1

1 Inheritance is the transmission of genetic information from generation to generation.

The boxes on the left show some of the terms used when describing inheritance.

The boxes on the right show definitions for these terms.

Draw four straight lines to link each term with its definition.

term definition

an allele that is expressed if it is present

dominant

genetic make-up of an organism

genotype

having two different alleles of a particular gene

heterozygous

having two identical alleles of a particular gene

phenotype

observable features of an organism

[4]

[Total: 4]
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2 The photograph shows a guinea pig with a rough coat and a guinea pig with a smooth coat.

The allele for a rough coat is dominant and represented by the letter R.
The allele for a smooth coat is recessive and represented by the letter r.

The pedigree diagram shows the inheritance of coat texture in some guinea pigs.

State the total number of male guinea pigs in the pedigree diagram.

.................................................................................................................................................. [1]

[Total: 1]
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3 .

Complete the sentence about breeding.

Two identical homozygous individuals that breed together will be

..................................................... -breeding. [1]

[Total: 1]
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4 The photograph shows a guinea pig with a rough coat and a guinea pig with a smooth coat.

The allele for a rough coat is dominant and represented by the letter R.
The allele for a smooth coat is recessive and represented by the letter r.

The pedigree diagram shows the inheritance of coat texture in some guinea pigs.

State the total number of guinea pigs with smooth coats in the pedigree diagram.

.................................................................................................................................................. [1]

[Total: 1]
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5 The photograph shows a guinea pig with a rough coat and a guinea pig with a smooth coat.

The allele for a rough coat is dominant and represented by the letter R.
The allele for a smooth coat is recessive and represented by the letter r.

The pedigree diagram shows the inheritance of coat texture in some guinea pigs.

State the letter of a guinea pig that has a homozygous dominant genotype in the pedigree diagram.

.................................................................................................................................................. [1]

[Total: 1]
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6 The photograph shows a guinea pig with a rough coat and a guinea pig with a smooth coat.

The allele for a rough coat is dominant and represented by the letter R.
The allele for a smooth coat is recessive and represented by the letter r.

Two guinea pigs are bred together.

• The genotype of the male guinea pig is RR .

• The genotype of the female guinea pig is Rr.

Complete the Punnet square to show the:

• possible genotypes of the offspring from this cross

• the probability of offspring having a smooth coat.
male

......................... .........................

......................... ......................... ........................

female
......................... ......................... .........................

probability of offspring having a smooth coat .....................................................

[3]

[Total: 3]
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7 Abnormal red blood cells occur because of a mutation in the gene for haemoglobin.
A
The allele for the normal form of haemoglobin is Hb .
S
The allele for the abnormal form of haemoglobin is Hb .

Draw a genetic diagram to determine the probability of two heterozygous parents having a child
S
who does not have the Hb allele.

offspring genotypes ..................................................................................................................

S
probability of offspring not having the Hb allele ...................................................................... [5]

[Total: 5]
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8 Colour blindness can be caused by a mutation in a gene. The gene is located on the X chromosome.

The pedigree diagram is for a family which has several people who are colour-blind.

Colour blindness is sex-linked.

State the genotype of person 5.

Use the symbols X and Y for the sex chromosomes and A for the dominant allele and a for the
recessive allele of the gene for colour blindness.

.................................................................................................................................................. [2]

[Total: 2]
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9 Colour blindness can be caused by a mutation in a gene. The gene is located on the X chromosome.

The pedigree diagram is for a family which has several people who are colour-blind.

Colour blindness is sex-linked.

State the evidence from the pedigree diagram that supports the idea that colour blindness is
sex-linked.

..................................................................................................................................................

..................................................................................................................................................

.................................................................................................................................................. [1]

[Total: 1]
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10 CFTR proteins in the cells lining the pancreatic duct move chloride ions out of the cells into the
duct.

If CFTR proteins do not move chloride ions, the liquid in the pancreatic duct becomes very sticky
and the duct can become blocked.

Blocked pancreatic ducts are one effect of cystic fibrosis, which is an inherited disease. Cystic
fibrosis is caused by a mutation of the gene that codes for the CFTR protein.

The diagram shows the pedigree diagram of a family that has two people who have cystic fibrosis.

The allele that causes cystic fibrosis is a recessive allele.

Describe and explain the evidence shown in the pedigree diagram that cystic fibrosis is caused by
a recessive allele.

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

.................................................................................................................................................. [2]

[Total: 2]
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11 CFTR proteins in the cells lining the pancreatic duct move chloride ions out of the cells into the
duct.

If CFTR proteins do not move chloride ions, the liquid in the pancreatic duct becomes very sticky
and the duct can become blocked.

Blocked pancreatic ducts are one effect of cystic fibrosis, which is an inherited disease. Cystic
fibrosis is caused by a mutation of the gene that codes for the CFTR protein.

The diagram shows the pedigree diagram of a family that has two people who have cystic fibrosis.
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Person 7 is expecting a child with a man who is heterozygous for cystic fibrosis.

Complete the genetic diagram to predict the probability of person 7 and the heterozygous man
having a child with cystic fibrosis.

Use the symbol A for the dominant allele and a for the recessive allele.

genotypes of offspring ..............................................................................................................

phenotypes of offspring ............................................................................................................

probability of having a child with cystic fibrosis ........................................................................ [5]

[Total: 5]
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12 Colour blindness can be caused by a mutation in a gene. The gene is located on the X chromosome.

The pedigree diagram is for a family which has several people who are colour-blind.
 14

Colour blindness is sex-linked.

Use the information in the pedigree diagram to complete the genetic diagram to show the probability
of person 3 and person 4 having another child with colour blindness.

offspring
genotypes ..........................................................................................................................

offspring
phenotypes ........................................................................................................................

probability of a child having colour blindness .................................................................... [5]

[Total: 5]
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13 The diagram shows the results of crossing a plant with red flowers with a plant with white flowers.

Both of the parent plants were homozygous for flower colour.

All of their offspring had red flowers.

The gene controlling flower colour in this plant species has two alleles:

• R is dominant and represents the allele for red flowers

• r is recessive and represents the allele for white flowers.

Describe the evidence shown in the diagram that supports the fact that R is the dominant allele for
flower colour in this species of plant.

..................................................................................................................................................

..................................................................................................................................................

.................................................................................................................................................. [1]

[Total: 1]
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14 The diagram shows the results of crossing a plant with red flowers with a plant with white flowers.

Both of the parent plants were homozygous for flower colour.

All of their offspring had red flowers.

The gene controlling flower colour in this plant species has two alleles:

• R is dominant and represents the allele for red flowers

• r is recessive and represents the allele for white flowers.

Another plant with red flowers was crossed with a plant with white flowers.

Some of the offspring plants from this cross had red flowers and some of the offspring plants had
white flowers.
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Complete the genetic diagram to show the results of this cross.

offspring genotypes ..................................................................................................................

offspring phenotypes ................................................................................................................ [5]

[Total: 5]
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15 The diagram shows the results of crossing a plant with red flowers with a plant with white flowers.

Both of the parent plants were homozygous for flower colour.

All of their offspring had red flowers.

State what is meant by the term homozygous.

..................................................................................................................................................

..................................................................................................................................................

.................................................................................................................................................. [1]

[Total: 1]
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16 The diagram shows a fruit fly with normal wings and a fruit fly with vestigial wings.

A gene determines whether fruit flies have normal wings or vestigial wings.

There are two alleles for this gene:

• A is dominant and represents the allele for normal wings

• a is recessive and represents the allele for vestigial wings.

A homozygous dominant fruit fly was crossed with a heterozygous fruit fly.
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Complete the genetic diagram to predict the probability of the offspring having vestigial wings.

[5]

[Total: 5]
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17 The diagram shows a fruit fly with normal wings and a fruit fly with vestigial wings.

A gene determines whether fruit flies have normal wings or vestigial wings.

There are two alleles for this gene:

• A is dominant and represents the allele for normal wings

• a is recessive and represents the allele for vestigial wings.

State the genotype of a pure-breeding fruit fly that has normal wings.

.................................................................................................................................................. [1]

[Total: 1]
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18 There are four blood groups in the ABO system in humans: A, B, AB and O.
A B o
The gene that determines blood group has three alleles: I , I and I .
A o B o
Parents with the genotypes I I and I I are planning to have more children.

Complete the genetic diagram to determine the probability that the next child will have blood
group O.

parental blood groups A B

A o B o
parental genotypes I I I I

Punnett square

phenotypes of the children .......................................................................................................

probability that the child will have blood group O ..................................................................... [4]

[Total: 4]

19 There are four blood groups in the ABO system in humans: A, B, AB and O.
A B o
The gene that determines blood group has three alleles: I , I and I .

Explain why the ABO blood group system is an example of co-dominance.

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

.................................................................................................................................................. [2]

[Total: 2]

20 The diagram is a Punnett square used to show the inheritance of sex in humans.
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(a) (i) Complete the Punnett square in the diagram.

male parent chromosomes

X Y

X
.................... ....................
female parent
chromoromes .

.................... .................... ...................

[2]

(b) Circle the percentage chance of a baby being male.

0 25 50 75 100 [1]

[Total: 3]
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21 The American writer Ernest Hemingway lived on the island of Key West in Florida, USA in the
1930s. During this time he was given a male cat by a sea captain.

The cat had more toes than usual. This inherited condition is called polydactyly. The allele for
polydactyly is dominant.

Here is part of a pedigree diagram for Hemingway’s cats.

State the genotypes of cats 5, 6 and 14 in the pedigree diagram.

Use the letters T and t.

cat 5 .........................................................................................................................................

cat 6..........................................................................................................................................

cat 14........................................................................................................................................ [3]

[Total: 3]
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22 The king cheetah is a rare variety of A. jubatus that has inherited striped fur markings.

The photographs shows a cheetah with spots and a king cheetah.

The diagram shows a pedigree diagram of a population of cheetahs.

Predict the probability of cheetah 14 being a king cheetah.

.................................................................................................................................................. [1]
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[Total: 1]
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23 The king cheetah is a rare variety of A. jubatus that has inherited striped fur markings.

The photographs shows a cheetah with spots and a king cheetah.

The diagram shows a pedigree diagram of a population of cheetahs.

Deduce the genotype of cheetah 11.

.................................................................................................................................................. [1]
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[Total: 1]

24 Colour blindness is a characteristic that is inherited. Colour blindness is more common in males
than in females.

Here is a pedigree diagram showing the inheritance of colour blindness in a family.

Using the symbols B and b, state the genotypes of individual 5 and individual 8 in the
pedigree diagram.

5 ...............................................................................................................................................

8 ............................................................................................................................................... [3]

[Total: 3]
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25 Colour blindness is a characteristic that is inherited. Colour blindness is more common in males
than in females.

Here is a pedigree diagram showing the inheritance of colour blindness in a family.

There was no history of colour blindness in the parents and grandparents of individuals 1 and 2.

Suggest how colour blindness first occurred in the family in the pedigree diagram.

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

.................................................................................................................................................. [2]

[Total: 2]
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26 Colour blindness is a characteristic that is inherited. Colour blindness is more common in males
than in females.

Here is a pedigree diagram showing the inheritance of colour blindness in a family.

Individual 3 is a carrier of colour blindness because she has one copy of the allele for
colour blindness but has normal colour vision.

Describe the evidence from the pedigree diagram that shows that individual 3 is a carrier.

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

.................................................................................................................................................. [3]

[Total: 3]
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27 The king cheetah is a rare variety of A. jubatus that has inherited striped fur markings.

The photographs shows a cheetah with spots and a king cheetah.

The diagram shows a pedigree diagram of a population of cheetahs.

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Describe how a breeder could determine the genotype of cheetah 17.

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

.................................................................................................................................................. [2]

[Total: 2]
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28 The American writer Ernest Hemingway lived on the island of Key West in Florida, USA in the
1930s. During this time he was given a male cat by a sea captain.

The cat had more toes than usual. This inherited condition is called polydactyly. The allele for
polydactyly is dominant.

Here is part of a pedigree diagram for Hemingway’s cats.

Explain why none of the offspring of cats 3 and 4 have inherited polydactyly.

Use the information from the pedigree diagram in your answer.

..................................................................................................................................................

..................................................................................................................................................

.................................................................................................................................................. [1]

[Total: 1]
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29 The length of hair in cats is controlled by a single gene.

• The allele for short hair is dominant – H

• The allele for long hair is recessive – h

The photograph is of two cats.

cat A cat B

State the genotype of a pure-breeding short-haired cat.

.................................................................................................................................................. [1]

[Total: 1]
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30 The length of hair in cats is controlled by a single gene.

• The allele for short hair is dominant – H

• The allele for long hair is recessive – h

The photograph is of two cats.

cat A cat B

Two cats with the genotypes HH and hh were bred together.

Predict the percentage of offspring that are heterozygous.

.....................................% [1]

[Total: 1]
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31 The length of hair in cats is controlled by a single gene.

• The allele for short hair is dominant – H

• The allele for long hair is recessive – h

The photograph is of two cats.

cat A cat B

The table shows some of the genetic and physical features of the cats in the photograph.

Complete the table.

cat A cat B

phenotype long hair .................................................................

genotype ................................................................. HH or ......................................................

[3]

[Total: 3]

32 There are four blood group phenotypes A, B, AB and O in humans.

State the name of the type of inheritance that is shown by blood groups.

.................................................................................................................................................. [1]
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[Total: 1]

33 There are four blood group phenotypes A, B, AB and O in humans.

Define the term phenotype.

..................................................................................................................................................

..................................................................................................................................................

.................................................................................................................................................. [1]

[Total: 1]

34 There are four blood group phenotypes A, B, AB and O in humans.

State the two possible genotypes for a person who has the phenotype blood group A.

1 ...............................................................................................................................................

2 ............................................................................................................................................... [2]

[Total: 2]
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35 The photograph shows a cat with an inherited condition that means the cat has extra toes.

The allele that causes this condition is dominant to the allele for the normal condition.

The diagram shows the inheritance of this condition in a family of cats.

Complete the table by stating the genotypes of the numbered individuals.

Use B for the dominant allele and b for the recessive allele.

number of individual in the diagram genotype of individual

14

[4]

[Total: 4]
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36 Sickle-cell anaemia is an inherited disease.

The photomicrograph is of some blood cells from a person who has sickle-cell anaemia.

Some people who have sickle-cell anaemia have parents who do not have sickle-cell anaemia.

Explain how people with sickle-cell anaemia inherit the disease.

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................

.................................................................................................................................................. [4]

[Total: 4]

37 Petal colour in the flowers of snapdragon plants shows co-dominance.

The gene for petal colour has two co-dominant alleles:

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R
• C for red petals

W
• C for white petals

The table shows the genotypes and phenotypes of snapdragon plants with different petal colours.

genotype phenotype
R R
C C red
W W
C C white
R W
C C pink

(a) Explain the term co-dominance.

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

........................................................................................................................................... [2]

(b) A botanist crossed two snapdragon plants with pink flowers.

Complete the genetic diagram to show the ratio of expected phenotypes in the offspring.

offspring genotypes ..........................................................................................................

offspring phenotypes ......................................................................................................

phenotypic ratio .............................................................................................................. [4]

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(c) The botanist wanted to produce a generation of snapdragons that all had pink flowers.

State the phenotypes of the parent plants that the botanist would need to cross.

Explain your answer.

parent phenotypes ...........................................................................................................

explanation .......................................................................................................................

...........................................................................................................................................

........................................................................................................................................... [2]

[Total: 8]