Lecture 6

Question 1

Meiosis

Answer 1

• reduced amount of genetic material by half
• produces hapliod gametes or spores, each containing one member of a homologous pair of chromosomes

Question 2

Meiotic event

Answer 2

Genetic exchange between members of homologous pairs of chromosomes

Question 3

Meiosis I

Answer 3

reductional division

Question 4

Meiosis II

Answer 4

Equational division

Question 5

When does DNA synthesis occur during meiosis

Answer 5

• occurs during interphase, before the beginning of meiosis I
• doesn’t occur again before meiosis II

Question 6

Meiosis I - Prophase I

Answer 6

5 substages each with specific events

Question 7

What indicated the end of prophase I?

Answer 7

centromeres are present on the equatorial place

Question 8

Leptonema

Answer 8

chromosomes appear as long, single threads unassociated with each other (chromomeres)

Question 9

Zygonema

Answer 9

• synapsis
• each pair of homologous chromosomes is know as bivalent
• chromatin still present

Question 10

Pachynema

Answer 10

• each bivalent becomes shorter, thicker, and splits into 2 sister chromatids called tetrads
• homologous pairs line up

Question 11

crossing over

Answer 11

exchange of genetic material between nonsister chromatids, promotes genetic variation

Question 12

Diplonema

Answer 12

• within tetrads, sister chromatids separate
• chiasma: where chromatids are still intertwined

Question 13

Diakinesis

Answer 13

• nucleus and nuclear envelope break down
• centromeres attach to spindle fibers

Question 14

metaphase I

Answer 14

chromosomes at maximum shortness

Question 15

terminal chiasmata

Answer 15

-holding non-sister chromatids together

Question 16

what moves chromatids to metaphase plate

Answer 16

centromeres binding to spindle fibers

Question 17

Anaphase I

Answer 17

• cohesion is degraded between sister chromatids
• homologous chromosomes separate
• nondisjunction may occur

Question 18

First division: Meiosis I-Telophase I

Answer 18

• cytokinesis
• 2 haploid cells result
• nuclear membranes forms
• nuclei enter interphase

Question 19

What occurs during metaphase, anaphase, and telophase I?

Answer 19

• homologous chromosomes separate and move toward the poles
• sister chromatids remain attached at centromeres
• duplicated chromosomes reach poles, each pole now has haploid set of chromosomes
• cytokinesis: 2 haploid daughter cells are formed
• nuclear envelope forms around chromosomes in some species

Question 20

Prophase II

Answer 20

each dyad is composed of one pair of sister chromatids attached by the common centromeric region

Question 21

dyad

Answer 21

group of 2 things

Question 22

Metaphase II

Answer 22

the centromeres are positioned on the equatorial plate

Question 23

Anaphase II

Answer 23

• sister chromatids are separated to opposite poles
• each haploid daughter cell from meiosis II has one member of each pair of homologous chromosomes

Question 24

Telophase II

Answer 24

• one member of each pair of homologous chromosome is now a monad

Question 25

second round of cytokinesis...

Answer 25

results in 4 haploid cells

Question 26

spermatogenesis

Answer 26

production of male gametes in testes

Question 27

oogenesis

Answer 27

production of female gametes in ovary - formation of ova in the ovaries - 4 daughter cells do not receive equal cytoplasm - only 1 daughter cell receives cytoplasm (primary polar body) - undergoes meiosis I and II - develops into ovum

Question 28

Primary spermatocyte

Answer 28

- undergoes meiosis I - produces 2 secondary spermatocytes

Question 29

Secondary spermatocyte

Answer 29

- undergo meiosis II - produces a total of 4 haploid spermatids

Question 30

Fungi life cycles

Answer 30

haploid vegetative cells arise via meiosis-proliferate via mitotic cell division

Question 31

Plants life cycles

Answer 31

life cycle alternates between diploid, sporophyte stage and haploid gametophyte stage

Question 32

Chromosomes

Answer 32

- visible only during mitosis and meiosis - chromatin fibers that make up chromosomes coil and condense

Question 33

folded-fiber model

Answer 33

electron microscope of mitotic chromosomes in varying states of coiling led to this model