Non-Mendelian Genetics

Non-Mendelian Genetics Some traits don’t follow the simple dominant/recessive rules that Mendel first applied to genetics. Traits can be controlled by more than one gene. Some alleles are neither dominant nor recessive.

Incomplete Dominance One allele is not completely dominant over another. The heterozygous phenotype is a blending of the two homozygous phenotypes. Example: four o’clock flowers rr=red ww=white rw=pink (blending of the two alleles)

Check for Understanding: Spongebob and his friend, Patrick, love to go jellyfishing at jellyfish fields! The fields are home to a special type of green jellyfish known as Goobers. Many of the Jellyfish are yellow (YY) or blue (BB), but some end up green because of incomplete dominance. What is the genotype of a “Goober” green jellyfish?

What would happen if Spongebob and Patrick crossed two “Goober” green jellyfish? Complete the punnett square to determine the offspring phenotypes.

What would happen if they crossed a yellow jellyfish (YY) with a “Goober” green jellyfish? Complete the punnett square to determine the color of the offspring.

Codominance Two alleles are both expressed as a dominant phenotype Ex: Coat color in cows RR: Red WW: White RW: Roan, white with red spots (NOT pink!)

Check for Understanding: How is codominance different from incomplete dominance?

In some cats, the gene for fur color is codominant In some cats, the gene for fur color is codominant. The allele for black is B and the allele for orange is O. The heterozygous phenotype is known as calico. What is the genotype for black cats? What is the genotype for orange cats? What is the genotype for a calico cat?

If two calico cats were crossed, what is the probability of having an all black kitten? Use the punnett square to determine the probability.

Multiple-Allele Traits Codominance More than two choices of alleles are present for a trait ABO blood type has three alleles ABO Blood types: If both A and B are present, type is AB Neither is recessive Individuals can be type A, B, AB, or O (recessive)

What is blood made up of? The red blood cells The white blood cells contain hemoglobin. Red blood cells transport O2 and CO2 to and from body tissues. The white blood cells fight infection. The platelets help the blood to clot The plasma Fluid which contains salts and various kinds of proteins.

Determining Blood Type                                                                                               (not actual shape or size of antigens)                                                                                               (not actual shape or size of antigens)                                                                                               (not actual shape or size of antigens) Determining Blood Type Protein molecules found on the surface of RBC’s and in the blood plasma determine the blood type of an individual. Antigens are located on the surface of the red blood cells Antibodies are in the blood plasma.

What are the different blood groups? Blood group A (IA, IA ), (IA, i) have A antigens on the surface of red blood cells and B antibodies in blood plasma. Blood group B (IB, IB ), (IB, i) have B antigens on the surface of red blood cells and A antibodies in blood plasma.

What are the different blood groups? Blood group AB (IA, IB ) have both A and B antigens on the surface of red blood cells and no A or B antibodies in blood plasma. Blood group O (i, i) have neither A or B antigens on the surface of red blood cells but have both A and B antibodies in blood plasma.

Blood transfusions – who can receive blood from whom? The transfusion will work if a person who is going to receive blood has a blood group that doesn't have any antibodies against the donor blood's antigens.

People with blood group 0 are called "universal donors" and people with blood group AB are called "universal receivers."

Sex-Linked Inheritance

Review Males have an X and a Y chromosome Females have two X chromosomes These chromosomes determine sex, so genes located on these chromosomes are known as sex-linked genes.

The X chromosome is much larger than the Y, so it carries more genes than the Y chromosome, so sex-linked genes are always carried on the X. Disorders that are sex-linked are much more common in males, because they would only need 1 recessive allele to have the trait; rather than the two recessive alleles the females need.

Hemophilia Recessive trait Disorder where individuals are missing the normal blood clotting protein. Uncontrolled bleeds from minor cuts or bruises. Female genotype with Hemophilia: Male genotype with Hemophilia:

Colorblindness Recessive Inability to see certain colors Female genotype with Colorblindness: Male genotype with Colorblindness:

Duchenne Muscular Dystrophy Recessive Progressive weakening and loss of skeletal muscle. Defective version of gene that codes for muscle protein Female genotype: Male genotype:

Check for Understanding: A woman who is heterozygous for normal vision (XBXb) marries a man who is colorblind (XbY). What are the chances of them having a son or daughter who is colorblind? Remember: Colorblindness is a recessive trait.

A woman who is homozygous (XHXH) for normal blood clotting marries a man who has hemophilia (XhY). What are the chances of them having a son or daughter with hemophilia?

Sources credited to:. castle High School &. john hopkins medical Sources credited to: castle High School & john hopkins medical institute