Genetics Workbook: Solutions for Biology Students - Genetics

This document provides a comprehensive solution set for a genetics workbook, addressing various concepts in Mendelian genetics. The solutions include detailed Punnett squares, genotype and phenotype ratios for monohybrid crosses involving dominant and recessive traits (e.g., eye color, widow's peak, premature grey hair, and fainting in goats). The workbook also explores incomplete dominance, codominance (blood types), and sex-linked inheritance (hemophilia). The solutions cover a range of problems, from basic crosses to more complex scenarios involving multiple alleles and inheritance patterns. Furthermore, the document includes an explanation of the importance of sex-linked characteristics in evolution, highlighting their role in the transmission of genetic information and the determination of sex. The student work shows step-by-step solutions, making it an excellent resource for students studying genetics.

Genetics
Workbook
How to complete this workbook:
Work through each answer in the workbook as you go. If you run out
of space, simply use one of the additional sheets to record your
answer. Remember to add your name and the question number.
Remember to show your working out for each question!
You MUST answer ALL of the questions.
1

Show the punnet square and give the Genotype and Phenotype for the
following problems.

2
Show the punnet square and give the Genotype and Phenotype for the
following problems.
Q1 In humans brown eyes are dominant over blue eyes. What type
of offspring would you expect if you crossed a heterozygous
brown eyed person to a heterozygous brown eyed person?
B = brown eyes
b = blue eyes
Bb x Bb
Genotypes
BB = ¼ = 25%
Bb = ½ = 50%
Bb = ¼ = 25%
Phenotypes
Brown = 75%
Blue = 25%
Mark:

3
Show the punnet square and give the Genotype and Phenotype for the
following problems.
Q2 A widow’s peak hairline is dominant to straight
hairline. Cross a heterozygous widow’s peak hairline
person to a straight hairline person
W = widows peak
w = straight hairline
Hh x hh
Genotypes
Hh = ½ = 50%
Hh = ½ = 50%
Phenotypes
widows peak = 50%
straight hairline = 50%
Mark:

4
Q3 In humans premature grey hair is dominant over normal
hair colouring. Cross a homozygous premature grey haired
person to a homozygous normal haired person
G = grey hair
g = normal colouring
GG x gg
Genotypes
Gg = 4/4 = 100%
Phenotypes
Grey hair = 100%
Mark:

Q4 In goats, a recessive gene causes the goats to "faint" when
they are startled. A farmer breeds two goats (that have
never fainted) and their first offspring faints two days after
its birth. What must the parent's genotypes have been?
Show the cross to prove it.
Key
F : not faint
f : faint
Male : Ff

Female : Ff
Genotypes
FF = ¼ = 25%
Ff = 2/4 = 50%
Ff = ¼ = 25%
Phenotypes
Fainting = ¼
Normal = ¾
Mark:
5

Q5 Cross two heterozygous tan cows. Give genotypic and
phenotypic ratios.
BB=Black
BW=tan
WW=white
BW x BW
Genotype
BB = ¼ = 25%
BW= ½= 50%
WW = ¼ = 25%
Phenotype
Black = 25%
Tan = 50%
White = 25%
Genotype ratio: 1:2:1
Phenotype ratio : 1:2:1
Mark:
6

Q6 Fur color in rabbits shows incomplete dominance.
FBFB individuals are brown, FBFW individuals are cream,
FWFW individuals are white. What is the expected
ratio of a FBFW x FWFW cross?
BW x WW
Genotype
BW = 50%
WW = 50%
Phenotype
Cream = 50%
White = 50%
Genotype Ratio: 1:1
Mark:
7