Mendelian ExceptionsMendelian Exceptions
Mendel’s Principles Revisited
Inheritance of biological _____________ is determined by individual units known as ______.
During sexual reproduction, genes are passed from parents to _________.
Two or more forms of the gene for a single _____ exist, some forms of the gene may be _________ and others may be recessive.
characteristicscharacteristics
offspringoffspring
genesgenes
traittraitdominantdominant
Mendel’s Principles Revisited
Organisms typically have ____copies of each gene, (one from each _______)
An organism’s _____ of genes (2 alleles) are segregated from each other when ________ are formed.
Alleles for different ______ usually segregate _____________ of one another. (through meiosis)
(Law of Independent Assortment)(Law of Independent Assortment)
independentlyindependently
parentparenttwotwo
gametesgametes
genesgenes
pairpair
Independent Assortment in Peas
__ Round yellow__ Round green__ Wrinkled yellow__ Wrinkled green
99333311
Incomplete Dominance
In incomplete dominance, neither allele is __________ so there is a blending of ______ when two different alleles for the same trait occur together.
Colors blendblend together (______________
individuals = 3rd phenotype)
dominantdominanttraitstraits
heterozygousheterozygous
red whitepink
Incomplete Dominance
In Four O’ Clocks, if you cross a red _____(which is always pure) with a white _____ (that is also always pure) , you get apink _____ (whichis always hybrid /heterozygous
RRRRWWWW
RWRW
RWRW
RW RW
Incomplete Dominance
In another flower, if red ____ and blue ____ flowers are crossed, they produce a 3rd purple ____ flower
What would be the genotype ratio and phenotype ratio if you crossed two purple flowers?
RRRRBBBB
RBRB
Incomplete Dominance Cross of two purple flowers
____ X ____ What are gamete possibilities? genotype ratio
1RR : 2RB : 1BB1RR : 2RB : 1BB phenotype ratio
1red : 2 purple : 1 blue1red : 2 purple : 1 blue Can you have a
heterozygous red orhybrid blue flower? ___
B
R
R B
BBRB
RR RBred purple
purple blue
RBRB RBRB
nono
Familial Hypercholesterolemia
FF = cholesterol about 200 mg/dL Ff = cholesterol about 400 mg/dL ff = cholesterol about 800 mg/dL Ff have heart attacks in 20’s ff have heart attacks as children What type of inheritance is this?
Familial Hypercholesterolemia
F is allele for receptors in the liver that remove excess cholesterol from the blood
FF makes enough receptors removes the right amount of cholesterol
Ff only makes half the needed receptors ff makes no receptors This trait represents incomplete dominance
Problem
Tom is a 21 year old college student. His father died of a heart attack at age 25.
Tom is a vegetarian and eats no junk food. He has a fasting cholesterol of 435.
Tom’s wife, Mary, has a fasting cholesterol of 177.
They are contemplating having children What is the chance they will have a child
with abnormal cholesterol?
f
F
F FF
Ff
FF
Ff
F
FF = 200
Ff = 400
ff = 800
50% chance for abnormal cholesterol
California Court Case
1946 the California supreme court ruled that Charlie Chaplin was the biological father of child he claimed was not his.
His defense was that the baby had type B blood. He had type A and the woman who sued him had type O (These may not be the actual blood types, but it illustrates the point)
Was the court correct?
O
O
A AO
OO
AO
OO
O
AA, AO = Type A
BB, BO = Type B
AB = Type AB
OO = Type O
The judge should take a course in genetics!
Codominance Both _______ contribute to the phenotype
of the organism by showing up simultaneously (at the same time) in heterozygous
individuals. In cattle and horses, if you cross
a pure ____ (RR) with a pure ______ (WW), you get (RW) which produces the color _____.
allelesalleles
redredwhitewhite
roanroan
Codominance
These cattle or horses actually have both red and white hairs intermixed, or are spotted. Roan is a third ___________.
If you cross a roan with a white…
W
W
R W
WWRW
RW WW
phenotypephenotype
roan
roan
white
white
Codominance Andalusian chickens also show this
pattern of inheritance. If you cross a black (BB) chicken With a white (WW) chicken You get black+white speckled (BW) chicken
Multiple Alleles
In this pattern of inheritance, the genes have more than _____ alleles controlling them and are therefore said to have multiple alleles. No individual has more than _____ alleles, but there are more than _____ possible alleles in a population, so a ______ will be expressed in more than two forms.
twotwo
twotwotwotwo
traittrait
Multiple Alleles
Blood type in humans is an example of this inheritance pattern.
The ______ different blood groups:
A, B, O, and AB Are produced
by ______ different alleles:
A, B, and O
fourfour
threethree
Phenotype Genotype
A AA or AO
B BB or BO
AB AB only
O OO only
Multiple Alleles Examples of Blood type crosses
Phenotype(Blood Type
Multiple Alleles
Genotype
Blood Groups
Antigen on Red Blood Cell
Safe Transfusions
To From
Multiple Alleles
The example of _______ hair color, which has at least four different alleles, is seen in these different Rex rabbits.
rabbitrabbit
Polygenic Traits
Traits controlled by two or more genes Show a wide range of phenotypes The phenotype
is produced by the interaction of more than ________ of genes.
1 pair1 pair
Polygenic Traits These are called ___________ traits,
which means “having _______ genes”. In humans, _____ color, _____ color,
polygenicpolygenicmanymany
skinskineyeeye
Polygenic Traits These are called ___________ traits,
which means “having _______ genes”. In humans, _____ color, _____ color, and _____ color
polygenicpolygenicmanymany
skinskineyeeye
hairhair
Polygenic Traits These are called ___________ traits,
which means “having _______ genes”. In humans, _____ color, _____ color, and _____ color are just a few of
the many traits __________ by many genes.
polygenicpolygenicmanymany
skinskin
controlledcontrolled
eyeeye
hairhair
Polygenic Traits Sometimes the combination of the
different genes results in continuous __________ of these traits.
The combined size of all the ______ parts from head to foot, determines the _______ of the person.
variationvariation
bodybody
heightheight
James Bond Height Chart
Epistasis
One gene affects the expression of another H allele
Produces protein for A and B antigens to attach to red blood cells
h allele Protein has wrong shape and cannot attach to A and B
antigens A and or B antigens will fall off.
hh genotype + genotype for A,B or AB blood will have type O blood
Recessive epistasis in Labrador Retrievers
Penetrance
100% Everyone with the allele for a trait will have the
trait Less than 100%
Some individuals with the allele will not express the trait Due to interactions of other genes
Incomplete Penetrance for Polydactylism
Adam
Ben Joe Bill Don
Polydactyle
Normal
MarkFrank
TonyJohn
Bill did not express polydactylism
Expressivity
Symptoms vary in intensity in different people Due to gene interaction
Number of extra digits varies in people with polydactylism
Phenocopy
Trait caused by the environment that is similar to an inherited trait
Thalidomide causes symptoms of inherited phocomelia
Deafness
May be caused by 132 different recessive genes Man has aa for deafness on chromosome 1 & BB
for normal hearing on chromosome 5 Woman has bb for deafness on chromosome 5 &
AA for normal hearing on chromosome 1 What is the chance their children will inherit
deafness?
A
a
A Aa
Aa
Aa
Aa
a
AA = Normal
Aa = normal
aa = deaf
0% chance for deafness
BB = Normal
Bb = normal
bb = deaf
B
b
B Bb
Bb
Bb
Bb
b
Mitochondria
Release energy from food Have their own DNA
Mitochondrial DNA Many copies in each
motochondrion Mutate faster than nuclear
DNA Exposed to oxygen free
radicals No DNA repair enzymes
Mitochondria
Similar to DNA of prokaryotic cells Prokaryotic cells
Engulfed into eukaryotic cells in ancient times Have enzymes to release much more energy from
food
Mitochonria
Oocyte
Only nucleus of sperm enters oocyte. The baby will get all mitochondia from his mother.
Mitochondrial TraitsOnly inherited from mother
Mitochondrial DNA
37 genes Used for metabolic reactions that release
energy from food Mitochondrial myopathies
Weak muscles Cannot produce enough energy