Meiosis and Genetics Fundamentals

Flashcards covering the definitions and processes of meiosis, chromosomal structure, and genetic terminology as discussed in the lecture.

Meiosis

A process of cell division that starts with one somatic cell and ends with four haploid gametes containing half the number of chromosomes of the original cell.

Gametes

Reproductive cells, such as egg and sperm, that are haploid and contain $23$ chromosomes in humans.

Haploid

Cells that contain only one half of the number of chromosomes of a somatic cell.

Asexual reproduction

A form of reproduction, such as budding in hydra, where there is no involvement of egg and sperm, resulting in an identical copy of the parent.

Histones

Proteins around which DNA is tightly wrapped to form chromosomes.

Gene

A segment of DNA consisting of a specific sequence of nucleotides that codes for a specific protein.

Karyotype

A display of an organism's chromosomes, often prepared by halting mitosis at metaphase and using dyes to show color patterns.

Homologous chromosomes

Pairs of chromosomes that are very similar in nucleotide sequences, carry the same genes, and exhibit the same color patterns in a karyotype.

Autosomes

The first $22$ pairs of chromosomes in a human karyotype, labeled $1$ to $22$.

Sex chromosomes

The last pair of chromosomes, labeled X and Y, which determine the sex of an individual.

Trisomy 21

A medical condition also known as Down syndrome, characterized by having an extra chromosome at pair number $21$.

Gene locus

The specific location of a gene on a chromosome.

Diploid

A cell that contains the full set of chromosomes, which in humans is $46$ chromosomes.

Allele

Different versions of a particular gene characterized by a precise nucleotide sequence.

Dominant allele

An allele that is more common or commonly expressed, traditionally represented with an uppercase letter.

Recessive allele

An allele that is less common or less commonly expressed, traditionally represented with a lowercase letter.

Zygote

A diploid cell formed by the fusion of egg and sperm nuclei during fertilization, containing $46$ chromosomes in humans.

Crossing over

An event in prophase I where homologous chromosomes pair up and exchange segments of genetic material.

Recombinase

The specific enzyme that facilitates the process of crossing over.

Law of segregation

The principle that during gamete formation, each cell receives only one member of a pair of homologous chromosomes.

Law of independent assortment

The principle that chromosomes assort independently of each other during meiosis, meaning the fate of one chromosome does not affect another.

Non-disjunction

The failure of homologous chromosomes to segregate in meiosis I or sister chromatids to separate in meiosis II, resulting in cells with extra or too few chromosomes.