Meiosis and Genetic Variation

These flashcards cover key vocabulary terms related to meiosis, chromosomal behavior, and genetic variation based on the lecture notes.

Homologous chromosomes

Chromosomes that have the same genes at the same loci but may carry different alleles.

Diploid

A cell containing two sets of homologous chromosomes; in humans, this is represented as 2n=46.

Haploid

A cell containing one set of chromosomes; in humans, gametes (sperm and eggs) are haploid, denoted as n=23.

Crossing over

The exchange of corresponding segments between nonsister chromatids of homologous chromosomes during meiosis I.

Independent orientation

The random arrangement of homologous chromosome pairs at metaphase I, leading to genetic variation in gametes.

Nondisjunction

The failure of homologous chromosomes or sister chromatids to separate properly during cell division, resulting in gametes with abnormal chromosome numbers.

Karyotype

A photographic inventory of an individual’s chromosomes, used to identify chromosomal abnormalities.

Trisomy 21

A chromosomal condition resulting from an extra copy of chromosome 21, commonly known as Down syndrome.

Meiosis I

The first division of meiosis, where homologous chromosomes pair and are separated into two daughter cells.

Meiosis II

The second division of meiosis, similar to mitosis, where sister chromatids are separated into haploid cells.

What is the primary purpose of meiosis?

To produce haploid gametes (sperm and egg cells) for sexual reproduction, ensuring genetic variation.

Aneuploidy

A condition in which a cell has an abnormal number of chromosomes, either more or fewer than the normal diploid set.

What is the net outcome of meiosis from one diploid cell?

Four genetically unique haploid daughter cells.

What are the key mechanisms contributing to genetic variation during meiosis?

Crossing over, independent orientation of homologous chromosomes, and random fertilization are key contributors.