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
for a dihybrid cross how many things are crossed
4 with 4
eg AaBb with AABB
What are the 2 generations when crossing
F1- offspring genotypes of first cross
F2- new offspring genotypes of previous offspring
what is the genetic cross called
a punnet square
what are the 4 blood types
A, B, O, AB
Is blood group O dominant or recessive
recessive
therefore you need 2 blood group O alleles to be blood group O
In a dihibrid cross why do we sometimes not get the expected ratio
sex linkage
autosomal linkage
epistasis
what chromosomes do females have
XX
what chromosomes do males have
XY
What is sex linkage
when an allele is located on a sex chromosome
eg colour blindness
haemophilia
in sex linkage does the Y chromosome on a male carry anything
no
what is autosomal linkage
when the 2 genes are found on the same chromosome
Therefore inherited together
what is the expected ratio when crossing 2 normal heterozygous individuals
9:3:3:1
in epistasis what is the ratio for a dihribyrid cross involving a recessive allele
9:3:4
in epistasis what is the ratio for a dihribyrid cross involving a dominant allele
12:3:1
what is a gene pool
the complete range of alleles present in a population
which hardy Weinberg equation predicts allele frequency
p + q = 1
which hardy Weinberg equation predicts genotype and phenotype frequency
p2 + 2pq +q2 = 1
in the hardy Weinberg equation what does p stand for
homozygous dominant
in the hardy Weinberg equation what does q stand for
homozygous recessive
in the hardy Weinberg equation what does pq stand for
heterozygous
