PPT 12

Transcription-based vocabulary flashcards covering the processes of meiosis, genetic variation, and sexual reproduction life cycles.

Asexual reproduction

A form of reproduction where organisms produce genetically identical clones of themselves.

Sexual reproduction

A process where parents produce gametes (1n) that fuse to form a genetically unique zygote (2n).

Gametes

Specialized sex cells containing one set of chromosomes (1n) produced by meiosis.

Zygote

A fertilized egg formed when two gametes unite, containing two sets of chromosomes (2n).

Haploid

Cells containing one set of chromosomes, designated as 1n.

Diploid

Cells containing two sets of chromosomes, designated as 2n.

Somatic cells

All cells of a multicellular organism except the gametes.

Homologous chromosomes

Paired chromosomes of a diploid individual containing the same genes in the same location.

Meiosis

A type of nuclear division that forms 1n cells from 2n cells, involving one round of chromosome replication and two rounds of nuclear division.

Synaptonemal complex

A lattice of proteins that connects homologous chromosomes during prophase I.

Synapsis

The tight pairing of homologous chromosomes where genes are aligned perfectly with each other.

Crossing over

The exchange of chromosomal segments between non-sister chromatids, serving as the first source of genetic variation in meiosis.

Recombination nodules

Large protein assemblages that aid the crossing over process by allowing DNA to be cut and reattached.

Tetrad

Pairs of attached homologous chromosomes where all four sister chromatids are visible.

Independent assortment

A second source of genetic diversity occurs during Metaphase I, where homologous chromosomes align randomly and independently, resulting in 2^n possible combinations.

Interkinesis

A short interphase between meiosis I and meiosis II that lacks an S phase, meaning DNA is not duplicated.

Red Queen Hypothesis

An evolutionary theory proposed by Leigh Van Valen stating that species must constantly evolve and adapt to maintain fitness because they coevolve with competing organisms.

Germ cells

Specialized diploid cells produced in the gonads (testes and ovaries) that are capable of both mitosis and meiosis.

Gametophyte

A haploid multicellular plant stage that produces gametes from special cells through mitosis.

Sporophyte

A multicellular diploid plant stage formed by mitotic divisions of the zygote that undergoes meiosis to produce haploid spores.