Chapter 6 Chromosomes and genomes | Biology for VCE Units 1&2

gene

a section of DNA that has a functional purpose, such as coding for a protein that determines a trait

gene expression

the process of converting the instruction in a gene to a product, which is usually a protein

enzyme

a protein that speeds up biochemical reactions

allele

an alternative form of a gene

genome

the complete set of genetic material in a cell of an organism

somatic cell

a cell in an organism other than the reproductive cells

genomics

a branch of biology that investigates genomes

histone

the protein that DNA wraps around to form nucleosomes

nucleosome

DNA wrapped around histone proteins

homologous chromosomes

a pair of chromosomes, one maternal and one paternal, that have the same number and position of genes

locus

the location of a gene on a chromosome

sex chromosome

a chromosome that determines the sex of an organism

autosome

a chromosome that is not involved in sex determination

homogametic

an organism that has two of the same sex chromosomes, e.g. XX

heterogametic

an organism that has two different sex chromosomes, e.g. XY

X-inactivation

the process by which one X chromosome in females in inactivated

Barr body

a small dense structure containing an inactivated X chromosome

linked genes

genes located close together on the same chromosome that are generally inherited together

diploid

a nucleus or cell that contains two sets of chromosomes, one from each parent (2n)

haploid

a nucleus or a cell (usually an ovum or a sperm) that contains one set of chromosomes, so the chromosomes are not in pairs (n)

karyotype

the visual representation of the chromosomes from a cell nuclei of an individual

aneuploidy

a genetic abnormality in which an individual has an abnormal number of chromosomes

trisomy

a genetic abnormality in which an individual has an extra copy of a chromosome

monosomy

a genetic abnormality in which one chromosome of a pair of homologous chromosome is missing

meiosis

a type of cell division that produces gametes

germline cell

a diploid cell in ovaries or testes that undergoes meiosis to form gametes

crossing over

the process during prophase I of meiosis when homologous chromosomes exchange genetic material

recombinant chromosome

a chromosome formed after the crossing over of genetic material between homologous chromosomes

disjunction

the organised separation of chromosomes during meiosis

law of independent assortment

a law that states that homologous chromosomes orient themselves randomly along the middle of the cell during metaphase I

ovum

a female gamete

spermatogenesis

the meiotic process of sperm production in the testes

oogenesis

the meiotic process of ovum production in the ovaries

polar body

a small cell that buds off a developing ovum during oogenesis and does not develop into ova