Unit 3 Chapter 12: Meiosis

Question 1

What must happen before sexual reproduction

Answer 1

homologs must be reduced by half

Question 2

What is fertilization

Answer 2

when and egg and sperm unite

Question 3

What is meosis

Answer 3

• sexual reproduction
• a reduction division
• nuclear division that leads to halving the chromosome number
• precedes the formation of eggs and sperm in animals

Question 4

What are autosomes

Answer 4

chromosomes that are not x/y sex chromosomes

Question 5

What are homologous chromosomes (homologs)

Answer 5

• 2 chromosomes of the same type

- carry the same genes but each may have different alleles

Question 6

What is a gene

Answer 6

a section of DNA that influences some hereditary trait in an individual

Question 7

What is a trait

Answer 7

a characteristic

Question 8

What is an allele

Answer 8

different versions of the same gene

Question 9

What does diploid mean

Answer 9

2 copies of each chromosome ie. human body cells

Question 10

What does haploid mean

Answer 10

1 copy of each chromosome ie. human gametes

Question 11

How does the ploidy of meiosis work

Answer 11

after meiosis 1: diploid parent cell makes 2 haploid daughter cells (each chromosome is replicated though ie. 2 sister chromatids)
after meiosis 2: 4 haploid cells produced (each chromosome in unreplicated though)

Question 12

What is a zygote

Answer 12

diploid cell produced from fusion of 2 haploid gametes

Question 13

What is meiosis 1

Answer 13

• begins after chromosomes have been replicated during S phase
• interphase
• early prophase 1
• late prophase 1
• metaphase 1
• anaphase 1
• telophase/cytokinesis 1

Question 14

What is synapsis

Answer 14

-occurs during early prophase 1, homologous chromosome pairs come together forming tetrads

Question 15

What are tetrads

Answer 15

• form from synapsis

- 2 homologous chromosomes which each has 2 sister chromatids

Question 16

What is crossing over

Answer 16

• occurs during late prophase 1
• when paternal and maternal chromatids break and rejoin at each chiasma (x shaped structure) producing chromatids that have a mix of maternal and paternal segments

Question 17

What happens during early prophase 1

Answer 17

• replicated chromosomes condense
• spindle forms and nuclear envelope disappears
• synapsis of homologs forms tetrads
• kinetochore microtubules attach to kinetochores

Question 18

What happens during late prophase 1

Answer 18

-crossing over

Question 19

What happens during metaphase 1

Answer 19

tetrads line up at metaphase plate

Question 20

What happens during anaphase 1

Answer 20

homologs separate and move to opposite poles

Question 21

What happens in telophase 1

Answer 21

homologs finish moving to poles, sometimes nuclear envelope reappears, cell divides

Question 22

What happens during prophase 2

Answer 22

-spindle forms (kinetochore microtubules attach to each side of every chromosome-one per sister chromatid)

Question 23

What happens during metaphase 2

Answer 23

-replicated chromosomes line up at metaphase plate

Question 24

What happens during anaphase 2

Answer 24

-sister chromatids separate, and unreplicated chromosomes move to poles of the cell

Question 25

What happens in telophase 2

Answer 25

- chromosomes finish moving to opposite poles | - nuclear envelope reforms

Question 26

What is the synaptonemal complex

Answer 26

a network of proteins that hold 2 pairs of non-sister chromatids together

Question 27

When do most mitotic divisions in plants occur

Answer 27

after meiosis 2

Question 28

What is the principle of independent assortment

Answer 28

when pairs of homologs line up in meiosis 1 and the separate, a variety of combinations of maternal and paternal chromosomes can result

Question 29

How do you determine how many combinations of maternal and paternal chromosomes are distributed to daughter cells

Answer 29

2^n where n=number of chromosomes

Question 30

What is recombination

Answer 30

any change in the combination of alleles on a given chromosome -ie. crossing over produces combination that were not present in either parent

Question 31

What is trisomy

Answer 31

3 copies of a chromosome, ie. down syndrome

Question 32

What is nondisjunction

Answer 32

if both homologs or sister chromatids move to the same pole of the cell during meiosis

Question 33

What is Klinefelter syndrome

Answer 33

XXY in males

Question 34

What is Turner syndrome

Answer 34

XO females (missing an x); female and sterile

Question 35

What is a consequence of odd ploidy

Answer 35

tend to be sterile as there is are unpaired homologs in metaphase 1

Question 36

Meiosis 2 is similar to which process

Answer 36

mitosis in haploid cells