Advanced higher biology key area 2.3 ( variation and sexual reproduction)

Chiasmata

A point at which paired chromosomes remain in contact during the first metaphase of Meosis and at which crossing over and exchange of genetic material occurs between the two strands

Crossing over

The exchange of genetic material between non sister chromatids of two homologous chromosomes that result in recombinant chromosomes during Meosis

Cytokenesis

The physical process of cell division which divides the cytoplasm of a parental cell into two daughter cells

Hermaphrodites

Species that have both functioning male and female reproductive organs

Heterogametic

Dissimilar sex chromosomes,

Homogametic

Sex chromosomes that do not differ in morphology ( results in only one type of gamete)

Homologous pair

A pair of chromosomes of the same size, centromere position and sequence of gene

Horizontal gene transfer

Inheritance of genetic material within a generation

Independent assortment

Formation of random combinations of chromosomes in Meosis and of homologous chromosomes by the passage of one of each diploid pairs of homologus chromosomes into each gamete indépendant of each other pair

Linked genes

Genes located on the same chromosome

Meosis

The division of cells in the nucleus, creating haploid gametes from a diploid gametocyte

Parthogenesis

Development of an offspring from a female gamete without fertilization

Recombination

The establishment of new combinations of alleles following crossing over

Sex chromosomes

A pair of chromosomes that can determine sex in some species

Sister chromatids

The genetically identical strands of chromosomes

SRY gene

Gene on the Y chromosome that determines the development of a male by expressing a protein called testes determing factor ( TDF)

Vegetative cloning

Any form of asexual reproduction occurring in plants in which a new plant grows from a fragment of the parent plant of specialised reproductive structure

X-chromosome inactivation

A process by which most of one X chromosome is randomly inactivated to prevent a double dose of gene products, which could be harmful to cells