Offspring acquire genes from parents by inheriting chromosomes.
genes: segments of DNA that code for the basic units of hereditary and are transmitted from one generation to the next
gametes: reproductive cells that transmit genes from one generation to the next
locus: the location of a gene on a chromosome
Asexual reproduction: a single parent is the sole parent and passes copies of all its genes to its offspring (clone)
Sexual reproduction: two individuals contribute genes to the offspring
Fertilization and meiosis alternate in several life cycles.
life cycle: the generation to generation sequence of stages in the reproductive history of an organism
somatic cells: (46 chromosomes) any cells in the body that are not gametes
karyotype: picture of its complete set of chromosomes, arranged in pairs of homologous chromosomes from the largest pair, to the smallest pair
-meiosis and fertilization are the key events in sexually reproducing life cycles
fertilization: the combination of a sperm cell and an egg cell, one haploid gamete from the father fuses with one haploid gamete from the mother
meiosis: the type of cell division that reduces the numbers of sets of chromosome from two to one
Meiosis reduces the number of chromosome sets from diploid to haploid.
-the final result of meiosis is 4 daughter cells each of which has half as many chromosomes as the parent cell
Genetic variation produced in sexual life cycles contribute to evolution.
crossing over: during prophase I the exchange of genetic material on homologous chromosomes between nonsister chromatids occur
random fertilization: because each sperm and egg is different, as a result of independent assortment and crossing over, each combination of egg and sperm is unique
independent assortment of chromosomes: in metaphase I when the homologous chromosomes are lined up on the metaphase plates, they can pair up in any combination with any of the homologous pairs facing either pole