Question

Now, Danielle wants to know how her twins could look so diffe skin and Michael Jr. having dark skin. First, Danielle neede types of twins. Identical twins have exactly the same genes, since in a developing embryo splits into two embryos. Part III: Why do the twins look so different? er twins could look so different, with Michelle having light dark skin. First, Danielle needs to understand that there are two exactly the same genes, since identical twins originate when 7. How do you know that Michelle and Michael Jr. are not identical to Michelle and Michelle are tranternal twins, the re of a diftent eggs and spen as and sperm had differet alleles of the that influence skin color so they wone interited diffunt gene Michelle and Michael Jr. are fraternal twins, the result of two different eggs, each fertilized by a differer merent sperm. These different eggs and sperm had different alleles of the genes that influence skin cold in color, so Michelle and Michael Jr. inherited different alleles of these genes. To begin to underst Genotype Phenotype (skin color in to understand how Michelle could have light BB dark brown n and her twin brother, Michael Jr., could have dark Bb light brown skin, we w m, we will consider two alleles of one of the genes bb tan or skin color, Notice that for this gene, a heterozygous as an intermediate phenotype, halfway between the two homozygous individ individual has an intermedi When the phenotype of a two different types of homozygº hotype of a heterozygous individual is intermediate between the phenotypes of ent types of homozygous individual, this is called incomplete dominance. 8a. Explain how incomplete w incomplete dominance differs from a dominant-recessive pair of alleles. (h nk about the phenotypes of heterozygous individuals.) . OD. Explain how incomplete dominance differs from co-dominance. 3. The parents, Michael and Danielle, both have light brown skin and the Bb genotype. Draw a Punnett square and explain how these parents could have two babies with different color skin- one dark brown and the other tan.

Answer 1

Answer

Quesion 8 a.

In Incomplete dominance, two heterozygous alleles expressed together to develop a phenotypic trait. Here one allele is not completelety expressed over the other allele of the gene. Here a third phenotype is produced by the combination of the two alleles. In other words, neither of the allele is dominant over other.

In dominant - recessive pair of alleles, one allele is dominant and other allele is recessive when present in heterozygous condition. The dominant allele mask the expression of recessive allele. Here the phenotypic trait is influence by the dominant allele.

Question 8 b.

1. Incomplete dominance - Both the alleles are expressed together and phenotypes blend together to produce a third phenotype.

Co dominance - Both the alleles mix up and produce the phenotype equally

2. Incomplete dominance - A new phenotype is produced

Co dominance - new phenotype is not produced

3. Incomplete dominance - Neither of the parental phenotype is seen in offsprings

Co dominance - Both parental phenotype is seen in the offsrpings

4.   Incomplete dominance - Neither alleles is dominant

Co dominance - both the alleles are dominant

Question 9.

In the explanation, both the parents have light brown skin colour and the genotype is Bb.The cross is shown below with the help of Punnet square.

Parents phenotype - Light brown   x Light brown

Parents genotype - Bb x Bb

Gametes - B and b x B snd b

Cross   

  

gametes	B	b
B	BB	Bb
b	Bb	bb

Here BB individual is dark brown, Bb individual is light brown and bb individual is tan. When cross between two parents having Bb genotype, all the three phenotypes are seen in offsprings.