GENETICS Flashcards
How does genetic variation occur
Inherited mutations during S phase
Crossing over
Independant segregation
Random fertilisation
Define epistasis
Where an allele of one gene MASKS the expression of another gene
Eg - flower colour
Define a gene
a sequence of bases on a DNA molecule that codes for a protein which results in a characteristic
eg a gene for eye colour
define an allele
A different version of a gene
for example the gene is eye colour
the allele could be blue, green or brown
What is a genotype
the genetic makeup of an organism
what alleles does the organism have?? Aa AA aa
what is a phenotype
the expression of the genetic makeup and its interaction with the environment
eg brown eyes is shown
what is dominant
Shown by a capital letter, if one present its shown in phenotype
They over power the other allele
eg AA or Aa
what is recessive
only shown in phenotype if 2 recessive present
gets overpowered by a dominant allele
eg aa
what is codominant
Both alleles are expressed in the phenotype, neither one is recessive
eg sickle cell anaemia
What is a locus
the point on a chromosome where the alleles and genes are found
what is homozygous
2 copies of the same allele
eg AA or aa
what is heterozygous
carries 2 different alleles
eg Aa
what is a carrier
a person which carries an allele which can be passed onto offspring but is not shown in the phenotype
eg haemophilia
why are humans diploid
contain 2 sets of chromosomes
2 alleles for each gene
for a monohybrid cross how many things are crossed
2 with 2
eg AA with Aa