Meiosis and Sexual Life Cycles

Flashcards covering key vocabulary terms related to meiosis, sexual life cycles, heredity, variation, and the mechanisms of genetic diversity.

Heredity

The transmission of traits from one generation to the next.

Variation

The differences in appearance that offspring show from parents and siblings.

Genetics

The scientific study of heredity and variation.

Asexual Reproduction

A type of reproduction where a single individual passes genes to its offspring without the fusion of gametes.

Clone

A group of genetically identical individuals from the same parent.

Sexual Reproduction

A type of reproduction where two parents give rise to offspring that have unique combinations of genes inherited from the fusion of gametes.

Life Cycle

The generation-to-generation sequence of stages in the reproductive history of an organism.

Homologous Chromosome Pairs

Pairs of chromosomes, one from each parent, that are established by fertilization.

Meiosis

A process that separates homologous pairs, creating haploid gametes, reducing the number of chromosome sets from diploid to haploid.

Diploid (2n)

A cell or organism containing two complete sets of chromosomes, one from each parent.

Haploid (n)

A cell or organism containing a single set of unpaired chromosomes.

Gametes

Haploid cells (sperm or egg) produced by meiosis, involved in sexual reproduction.

Zygote

A diploid cell formed by the fertilization of two haploid gametes.

Meiosis I

The first meiotic division, where homologous chromosomes separate.

Prophase I (Meiosis I)

• Chromosomes condense.

• Homologous chromosomes pair up (synapsis) to form bivalents.

• Crossing over occurs between non-sister chromatids.

• Nuclear envelope fragments.

• Spindle fibers begin to form.

Metaphase I (Meiosis I)

• Homologous chromosome pairs (bivalents) align at the metaphase plate.

• Each pair orientates randomly with respect to the poles, contributing to independent assortment.

Anaphase I (Meiosis I)

• Homologous chromosomes separate and move towards opposite poles.

• Sister chromatids remain attached.

Telophase I (Meiosis I)

• Chromosomes arrive at the poles.

• Each pole now has a haploid set of chromosomes, each still consisting of two sister chromatids.

• Cytokinesis usually occurs, forming two haploid daughter cells.

Meiosis II

The second meiotic division, where sister chromatids separate.

Prophase II (Meiosis II)

• Chromosomes, each still composed of two sister chromatids, move towards the metaphase II plate.

• Spindle apparatus forms.

Metaphase II (Meiosis II)

• Sister chromatids align at the metaphase plate.

• The kinetochores of sister chromatids attach to microtubules extending from opposite poles.

Anaphase II (Meiosis II)

• Sister chromatids separate and move as individual chromosomes towards opposite poles.