Allele
an alternative form of a gene
Chromosome
a structure in the nucleus made up of DNA which holds the genetic information of an organism
Homologous pair
a pair of chromosomes with the same genes but may have different alleles
Diploid
full or complete number of chromosomes 2n / 2 sets (= 46 in humans)
Dominant
an allele that is always expressed if present (only one copy needed)
Gamete
sex cell. Egg or sperm in humans
Somatic cells
body cells other than the sex cells.
Gene
a section of a DNA molecule that codes for a protein/characteristic
Gene pool
the total variety of alleles present in a sexually reproducing population available to be passed on to the next generation.
Genome
all of an organism's genes.
Haploid
half the normal number of chromosomes n / 1 set ( 23 in eggs or sperm)
Heterozygous
alleles are different eg. Tt
Homozygous
both alleles are the same eg. TT, tt
Linked Genes
Genes that are located on the same chromosome
Locus
position of a gene on a chromosome
Meiosis
type of cell division producing four daughter cells each genetically different, with half the number of chromosomes of the parent cell (produces gametes)
Crossing-over
exchange of genetic material between homologous chromosomes (the inner chromatids) during meiosis
Independent assortment
Each homologous pair of chromosomes are lined up randomly and are sorted independently of the other pairs during meiosis putting chromosomes/alleles into new combinations increasing genetic variation
Segregation
In meiosis the pair of alleles of a gene become separated into different gametes (so the allele can join with a different allele of that gene at fertilisation)
Mutation
a sudden change in the genetic make up / in base order of DNA of an organism
Phenotype
how the gene is expressed/what the organism looks like. eg. tall.
Recessive
an allele that only expressed when it is present in two copies - the dominant allele must be absent