BIO 101 Ch9 Sexual Reproduction and Meiosis

What does meiosis produce?

Four genetically different gametes (sperm or egg), each with half the normal chromosome number.

Why must gametes have half the chromosomes?

So fertilization restores the full number: one set from each parent.

Haploid vs diploid?

Haploid (n) has one set of chromosomes. Diploid (2n) has two sets. Gametes are haploid and body cells are diploid.

Mitosis vs meiosis: number of divisions and daughter cells?

Mitosis: one division, two identical diploid cells. Meiosis: two divisions, four different haploid cells.

Why is meiosis called mitosis with extra steps?

It adds a second round of division and genetic shuffling, so it builds on the same phases.

What is crossing over?

Homologous chromosomes swap segments during prophase I, creating new allele combinations.

What is independent assortment?

Homologous pairs line up randomly at metaphase I, so each gamete gets a random mix of maternal and paternal chromosomes.

What separates in meiosis I?

Homologous chromosomes separate (this is what makes cells haploid).

What separates in meiosis II?

Sister chromatids separate, like mitosis.

Why does sexual reproduction increase variation?

Crossing over, independent assortment and random fertilization all shuffle genes.

What is isogamy?

Sexual reproduction where gametes look the same and are just called plus and minus types, not male or female. Seen in algae and protists.

How did male and female evolve?

Through gamete size asymmetry: small numerous sperm and large resource-rich eggs.

Germline vs somatic mutations?

Germline mutations are in gametes and can be inherited. Somatic mutations are in body cells and are not passed to offspring.

What is nondisjunction?

Chromosomes fail to separate properly in meiosis, giving gametes with extra or missing chromosomes (example: Down syndrome, trisomy 21).

How many chromosomes do humans have in body cells and gametes?

46 in body cells (23 pairs) and 23 in gametes.

How do you prep for a meiosis test per Dr. Hinn?

Make sure mitosis is solid first. Finishing the meiosis interactive means you are ready.

Mitosis or meiosis: growth and repair?

Mitosis.

Mitosis or meiosis: makes gametes?

Meiosis.