Unit 2, Topic 3

Chiasmata

a point at which paired chromosomes remain in contact during the first metaphase of meiosis, and at which crossing over and exchange of genetic material occurs between the strands

Crossing over

the exchange of genetic material between non-sister chromatids of two homologous chromosomes that results in recombinant chromosomes during meiosis

Cytokinesis

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

Hermaphrodites

species that have functioning male and female reproductive organs in each individual

Heterogametic

dissimilar sex chromosomes, for example mammalian males where the Y chromosome is much smaller than the X chromosome, resulting in two kinds of gamete

Homogametic

sex chromosomes that do not differ in morphology, resulting in only one kind of gamete

Homologous pair

a pair of chromosomes of the same size, centromere position and sequence of gene! one is of maternal origin and the other paternal

Horizontal gene transfer

inheritance of genetic material within a generation

Independent assortment - formation of random combinations of chromosomes in meiosis and of genes on different pairs of homologous chromosomes by the passage of one of each diploid pair of homologous chromosomes into each gamete independently of each other pair

Linked genes

genes located on the same chromosome

Meiosis

the division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte

Parthenogenesis

development of an offspring from a female gamete without fertilisation

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 development of a male by expressing a protein! called testes-determining 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 or a 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