ch 13: meiosis and sexual life cycles

meiosis

produces cells w/ half the chromosomes of the parent cell (haploid gametes); occurs only in specialized cells

fertilization

unites a sperm and egg, re-establishing pairs of homologous chromosomes w/ both parental and maternal genes (diploid zygote)

fertilization vs meiosis

n + n → 2n vs 2n → n

inheritance/heredity

transmission of traits from parents to offspring

variation

differences between offsprings and their parents

genetics

study of heredity and variation

genes

units of heredity; made up of segments of DNA

locus

specific position of a gene on a chromosome

gametes

reproductive cells that transmit genes to offspring (sperm and egg cells)

how many chromosomes do humans have?

somatic cell → 46 chromosomes

gametic cell → 23 chromosomes

asexual reproduction

one parent → genetically similar offspring/clones; no fusion of gametes

sexual reproduction

two parents → genetically unique offspring/variation; fusion of gametes

homologous chromosomes

one from each parent; same type of genes at same loci; may carry diff versions of those genes

pairs of chromosomes in humans

22 pairs of autosomes + 1 pair of sex chromosomes (XX or XY) → 23 pairs

diploid cell (2n)

two sets of chromosomes (human somatic cell: 2n=46)

haploid cell (n)

one set of chromosomes (human gamete: n=23)

life cycle

gen-to-gen sequence of stages in the reproductive history of an organism, from conception to production of its own offspring

overview of meiosis

1. interphase → DNA replication (1 diploid cell)

2. meiosis I → homologous chromosomes separate (2 haploid cells)

3. meiosis II → sister chromatids separate (4 haploid cells)

overview of meiosis I

1. prophase I

2. metaphase I

3. anaphase I

4. telophase I + cytokinesis