Meiosis and Sexual Life: Chp 13

Question 1

genes

Answer 1

segments of DNA that code for the basic units of heredity and are transmitted from one generatioN to the next

Question 2

Gametes

Answer 2

reproductive cells that transmit genes from one generation to the next

Question 3

locus

Answer 3

the location of a gene on a chromosome

Question 4

asexual reproduction

Answer 4

a single parent is the sole parent and passes copies of all its genes to its offspring. therefore, it gives rise to a clone

Question 5

sexual reproduction

Answer 5

two individuals contribute genes to the offspring. this form of reproduction results in greater genetic variation in the offspring than asexual reproduction

Question 6

life cycle

Answer 6

the generation to generation sequence of stages in the reproductive history of an organism, from conception to production of its own offspring

Question 7

somatic cells

Answer 7

any cells in the body that are not gametes

Question 8

karyotype

Answer 8

a picture of an organisms complete set of chromosomes, arranged in pairs of homologous chromosomes from the largest pair to the smallest pair

Question 9

homologous chromosomes

Answer 9

both chromosomes of each pair carry genes that control the same inherited characteristics

Question 10

autosomes

Answer 10

nonsex chromosomes

Question 11

gametes

Answer 11

sperm and egg (haploid cells)

Question 12

fetilization

Answer 12

the combination of a sperm cell and an egg cell

Question 13

zygote

Answer 13

fertilized egg

Question 14

meiosis

Answer 14

the type of cell division that reduces the numbers of sets of chromosomes from two to one

Question 15

interphase

Answer 15

each of the chromosomes makes a copy of itself; therefore, each chromosome replicates its DNA

Question 16

Meiosis 1

Answer 16

the first cellular division made up of prophase 1, metaphase 1, anaphase 1, telophase 1, and cytokinesis

Question 17

prophase 1

Answer 17

1: the chromosomes condense, resulting in two sister chromatids attached at their centromeres.
2: synapsis occurs, forming tetrads
3: crossing over occurs between homologous chromosomes in the tetrads
4: crossing over increases genetic variation
5: areas of crossing over form chiasmata
6: the nuclear envelope disintegrates, allowing the spindle to attach to the homologs

Question 18

metaphase 1

Answer 18

1: the homologous pairs of chromosomes are lined up at the metaphase plate
2: microtubules from each pole attach to each member of the homologous pairs in preparation for pulling them to opposite ends

Question 19

anaphase 1

Answer 19

1: the spindle apparatus helps to move the chromosomes toward opposite ends of the cell
2: sister chromatids stay connected and move together toward the poles

Question 20

telophase 1 and cytokinesis

Answer 20

1: the homologous chromosomes move until they reach the opposite poles
2: each pole contains a haploid set of chromosomes, with each chromosome still consisting of two sister chromatids
3: cytokinesis is the division of the cytoplasm and occurs during telophase-a cleavage furrow forms in animal cells and cell plates form in plant cells

Question 21

meiosis 2

Answer 21

the second cellular division in meiosis. consisting of prohase 2, metaphse 2, anaphase 2, telophase2, and cytokinesis

Question 22

prophase 2

Answer 22

a spindle apparatus forms, and sister chromatids move toward the metaphase plate

Question 23

metaphase 2

Answer 23

the chromosomes are lined up on the metaphase plate, and the kinetochores of each sister chromatid prepare to move to the opposite poles

Question 24

anaphase 2

Answer 24

the centromeres of the sister chromatids separate, and individual chromosomes move to the opposite ends of the cell

Question 25

telophase 2 and cytokinesis

Answer 25

the chromatids have moved all the way to opposite ends of the cells, nuclei reappear, and cytokinesis occurs. each of the four daughter cells has the haploid number of chromosomes and is genetically different from the other daughter cells and from the parent cell

Question 26

three events that occur during meiosis 1 that does not occur in mitosis

Answer 26

1: synapses and crossing over normally do not occur during mitosis
2: at metaphase 1, paired homologous chromosomes (tetrads) are positioned on the metaphase plate, rather than individual replicated chromosomes, as in meiosis
3: at anaphase 1, duplicated chromosomes of each homologous pair separate but the sister chromatids of each duplicated chromosomes stay attached. in mitosis, the chromatids separate

Question 27

three important processes that contribute to genetic variation

Answer 27

crossing over, independent assortment of chromosomes, and random fertilization

Question 28

crossing over

Answer 28

exchange of genetic material on homologous chromosomes between nonsister chromatids

Question 29

independent assortment of chromosomes

Answer 29

in metaphase 1, when the homologous chromosomes are lined up on the metaphase plate, they can pair up in any combination, with any of the homologous pairs facing either pole

Question 30

random fertilization

Answer 30

because each egg and sperm is different, each combination of egg and sperm is unique