Question

Jaden and Jordan are twins. Jaden has sickle cell trait, a genetically inherited disorder of the hemoglobin. Jordan does not have sickle cell trait. Are Jaden and Jordan fraternal or identical twins? Explain how these type of twins form. A woman with type A blood just had her first child. The child had type A blood. What are all of the possible blood types of the father? Explain you answer.

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A woman with type A blood just had her first child. The child had type A blood. What are all of the possible blood types of the father? Explain you answer.

Answer 1

1st question -

Sickle cell anaemia is an autosomal recessive condition where the person having homozygous recessive alleles are affected and the persons who are heterozygous i.e. they have one Normal allele and other affected allele are phenotypically Normal but the carrier of the disease. The gene responsible for the Haemoglobin beta-chain is mutated in case of sickle cell anaemia. This mutation is a single base mutation in which the GAG codon is replaced by GTG, thus the original amino acid glutamic acid is replaced by valine amino acid in case of sickle cell anaemia condition.  This one base change causes the allele to be sickle celled anaemia. The sickle cell anaemia is diagnosed by sickle-shaped RBC which infers with the oxygen-carrying capacity of the RBC and reduces the oxygen-carrying capacity.

Twins are those children who take birth by the same mother at the same time. Twins can be of two types: identical twins and fraternal twins.

Identical twins have completely the same genetic material as they formed from the same fertilised zygote. The zygote is somehow divided into two embryos after the fertilisation and the two offsprings develop into two identical offsprings.

Fraternal twins are not exactly similar to each other, They differ in their genetic structure. This difference in genetic differences arises because both the offsprings are developed by the two different egg cell fertilised by two different sperm cells but at the same time.

Here, Jaden and Jordan are twins. Jaden has sickle cell trait but Jordan does not have sickle cell trait. This clearly means that the two twins are different in their genetic make-up and this clearly indicates that they are fraternal twins.

2nd question -

Blood group in humans is determined by three different alleles of the gene. Thus it is a case of multiple alleles.
Also, it shows the phenomenon of co-dominance. Co - dominance is the phenomenon in which the two alleles of the genes are equally dominant to each other and when the two alleles are present in the heterozygous condition both the alleles show their effects equally.

If the red blood cell exhibits both the cell surface antigens designated glycoproteins A and B, we designated the blood type as AB. If the red blood cell exhibits in the cell surface antigen designated glycoproteins A, we designated the blood type as A. If the red blood cell exhibits in the cell surface antigen designated glycoproteins B, we designated the blood type as B. If the red blood cell exhibits none of cell surface antigens (designated glycoproteins A and B), we designated the blood type as O.

Also, it shows the phenomenon of co-dominance. Co - dominance is the phenomenon in which the two alleles of the genes are equally dominant to each other and when the two alleles are present in the heterozygous condition both the alleles show their effects equally.

IA allele is responsible for the cell surface antigen glycoproteins A and thus gives blood type A. IB allele is responsible for the cell surface antigen glycoproteins B and thus gives blood type B. Both IA and IB alleles are co-dominant to each other. While i is the recessive allele to both  IA and IB alleles. 'i' allele is responsible for none of the cell surface antigen glycoproteins and gives blood type O.

Thus, the following are the possible genotype and corresponding phenotype:

IA IA / IAi = blood type A

IBIB / IBi =  blood type B

IAIB =  blood type AB

ii =  blood type O
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