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'...Read More

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

Q7 Blood type is controlled by 3 alleles: A, B, O. A & B
are codominant, O is recessive. Complete the punnet
square:
Mark:
8

Q8 In humans, hemophilia is a sex-linked recessive trait. If a
female who is a carrier for hemophilia marries a male
with normal blood clotting, answer the following
questions. Plot the punnet square.
Mark:
9

Q9 Explain the importance of sex linked characteristics in
terms of evolution.
The humans consist of the sex chromosomes that helps them to
carry out their progeny in a very effective manner. Most of the
traits that are been owned by the individual is been passed to him/
her through the means of the somatic cells and the DNA. The
DNA consists of the genetic information that helps the individual
to show out the traits or the features that are been possessed by
their parents. The chromosomes comprise 33 pairs which include
one pair of sex chromosomes. These sex chromosomes help in the
better management of the inherited traits and lead to the
determination of the gender of the individual. The X chromosomes
is for the female and the Y chromosome is for the male.
These sex linked characteristics are very important for the
better management of the offspring's and meeting of the genetic
requirements of the person during the development. But most
important is that they play a very crucial role in the evolution
process. The sex linked characteristics kept intact the
characteristics that are been owned and showed by our ancestors,
without or with very less alteration. This also helped in getting the
idea of genetic modification or mutation that is been caused due to
various ergonomic or environmental factors and give the best of
the solution to the various genetic problems that are been faced or
occur during the finding the better cure of the various genetic
issues or disorder.
Mark:
10

Student Name: Sheet Number:
Q.
Mark:
11