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