Question

if a child has cystic fibrosis then what do we know about the parents, did Did they each had to have at least one recessive allele? Did both parents and have a dominant alone? Did at least one parent have homozygous dominant? Or did both parents have to be homozygous recessive?

Answer 1

If a child has cytic fibrosis, then we can say that;

* Yes, ecah parent has one recessive allele.

We can say that each parent has one recessive allele. Each parents pass recessive allele in gamete. There is found fusion of gametes occur. This leads to homozygous recessive genotype and leads to disease in the child

* No,the both parents does not have homozygous dominant.

Because the dominant allele passes in the gamete. And the child can't be custic fibrosis.

* No, the atleast parent having homozygous dominant can not pass the disease to the child.

Because of presence of dominant allele bearing gamete passes to the child. That's why the child don't have diseases.

* Yes, this is possible.because each parent passes recessive allele to the gamete. That's why the child have disease be ause of homozygoys recessive genotype.