Bio Ch 10 Flashcards
Meiosis
type of nuclear division that reduces the chromosome number from the diploid (2n) number to the haploid (n) number
Diploid (2n) number
total number of chromosomes, which exists in 2 sets
Haploid (n) number
half the diploid number, or a single set of chromosomes
Gametes
reproductive cells (often the sperm and egg); usually have the haploid number of chromosomes
Sexual reproduction
haploid gametes are produced during meiosis that subsequently merge into a diploid cell called a zygote
Zygote
diploid cell formed by the union of 2 gametes; the product of fertilization
Homologous chromosomes (homologues)
member of a pair of chromosomes that are alike and come together during synapsis during prophase of the first meiotic division
Alleles
alternate forms of a gene
Synaptonemal Complex
homologous chromosomes come together and line up side by side
Synapsis
Process of forming synaptonemal complex
Bivalent (tetrad)
2 homologous chromosomes that stay in close association during the 1st two phases of meiosis I; contains 4 chromatids
Crossing-over
exchange of genetic material between non-sister chromatids of a bivalent during meiosis I
Genetic recombination
process in which chromosomes are broken and rejoined to form novel combinations; in this way offspring receive alleles in combinations different from their parents
Independent assortment
the homologous chromosome pairs separate independently (in a random manner)
Fertilization
union of the male and female gametes
Interkinesis
short rest period prior to beginning the second nuclear division (meiosis II); DNA replication does NOT occur because the chromosomes are already duplicated
Spores
reproductive cells that develop into new multicellular structures without the need to fuse with another reproductive cell
Alternation of generations
life cycle, typical of land plants, in which a diploid sporophyte alternates with a haploid gametophyte
Life cycle
all the reproductive events that occur from one generation to the next similar generation
Gametophyte
haploid generation
Sporophyte
diploid generation
Gametogenesis
production of gametes
Spermatogenesis
in males, meiosis is a part of this, which occurs in the testes and produces sperm
Oogenesis
in females, meiosis is a part of this, which occurs in the ovaries and produces eggs
Secondary oocyte
in oogenesis, the functional product of meiosis I; becomes the egg
Polar body
nonfunctional product of oogenesis produced by the unequal division of cytoplasm in females during meiosis; in humans 3 of the 4 cells produced by meiosis are polar bodies
Nondisjunction
failure of chromosomes to separate; results in gain or loss of chromosomes
Euploidy
the correct number of chromosomes in a species
Aneuploidy
a change in the chromosome number resulting from nondisjunction during meiosis; seen in plants & animals; monosomy & trisomy are 2 aneuploid states
Monosomy (2n - 1)
occurs when an individual has only one of a particular type of chromosome when they should have two
Trisomy (2n + 1)
occurs when an individual has 3 of a particular type of chromosome when they should have two
Karyotype
a visual display of the chromosomes arranged by size, shape, and banding pattern; may be performed to identify babies with Down syndrome and other aneuploid conditions
Barr body
any additional X chromosomes become an inactive mass called this; provides a natural method for gene dosage compensation of the sex chromosomes and explains why extra sex chromosomes are more easily tolerated than extra autosomes
Deletion
occurs when an end of a chromosome breaks off or when two simultaneous breaks lead to the loss of an internal segment
Duplication
presence of a chromosomal segment more than once in the same chromosome
Inversion
occurs when a segment of a chromosome is turned around 180 degrees
Translocation
movement of a chromosome segment from one chromosome to another, nonhomologous chromosome
