Addenda: Heredity and Evolution
There was a slight confusion regarding a question in the NCERT which states:
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O is dominant? Why or why not?
Answer:
The information is INSUFFICIENT to tell whether A or O is dominant.
If ‘A’ is dominant, then:
Father (genotype may be AA/AO) since he has blood group A.
Mother is O, thus, genotype is OO (assuming that it is recessive).
Then it is possible to obtain a child with blood group O when father’s blood group is AO and mother’s is OO.
If ‘O’ is dominant, then:
Father’s Blood group A will be AA.
Mother’s blood group O will be OA or OO.
In this case also, after drawing the cross, we see that the child may have blood group O since OA also represents O.
Therefore, since on either of the assumptions the child can have blood group O, we CANNOT establish which characteristic is dominant.
Any queries regarding this can be written in the comments or mailed to nalinichandola@gmail.com OR agrim.singh@gmail.com
All the best for the boards to one and all! Only 12 days (sigh!) to go!
Agrim
February 18, 2009 at 10:47 am
Good eyes (and mind too)! Who spotted this error?
Best of luck to you too! But I think 12 days is MORE than enough to fine-tune everything.
March 6, 2009 at 5:35 pm
this has been a debatable question since it cropped up last year in the boards for science….its also there in the ncert and one couldn’t find a fixed answer for this…..no wonder only 4 kids got 100 in science last year in delhi!