Chromosomes & InheritanceGene Segregation during MEIOSIS3 significant results1. Haploid cells because of 2 divisions following only 1 DNA replication. Fusion of haploid nuclei (sexual reproduction) restores the diploid number

2. Metaphase 1- maternal & paternal chromosomes have equal chances of aligning on the equator, resulting in combinations of chromosomes from both parents

Chromosomes & InheritanceGene Segregation during MEIOSIS

2. Number of possible chromosome combinations in haploid nuclei from meiosis is LARGE (greater with more chromosomes)!Formula for possible chromosomal combinations in the resulting nuclei is 2n (n=number of chromosome pairs)3. Crossing-over generates more variation. It occurs every meiosis and sites vary every meiosis.

Chromosomes & InheritanceMEIOSIS in Animals & PlantsANIMALS•Most are diploid•Meiosis produces haploid gametes•Fusion of haploid gametes produces a diploid zygote during fertilization, which then carries out mitosis (sexual reproduction)•Gametes are the only haploid stage of the life cycle (formed in specialized cells)

•Males – sperm (spermatogenesis)•Spermatozoa (sperm) produced in testes

Chromosomes & InheritanceMEIOSIS in Animals & Plants

•Ovum (eggs) are produced in the ovaries

•Females – egg (oogenesis)

Chromosomes & InheritanceMEIOSIS in Animals & Plants

•Sexually reproducing plants have 2 phases1. Gametophyte (haploid) – gametes are

produced

PLANTS

2. Sporophyte (diploid) – haploid spores are produced

•Angiosperm (flowering plants)• Flower is where sexual reproduction

takes place

Chromosomes & InheritanceMEIOSIS in Animals & Plants

• Female reproductive organs:• Pistils – stigma, style, ovary• Stigma – sticky surface to collect

pollen • Style – thin stalk down which the pollen

tube grows from the stuck pollen

• Ovary – contains ovules (embryo sac with a single egg cell)

Chromosomes & InheritanceMEIOSIS in Animals & Plants

• Male reproductive organs:• Stamen – anther, filament• Anther – release the pollen• Filament – the stalk

Chromosomes & InheritanceMEIOSIS in Animals & Plants

• Plants produce gametes from “gametophytes”

• Plants life cycles include 2 phases called the alternation of generations1. Haploid gametophyte generation

• Begins with spores produced during meiosis

• In flowering plants the spores become pollen and embryo sac

Chromosomes & InheritanceMEIOSIS in Animals & Plants

2. Diploid Sporophyte generation• Initiated by fertilization• Specialized haploid cells (spores)

produced