Jacaranda Science 2
9.4 Pedigrees
Name:
Activities
Think and discuss
1.Use Punnet squares and the dominant and recessive table on page 193 to help you answer the following questions.
(a)Find the probability (chance) that Sally (who is a pure-breeder for Darwin’s point) and Tom (who has no Darwin’s point) will have a child that has a Darwin’s point.
(b)Jenny has red hair and her husband Declan has dark hair. They have three children: one is a redheaded boy and the other two (a boy and a girl) have dark hair. Draw a small pedigree chart for this family’s hair colour, showing red-haired individuals as shaded boxes or circles, as shown on the opposite page.
(c)What is the chance of two parents who are both hybrids for tongue rolling having a child who can’t tongue roll?
(d)Michael is hybrid for a widow’s peak, whereas Debbie does not have a widow’s peak. What is the chance that they will have a child who has a widow’s peak?
2.The pedigree chart below shows how a characteristic called ‘hitch-hiker’s thumb’ is passed down through a family.
Given that ‘hitch-hiker’s thumb’ is a dominant trait (T), use the chart to complete the following table. If it is impossible to determine the genotype of a particular individual for the third column, just write ‘unknown’.
Name / Phenotype / GenotypeAl
Barbra
Colin
Diane
Eve
Fran
Greg
Heidi
Ivana
Jenni
Kitt
Liam
3.The pedigree below traces the recessive trait of albinism in a family. The shaded individuals lack pigmentation and are described as being albinos.
(a)List any observations from the pedigree that support albinism being a recessive trait.
(b)If the albinism allele was represented as n and normal skin pigmentation as N, state the possible genotypes for each of the individuals in the pedigree.
4.The pedigree below traces the dominant trait, a widow’s peak, in a family.
(a)List any observations from the pedigree that support the widow’s peak being a dominant trait.
(b)If the widow’s peak allele was represented as W and the straight hairline as w, state the possible genotypes for each of the individuals in the pedigree.
(c)If Jo and Mark were to have another child, what would be the chance of it having a widow’s peak?
(d)If Ronnie had a child with a man who did not have a widow’s peak, what is the probability that their child would have a widow’s peak?
(e)If Norm and Rona were to have another child, what is the probability that they would have a child without a widow’s peak?
Notes:
©John Wiley & Sons Australia, Ltd1