Transcript Patterns of Inheretance

6 Patterns of Inheritance
1) Complete Dominance
(Mendelian Dominance) Homozygous
dominant and heterozygous individual has
same phenotype.
• TT = tall ; Tt = tall
• Results in only 2 variations
Polydactylism:
• Complete dominance
Other more complex types of
Inheritance
• Roses have flowers
of many different
colors
• Some alleles are
neither dominant
nor recessive, and
many traits are
controlled by
multiple alleles or
multiple genes
2) Incomplete Dominance
When one allele is not completely dominant over the
other.
• Heterozygous phenotype is in-between the two
homozygous phenotypes.
• Neither allele is dominant over the other, so they
mix
• New allele format
Snap dragons (four o-clocks) flower color
varieties: red, white, and pink
Red = F
White = F’
Incomplete Dominance
A cross
between 2
pink four
o’clock plants
produces
what
phenotypic
ratios?
3) Codominance
Phenotypes of both homozygotes produced
in heterozygote.
• Neither allele is dominant over the other
(both expressed).
• Chickens that have white feathers, black
feathers, and black and white feathers
• New allele format:
• B = black feathers
• W = white feathers
WW
BW
BB
What type of inheretance?
• MM’= Medium length legs
• Hh= hitch hikers thumb
• RB=red and black striped flower
4) Sex Linked:
• In humans, 46 total chromosomes w/ 23
pairs
• 22 of those are homologous = autosomal
• 1 pair are the sex chromosomes (different
for males and females)
4) Sex Linked:
• What are the chances of getting a boy to a
girl?
• With sex linked traits the gender will also
affect the probability.
• Some traits besides just sex determination
are found on the X chromosomes.
• Traits located on X chromosome
• Boys need only 1 allele to express trait.
• Colorblind
5) Multiple Allele:
When genes can have more than 2
possible alleles for a characteristic in the
gene pool.
Any one individual can still only inherit 2 of
those alleles however.
Different combinations of alleles result in the
colors shown here.
KEY
C=
full color; dominant
to all other alleles
cch = chinchilla; partial
defect in pigmentation;
dominant to
ch and c alleles
ch = Himalayan; color in
certain parts of the
body; dominant to
c allele
chhc
ch,cCc
h
ch
AIbino:
Chinchilla:
Himalayan:
cc CC,
cc
c,hCc
, or
cch
c,hhor
cch
c
Full color:
, or
Cc
Could a chinchilla bunny have a
himalayan baby if dad is full color?
c = albino; no color;
recessive to all other
alleles
5) Multiple Allele:
Ex: Many codominant alleles in human blood
types.
• The gene encodes an enzyme that adds sugar
molecules to the plasma membrane of red blood
cells. Act as recognizing markers for the
antibodies for the immune system.
• Gene is designated I and has 3 possible alleles.
• IA, IB, and i
• IA and IB are codominant.
• Both I’s are completely dominant over i.
• Figure out how to get the A, B, AB, and O blood
types
6) Polygenic Inheritance:
The inheritance pattern that is controlled by
many (2 or more) genes
When several genes reflect multiple additive
contributions to a single phenotype.
This results in traits that have a variety over
a wide range.
Ex: Height, Weight, Skin Pigment
The greater the # of genes, the wider the
range of variety.
6) Polygenic Inheritance:
Ex: 3 genes control the mass of bristle worms, and every dominant
allele contributes 1 g.
How many alleles/gene?
How many alleles are there for mass in bristle worms?
Homozygous skinny = 2g (genotype?)
How much mass would the fattest bristle worm have?
The mass of most bristle worms would be?
6) Polygenic Inheritance: