genetics and inheritance Flashcards
genotype
all the genetic makeup of the organism
genepool
ll the alleles within an interbreeding population
population
all the individuals of the same species that occupy the same area
phenotype
expression of its genetic constitution and its interaction with the environment
alleles
different versions of the same gene
locus
position of allele on the homologous chromosomes
homozygous
two copies of a gene
heterozygous
two copies of gene are different alleles
co-dominant alleles
equally expressed in the phenotype
gene pool definition
all of the alleles of all the genes of all the individuals in a population at a given time
allelic frequency
The number of times an allele occurs within a gene pool
Hardy-Weinberg principle predicts that:
the allelic frequencies from one generation to the next will remain constant
factors affecting the Hardy-Weinberg principle
-no migration
-no gene mutation
-no selection for a particular allele
-large population
-random mating
Hardy-Weinberg equations
P + q = 1.0
P2 + 2Pq + q2 = 1.0
monohybrid inheritance meaning
inheritance of a single gene which determines a single characteristic
monohybrid inheritance -Codominance
do not show a standard dominant/recessive relationship
superscript letters are used for the allele
monohybrid inheritance - multiple alleles
several genes in a population
dominance hierarchy
There was 850 fruit flies in a population.
510 fruit flies had the genotype W(H)W(N)
255 fruit flies had the genotype W(N)W(V)
85 fruit flies had the genotype W(V)W(V)
CALCULATE ALLELE FREQUENCY OF ALLELE W(V)
1700 alleles in frequency
2x85=170
1x255=255
255+170=425
424/1700
0.25
950 flies in population
frequency of W(V) allele. was 0.2
calculate the number of expected individuals with the genotype W(N)W(V)
2X0.2X0.8=0.32
0.32X950=
304
dominant characteristics rules
- affected offspring must have at least one affected parent
- unaffected parents only have unaffected offspring
- if both parents are affected but child is unaffected, both parents must be heterozygous
recessive characteristics
unaffected parents can have an affected offspring
sex linked characteristics
controlled by genes located on one of sex chromosomes
what are the male chromosomes
XY
what are the female characteristics
XX
why do men have more genetic diseases
For sex-linked genes, a female would have to have two copies of a recessive allele for it to appear in the phenotype, whereas males only need one.
sex-link rules for recessive allele
-dads and daughters
daughter is affected
father is not affected
is recessive disease
so not sex-linked
Dihybrid inheritance definition
a phenotype is inherited as a result of two different genes, thus two characteristics
what is the ratio of dihybrid inheritence between homozygous parents?
9:3:3:1
Autosomal linkage
chromosomes that are not directly involved in determining the sex of an organism.
Crossing over process
Non sister chromatids on homologous pairs cross over to form a bivalent
Then forms a chiasma
Exchange of alleles to produce random recombinant offspring which display new combination of alleles
Linkage group definition
Set of genes on the same chromosomes which tend to be inherited together
What happens to the expected ratio when two genes are autosomal linked
Does not follow the expected phenotypic ratio
What happens when genes are autosomal linked
Don’t follow the expected phenotypic ratio
sex-linkage males vs females
female needs two copies of a recessive allele for it to appear in the phenotype, whereas males only need one
sex link rules - how to look if it is not sex-linked
-if daughter is affected, father is not (recessive)
-if son is affected, mother is not affected (domindant)
epistasis definition
interaction between two genes where one allele influences the expression of another
