Genetics

Inheritance Patterns Dominant / Recessive Traits Incomplete 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 Complete Dominance Incomplete Dominance Codominance

Incomplete Dominance When an intermediate phenotype occurs and no allele dominates, incomplete dominance results. “blending inheritance”

Red Flower x White Flower

Incomplete dominance: F1 generation Homozygous R R W R W R W W R W R W Homozygous

Incomplete dominance: F1 generation 100% pink offspring R R W R W R W W R W R W

Incomplete dominance: F2 generation Heterozygous R W R R R R W W R W W W Heterozygous

Incomplete Dominance F2 generation Heterozygous A 1:2:1 ratio with 25% red, 50% pink & 25% white offspring R W R R R R W W R W W W Heterozygous

INCOMPLETE DOMINANCE DON’T SEE __________ expected _____ ratio in F2 generation _____________ organisms with one dominant and one recessive allele show a _________ in-between trait 3:1 Heterozygous BLENDED Image modified from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html

RR WW RW

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 type Allele choices ___ ___ ___ choices MORE than 2 MULTIPLE ALLELE TRAIT A B O

The pattern of sugars that is attached is determined by genes BLOOD TYPES have more than 2 allele choices = _________________________ MULTIPLE ALLELE TRAIT The pattern of sugars that is attached is determined by genes Allele choices are: _____ ____ ____ A B O

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-DOMINANCE Both traits are expressed together (NO BLENDING) in heterozygote Persons with an A allele AND a B allele have blood type AB

Membrane proteins with _______ attached that help cells recognize self REMEMBER Membrane proteins with _______ attached that help cells recognize self = ______________ sugars GLYCOPROTEINS http://www.mannanw.com/super-sugars.htm

BLOOD TYPES An A allele tells the cell to put “A” glycoproteins on 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 glycoproteins on its surface

A and AB see A as “like me” as Different! DONOR BLOOD A and AB see A as “like me” B and O see A as Different! IMMUNE SYSTEM ATTACKS! Body images modified from: http://www.new-fitness.com/images/body_shapes.jpg

B and AB see B as “like me” as Different! DONOR BLOOD B and AB see B as “like me” A and O see B as Different! IMMUNE SYSTEM ATTACKS! Body images modified from: http://www.new-fitness.com/images/body_shapes.jpg

O ____ can donate to EVERY BLOOD TYPE = _____________________ DONOR BLOOD O ____ can donate to EVERY BLOOD TYPE = _____________________ Nothing on surface to recognize as “NOT SELF” UNIVERSAL DONOR YOU DON’T HAVE ANYTHING I DON’T HAVE! Body images modified from: http://www.new-fitness.com/images/body_shapes.jpg

Only AB sees AB as “like me” DONOR BLOOD Only AB sees AB as “like me” A, B, and O see AB as Different! IMMUNE SYSTEM ATTACKS! Body images modified from: http://www.new-fitness.com/images/body_shapes.jpg

AB can only GIVE to AB BUT . . . ______ can RECEIVE FROM EVERY BLOOD TYPE = ________________________ UNIVERSAL RECIPIENT Body image modified from: http://www.new-fitness.com/images/body_shapes.jpg

BLOOD TYPE FREQUENCY IN USA 40% B 10% AB 4% O 46% http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/newton/BldTyping.html

Codominance: in humans Blood Type: phenotypic ratio 1:1:1:1 1 type A 1 type B 1 type AB 1 type O IA i IB IA IB IB i IO IA i i i

ABO SYSTEM is NOT THE ONLY ONE Rh+ Rh-

OTHER BLOOD TYPES ____________________ IF: NO PROBLEMS Rh+ MOM is _____ & BABY is ____ Rh+ MOM is _____ & BABY is _____ Rh+ Rh- Image modified from: http://www.wsd1.org/lessonplans/images/Body.gif

Can be a ___________ IF: Mom is _____ Baby is _____ PROBLEM Can be a ___________ IF: Mom is _____ Baby is _____ Rh+ Rh- 1st baby OK but few baby cells entering mom’s bloodstream put mom’s immune system on alert for + cells. Next + baby, mom’s immune system can attack baby as it is growing Mom given shot after 1st birth prevents this Image modified from: http://www.wsd1.org/lessonplans/images/Body.gif

Anything that can trigger this immune response is called an antigen 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 Patterns Dominant / Recessive Traits Incomplete Dominance Co-dominance Environmentally Influenced Multiple Alleles Polygenic Sex-linked Sex-Influenced

Polygenic Inheritance Two 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