Heredity not following the Rules Learning Goal: predict possible outcomes of various genetic combinations such as non-Mendelian inheritance.

Heredity not following

the Rules

Learning Goal:predict possible outcomes of various genetic combinations such as non-Mendelian inheritance

Incomplete dominance=Blending

A heterozygous condition in which both alleles are partially expressed, often producing an intermediate or blended phenotype (which is different than either of the homozygous forms).

Snapdragons

Incomplete dominance

Snapdragons

Incomplete dominance

RRR’R’

In Incomplete DOMINANCE, use the SAME letters since they both are weak!

RR’

RR RR’ RR’ R’R’

Incomplete dominance

Palomino horses are a cross between a chestnut horse and a cremello (white) color horse.

Practice the cross using a Punnett Square.

HH’ HH’

HH’ HH’

H

H

H’ H’

Codominance=Both Show

Codominance –Both phenotypes are dominant. Instead, the heterozygous individual expresses both phenotypes.

Co – bothboth are dominant enough to be expressed!!

Dominique chickens

Codominance

BB - Black WW - White BW - Black and White

BW BW

BW BW

B

B

W WCross a black Cross a black chicken with a chicken with a

white chicken and white chicken and what to you get if what to you get if

the traits are the traits are CODOMINANT?CODOMINANT?

Predict the Predict the outcome if BOTH outcome if BOTH

chickens are chickens are dominique dominique

(black and white) (black and white) ????????

In CODOMINANCE, use DIFFERENT letters since they both are strong!

Codominance

BB - Black WW - White BW - Black and White

BB BW

BW WW

B

W

B W

BB=1

BW=2WW=1

Codominance

Another example of codominance is ABO blood typing. The blood types A and B are codominant to each other; however, type O is actually recessive to A and B.

Codominance

IBIB or IBi

IAIA or IAiIAIB

ii

When both alleles exist, both are present!

Codominance

Blood Group

AntibodiesCan give

blood to…

Can receive

blood from

AB None ABA, B, AB,

and O

A B A and AB A and O

B A B and AB B and O

O A and BA, B, AB,

and OO

Which group is the universal donor?Which group is the

universal recipient?

Practicing Blood Types

A man of blood type IAIA marries a woman with blood type IAIB. What is the chance they will have a child with type IAIB blood?

IAIA IAIB

IAIA IAIB

IA

IA

IA IB

AB?

Practicing Blood Types #2

A man of blood type B marries a woman with blood type O. What is the chance they will have a child with type O blood?

IBi IBi

IBi IBi

IB

IB

i i

O?

IBi IBi

ii ii

IB

i

i i

There could be 2 genotypes for the man: BB or BO

Multiple Alleles

Each individual can only have 2 homologous chromosomes thus 2 alleles for a trait, but there could be more than 2 alleles present in a population. This type of inheritance is known as multiple alleles.

Why can you only have 2 genes for each trait?

Because… you only have 2 of each type of chromosome!!

Multiple Alleles - examples

Blood Type is an example of a trait that has multiple alleles. There are 3 possible alleles that could be inherited – A, B, and O, but you can only inherit 2 of them.

Coat color in rabbits is inherited as a series of multiple alleles.

Multiple Alleles - examples

How many alleles

are there for

rabbit coat color?

Multiple Alleles - examples

What are all of the possible genotypes for a 1. dark-gray coated rabbit? (4)

CC Ccch Cch Cc2. chinchilla rabbit (3)

cchcch cchch cchc3. Himilayan rabbit(2)

chch chc4. White rabbit (1)

cc

Why is dark gray

a capital C?

Multiple Alleles - examples

Predict the phenotype for a rabbit with a cchch. Chinchilla

Is it possible to obtain a white rabbit if one parent is white and the other is chinchilla?

Yes. Only if the chichilla is cchc

Polygenic Inheritance

Polygenic inheritance is the inheritance pattern of a trait that is controlled by two or more genes. The genes may be on the same chromosome or on different chromosomes. Height in humans Skin color

Polygenic Inheritance

Gametes  ABC   ABc   AbC   Abc   aBC   aBc   abC   abc 

ABC 6 5 5 4 5 4 4 3

ABc 5 4 4 3 4 3 3 2

AbC 5 4 4 3 4 3 3 2

Abc 4 3 3 2 3 2 2 1

aBC 5 4 4 3 4 3 3 2

aBc 4 3 3 2 3 2 2 1

abC 4 3 3 2 3 2 2 1

abc 3 2 2 1 2 1 1 0

Polygenic inheritance in people showing a cross between two bi-racial parents (AaBbCc x AaBbCc). Skin color is controlled by 3 different genes. The offspring contain seven different shades of skin color based on the number of capital letters in each genotype.

Sex-Linked Inheritance

X and Y Chromosomes are sex chromosomes

Remember that genes are located on chromosomes

XX are female and XY are male

Sex-Linked Inheritance

X and Y Chromosomes The X and Y chromosome carry different

genes, so they are NOT homologous.

Sex-Linked Inheritance

How Sex is Determined Treat the cross the same as a monohybrid Father has genotype XY Mother has genotype XX

XX XX

XY XY

X

Y

X XThe chance of

each sex being

born is 50%

Sex-Linked Inheritance

Traits found only on the X chromosome only are called sex-linked

Males will only have one copy of this gene, either the dominant or recessive form

Females will have two copies, and can be homozygous dominant, heterozygous, or homozygous recessive

Sex-Linked Inheritance

The Y chromosome is missing this portion of the X chromosome

X chromosome contains over 2300 genes

Y chromosome contains only 25 genes, including the sex-determining gene SRY SRY directs the formation of male

anatomy

Sex-linked genes

Sex-Linked Inheritance

Sex-Linked Crosses Write alleles so X is shown with a superscript

for the trait (XH Xh) Y has no superscript (Y) Females who are heterozygous for a

recessive trait are called carriers – they will not show the trait, but can pass it to offspring

Sex-Linked Inheritance

Sex-linked crosses Practice Problem Hemophilia, a disease where blood does

not clot properly, is caused by a recessive sex-linked allele. A female, who is a carrier for hemophilia and a normal male have a child. What is the probability that the child will be born with hemophilia?

XHXH XHXh

XH Y XhY

XH

Y

XH Xh

25%

chance

Hemophilia inheritance

POPQUIZ!! (Just kidding)

A roan cow is the product of a red cow and a white cow. What type of inheritance is exhibited?

A. Complete dominance

B. Codominance

C. Incomplete dominance

D. Sex-linked

E. Multiple alleles

F. Polygenic

POPQUIZ!!

Curly haired people have the genotype HH, while straight haired people have the genotype hh. A wavy haired person is heterozygous. What type of inheritance does this exhibit?A. Complete dominanceB. CodominanceC. Incomplete dominanceD. Sex-linkedE. Multiple allelesF. Polygenic

POPQUIZ!!

How well a person performs on an IQ test is controlled by multiple genes. Which of the following types of inheritance does this exhibit?

A. Complete dominanceB. CodominanceC. Incomplete dominanceD. Sex-linkedE. Multiple allelesF. Polygenic

POPQUIZ!!

Hair loss is a trait caused by a gene located on the X chromosome. This trait would be considered -

A. Complete dominance

B. Codominance

C. Incomplete dominance

D. Sex-linked

E. Multiple alleles

F. Polygenic

BTW

POPQUIZ!!

Kim has always wondered why her 2nd toe is longer than her first. She recently discovered that it is a dominant trait. This trait is considered to exhibit -

A. Complete dominanceB. CodominanceC. Incomplete dominanceD. Sex-linkedE. Multiple allelesF. Polygenic

POPQUIZ!!

Here is an easy one! Blood types fall under the category of which type of inheritance?

A. Complete dominance

B. Codominance

C. Incomplete dominance

D. Sex-linked

E. Multiple alleles

F. Polygenic

HEE HEE