2C Gene expression and GENETICS Flashcards
types of point mutation
• substitution
• deletion
• insertion
substitution mutation
type of point mutation; one base in a gene is substituted for another
deletion mutation
type of point mutation; a base is completely lost
insertion mutation
type of point mutation; an extra base is added into a gene
mutation
a permanent change in the DNA of an organism
gametes
haploid sex cells that fuse to form a new diploid cell (zygote) in sexual reproduction
chromosomal mutations
changes in the position of entire genes within a chromosome
whole-chromosome mutations
the loss of duplication of a whole chromosome
• e.g. down syndrome is caused by a whole-chromosome mutation at chromosome 21
mutagent
anything that increases the rate of mutation
e.g. X-rays, ionising radiation
variation
difference between organisms which may be the result of different genes or the environment they live in
phenotype
the physical traits, including biochemical characteristics, expressed as a result of the interactions of the genotype with the environment
genotype
the genetic make-up of an organism with respect to a particular feature
homologous pairs
matching pairs of chromosomes in an individual which both carry the same genes, although they may have different alleles
locus
the site of a gene on a chromosome
alleles
versions of a gene, variants
homozygote
an individual where both alleles coding for a particular characteristic are identical
heterozygote
an individual where the two alleles coding for a particular characteristic are different
dominant
a characteristic which is expressed in the phenotype whether the individual is homozygous or heterozygous for that allele
recessive
a characteristic which is only expressed when both alleles code for it; in other words, the individual is homozygous for the recessive trait
true breeding
a homozygous organism which will always produce the same offspring when crossed with another true-breeding organism for the same characteristic
monohybrid cross
a genetic cross where only one gene for one characteristic is considered
monohybrid cross
a genetic cross where only one gene for one characteristic is considered
codominance
in heterozygotes, where both alleles at a gene locus are fully expressed in the phenotype
sex-linked traits
characteristics which are inherited on the sex chromosomes