Chapter 13

Question 1

define heredity

Answer 1

heredity is the transmission of traits from one generation from the next

Question 2

defne variation

Answer 2

variation is demonstrated by the differences in appearance that offspring show from parents and siblings

Question 3

define genetics

Answer 3

genetics is the scientific study of heredity and variation

Question 4

what is inherited from parents?

Answer 4

genes are inherited from parents

Question 5

what are genes?

Answer 5

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

Question 6

what are gametes?

Answer 6

reproductive cells (sperm and eggs)

Question 7

what is a locus?

Answer 7

a gene’s specific position along a chromosome

Question 8

what happens in asexual reproduction?

Answer 8

a single individual passes all of its genes to its offspring without the fusion of gametes

Question 9

what is a clone?

Answer 9

a clone is a group of genetically identical individuals from the same parent

Question 10

what happens in sexual reproduction?

Answer 10

two parents give rise to offspring that have unique combinations of genes inherited from two parents

Question 10

how many chromosomes are in somatic cells?

Answer 10

46 in total; 23 pairs

Question 11

what is a karyotype?

Answer 11

a karyotype is an ordered display of the pairs of chromosomes from a cell

Question 11

mitosis vs meiosis and amount of end chromosomes

Answer 11

in mitosis if you start with 46 chromosomes and you copy them,
- you start with and end with the same number of chromosomes
in meiosis, you use less chromosomes
**only diploid cells undergo miosis

haploid: have one complete set

Question 12

what are female chromosomes?

Answer 12

they have a homologous pair of X chromosomes

Question 13

what are male chromosomes?

Answer 13

males have one X and one Y chromosome

Question 14

what are autosomes?

Answer 14

the remaining 22 pairs of chromosomes

Question 15

what happens in metaphase one?

Answer 15

pairs of homologs line up at the metaphase plate, with one chromosome facing each pole

Question 16

what happens in anaphase one?

Answer 16

separating homologous chromosomes, one of each moves to opposite poles, sister chromatids are attached at centromere and move as one unit, which reduces the number of chromosomes

Question 17

when does crossing over take place and what happens?

Answer 17

in prophase 1: each chromosome pairs with its homolog and crossing over occurs

Question 18

what happens in telophase one?

Answer 18

each half of the cell has a haploid set of chromosomes, each still has 2 sister chromatids, cytokinesis occurs simultaneously forming two haploid daughter cells

Question 19

what happens at the end of meiosis 2?

Answer 19

you end up with 4 daughter cells (gametes) that are all haploids

Question 20

if you have 6 sets, how many sets would gametes have?

Answer 20

3; it reduces in half

Question 21

what is a diploid cell?

Answer 21

a diploid cell has two sets of chromosomes (2n)
- for humans the diploid number is 46 (2n=46)

Question 22

what are sister chromatids?

Answer 22

sister chromatids are when each replicated chromosome consists of two identical sister chromatids the > < parts in the
>< chromosome are sisters

Question 23

if a cell which was 2n=6 (diploid with 6 chromosomes) underwent meisois, what would be produced?

Answer 23

3 haploid daughter cells

Question 24

what is haploid?

Answer 24

a gamete (sperm or egg) contains a single set of chromosomes and is haploid

Question 25

what is a life cycle?

Answer 25

a life cycle is the generation to generation sequence of stages in the reproductive history of an organism

Question 26

what are gametes produced by in comparison to other human cells?

Answer 26

gametes are produced by meiosis, everything else by mitosis

Question 27

how many sets of chromosomes are in each gamete as a result of meiosis?

Answer 27

one set of chromosomes in each gamete

Question 28

how does mitosis interact with gametes?

Answer 28

gametes fuse to form a diploid zygote that divides by mitosis to develop into a multicellular organism

Question 29

which cells can undergo meiosis?

Answer 29

only diploid cells

Question 30

which cells can undergo mitosis?

Answer 30

either haploid or diploid cells can divide by mitosis

Question 31

what are sites of crossover called?

Answer 31

chiasmata

Question 32

what is the main purpose of meiosis one?

Answer 32

to separate homologous chromosomes

Question 33

what happens during crossing over?

Answer 33

occurring in prophase I, sister chromatids held together by cohesins and nonsister chromatids are broken at corresponding positions, dna breaks are repaired, joining DNA from one nonsister chromatid to corresponding segement of another

Question 34

what does mitosis produce?

Answer 34

cells genetically identical to parent cell

Question 35

what does meiosis produce?

Answer 35

cells that differ genetically from each other and from parent cell

Question 36

where does synapsis of homologous chromosomes occur?

Answer 36

only in meiosis

Question 37

how many division are apart of mitosis?

Answer 37

one: pmat

Question 38

how many divisions are apart of meiosis?

Answer 38

2; each with pmat

Question 39

what are events unique to meiosis?

Answer 39

• synapsis and crossing over in prophase I: homologous chromosomes physically connect and exchange genetic info
• homologous pairs lining up at the metaphase plate in metaphase I
• separation of homologs during anaphase I

Question 40

what happens in mitosis relating to cohesions?

Answer 40

cohesins are cleaved at the end of metaphase

Question 41

what happens in meiosis relating to cohesions?

Answer 41

cohesins are cleaved along the chromosome arms in anaphas 1 (separation of homologs)

Question 42

which mechanisms contribute to genetic variation?

Answer 42

• independent assortment of chromosomes
• crossing over
• random fertilization

Question 43

what does crossing over produce?

Answer 43

recombinant chromosomes: which combine DNA inherited from each parent