BIO Notes - BIO Notes Inheritance Blending does not...

BIO Notes
Inheritance
Blending – does not exist (black + white  gray) isn’t true
Gregory Model
Alleles – different forms of a gene (the ones you get from mom/dad)
EX: S = round; s = wrinkled
Capitilization indicated dominancy; S is dominant, s is recessive
With 2 genes: you have possibilites
SS = dominant homozygous (round), Ss – heterozygous (round)
Ss = recessive homozygous (wrinkled)
Punnet
Square
S s
S SS Ss
s Ss Ss
Phenotype – what you see (a gene being expressed)
Genotype – the genes you have (whether expressed or not)
Incomplete Dominance – heterzygote form blends character together (not really blending)
Segregation – in gamete formation, the 2 genes of a parent separate in Meiosis 1 so that each
daughter cell (gamete) receives only one of the genes,
Generations – parent (P), first filial (F1), second filial (F2)
Phenotypes vs. Genotypes
How to determine if homozygous dominant (EE) vs. heterzygous (Ee)
•
To do this, cross with recessive homozygous (ee)
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If it is homozygous (dominant (EE)), all genotpes will be
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If it is heterozygous (Ee), half of the genotpyes will be recessive
Independent Assortment – 2 different traits on different non-homologous chromosomes will
segregate without regard to each other. (SsYy)
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Phenotypic ratios if heterozygous for both traits
Parental Generation (P)
F1 Generation
F2 Generation

Sperms
Eggs SY Sy sY sy
SY SSYY SSYy SsYY SsYy
Sy SSYy SSyy SsYy Ssyy
sY SsYY SsYy ssYY ssYy
sy SsYy SSyy SsYy ssyy
9 are round yellow
3 are wrinkle yellow
3 are round green
1 is wrinkled green
Incomplete Dominance : blending of different forms of alleles
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Differs from old idea of blending
Co Dominance – both alleles exposed in heterozygote
EX type AB blood cells
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There is Type A, B, O and AB (which isn’t A or B)
Multiple Alleles (more than 2 forms of a gene)
Blood Type Genotype Antibodies Made
A [A]A or [A]O Anti B
B [B]B or [B]O Anti A
AB [A]B Neither anti A nor Anti B
O [O]O Both Anti A and Anti B
Epitasis : One gene masks expression of any other genes affecting a trait
Example: Hair color has a lot of genes that affect it, sometimes there is a gene that masks
all other genes which is called epitasis
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In Labrador retrievers, the black gene is the epitasis (covers yellow genes).
There are several genes for one characteristic; an epitasis will mask all others
Pleiotropy – expression of an allele can affect expression of an unrelated phenotype

Example: a gene that affects shape of hemoglobin – sickle cell anemia (gene is for
hemoglobin but affects shape of cell)
Continuous Variation
Sex Chromosomes
Karyotyping : distinguishing among the different chromosomes – autosomes vs. sex
chromosomes

These determine the sex of an individual
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Females have XX (homozygous) males have XY (heterozygous)
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In mammals, male determines sex of offspring (in birds, females determine sex of
offspring)
Because Y chromosome is much shorter than X, for some genes there is no counterpart on the Y.
This is called a sex-linked characteristic because there is no counterpart on Y which allows an