Chapter 19 Flashcards
allele
An alternative form of a gene; for a given gene, many alleles
may exist in the gene pool of the species.
asexual reproduction
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
bivalent
Structure formed when a duplicated chromosome pairs
with its homolog at the beginning of meiosis; contains four
sister chromatids.
chiasma
X-shaped connection between paired homologous
chromosomes during meiosis; represents a site of crossingover between two non-sister chromatids.
crossing-over
Process whereby two homologous chromosomes break at
corresponding sites and rejoin to produce two recombined
chromosomes that have physically exchanged segments of
DNA.
diploid
Describes a cell or organism containing two sets of
homologous chromosomes, one inherited from each
parent. (See also haploid.
gamete
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.
genotype
enotype
The genetic makeup of a cell or organism, including which
alleles (gene variants) it carries.
germ line
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
haploid
Describes a cell or organism with only one set of
chromosomes, such as a sperm cell or a bacterium. (See
also diploid.)
homolog
A gene, chromosome, or any structure that has a close
similarity to another as a result of common ancestry
homologous recombination
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
meiosis
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
pairing
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.
phenotype
enotype
The observable characteristics of a cell or organism.