Mitosis, Meiosis, Chromosomes, and Reproduction

Flashcards covering key vocabulary related to mitosis, meiosis, chromosome structure and number variations, and different life cycles and reproductive strategies, as discussed in the lecture.

Meiosis

The process of cell division that moves from diploid to haploid cells, resulting in a reduction of the chromosome count by half.

Tetrad (Bivalent)

A larger structure formed during meiosis where homologous pairs (sister chromatids and homologous chromosomes) associate, permitting crossing over of genetic material.

Crossing Over

The process where chunks of chromosomes move from one to another within a tetrad/bivalent, increasing genetic variation during division.

Synapsis

The process by which pairs of sister chromatids associate and stick together during meiosis.

Synaptonemal Complex

A sticky area between associating chromosomes during synapsis that connects them together, though not strictly required for pairing or recombination.

Chiasma

The visible joint or contact point between homologous chromosomes where crossing over has occurred, observed during meiosis.

Punnett Square

A diagrammatic tool used to look at the frequencies of different gene combinations and interpret them.

Independent Assortment

The random orientation of each homologous pair on the spindle axis during metaphase I of meiosis, leading to different combinations of parental chromosomes in gametes.

Anaphase I (Meiosis)

The stage in meiosis where homologous chromosomes separate and move to opposite poles, with sister chromatids remaining fused.

Meiosis II

A second round of meiotic division that immediately follows meiosis I without an S phase, where sister chromatids separate.

Diploid Dominant Life Cycle

A life cycle, common in most animal species, where the multicellular portion is diploid, and the haploid portion (gametes) is brief and intermittent.

Haploid Dominant Life Cycle

A life cycle, common in fungi and protists, where haploid cells become multicellular and grow, and the diploid zygote immediately engages in meiosis.

Alternation of Generations (Plants/Algae)

A life cycle where both the haploid (gametophyte) and diploid (sporophyte) portions engage in multicellularism and grow.

Gametophyte

The multicellular haploid plant generation in species with alternation of generations (e.g., ferns, mosses).

Sporophyte

The diploid plant generation in species with alternation of generations that produces haploid spores.

Euploid

Refers to an organism or cell having the anticipated or normal number of chromosomes for its species.

Aneuploidy

A condition where an organism has one extra chromosome or one chromosome missing, rather than an entire set of chromosomes.

Trisomy

A type of aneuploidy where there is one extra chromosome, resulting in three copies of a particular chromosome instead of the usual pair.

Monosomy

A type of aneuploidy where one chromosome is missing, resulting in only one copy of a particular chromosome instead of the usual pair.

Nondisjunction

An error made during meiosis where chromosomes in bivalents fail to separate during meiosis I, or sister chromatids fail to separate during meiosis II, leading to aneuploidy.

Polyploidy

A condition characterized by duplication events and increased numbers of chromosome sets present, common in plants (e.g., tetraploid or hexaploid wheat).

Haplo-diploid Sex Determination

A system of sex determination, seen in some insects like bees, where females are produced from fertilized eggs (diploid) and males from unfertilized eggs (haploid).

G-banding Pattern

A distinct banding pattern observed when condensed chromosomes are stained with substances like Giemsa (ESA mentioned in notes), used for identifying different chromosomes.

Centromere

The area of a chromosome where kinetochore proteins link, serving as the attachment point for spindle fibers during cell division.

Centrosome

The microtubule-organizing center in eukaryotic cells (specifically at the poles of a dividing cell) from which the spindle forms.

Centriole

Structures associated with microtubule organizing centers, found only in animal eukaryotic cells.

Deletion (Chromosomal Mutation)

A chromosomal mutation where a piece of a chromosome is missing, potentially affecting genes.

Duplication (Chromosomal Mutation)

A chromosomal mutation where a portion of a chromosome is repeated, potentially leading to overproduction of proteins.

Inversion (Chromosomal Mutation)

A chromosomal mutation where a portion of the chromosome is flipped, which can cause problems in gene encoding.

Translocation (Chromosomal Mutation)

A chromosomal mutation where a piece of a chromosome is moved entirely to another chromosome.

Hexaploid Wheat

A variety of wheat that has six pairs of chromosomes, often bred for features like cold tolerance and increased production.