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Inheritance
genotype Thegenetic constitution of an organism
phenotype expression of genotype genetic constitution and its interaction with the environme
Dominant Allele alwaysexpressed in phenotype
Recessive Allele onlyexpressed when homozygous in absence of dominantallele
dominant Andes If bothpresent bothexpressed in phenotype
Co
seelinkedgene genelocated on only I seechromosome
autosomally linkedgenes genes on same chromosome
whydoresults of breeding experiment deviateslightlyfromexpectedratio
fertilisation israndom
not largeenoughsamplesize
largedeviation
Genes autosomallylinked or sexlinked
Epistasis
HOWdoes meiosis createthesegametes
separates alleles chromosomes
Independent assortment means either of X x can so w My
, hybrid Inheritance
Mono
Inheritance of a single gene
parentsgenecould be BB homozygous dominant Bb heterozygous bb homozygous recessive
eachgametecontainsonlyone allele fromgenotype
eg Bb B or b
Mendel
peaplants
A purple a white recessive
Bred 2 pureparents AA aa
gametes Aand A a and a
A Aa Aa
Aaa a
F all heterozygous purple
Bred 2 F offspring Aa A AA Aa
a Aa aa
Fz 751purple 2St white
, DihybridInheritance
Inheritance of 2 genes on 2 different chromosomes homologous pairs
note homozygous bothgenes homozygous
heterozygous bothgenesheterozygous
parents gametes
RRYT RY
Rrty RY Ry ry ry
ry
rryy
example cross parents Harb t AA
Bb
151 s'han
AB Ab AB ab
AB AABB Bb
BBAa
AABb Aa 8 whitebig
Ab AA
Bb AAbb Harsh Aabb s whitesmall
examplecross 2x heterozygous AaBbl
AB Ab AB ab
AB AABB Bb AaBB
AA AaBb 9whitebig
Ab Bb
AA AAbb AaBb Aabb 3 whitesmall
aB AaBB Bb
Aa aare aaBb 3 blackbig
ab Aa
Bb Aabb aaBb aabb blacksmall
note dihybridcross between 2x heterozygous is always 9 3 3 I
ad ar ra rr
a dominantphenotype
r recessive phenotype
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