Q1. A recently married couple are expecting their first child. 


(a) Given the information in the partly completed diagram, complete the diagram to show the possible combinations of sex chromosomes that the baby could have.


(b) What will be the probability of the first child being a boy?


(c) From the information given, draw a punnet square to show the possible combinations of sex chromosomes that the mother and father's baby could have.



Q2. A male child has parents who are heterozygous for the polydactyly allele. Draw a punnet square and identify any offspring with this condition, also write to the ratio of affected to unaffected offspring (4 marks)


Q3. Jane and Mark are a couple. Jane has dimples in her cheeks, but Mark does not. The presence of dimples is thought to be caused by the presence of a dominant allele D. The recessive form of the allele is represented as d and we know that Jane is heterozygous for this dimples gene. (5 marks total).


(a) Should they decide to have children, what is the probability that their first baby will have dimples?


(b) Draw a genetic diagram and/or a punnet square to show the possible inheritance of the dimples gene. 


(c) Identify the phenotype of each possible outcome.



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