Presentation is loading. Please wait.

Presentation is loading. Please wait.

Incomplete dominance This is when neither allele is dominant.

Similar presentations

Presentation on theme: "Incomplete dominance This is when neither allele is dominant."— Presentation transcript:

1 Incomplete Dominance, Codominance, Multiple Alleles, and Sex-Linked Genes

2 Incomplete dominance This is when neither allele is dominant.
Both alleles are expressed and contribute equally to the phenotype. A heterozygous genotype has an intermediate phenotype as there is partial influence from both alleles. Example: Red + White = Pink flower flower flower

3 Incomplete dominance Snapdragons can be
red (alleles = RR) white (alleles = rr) pink (alleles = Rr) If you cross a two pink flowers, is it possible to produce a white flower? ¼ Red ¼ White ½ Pink Yes!

4 Codominance Both alleles are dominant.
They are independent, so there is no 'blending' as in the snapdragons, instead the phenotype is a result of the full expression of both alleles. Example: black + White = B&W spotted dog dog dog

5 Codominance Dogs can be Black (alleles = BB) White (alleles = bb)
Spotted (alleles = Bb) Is it possible for a black dog to have one parent that is white? No!

6 Multiple alleles (blood typing)
In the case of the ABO blood grouping, there are 3 alleles for one gene They are written a little differently: i : this allele is recessive IA : this allele is co-dominant IB : this allele is co-dominant

7 Multiple alleles (blood typing)
Blood group (phenotype): A …………………………….. B …………………………….. AB …………………………… O …………………………….. Possible genotype: IA IA or IAi IBIB or IBi IAIB ii

8 Multiple alleles (blood typing)
A father with homozygous type A blood has a child with a mother that has heterozygous type B blood. Is it possible for them to have a child with type O blood?

9 Sex determination Gender is determined by sex chromosomes in many animals. The XY System: Female are XX, males are XY Y makes the guy!!! What are the odds that a couple have a boy? 50/50

10 Sex-linked genes Some genes are linked to the sex chromosomes and are inherited with them. Hemophilia is carried on the X chromosome. The normal allele is dominant (H) The allele for hemophilia is recessive (h)

11 Sex-linked genes XHXH = normal female XHXh = carrier female
XhXh = female w/hemophilia XHY = normal male XhY = male w/hemophilia A carrier does not have the disease, but can pass it on to their offspring.

12 Sex-linked genes If a female carrier has offspring with a normal male, what is the chances that their offspring will have hemophilia? 25%

13 Sex-linked genes In cats the allele for coat color is carried on the X chromosome. The alleles are black and orange but they are codominant. XBXB = black female XBY = black male XbXb = orange female XbY = orange male XBXb = tortoiseshell female

14 Sex-linked genes Can an orange male and a black female produce a tortoiseshell male? No!

15 Sex-linked genes What is the genotype of the father?

16 Sex-linked genes Mother can provide XB or XO
Father can provide Y plus 1 other allele. Since 1 offspring is XO XO, the father must provide 1 of these allele. Therefore, the father's genotype is XOY

Download ppt "Incomplete dominance This is when neither allele is dominant."

Similar presentations

Ads by Google