Question

Type AB blood, Rh positive Type AB blood, Rh negative Type A blood, Rh negative Type AB blood, Rh negative Type B blood, Rh positive Type O blood, Rh negative -00 0.00 Type AB blood, Rh positive Type AB blood, Rh positive Type B blood, Rh negative

There are three main alleles in the ABO blood group system - I^A, I^B, and i. We've talked about the ABO system in class, you can find a brief explanation below and here.

The I gene encodes for a glycosyltransferase that modifies at the H antigen.

The glycosyltransferase encoded by I^A adds an 'A' sugar group to antigen H, the glycosyltransferase encoded by I^B adds a 'B' sugar group and i encodes an inactive glycosyltransferase that leaves the H antigen unmodified.

I^A leads to Type A blood; I^B to Type B; and ii to Type O. I^A is codominant to I^B and both I^A and I^B are dominant to i.

The H antigen itself is encoded by another gene - H. A rare mutation leads to an absence of H antigen (i.e., the person cannot make H antigen). The loss of H antigen is recessive (hh = loss of H antigen). This (hh) is called the Bombay phenotype. Because of the loss of H antigen individuals with the Bombay phenotype appear to have Type O blood regardless of their genotype at O (why doesn't really matter but you can find out more here).

H and I are on separate chromosomes and sort independently but if an individual is hh you won't be able to tell what their ABO phenotype is (remember the glycosyltransferase encoded by I modifies the H antigen, no antigen = nothing to modify).

There is one other common blood group factor - Rh.

Rh factor is a protein that can be present or absent on red blood cell surfaces. If you're Rh^- you don't have the protein on your red blood cells, if you're Rh⁺ you do. Rh^- is recessive to Rh⁺.

1) Which individual can you be certain has the Bombay phenotype?

Hint: look for offspring that don't make sense phenotypically based on what you know of their parents.

Select one:

a. II-2

b. I-3

c. I-2

d. II-1

e. III-3

2.) What is the genotype of II-1 at I and Rh?

Select one:

a. You don't have enough information to tell for sure

b. I^BI^BRh⁺Rh^-

c. I^BI^bRh⁺Rh^-

d. I^Bi Rh⁺Rh⁺

e. I^Bi Rh⁺Rh^-

^3.III-2 is expecting a child with III-1. III-1 has Type B blood and there is no history of the Bombay phenotype in III-1's family. If the carrier rate for the population is 1/50 what is the likelihood that their child will have the Bombay phenotype?

Select one:

a. 1/200

b. 1/500

c. 1/4

d. 1/4 or 0

e. 1/2500

4. You now know the phenotype of III-5; she is Type O blood Rh positive. Who do you know for certain are the carriers of the Bombay phenotype allele h (i.e., they are Hh)?

Select one or more:

a. II-1

b. I-3

c. III-6

d. I-4

e. II-2

Answer 1

ABO system determine if we would have blood group A,B, AB or O. I gene is responsible for this. And the activation of the I gene depends on H gene. I gene encodes glycosyltransferase which modifies H antigen and due to H antigen we have antigen A, B over RBC plasma.

Bombay phenotye is also called blood group O-. It do not have antigens. Bombay phenotye is a Homozygous Recessive condition shows when hh. It occurs when parents are either carrier (1/4) or are themselves hh. The parents with any blood group have a child with hh will have O- blood group.

Ans 1) the individual that I am certain has Bombay phenotye is ------ II 2.

Because his parents are A- and AB-. Offspring has different blood group from their parents. This means both his parents are carrier for h. And when both are Hh then 1/4 probability is of having a hh child.

Remember his parents can't be hh as they have A and AB blood group and Bombay phenotye always results in O- blood group due to failure in modification of H antigen.

Ans 2) Genotype of II -1 at I and Rh is ----

Blood group of II-1 = B+

His parents i.e. I-1 and I-2 = AB+ and AB-

Rh+ is Dominant over Rh-.

	IA	IB
IA	IAIA	IAIB
IB	IAIB	IBIB

So, Genotype I = IBIB

And Rh is Rh+Rh- ==== as one parent is Rh- and one is Rh +

Answe is Option b.

Ans 3) III -2 parents are II-1 and II-2. II -2 is affected from his parents I-3 and I-4 who were carriers so,

II-2 is affected by probability = 1/4 ( as 1/2 * 1/2 from parents).

II-1 is treated as Homozygous HH as it has no affected one and we have no further information too. = 1

So their offspring III-2 = 1/4 * 1 = 1/4 . So III-2 is carrier by 1/4 he is not affected one.

Now, III-1 has no history so = 1.

There is 1/50 carrier rate. So, the III-1 can be carreir by 1/50. So

probability of getting affected one = 1/50 *1/4

= 1/200

Option A is answer.

Ans 4) if III-5 have old group = O- ,then the individual II-1 is Carrier as II-2 is affected one. For the offspring to be affected it must get recessive gene from both the parents. If II-1 is Carrier then it's parents must be a carrier or anyone as they do not possess the phenotye.

II-2 is affected and his parents do not possess the phenotye then it means both his parents are carriers.I-3 and I-4.

So, from given options those who are carriers are Option a,b,c and d. II-1, I-3, I-4 and III-6 .

III-6 is Carrier as his parents II-1 is Hh and II-2 is hh. So,they will have offsprings with Genotype Hh and hh. And III-6 is not affected so not hh therefore he is a carrier.

Thank you....???