Sexual Reproduction and Meiosis

Asexual reproduction

only one parent; offspring are genetically identical; mutations are only source of variation

Sexual reproduction

two parents; offspring have unique combo of genes; lots of genetic variation

Haploid (n)

cell with one set of chromosomes

Diploid (2n)

cell with two sets of homologous chromosomes

Homologous chromosome (homologs)

chromosomes with same genes in the same order

Non-homologous chromosome

carry different sets of genes

Alleles

different versions of the same gene

Somatic cell

any cells other than reproductive cells

Germ cell

special cells that produce gametes

Egg

female gamete

Sperm

male gamete

Karyotype

preparation of metaphase chromosomes viewed under the microscope

Autosomes

chromosomes 1 through 22

Sex chromosomes

X and Y (XX female; XY male)

Gamete

haploid cells that don’t divide during meiosis

Zygote

product of two haploid cells’ fusion

Mitosis

how eukaryotic cells reproduce asexually

Meiosis

production of haploid gametes from diploid cells

Meiosis I

separates homologous chromosomes; produces haploid cells with replicated chromosomes

Meiosis II

separates sister chromatids; produces haploid gametes with unreplicated chromosomes

Prophase 1

replicated chromosomes condense, nuclear envelope breaks down; synapsis; spindle forms

Synapsis

when homologous chromosomes pair during Prophase I

Metaphase I

tetrads lined up at metaphase I plate by spindle microtubules

Anaphase I

homologous chromosomes separated; sister chromatids remain together

Telophase I; cytokinesis

pairs of chromatids moved to opposite poles, cell divides

Products of Meiosis I

2 haploid cells with replicated chromosomes

Tetrad

group of two homologous chromosomes

Independent assortment

the random alignment of maternal and paternal homologs at the metaphase I plate during meiosis I

Recombination (crossing over)

exchange of equivalent genetic material between homologous chromosomes during prophase I

Recombinant chromosomes

individual chromosomes that carry genes (DNA) derived from two different parents