Kapitel 19

Question 1

An alternative form of a gene; for a given gene - many alleles may exist in the gene pool of the species.

Answer 1

allele

Question 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.

Answer 2

asexual reproduction

Question 3

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

Answer 3

bivalent

Question 4

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

Answer 4

chiasma (plural chiasmata)

Question 5

Experimental techniques used to isolate the genes responsible for an interesting phenotype.

Answer 5

classical genetic approach

Question 6

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

Answer 6

complementation test

Question 7

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

Answer 7

crossing-over

Question 8

Describes a cell or organism containing two sets of homologous chromosomes - one inherited from each parent. (See alsohaploid.)

Answer 8

diploid

Question 9

The fusion of two gametes—sperm and egg—to produce a new individual organism.

Answer 9

fertilization

Question 10

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

Answer 10

gain-of-function mutation

Question 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 germ cell.

Answer 11

gamete

Question 12

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

Answer 12

genetic map

Question 13

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

Answer 13

genetic screen

Question 14

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

Answer 14

genetics

Question 15

The genetic makeup of a cell or organism - including which alleles (gene variants) it carries.

Answer 15

genotype

Question 16

Describes a cell or organism with only one set of chromosomes - such as a sperm cell or a bacterium. (See alsodiploid.)

Answer 16

haploid

Question 17

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

Answer 17

haplotype block

Question 18

Possessing dissimilar alleles for a given gene.

Answer 18

heterozygous

Question 19

A gene - chromosome - or any structure that has a close similarity to another as a result of common ancestry. (See alsohomologous chromosome.)

Answer 19

homolog

Question 20

In a diploid cell - one of the two copies of a particular chromosome - one of which comes from the father and the other from the mother.

Answer 20

homologous chromosome

Question 21

Possessing identical alleles for a given gene.

Answer 21

homozygous

Question 22

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

Answer 22

law of independent assortment

Question 23

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.

Answer 23

law of segregation

Question 24

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.

Answer 24

loss-of-function mutation

Question 25

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.

Answer 25

meiosis

Question 26

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

Answer 26

pairing

Question 27

Chart showing the line of descent - or ancestry - of an individual organism.

Answer 27

pedigree

Question 28

The observable characteristics of a cell or organism.

Answer 28

phenotype

Question 29

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

Answer 29

polymorphism

Question 30

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

Answer 30

sexual reproduction

Question 31

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

Answer 31

zygote

Question 32

A heritable characteristic whose transmission to progeny does not appear to obey Mendel’s laws. Such characteristics - for example height - usually result from the interaction of multiple genes.

Answer 32

complex trait