Unit 5 Chapter 10

Meiosis

Heredity

The transmission of traits from one generation to the next

Variation

Differences between members of the same species.

Genetics

The scientific study of heredity and hereditary variation

Genes

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).

Gametes

A haploid reproductive cell, such as an egg or sperm. Gametes unite during sexual reproduction to produce a diploid zygote.

Somatic Cells

Any cell in a multicellular organism except a sperm or egg or their precursors.

Locus

A specific place along the length of a chromosome where a given gene is located.

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

Homologous chromosomes

A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism’s father, the other from the mother. Also called homologs, or a homologous pair.

Sex Chromosomes

A chromosome responsible for determining the sex of an individual.

Autosomes

A chromosome that is not directly involved in determining sex; not a sex chromosome.

Ferilization

1). The union of haploid gametes to produce a diploid zygote.

2). THe addition of mineral nutrients to the soil.

Zygote

The diploid cell produced by the union of haploid gametes during fertilization; a fertilized egg

Meiosis

A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division buy only one round of DNA replication. It results in cells with half the number of chromosome sets as the original cell.

Meiosis 1

The first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Meiosis 2

The second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Synapsis

The pairing and physical connection of duplicated homologous chromosomes during prophase 1 of meiosis.

Crossing over

The reciprocal exchange of genetic material between nonsister chromatids during prophase 1 of meiosis.

Chiasmata

The X- shaped, microscopically visible region where crossing over has occurred earlier in prophase 1 between homologous non sister chromatids. Chiasmata become visible after synapsis ends, with the two homologs remaining associated due to sister chromatid cohesion.

Recombinant chromosomes

A chromosome created when crossing over combines DNA from two parents into a single chromosome.

Diploid (2n)

A cell containing two sets of chromosomes (2n), one set inherited from each parent.

Haploid (n)

A cell containing only one set of chromosomes (n).