Ch 19 - Sexual Reproduction and Genetics

Question 1

allele

Answer 1

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

Question 2

asexual reproduction

Answer 2

mode of reproduction in which offspring arise from a single parent, producing an individual, genetically identical to that parent; includes budding, binary fission and parthenogenesis

Question 3

bivalent

Answer 3

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

Question 4

chiasma (plural chiasmata)

Answer 4

X-shapes connection between paired homologous chromosomes during meiosis; represents a site of crossing over between two non-sister chromatids

Question 5

classical genetic approach

Answer 5

experimental techniques used to isolate the genes responsible for an interesting phenotype

Question 6

complementation test

Answer 6

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

Question 7

crossing-over

Answer 7

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

Question 8

diploid

Answer 8

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

Question 9

fertilization

Answer 9

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

Question 10

gain-of-function mutation

Answer 10

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

Question 11

gamete

Answer 11

cell type in a diploid organism that carries only one set of chromosomes and is specialized for sexual reproduction. a sperm or an egg; also called a germ cell

Question 11

genetic map

Answer 11

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

Question 12

genetic screen

Answer 12

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

Question 13

genetics

Answer 13

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

Question 14

genotype

Answer 14

the genetic makeup of a cell or organism, including which alleles (gene variants) it carries

Question 15

germ line

Answer 15

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 16

haploid

Answer 16

describes a cell or organism with only one set of chromosomes, such as a sperm cell or bacterium

Question 17

haplotype block

Answer 17

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

Question 18

heterozygous

Answer 18

possessing dissimilar alleles for a given gene

Question 19

homolog

Answer 19

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

Question 20

homologous recombination

Answer 20

mechanism by which double-strand breaks in a DNA molecule can be repaired flawlessly; uses an undamaged, duplicated or homologous chromosome to guide the repair. during meiosis, the mechanism results in an exchange of genetic information between the maternal and paternal homologs

Question 21

homozygous

Answer 21

possessing identical alleles for a given gene

Question 21

law of independent assortment

Answer 21

principle that, during gamete formation, the alleles for different traits segregate independently of one another; Mendel’s second law of inheritance

Question 22

law of segregation

Answer 22

principle that the maternal and paternal alleles for a trait separate from one another during gamete formation and then reunite during fertilization; Mendel’s first law of inheritance

Question 23

loss-of-function mutation

Answer 23

a genetic alteration that reduces or eliminates the activity of a gene. such mutations are usually recessive; the organism can function normally as long as it retains at least one normal copy of the affected gene

Question 24

meiosis

Answer 24

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 25

pairing

Answer 25

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

Question 26

pedigree

Answer 26

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

Question 26

phenotype

Answer 26

the observable characteristics of a cell or organism

Question 27

polymorphism

Answer 27

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

Question 28

sexual reproduction

Answer 28

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

Question 29

sister chromatid

Answer 29

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

Question 30

SNP (single-nucleotide polymorphism)

Answer 30

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 31

somatic cell

Answer 31

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

Question 32

zygote

Answer 32

diploid cell produced by fusion of a male and a female gamete. a fertilized egg