CHAPTER 11 (MEIOSIS)

Question 1

meiosis

Answer 1

the form of cell division by which gametes, with half the number of chromosomes, are produced; sexual reproduction
TWO DIVISIONS:
MEIOSIS I
MEIOSIS II

Question 2

fertilization

Answer 2

the fusion of a sperm and egg to form a zygote

Question 3

zygote

Answer 3

fertilized egg

Question 4

interphase I

Answer 4

similar to mitosis interphase; chromosomes replicate (S phase); each duplicated chromosome consist of two identical sister chromatids attached at their centromeres; centriole pairs also replicate; nucleus and nucleolus visible

Question 5

meiosis I

Answer 5

cell division that reduces the chromosome number by one-half
HAS FOUR PHASE:
PROphase I
METAphase I
ANAphase I
TELOphase I

Question 6

prophase I

Answer 6

longest and most complex phase (90%); chromosomes condense; synapsis occurs

Question 7

synapsis

Answer 7

where homologous chromosomes come together to form a tetrad

Question 8

tetrad

Answer 8

two chromosomes or four chromatids (sister and nonsister chromatids)

Question 9

homologous chromosomes

Answer 9

pair of chromosomes (maternal and paternal) that are similar in shape and size; homologous pairs carry genes controlling the same inherited traits; each locus is in the same position on homologues; humans have 23 pairs (22 pairs of autosomes and 1 pair of sex chromosomes)

Question 10

locus

Answer 10

position of a gene

Question 11

karyotype

Answer 11

method of organizing the chromosomes of a cell in relation to number, size, and type

Question 12

autosomes

Answer 12

code for most of the offspring’s trait

Question 13

21 trisomy (down syndrome)

Answer 13

extra autosome in the 21st chromosome (3 chromosomes)

Question 14

sex chromosomes

Answer 14

code for the sex of the offspring
-if offspring has TWO “X” chromosomes it will be a FEMALE
-if offspring has ONE “X” chromosome and ONE “Y” chromosome it will be a MALE

Question 15

crossing over (variation)

Answer 15

may occur between nonsister chromatids at the chiasmata; segments of nonsister chromatids break and reattach to the other chromatid

Question 16

chiasmata (chiasma)

Answer 16

are the sites of crossing over

Question 17

metaphase I

Answer 17

shortest phase; tetrads align on the metaphase plate; independent assortment occurs

Question 18

independent assortment

Answer 18

-orientation of homologous pair to poles i random
-variation
-formula 2^n
HUMAN MALE can produce 8 million combinations of sperm 2^23

Question 19

anaphase I

Answer 19

homologous chromosomes separate and move towards the poles; sister chromatids remain attached at their centromeres

Question 20

telophase I

Answer 20

each pole now has a haploid set of chromosomes; cytokinesis occurs and two haploid daughter cells are formed

Question 21

meiosis II

Answer 21

-no interphase II (or very short - no more DNA replication)
-similar to MITOSIS

Question 22

prophase II

Answer 22

same as PROPHASE in MITOSIS

Question 23

metaphase II

Answer 23

same as METAPHASE in MITOSIS

Question 24

anaphase II

Answer 24

same as ANAPHASE in MITOSIS; sister chromatids separate

Question 25

telophase II

Answer 25

same as TELOPHASE in MITOSIS; nuclei form; cytokinesis occurs; four haploid daughter cells produced

Question 26

variation

Answer 26

important to population as the raw material for natural selection

Question 27

What are the three sexual sources of genetic variation?

Answer 27

-crossing over (PROPHASE I)
-independent assortment (METAPHASE I)
-RANDOM FERTILIZATION