BIOL 111 Chapter 11

A collection of vocabulary flashcards covering key terms and concepts related to meiosis and reproduction based on lecture notes.

How are human chromosomes organized (23 pairs, 46 total)?

As homologous pairs: one chromosome of each pair from each parent. Pairs 1–22 = autosomes; pair 23 = sex chromosomes (XX or XY).

Define ploidy; diploid vs haploid.

Ploidy = # of chromosome sets. Diploid (2n) has 2 sets; haploid (n) has 1 set.

What is meiosis?

A 2-division process that reduces a diploid cell (2n) to four genetically unique haploid gametes (n).

Stages of Meiosis I (brief).

Prophase I (synapsis, crossing over), Metaphase I (tetrads align), Anaphase I (homologs separate), Telophase I (2 haploid duplicated cells).

Stages of Meiosis II (brief).

Prophase II → Metaphase II → Anaphase II (sister chromatids separate) → Telophase II (4 haploid unduplicated cells)

Ploidy before Meiosis I.

2n, duplicated chromosomes (after S-phase).

Ploidy after Meiosis I.

n, duplicated chromosomes.

Ploidy after Meiosis II.

n, unduplicated chromosomes.

Key events of Prophase I.

Synapsis → tetrads form → crossing over → chiasmata visible → recombinant chromatids form.

Key event of Metaphase I.

Tetrads align at metaphase plate with random orientation (independent assortment).

What happens during Anaphase I?

Homologous chromosomes separate; sister chromatids stay attached.

What happens during Telophase I + Cytokinesis?

Nuclear envelope reforms; 2 haploid duplicated cells form.

How does Meiosis II compare to mitosis?

Mechanically similar to mitosis but starts with haploid cells and produces haploid products.

Define synapsis.

Pairing of homologous chromosomes during Prophase I.

Define crossing over.

Exchange of DNA between non-sister chromatids in Prophase I.

Define recombinant chromosomes.

Chromosomes containing DNA from both parents due to crossing over.

Define chiasmata.

Physical points where crossing over occurred.

Define tetrad.

Paired homologous chromosomes (4 chromatids).

When do homologous chromosomes pair, recombine, and separate?

Pair + crossover in Prophase I; separate in Anaphase I.

When do sister chromatids stay attached and when do they separate?

Stay attached during Meiosis I; separate in Anaphase II.

Final product of meiosis.

4 genetically unique haploid gametes.

What are gametes?

Haploid reproductive cells (sperm/egg) produced by meiosis.

Explain independent assortment.

Random orientation of tetrads in Metaphase I → random maternal/paternal combos → variation.

Mitosis vs meiosis (overall).

Mitosis → 2 identical diploid cells;

Meiosis → 4 unique haploid cells; crossing over/independent assortment only in meiosis.

What cells undergo meiosis?

Germ cells in gonads (testes/ovaries).

Difference: Prophase I vs prophase (mitosis).

Meiosis I → synapsis, tetrads, crossing over
Mitosis → no pairing, no crossing over

Difference: Metaphase I vs metaphase (mitosis).

Meiosis I → tetrads align;

Mitosis → single chromosomes (sister chromatids) align.

Difference: Anaphase I vs anaphase (mitosis).

Meiosis I → homologs separate;

Mitosis → sister chromatids separate.

Difference: Telophase I vs telophase (mitosis).

Meiosis I → 2 haploid duplicated cells
Mitosis → 2 diploid unduplicated cells

Difference: Meiosis II vs mitosis.

Same mechanism, but meiosis II starts with haploid cells and produces haploid gametes.

Define asexual reproduction.

One parent produces genetically identical offspring.

Ways asexual reproduction occurs.

Budding, binary fission, cloning, vegetative propagation, parthenogenesis.

Organisms that reproduce asexually.

Bacteria, many plants, some simple animals.

Advantages of asexual reproduction.

Fast, no mate needed, energy efficient.

Disadvantage of asexual reproduction.

No genetic variation.

Define sexual reproduction.

Fusion of two gametes → genetically variable offspring.

Advantage of sexual reproduction.

Genetic variation increases survival.

Disadvantages of sexual reproduction.

Slower + requires mate.

Evolutionary importance of sexual reproduction.

Increases diversity → better adaptation.

Define diploid-dominant life cycle.

Diploid stage is multicellular and predominant; haploid only as gametes.

Steps of diploid-dominant life cycle.

Fertilization → diploid zygote → mitosis → adult → meiosis → gametes.

Relationship between meiosis and sexual reproduction.

Meiosis makes haploid gametes for fertilization.

Where meiosis occurs.

Males: testes. Females: ovaries.

Variation method #1 — crossing over.

Exchange of DNA in Prophase I → recombinant chromatids.

Variation method #2 — independent assortment.

Random tetrad orientation in Metaphase I → random combos.

Variation method #3 — random fertilization.

Any sperm can fertilize any egg → ~70 trillion combos.

Differences between eggs and sperm.

Eggs: large, few, costly. Sperm: small, many, cheap.

Spermatogenesis.

In testes → primary spermatocyte (2n) → meiosis I/II → 4 spermatids → sperm.

Oogenesis.

In ovaries → primary oocyte (2n) → meiosis I/II → one ootid + polar bodies → ovum.