Question

The ABO blood groups.

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⁺.

Information

Flag question

Information text

Use the following pedigree to answer the next set of questions

Question 15

Not yet answered

Marked out of 1.00

Flag question

Question text

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. III-3

b. II-1

c. I-2

d. II-2

e. I-3

Clear my choice

Question 16

Not yet answered

Marked out of 1.00

Flag question

Question text

What is the genotype of II-1 at I andRh?

Select one:

a. I^Bi Rh⁺Rh^-

b. I^BI^BRh⁺Rh^-

c. I^BI^bRh⁺Rh^-

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

e. I^Bi Rh⁺Rh⁺

Clear my choice

Question 17

Not yet answered

Marked out of 1.00

Flag question

Question text

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. 1/4 or 0

b. 1/4

c. 1/500

d. 1/2500

e. 1/200

Clear my choice

Question 18

Not yet answered

Marked out of 2.00

Flag question

Question text

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. I-3

b. III-6

c. II-2

d. I-4

e. II-1

Answer 1