Chapter 13

Question 1

heredity

Answer 1

the transmission of traits from one generation to the next

Question 2

genetics

Answer 2

the scientific study of heredity and hereditary variation

Question 3

gametes

Answer 3

reproductive cells that are the vehicles to transmit genes from one generation to the next

Question 4

asexual reproduction

Answer 4

single individual is sole parent and passes copies of all its genes to its offspring without the fusion of gametes, offspring are clones of mom/dad
o Ex: single-celled eukaryotic organisms

Question 5

clone

Answer 5

a group of genetically identical individuals

Question 6

sexual reproduction

Answer 6

2 parents give rise to offspring with unique combinations of genes inherited from both parents

Question 7

life cycle

Answer 7

stages from conception to production of own offspring

Question 8

homologous chromosomes/homologs

Answer 8

when two chromosomes of a pair have the same length

Question 9

diploid cell

Answer 9

any cell with 2 chromosome sets

o Has 2n number of chromosomes

Question 10

haploid cell

Answer 10

cells in which gametes contain a single set of chromosomes

o Has n number of chromosomes, n=23

Question 11

fertilization

Answer 11

the union of gametes resulting from fusion of haploid sperm and egg

Question 12

meiosis

Answer 12

reduces number of sets of chromosomes from 2 to 1 in gametes

Question 13

alternation of generations

Answer 13

o includes diploid and haploid stages that are multicellular
o Exhibited by plant cells and certain types of algae
o Sporophyte

Question 14

sporophyte (alternation of generations)

Answer 14

multicellular diploid stage in which sporophyte generation produces gametophyte as offspring and gametophyte generation produces the next sporophyte generation
• Meiosis here produces haploid cells called spores

Question 15

Gametophyte (sporophytes)

Answer 15

multicellular haploid stage

Question 16

sister chromatids

Answer 16

2 copies of one chromosome

o Make up one duplicated chromosome

Question 17

Prophase I

Answer 17

o Centrosome moves
o Spindle is formed
o Nuclear envelope breaks down
o Chrom. condense
o Each chromosome pairs with its homolog
o Crossing over occurs
• Crossing over: when DNA molecules of non-sister chromatids are broken and rejoined
o Each homologous pair has a chiasmata where crossovers occurred
o Microtubules from one pole will attach to two kinetochores, one at the centromere of each homolog
o Homologous pairs then move toward metaphase plate

Question 18

Metaphase I

Answer 18

o Pair of homologous chromosomes are at metaphase plate
o Both chromatids of one homolog are attached to kinetochore microtubules from one pole. Those of the other homolog are attached to microtubules from the opposite pole

Question 19

Anaphase I

Answer 19

o Breakdown of proteins that are responsible for sister chromatid cohesion allow homologs to separate
o Homologs move toward opposite poles, guided by spindle apparatus
o Sister chromatid cohesion continues at centromere, causing chromatids to move as a unit toward the same pole

Question 20

Telophase I and Cytokinesis

Answer 20

o When telophase I begins, each half of cell has complete haploid set of duplicated chromosomes
o Each chromosome is composed of 2 sister chromatids
o One or both chromatids include regions of nonsister chromatid DNA
o Cytokinesis occurs along with telophase I, forming two haploid daughter cells
o Cleavage furrow forms
o Chromosomes decondense and nuclear envelopes form

Question 21

Prophase II

Answer 21

o Spindle apparatus forms
o Chromosomes still consist of 2 chromatids at the centromere
o Chromosomes move toward metaphase II plate

Question 22

Metaphase II

Answer 22

o Chromosomes are positioned at metaphase plate
o Two sister chromatids of each chromosome are not genetically identical
o Kinetichores of sister chromatids attach to microtubules extending from opposite poles

Question 23

Anaphase II

Answer 23

o Breakdown of proteins holding sister chromatids together at centromere allows chromatids to separate
o Chromatids move toward opposite poles as individual chromosomes

Question 24

Telophase II and Cytokinesis

Answer 24

o Nuclei form
o Chromosomes begin decondensing
o Meiosis of 1 parent cell has produced four daughter cells each with haploid set of chromosomes
o Four daughter cells are genetically distinct from each other and parent cell

Question 25

crossing over

Answer 25

o When DNA molecules of non-sister chromatids are broken and rejoined
o Occurs in prophase I

Question 26

chiasmata

Answer 26

• X-shaped region found in homologous pairs where crossovers have occurred
• Each homologous pair has a chiasmata where crossovers occurred
• Occurs in prophase I

Question 27

synaptonemal complex

Answer 27

• Zipper-like protein which forms between two homologous chromosomes during meiosis
• Supposedly helps with chromosome pairing, synapsis, and recombination

Question 28

synapsis

Answer 28

association during which DNA breaks are closed up so each broken end is joined to corresponding segment of non sister chromatid

Question 29

recombinant chromosomes

Answer 29

individual chromosomes that carry genes derived from two different proteins