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 Dominance 2.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
RWR RR W WW RR W W Homozygous Incomplete dominance: F 1 generation
RWR RR W WW RR W W 100% pink offspring
RRR RW W WW RW R W Heterozygous Incomplete dominance: F 2 generation
RRR RW W WW RW R W Heterozygous Incomplete Dominance F 2 generation A 1:2:1 ratio with 25% red, 50% pink & 25% white offspring Heterozygous
INCOMPLETE DOMINANCE __________ expected _____ ratio in F 2 generation _____________ organisms with one dominant and one recessive allele show a _________ in-between trait BLENDED DON’T SEE 3:1 Heterozygous Image modified from:
RR WW RW RRRWWW
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 ___ ___ ___ MULTIPLE ALLELE TRAIT A BO 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 BO 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. I A i, I A I A is Type A I B i, I B I B is Type B I A I B 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 = ______________ GLYCOPROTEINS REMEMBER sugars
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 “A” and “B” glycoproteins on its surface
B and O see A as Different! IMMUNE SYSTEM ATTACKS! Body images modified from: A and AB see A as “like me” DONOR BLOOD
A and O see B as Different! IMMUNE SYSTEM ATTACKS! Body images modified from: B and AB see B as “like me” DONOR BLOOD
Body images modified from: 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 DONOR BLOOD
A, B, and O see AB as Different! IMMUNE SYSTEM ATTACKS! Body images modified from: Only AB sees AB as “like me” DONOR BLOOD
Body image modified from: ______ can RECEIVE FROM EVERY BLOOD TYPE = ________________________ UNIVERSAL RECIPIENT ABAB AB can only GIVE to AB BUT...
BLOOD TYPE FREQUENCY IN USA A40% B10% AB4% O46%
IAIA IBIB IBIB IAIA i i ii IAIA i IBIB IOIO 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: MOM is _____ & BABY is _____ Rh + Rh - NO PROBLEMS
Can be a ___________ IF: Mom is _____ Baby is _____ Image modified from: 1 st 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 1 st 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?
cine/bloodtypinggame/ cine/bloodtypinggame/ Blood Typing – Remember the antibody will bond to something if it is present