Inheritance A2 Flashcards
define gene
a section of DNA that codes for a polypeptide
define allele
a version of a gene
define genotype
the genetic makeup of an organism
define phenotype
a person’s appearance due to the environment and genotype
define homozygous
when the alleles of a particular gene are identical
define heterozygous
when alleles of a particular gene are different
define dominant allele
an allele always shown in the phenotype
define recessive alleles
only shown in a phenotype if there are no dominant alleles
how many copies of a chromosome do haploid cells have
1
how many copies of each chromosome do diploids have
2
how many copies of each chromosome do polyploids have
many
define codominance
when both alleles are expressed in the phenotype
how to script codominance
with different superscripted letters e.g. C^w C^b
define multiple alleles
a gene with more than 2 possible alleles
define sex linked genes
a gene found on X or Y chromosomes
what sex chromosomes do males have
XY
what sex chromosomes do females have
XX
why are males more likely to be affected by an X linked condition
only have one X chromosome so only need one allele to be fully affected
no second X chromosome to mask condition
define dihybrid
two genes
different chromosomes
independent characteristics
one does not control the other
ratio for F2 generation
9:3:3:1
how to script dihybrid inheritance
four letters e.g. AaBB
define autosomal linkage
two genes on the same chromosome
what are the three possible genotypes in autosomal linkage
AABB, aabb, AaBb
process of autosomal linkage
GN and gn linked
gametes either GN or gn
only if crossing over occurs will there be Gn or gN gametes
so there will be fewer offspring with these alleles
why might the predicted ratios not occur in reality
only probabilities
small sample size
fusion of gametes is random
why use drosophila in experiments
short life cycle
small space needed
lays lot of eggs
not endangered
what are the two hardy-weinberg equations
p^2 + 2pq + q^2 = 1
p + q = 1
assumptions when doing a hardy weinberg
random mating no mutations large populations population genetically isolated no migration
evidence that proves it’s a recessive gene
2 parents don’t have condition but their child does
evidence that proves it’s a dominant gene
2 parents have condition but their child doesn’t
what does it mean for a parent to be a carrier
heterozygous with the condition on the recessive gene
evidence that proves it’s sex linked
dad always passes their X chromosome to daughter, if it is dominant the daughter will have it too
