Ch 13 Meiosis and sexual life cycles

Question 1

asexual reproduction

Answer 1

binary fission (bacteria) or mitosis (eukaryotes) without meiosis and the fusion of gametes involved.
organsims that undergo asexual reproduction include bacteria, yeast, hudra, planaria worms, and some plants

Question 2

sexual reproduction

Answer 2

reprodution done through the producton of gametes by meiosis; fertiliztion

Question 3

meiosis

Answer 3

essentioal for producing sperm in human testes and eggs in human ovaries.
all somatic cells and the zygote are diploid.
all the gamites (egg and sperm) are haploid

Question 4

dipliod

Answer 4

2 sets of chormosomes 2n=46

Question 5

haploid

Answer 5

one set of chromosomes n=23

each set of 23 consists of 22 autosomes and a single sex chromosome

Question 6

homologous chromosomes

Answer 6

a pair of chormosome of the same length and carrying the genes controlling the same inhereited characters. one homologous chromosome is inheritied from the father, the other from the mother

Question 7

karyotype

Answer 7

a pair of homologous chromosomes

Question 8

autosomes

Answer 8

the chromosomes other that x and y chromosomes in humans. there are 22 pairs of autosomes in humans.

Question 9

sex chromosomes

Answer 9

a pair of chromosomes responsible for determining the sex of an organism. also called x and y.
females xx
male xy

Question 10

genes

Answer 10

the units of heredity, and are made up of segments of DNA

Question 11

locus

Answer 11

a specific location of a gene on a certain chromosome

Question 12

meiosis

Answer 12

the cell divison process by which gamete (sperm and eggs) are produced.
2 cell divisions: meiosis I and meiosis II. the two cell divisions result in 4 genetically different daughter cells. each daughter cell has only half as many chromosomes as the parent cell.

Question 13

the stages of meiosis

Answer 13

meiosis I is proceeded by interphase, in wich chromosomes are replicated to form sister chromatids. the sister chromatids are genetically identical and joined at the centromere.
the single centrosome starts to replicate at the G1/S transision, forming 2 centrosomes, 2 chromosome have formed at the G2 of interphase

Question 14

prophase I

Answer 14

typically occupies more than 90% of the time required for meiosis, chromosomes begin to condense.
paired homologous chromosomes become physically connected to each other along their lengths by a zipper like protein structer call synaptonenal complex.
paired homologous chromsomes are at a state called synapsis

Question 15

crossing over in prophase 1

Answer 15

nonsister chromatids of homologous chromosomes exchange DNA segments.
each pair of chromosome form a tetrad
each tetrad usually has one or more chiasmata
chrossing over produces recombant chromosomes
begins very early in prophase I, as homologous chromsomes pair up gene by gene
homologous portions of 2 nonsis chromatids trade places
contributes to genetic variation by combing DNA from 2 parents into a single chromosome

Question 16

tetrad

Answer 16

group of 4 chromatids

Question 17

chiasmata

Answer 17

x shaped regions where crossing over occured

Question 18

recombant chromosomes

Answer 18

combine genes from each parent

Question 19

meiosis I

Answer 19

homologuos chromsomes separate

results in 2 haploid daughter cells with replicated chromosome; reductional division

Question 20

meiosis II

Answer 20

sister chromatids separate

results in 4 hapliod daughter cells

Question 21

metaphase I

Answer 21

tetrads line up at the mataphase plate with one chromosome facing each pole.
microtubules from one pole are attached to the kinetochore of one chromosome of each tetrad.
microtubules from the other pole are attached to the kinetochore of the other chromosome.

Question 22

anaphase I

Answer 22

pairs of homologous chromosome separate, one chromosome moves toward each pole, guided by the spindle apparatus.
sister chromatids remain attaached at the centromere and move as one unit toward the pole.