Chapter 19

Question 1

asexual reproduction definition

Answer 1

mode of reproduction in which offspring arise from a single parent, producing an individual genetically identical to that parent

Question 2

three types of asexual reproduction

Answer 2

budding
binary fission
pathogenesis

Question 3

sexual reproduction definition

Answer 3

mode of reproduction in which the genomes of two individuals are mixed to produce an individual that is genetically distinct from its parents

Question 4

diploid definition

Answer 4

describes a cell or organism containing two sets of homologous chromosomes, one inherited from each parent

Question 5

homolog definition

Answer 5

a gene, chromosome, or any structure that has a close similarity to another as a result of common ancestry

Question 6

gamete definition

Answer 6

cell type in a diploid organism that carries only one set of chromosomes and is specialized for sexual reproduction (sperm or egg)

Question 7

haploid definition

Answer 7

describes a cell or organism with only one set of chromosomes

Question 8

zygotes contain ________ from both the mother and father

Answer 8

homologous chromosomes

Question 9

germ line definition

Answer 9

the lineage of reproductive cells that contributes to the formation of a new generation of organisms, as distinct from somatic cells, which form the body and leave no descendants in the next generation

Question 10

somatic cell definition

Answer 10

any cell that forms part of the body of a plant or animal that is not a germ cell or germ-line precursor

Question 11

allele definition

Answer 11

an alternative form of a gene; for a given gene, many alleles may exist in the gene pool of the species

Question 12

meiosis definition

Answer 12

specialized type of cell division by which eggs and sperm cells are made
two successive nuclear divisions with only one round of DNA replication generate four haploid cells from an initial diploid cell

Question 13

what occurs during the meiotic prophase

Answer 13

each duplicated paternal chromosomes locates and then attaches itself along the entire length to the corresponding duplicated maternal homolog
also known as pairing

Question 14

pairing definition

Answer 14

in meiosis, the process by which a pair of duplicated homologous chromosomes attach to one another to form an aligned, linear structure containing four sister chromatids

Question 15

sister chromatid definition

Answer 15

copy of a chromosome, produced by DNA replication, that still remains bound to the other copy

Question 16

bivalent definition

Answer 16

structure formed when a duplicated chromosome pairs with its homolog at the beginning of meiosis; contains four sister chromatids

Question 17

the _______ will separate during meiosis I and the _______ will separate during meiosis II

Answer 17

maternal and paternal homologs
individual sister chromatids

Question 18

bivalents are/are not very stable

Answer 18

are

Question 19

homologous recombination definition

Answer 19

during meiosis, the mechanism results in an exchange of genetic information between the maternal and paternal homologs

Question 20

crossing-over definition

Answer 20

process by whereby two homologous chromosomes break at corresponding sites and rejoin to produce two recombined chromosomes that have physically exchanged segments of DNA

Question 21

what facilitates the crossing-over process

Answer 21

synaptonemal complex

Question 22

chiasma definition

Answer 22

X-shaped connection between paired homologous chromosomes during meiosis
representing a site of crossing-over between two non-sister chromatids

Question 23

crossing-over is required for the correct ________

Answer 23

segregation of the two duplicated homologs into separate daughter nuclei

Question 24

what do cohesion proteins do

Answer 24

keep the sister chromatids glued together along their entire length at meiosis I

Question 25

what is nondisjunction

Answer 25

when homologs fail to separate properly, causing some haploid cells to lack a chromosome while others have an extra copy

Question 26

what is aneuploidy

Answer 26

condition when eggs or sperm contain the wrong number of chromosomes

Question 27

fertilization definition

Answer 27

the fusion of two gametes-sperm and egg-to produce a new individual organism

Question 28

zygote definition

Answer 28

diploid cell produced by fusion of a mole and a female gamete

Question 29

genotype definition

Answer 29

the genetic makeup of a cell or organism, including which alleles it carries

Question 30

homozygous definition

Answer 30

possessing identical alleles for a given gene

Question 31

heterozygous definition

Answer 31

possessing dissimilar alleles for a given gene

Question 32

phenotype definition

Answer 32

the observable characteristics of a cell or organism

Question 33

law of segregation definition

Answer 33

mendel's first law of inheritance, which states that the two alleles for each trait separate during gamete formation and then unite at random with an allele from the other parent during fertilization

Question 34

pedigree definition

Answer 34

chart showing the line of descent, or ancestry, of an individual organism

Question 35

genetic map definition

Answer 35

a graphic representation of the order of genes in chromosomes spaced according to the amount of recombination that occurs between then

Question 36

loss-of-function mutation definition

Answer 36

a genetic alteration that reduces or eliminates the activity of a gene

Question 37

gain-of-function mutation definition

Answer 37

genetic change that increases the activity of a gene or makes it active in inappropriate circumstances usually dominant

Question 38

genetics definition

Answer 38

the study of genes, heredity, and the variation that gives rise to differences between one living organism and another

Question 39

classic genetic approach definition

Answer 39

a set of experimental techniques through which mutations are used to identify the genes responsible for an interesting phenotype

Question 40

genetic screen definition

Answer 40

experimental technique used to search through a collection of mutants for a particular phenotype

Question 41

what are conditional mutants

Answer 41

the protein product of a mutant gene is only defective under certain conditions

Question 42

complementation test definition

Answer 42

genetic experiment that determines whether two mutations that are associated with the same phenotype lie in the same gene or in different genes

Question 43

polymorphism definition

Answer 43

DNA sequence for which two or more variants are present at high frequency in the general population

Question 44

single-nucleotide polymorphism (SNP) definition

Answer 44

form of genetic variation in which one portion of the population differs from another in terms of which nucleotide is found at a particular position in the genome

Question 45

haplotype block definition

Answer 45

a combination of alleles or other DNA markers that has been inherited as a unit, undisturbed by genetic recombination, across many generations

Question 46

founder effect definition

Answer 46

a small number of individuals (some of whom by chance carry a particular mutation) become separated from the larger population. As this subpopulation expands, the frequency of the mutant allele becomes higher than it is in the population as a whole