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