Chapter 19

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

Answer 4

X-shaped connection between paired homologous

chromosomes during meiosis; represents a site of crossingover between two non-sister chromatids.

Question 5

crossing-over

Answer 5

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

Question 6

diploid

Answer 6

Describes a cell or organism containing two sets of
homologous chromosomes, one inherited from each
parent. (See also haploid.

Question 7

gamete

Answer 7

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 8

genotype

Answer 8

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

Question 9

germ line

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

haploid

Answer 10

Describes a cell or organism with only one set of
chromosomes, such as a sperm cell or a bacterium. (See
also diploid.)

Question 11

homolog

Answer 11

A gene, chromosome, or any structure that has a close

similarity to another as a result of common ancestry

Question 12

homologous recombination

Answer 12

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 13

meiosis

Answer 13

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 14

pairing

Answer 14

iring
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 15

phenotype

Answer 15

enotype

The observable characteristics of a cell or organism.

Question 16

sexual reproduction

Answer 16

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

Question 17

sister chromatid

Answer 17

Copy of a chromosome, produced by DNA replication, that

remains bound to the other copy

Question 18

somatic cell

Answer 18

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