Codominant vs Incomplete Dominant Whats the difference Beyond

Codominant vs Incomplete Dominant- What’s the difference?

Beyond Dominant and Recessive • Incomplete Dominance One allele is not completely dominant over the other – something in the middle is expressed Ex. Red and White Snapdragons Result can be heterozygous (Rr) or two separate dominant alleles (RW) each resulting in a mixture of both alleles

Another way that incomplete dominance can be expressed • Red= RR • White= WW • RW= pink- each allele is equally expressed to result in a blended product

One way to express incomplete dominance • RR (Red) X rr (White)= (Rr)Pink • Rr- results in a blended result of PINK

Incomplete Dominance Practice • In certain cats, tail length is determined by a gene that demonstrates incomplete dominance. The allele that causes a long tail (T) is not completely dominant over the allele that causes no tail (t). If a cat is heterozygous forthis trait (Tt), then the cat will have a short tail. What is the probability that the offspring will be manx cats (no tail) if a short – tailed cat is bred with a manx cat (no tail)?

Incomplete Dominance Practice • Incomplete dominance is seen in snapdragons. The allele that causes red flowers (F) is not completely dominant over the allele that causes white flowers (f). When a plant is heterozygous for the trait of flower color (Ff), pink flowers result. Cross two pink snapdragons, and provide the genotype and phenotype of all offspring.

Beyond Dominant and Recessive • Codominance Both alleles are expressed in the phenotype Ex. Cow Hair Color RR – Red WW – White RW – Roan (Red & White) Practice Codominance/Incomplete Dominance #1 -4

Beyond Dominant and Recessive • Multiple Alleles Genes have more then two alleles Ex. Blood Type A blood- AA or AO alleles A is dominant to O Type B blood- BB or BO alleles B is dominant to O Type AB- codominant- A and B alleles A nor B is dominant so both are expressed on organisms RBC Type O- recessive- OO alleles Both alleles must be recessive in order to have type O.

More on blood types…. . • The blood type determines what antibodies are located within the blood. Type A blood has type B antibodies. If type B blood is put into their bodies, their immune system reacts as if it were a foreign invader, the antibodies clump the blood - can cause death. • Type AB blood has no antibodies, any blood can be donated to them - they are called the "universal acceptors" • Type O blood has no surface markers on it, antibodies in the blood do not react to type O blood, they are called the "universal donors"

Co-dominance Practice • In humans, blood types A and B are equally dominant (codominant). Both types are dominant to type O. A man with type AB blood marries a woman with type O blood. Give the genotypes and phenotypes of all possible offspring.

Co-dominance Practice • If a man with blood type A, one of whose parents had blood type O, marries a woman with blood type O, what percentage of their offspring would have blood type OO?

Polygenic Traits • Traits that are controlled by the interaction of several genes. • Example: – Reddish brown eyes in varying degrees found in fruit flies is controlled by 3 genes – Human skin color is controlled by 4 different genes which result in a variety of skin color.

Sex-linked Genetics Ex. Colorblindness

Sex Chromosomes- last pair (23 rd) in a karyotype MALE KARYOTYPE FEMALE KARYOTYPE

Sex Chromosomes- last pair (23 rd) in a karyotype • Male – XY and Females – XX • The 23 rd pair of chromosomes will determine the gender of an individual • Very few genes are located on the Y chromosome……Most are located on the X • Sex linked alleles will ALWAYS be tracked on the X chromosome ONLY when we conduct practice genetic problems

Sex-Linked Genes • Ex. Colorblindness is carried on the sexchromosomes • It is a recessive trait – Xc How many genes do females need to express the trait (colorblindness)? 2 X c Xc How many genes do males need to express the trait (colorblindness)? 1 Xc. Y

Sex-Linked Punnett Square • Let C = Normal Vision and c = Colorblind • Cross: Normal Male ( ) x Carrier Female ( )

Sex-Linked Punnett Square C • Let C = Normal Vision and c = Colorblind • X C Y x X C X c = Normal Male x Carrier Female 1 st put male genotype C X Y on the top of the table & female genotype on the left side C X X c

Sex-Linked Punnett Square C • C – Normal Vision and c - Colorblind • X C Y x X C X c - Normal Male x Carrier Female 2 nd, cross them XC Y X C X c XC XC C X X c XCY c X Y

Sex-Linked Punnett Square C list the sex • C – Normal Vision and c - Colorblind 3 rd, and appearance C C c X Y x X X -Normal Male x Carrier Femaleof each possible offspring XC Y Offsprings: X C 1 Normal Female XC XC XCY 1 Normal (Carrier) Female 1 Normal Male X c C X X c c X Y 1 Colorblind Male

Sex-linked Practice • Hemophilia is a disease caused by a gene found on the X chromosome. Therefore, it is referred to as a sex – linked disease. The recessive allele causes the disease. A normal man marries a woman that is heterozygous for the trait. Give the genotypes and phenotypes of all possible offspring. Will any of their children have the disease?

PRACTICE and HW • Complete problems 1 -3 on the sex linked genetic practice problems sheet NOW! • Complete the remaining 3 Co-dominant and Incomplete dominant practice problems and Sex Linked practice problems # 4 -8 from today’s class for HW