Question

A family tree of sorts is called a pedigree. The symbols used for a pedigree are: O female, unaffected Siblings are placed in birth order from left to right and are labeled with Arabic numerals. Each generation is labeled with a Roman numeral. Therefore the male exhbiting the female, affected male, unaffected trait in the pedigree below in the bottom, center would be identified as Il-4. male, affected -utington's Disease REVIEW – Reading a pedigree and dominant/recessive Inheritance. For questions I and 2, refer to the chart below. 1. How many children did IIl and I12 have together? How many were girls? 2. Huntington's discase is a dominant disorder. Which members of the family (identified by both generation – I, II or III – and number individual; e.g. II 4) have Huntington's Disease? and 3. Fill out the Punnet Square below for Generation II 1 and 2 offspring. What is the probability that they will have a child with Huntington's disease? Use H for the allele for Huntington's, and h for the normal allele. 4. III 4 and 5 had a grandfather with Huntington's Disease. Is it possible for them to pass on the trait to their offspring? Why/why not? II III 5. Look at the pedigree ABOVE. Is this for a dominant or recessive disorder? How do you know?

Answer 1

1) II1 and II2 have 3 children, and 2 are girls ( females are represented by circles and males with squares).

2) Huntington's is a dominant trait so those individuals who are represented by shaded circles or shaded squares are affected by Huntington's disease.

I-1, II-2, II-3, II-7, III-3.

3) II-1 is not affected, so he is homozygous recessive hh, they have normal progenies so II-2 has to be heterozygous, II-2 is Hh.

Hh * hh

	H	h
h	Hh ( Huntington's disease)	hh ( normal)
h	Hh ( Huntington's disease)	hh ( normal)

4) No.Huntington's disease is a dominant trait, III-4 or III-5 are not affected means they did inherit H allele from their grandfather so they cannot pass the Huntington's disease to their progenies.