Question

You are a geneticist who has been approached by a family who suffers a mysterious disorder, which they called the Babbling disease. In order to study its inheritance, you interviewed different family members to record the incidence of the disorder throughout the generations. These are your data: Will and Sarah got married in 1965. Neither of them babbled. No one on Will’s side had the Babbling disorder. His dad Brett, his mother Victoria, his brother Jack or his sisters Nola and Valerie never showed signs of the disease. However, Sarah’s mother Sally, her brother Jim and her sister Tracy babbled, her dad Rick did not. Will and Sarah had four children Bob, Luke, Julie and Sue. Bob and Sue suffer from the Babbling disorder, Luke and Julie do not. Bob married Sarah, a non-babbler. They had two children, Josh and Jenn, none babble. However, he had a babbling daughter Melissa, from a first marriage with Suzie, a non-babbler. Luke married Lucy a non-babbler, they had a son Bill, who is not affected. Julie married Joe, they had two children; Marie who is affected by the Babbling disease and Robin who is not.

Using this information, draw the pedigree chart of this family, including the genotypes of all individuals and upload it in the next question (8 points).

What type of inheritance does this babbling disorder exhibit?

Autosomal Recessive

Autosomal Dominant

X linked Recessive

X linked Dominant

Y linked

Answer 1

The disease is inherited in an Autosomal Recessive manner.

If the normal allele is A and the allele causing the disorder is A^B, the genotypes are:

I-1 Brett A-
I-2 Victoria A-
I-3 Rick AA^B
I-4 Sally A^BA^B

II-1 Valeria A-
II-2 Nola A-
II-3 Jack A-
II-4 Will AA^B
II-5 Sarah AA^B
II-6 Tracy A^BA^B
II-7 Jim A^BA^B

III-1 Sarah A-
III-2 Bob A^BA^B
III-3 Suzie AA^B
III-4 Luke A-
III-5 Lucy A-
III-6 Julie AA^B
III-7 Joe AA^B
III-8 Sue A^BA^B

IV-1 Josh A-
IV-2 Jen A-
IV-3 Melissa A^BA^B
IV-4 Bill A-
IV-5 Marie A^BA^B
IV-6 Robin A-

Legend: A^BA^B are individuals affected by the disorder; A^BA are individuals which are definitely carriers of the disorder; A- individuals definitely have one normal copy of the allele and may/may not be carriers.