Genetics Flashcards
What is genetics?
Genetics is the study of variation and inheritance.
Define ‘gene’
A gene is a heritable factor that controls a specific characteristic.
Define ‘genome’
A genome is the whole of the genetic information of an organism.
Define ‘gene locus’
The position of a gene on a chromosome is called the gene locus.
Define ‘allele’
An allele is a form of a gene, differing from other alleles of the gene by a few bases at most and occupying the same locus as other alleles of that gene.
Define ‘gene mutation’
Gene mutation is a change to the base sequence of a gene.
What is ‘base substitution’?
When one base of a gene is replaced by another base.
Define ‘diploid’
When the nucleus contains two of each type of chromosome and has two full sets of chromosomes.
Define ‘haploid’
When cells only contain one of each type of chromosome and therefore have just one set.
Define ‘homologous’
Homologous chromosomes have the same gene as each other, in the same sequence, but not necessarily the same alleles of those genes.
Define ‘homozygous’
Having two identical alleles of a gene.
Define ‘heterozygous’
Having two different alleles of a gene.
Define ‘dominant allele’
An allele that has the same effect on the phenotype in a heterozygous individual (where it is combined with a recessive allele) as in a homozygous individual (where there are two copies of the dominant allele)
Define ‘recessive allele’
An allele that only has an effect on the phenotype in homozygous individuals (where there are two copies of the recessive allele). In heterozygous individuals the recessive allele is hidden by the dominant allele.
Define ‘genotype’
The alleles possessed by an organism.
Define ‘phenotype’
The characteristics of an organism.
What is sex linkage?
Sex linkage is the association of a characteristic with gender, because the gene controlling the characteristic is located on a sex chromosome.
What is a test cross?
In a test cross an individual that might be heterozygous is crossed with an individual that is homozygous recessive.
