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Ch. 10
Meiosis & Sexual Reproduction
33
Biology
Undergraduate 1
06/27/2012

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Term
Allele
Definition
Alternative form of a gene—alleles occur at the same locus on homologous chromosomes.
Term
Alteration of generations
Definition
Life cycle, typical of land plants, in which a diploid sporophyte alternates with a haploid gametophyte.
Term
aneuploidy
Definition
Individual whose chromosome number is not an exact multiple of the haploid number for the species.
Term
Barr body
Definition
Dark-staining body (discovered by M. Barr) in the nuclei of female mammals that contains a condensed, inactive X chromosome.
Term
Bivalent
Definition
Homologous chromosomes, each having sister chromatids that are joined by a nucleoprotein lattice during meiosis; also called a tetrad.
Term
crossing-over
Definition
Exchange of segments between nonsister chromatids of a bivalent during meiosis.
Term
deletion
Definition
Change in chromosome structure in which the end of a chromosome breaks off or two simultaneous breaks lead to the loss of an internal segment; often causes abnormalities—e.g., cri du chat syndrome.
Term
diploid (2n) number
Definition
Cell condition in which two of each type of chromosome are present.
Term
duplication
Definition
Change in chromosome structure in which a particular segment is present more than once in the same chromosome.
Term
euploidy
Definition
Cells containing only complete sets of chromosomes.
Term
fertilization
Definition
Fusion of sperm and egg nuclei, producing a zygote that develops into a new individual.
Term
gamete
Definition
Haploid sex cell; e.g., egg and sperm.
Term
gametogenesis
Definition
Development of the male and female sex gametes.
Term
gametophyte
Definition
Haploid generation of the alternation of generations life cycle of a plant; produces gametes that unite to form a diploid zygote.
Term
genetic recombination
Definition
Process in which chromosomes are broken and rejoined to form novel combinations; in this way offspring receive alleles in combinations different from their parents.
Term
homolougus chromosome
Definition
Member of a pair of chromosomes that are alike and come together in synapsis during prophase of the first meiotic division; a homologue.
Term
independent assortment
Definition
Alleles of unlinked genes segregate independently of each other during meiosis so that the gametes contain all possible combinations of alleles.
Term
interkenisis
Definition
Period of time between meiosis I and meiosis II during which no DNA replication takes place.
Term
inversion
Definition
Change in chromosome structure in which a segment of a chromosome is turned around 180°; this reversed sequence of genes can lead to altered gene activity and abnormalities.
Term
karyotype
Definition
Chromosomes arranged by pairs according to their size, shape, and general appearance in mitotic metaphase.
Term
meiosis
Definition
Type of nuclear division that occurs as part of sexual reproduction, in which the daughter cells receive the haploid number of chromosomes in varied combinations.
Term
monosomy
Definition
One less chromosome than usual.
Term
oogenesis
Definition
Production of eggs in females by the process of meiosis and maturation.
Term
polar body
Definition
In oogenesis, a nonfunctional product; two to three meiotic products are of this type.
Term
secondary oocyte
Definition
In oogenesis, the functional product of meiosis I; becomes the egg.
Term
sexual reproduction
Definition
Reproduction involving meiosis, gamete formation, and fertilization; produces offspring with chromosomes inherited from each parent with a unique combination of genes.
Term
spermatogenesis
Definition
Production of sperm in males by the process of meiosis and maturation.
Term
spore
Definition
Asexual reproductive or resting cell capable of developing into a new organism without fusion with another cell, in contrast to a gamete.
Term
sporophyte
Definition
Diploid generation of the alternation of generations life cycle of a plant; produces haploid spores that develop into the haploid generation.
Term
synapsis
Definition
Pairing of homologous chromosomes during meiosis I.
Term
translocation
Definition
Movement of a chromosomal segment from one chromosome to another nonhomologous chromosome, leading to abnormalities—e.g., Down syndrome.
Term
trisomy
Definition
Having three of a particular type of chromosome (2n _ 1).
Term
zygote
Definition
Diploid cell formed by the union of two gametes; the product of fertilization.
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