the cells that play a part in sexual reproduction

Question 21

What are homologous chromosomes?

Answer 21

Pairs of chromosomes that carry genes for the same traits

One member of the pair comes from female while the other comes from male

Question 22

What is meiosis?

Answer 22

A kind of cell division that results in gametes with half the number of chromosomes as the parent cell

Meiosis is the division of specialized cells to form sex cells called gametes
Results in haploid cells

Question 23

What is the difference between haploid and diploid cells?

Answer 23

Diploid cells have all the homologous chromosomes paired together while haploid only has one chromosome from each pair
(Diagram page 419)

Diploid - 2n
Haploid- n

Question 24

Difference between mitosis and meiosis?

Answer 24

Mitosis is the division of a diploid cell into two diploid cells that have the same amount of chromosomes as parent
Meiosis is the division of a diploid cell into four haploid cells that have half the amount of chromosomes as parent

Meiosis is the splitting of homologous chromosomes leading to non identical daughter cells while mitosis has daughter cells that are identical to eachother and the parent

The fundamental sequence of event in meiosis and mitosis is the same except in meiosis the division happens twice

Both undergo cytokinesis and both result in daughter cells as a result of parent cells

Mitosis produces somatic cells while meiosis produces gamete cells

Question 25

What differs from mitosis prophase and meiosis prophase I?

Answer 25

Mitosis it duplicates identical chromosomes that attach by a centromere but in meiosis each pair of double chromosomes is already made and lines up randomly with its homologous pair

Mitosis- |•|
Meiosis- |•| |•|

Question 26

What is synapsis and tetrad?

Answer 26

Synapsis is the pairing of two homologous pairs of chromosomes by their centromeres
The group of four chromatids is called a tetrad

Question 27

What is disjunction?

Answer 27

During the first meiotic division, the homologous chromosomes or each tetrad separate from eachother and move to opposite ends of the cell

Question 28

What is conjugation?

Answer 28

The type of sexual process most commonly found among simple organisms

It is the transfer of DNA by direct cell to cell contact that is mediated by the plasmids

Question 29

What are hermaphrodites?

Answer 29

Organisms that have both testes and ovaries. They are both sexes

Question 30

What is gametogenesis?

Answer 30

The process by which gametes develop in the gonads

Question 31

What is oogenesis compared to spermatogenesis?

Answer 31

Oogenesis is the formation of eggs in the ovaries while spermatogenesis is the formation of sperm in the testes

Question 32

What type of cell division to oogenesis and spermatogenesis go under?

Answer 32

Meiosis

Question 33

What is parthenogenesis? What animals does it take place in?

Answer 33

The development of an unfertilized egg into an adult animal without the fusion with sperm

Bees wasps ants

Question 34

What do unfertilized eggs from the queen turn into?

Answer 34

Male drones

Question 35

How is women’s oogenesis different from men’s spermatogenesis?

Answer 35

Females first stage of meiosis happens before birth then the second stage happens at puberty, then ends at 55ish (menopause). in males it happens from puberty till death