definitions Flashcards
define genotype
genotype is the genetic constitution of an organism. for a particular gene this refers to the alleles present eg BB, Bb or bb.
define phenotype
phenotype is the appearance of a characteristic due to the expression of the genotype and it’s interaction with the environment
define alleles
alleles are different forms of the same gene
define locus
locus is the position of a gene on a chromosome. alleles occupy the same locus on each member of a pair of homologous chromosomes.
define dominant allele
a dominant allele is always expressed in the phenotype. it is the allele that is required for the characteristic to be expressed in the phenotype.
define recessive allele
a recessive allele is only expressed when the genotype is homozygous recessive, and no dominant allele is present
define homozygous
homozygous refers to both alleles being the same ie BB or bb
what are :
BB
bb
BB is homozygous dominant
bb is homozygous recessive
define heterozygous
heterozygous refers to both alleles differing ie Bb
define codominance
codominance is where both alleles are expressed in the phenotype
define multiple allelism
multiple allelism is where there are more than two alleles of a particular gene. however, only two alleles can be present in the genotype ie one on each member of a pair of homologous chromosomes.
define sex linked gene
sex linked gene is where the gene is carried on only one type of sex chromosome, usually the X chromosome
define diploid number
diploid number is the total number of chromosomes
define genes
genes are the base sequence of DNA on a chromosome that codes for the production of one or more specific protein
define continuous variation
continuous variation is a range of data where nothing fits into a category eg height or weight
