Genetics

Inheritance PatternsDominant /

Recessive TraitsIncomplete Dominance Co-dominance

Environmentally Influenced

Multiple Alleles Polygenic

Sex-linked Sex-Influenced

• Recognize a variety of intermediate patterns of inheritance (codominance and incomplete dominance).

• • Interpret autosomal inheritance patterns: sickle cell anemia including the relationship to malaria (incomplete dominance), cystic fibrosis (recessive heredity), and Huntington’s disease (dominant heredity).

• • Solve and interpret codominant crosses involving multiple alleles including blood typing problems. (Blood Types: A, B, AB and O and Alleles: IA, IB, and i). Students should be able to determine if parentage is possible based on blood types.

• Recognize that some traits are controlled by more than one pair of genes and that this pattern of inheritance is identified by the presence of a wide range of phenotypes (skin, hair, and eye color). (polygenic)

• • Understand human sex chromosomes and interpret crosses involving sex-linked traits (color-blindness and hemophilia). Students should understand why males are more likely to express a sex-linked trait.

GENES are more complicated than MENDEL thought

3 Patterns of DOMINANCE

1. Complete Dominance2. Incomplete Dominance

3. Codominance

Incomplete Dominance

• When an intermediate

phenotype occurs and no

allele dominates, incomplete

dominance results.

• “blending inheritance”

• Red Flower x White Flower

RW R

R R

W

W W

R R

W

WHomozygous

Homozygous

Incomplete dominance: F1 generation

RW R

R R

W

W W

R R

W

W

Incomplete dominance: F1 generation

100% pink offspring

R R R

R W

W

W W

R W

R

WHeterozygous

Heterozygous

Incomplete dominance: F2 generation

R R R

R W

W

W W

R W

R

WHeterozygous

Incomplete Dominance F2 generation

A 1:2:1 ratio with

25% red, 50% pink

& 25% white

offspring

Heterozygous

INCOMPLETE DOMINANCE

__________ expected _____ ratio in F2 generation

_____________ organisms with one dominant and one recessive allele show a _________ in-between traitBLENDED

DON’T SEE

3:1

Heterozygous

Image modified from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html

RR WW

RW

RR RW WW

Type of Dominance?

Incomplete Dominance!

• In radishes, the gene that controls color exhibits incomplete dominance. Pure-breeding red radishes crossed with pure-breeding white radishes make purple radishes. What are the genotypic and phenotypic ratios when you cross a purple radish with a white radish?

• Parents ________ x _________• Genotype Ratio• Phenotype Ratio

codominance

• Not all alleles are dominant and

recessive. • Some alleles are equally strong

and neither are masked by the

other. • Alleles which are equally strong

are said to be "codominant“

codominance

• When both alleles are present,

they are both expressed in the

phenotype.

• When expressing codominant

alleles, both alleles are

represented by different

capitalized letters.

• A very common phenotype used in questions about codominance is roan fur in cattle. Cattle can be red (RR = all red hairs), white (WW = all white hairs), or roan (RW = red & white hairs together). A good example of codominance.

• What would be the genotype and phenotype ratio if a roan cow and a roan bull were crossed?

x

co- dominance

EX.

co- dominance

EX.

GENES are more complicated than Mendel thought

Some traits have ____________ allele __________

= ____________________

EX: blood typeAllele choices ___ ___ ___

MULTIPLE ALLELE TRAIT

A B O

MORE than 2 choices

BLOOD TYPES have more than 2 allele choices= _________________________

The pattern of sugars that is attached is determined by genes

Allele choices are:_____ ____ ____ A B O

MULTIPLE ALLELE TRAIT

Multiple Alleles• Multiple Alleles – more than 2 alleles in a

population for a trait, but a person can only inherit two. (one from father, one from mother)

Codominance: in humans

Blood Type:

A & B are equally strong.

(Co-dominant)

O is recessive.

IAi , IAIA is Type A

IBi, IBIB is Type B

IAIB is Type AB

ii is type O

CO-DOMINANCEBoth traits are expressed together

(NO BLENDING) in heterozygote

Persons with an A alleleAND a B allele have blood type AB

Membrane proteins with _______ attached that help cells recognize self

= ______________GLYCOPROTEINS

http://www.mannanw.com/super-sugars.htm

REMEMBER

sugars

BLOOD TYPESAn A allele tellsthe cell to put“A” glycoproteinson its surface

BLOOD TYPES A B allele tells the cell to put a different “B”

glycoprotein on its surface

BLOOD TYPES

An O allele tells the cell NOT to put

anything on the surface

A and B are CO-DOMINANT A cell with BOTH an A and a B allele has BOTH“A” and “B” glycoproteins on its

surface

B and O see Aas Different! IMMUNE SYSTEM

ATTACKS!Body images modified from: http://www.new-fitness.com/images/body_shapes.jpg

A and AB see Aas “like me”

DONORBLOOD

A and O see Bas Different! IMMUNE SYSTEM

ATTACKS!Body images modified from: http://www.new-fitness.com/images/body_shapes.jpg

B and AB see Bas “like me”

DONORBLOOD

Body images modified from: http://www.new-fitness.com/images/body_shapes.jpg

YOU DON’T HAVE ANYTHING I DON’T HAVE!

____ can donate to EVERY BLOOD TYPE = _____________________

Nothing on surface to recognize as “NOT SELF”

UNIVERSAL DONOR

O

DONORBLOOD

A, B, and O see AB as Different!

IMMUNE SYSTEM ATTACKS!Body images modified from:

http://www.new-fitness.com/images/body_shapes.jpg

Only AB sees ABas “like me”

DONORBLOOD

Body image modified from: http://www.new-fitness.com/images/body_shapes.jpg

______ can RECEIVE FROM EVERY BLOOD TYPE = ________________________UNIVERSAL RECIPIENT

AB

AB can only GIVE to ABBUT . . .

BLOOD TYPE FREQUENCY IN USA

http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/newton/BldTyping.html

A 40%B 10%

AB 4%O 46%

IA IB IB

IA i

i

i i

IA i

IB

IO

Codominance: in humans

Blood Type:

phenotypic ratio

1:1:1:1

1 type A

1 type B

1 type AB

1 type O

ABO SYSTEM is NOT THE ONLY ONE

Rh+ Rh-

MOM is _____& BABY is ____

OTHER BLOOD TYPES

____________________ IF:

Image modified from: http://www.wsd1.org/lessonplans/images/Body.gif

MOM is _____& BABY is _____

Rh+

Rh+

Rh+

Rh-

NO PROBLEMS

Can be a ___________ IF: Mom is _____ Baby is _____

Image modified from: http://www.wsd1.org/lessonplans/images/Body.gif

1st baby OK but few baby cells entering mom’s bloodstreamput mom’s immune system on alert for + cells.

Next + baby, mom’s immune system can attack baby as it isgrowing

Mom given shot after 1st birth prevents this

Rh+

PROBLEM

Rh-

• Anything that can trigger this immune response is called an antigen. An antigen can be a microbe such as a virus, or even a part of a microbe. Tissues or cells from another person (except an identical twin) also carry nonself markers and act as antigens. This explains why tissue transplants may be rejected.

• What are the possible blood types of the offspring between a woman whose blood type is heterozygous A and a man who has blood type 0?

• http://www.nobelprize.org/educational/medicine/bloodtypinggame/

• Blood Typing – Remember the antibody will bond to something if it is present

Inheritance PatternsDominant /

Recessive TraitsIncomplete Dominance Co-dominance

Environmentally Influenced

Multiple Alleles Polygenic

Sex-linked Sex-Influenced

Polygenic InheritanceTwo or more genes involved in determining

the phenotype of an organism. (wide variations)

In humans:• Height Nose length• Eye color Foot length• Intelligence • Behavior • Skin color

Polygenic Inheritance-does not follow Mendel’s laws