IBBiologySLTopic QuestionsContinuity & ChangeInheritance

Syllabus Edition

First teaching 2023

First exams 2025

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Inheritance (SL IB Biology)

Topic Questions

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1
Sme Calculator1 mark

Which of the following is not an example of how the external environment can influence gene expression?

  • Fur colouration of Siamese cats

  • Petal colour of snapdragons

  • Skin colouration after sun exposure

  • Sea turtle eggs hatching as females if incubated at 30°C

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21 mark

Which option correctly completes the sentence below?

Multiple alleles are present _________.

  • At the same locus on homologous chromosomes

  • At different loci on different chromosomes

  • At different loci on the same chromosome

  • On sister chromatids

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31 mark

Hair colour is a trait controlled by polygenic inheritance. Which statement is correct?

  • Hair colour shows discontinuous variation

  • Individuals show a wide range of phenotypes for hair colour

  • No two people have the same hair colour

  • Children always have the same hair colour as one of their parents

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41 mark

In fruit flies (Drosophila melanogaster) brown body is dominant to black body. 

If scientists want to find out the genotype of a fly with a brown body what genotype would they cross the fly with? 

  • Homozygous recessive

  • Heterozygous recessive

  • Homozygous dominant

  • Heterozygous dominant

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51 mark

Which of the following statements correctly describes co-dominance?

  • The alleles are both expressed to an equal extent in the phenotype.

  • Two alleles are 'blended together'.

  • One allele is dominant over the other. 

  • Neither allele is expressed in the phenotype. 

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6
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Which of the following statements is a feature of X-linked genetic diseases in humans?

  • Females can’t inherit the defective gene as they don’t possess a Y chromosome.

  • Females can either be normal, a carrier or have the disease.

  • Males can be a carrier for the defective allele.

  • Females can only be heterozygous for the defective gene.

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1
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Which of the following statements are true for the determination of sex?

  1. The chromosomes inherited through the maternal gametes determine the sex of the offspring
  2. Females have a larger quantity of DNA than males
  3. Sex is determined by the 23rd pair of chromosomes in humans
  4. Sex of an individual can be identified using an image taken of chromosomes during interphase

  • I and II only

  • III only

  • II and III only

  • I, III and IV only

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21 mark

The pedigree chart below shows the inheritance of Tay-Sachs disease which is an autosomal recessive trait, characterised by neurological problems caused by the death of nerve cells. 

In the pedigree chart, a filled in circle or square means the individual is affected and shows the genetic condition.

What is the probability that individuals 3 and 4 will have another child with Tay-Sachs disease?

UpV6A5dP_h-2

  • 25%

  • 50%

  • 75%

  • 100%

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31 mark

Which statements best explain why the ABO blood system in humans is an example of co-dominance?

  1. Allele IA and the allele IB are both expressed in the heterozygote/AB type blood.
  2. Neither allele IA or the allele IB can mask the expression of the other allele.
  3. There are three alleles of the gene that controls the blood group.
  4. There are more than two blood groups.

  • All of them.

  • I. II. and III.

  • I. and II.  

  • II. and III.

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41 mark

Two parents with normal factor VIII have a child with haemophilia.

Which is the correct statement?

  • The mother is normal but the father carries the defective gene.

  • Both parents are carriers for the defective gene.

  • Only the mother is a carrier for the defective gene.

  • The child must have been female.

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11 mark

Identical twins have the same DNA (genotype) but often display many observable physical differences (phenotype). Studies on twins have shown that one twin can be more susceptible to diseases like cancer or diabetes.

Which of the following statements best explains these differences between identical twins?

  • One twin is more prone to random mutations of DNA.

  • Epigenetic changes can affect the structure of proteins.

  • One twin inherited epigenetic modifications from a parent.

  • An organism's environment can influence gene expression patterns.

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21 mark

Which of the following statements about genes is not correct?

  • A gene may be found at a different locus in different individuals.

  • A gene is a section of DNA that codes for one polypeptide.

  • Genes are heritable factors.

  • The number of genes that a species has is not directly proportional to the size or complexity of the organism.

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31 mark

Which of the following statements about alleles are correct?

  1. New alleles can arise through mutation.
  2. There are two different versions, or alleles, of every gene.
  3. Every eukaryotic cell contains two alleles of every gene.

  • I only

  • I and II only

  • I and III only

  • II and III only

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41 mark

Which of the following explains why the father determines the sex of offspring and not the mother?

  • Only sperm cells contain the sex chromosomes.

  • Fathers can only pass on the Y chromosome to their offspring.

  • Females can only pass on the X chromosome to their offspring.

  • Female gametes only contain autosomes.

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51 mark

In humans, there are three alleles that determine blood groups, namely IO, IA and IB. The frequency of the IO allele in a particular population was found to be 0.72. There was an equal abundance of the remaining two alleles.

What would the frequency of the IB allele be in this population?

  • 0.44

  • 0.28

  • 0.14

  • 0.07

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61 mark

Which row(s) below give(s) correct statements about continuous variation?

I.

Most individuals are close to the mean value of a trait, with fewer individuals at the extremes

II.

There are distinct categories of the trait with no intermediate values

III.

A continuously variable trait tends to be regulated by multiple genes

IV.

Individuals are distributed approximately evenly and the environment cannot influence the trait

  • I only

  • I, III and IV

  • II and IV

  • I and III

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71 mark

Long hair in a species of rabbit is caused by the presence of the allele HL. These rabbits have either very long hair or moderately long hair. The 'wild-type' short-haired rabbit possesses the allele HS. The diagram below shows the results of two crosses involving one female and two male rabbits. q10_10-2_inheritance_ib_biology_hl_mcq

Which row of the table below shows the phenotypes of the rabbits with the genotypes HLHL and HLHS?

 

HLHL

HLHS
A

Long hair

Moderately long hair
B

Moderately long hair

Short hair
C

Moderately long hair

Long hair
D

Long hair

Short hair

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81 mark

A species of plant can have either blue or white flowers. The colour of the flower is controlled by a single gene where the dominant allele codes for blue flowers. 

Two heterozygous plants are crossed; which of the observed outcomes matches up most accurately to the expected ratio of blue to white flowers. 

  Blue White
A 93 46
B 77 203
C 107 33
D 127 42

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91 mark

Two parents have an equal chance of having a child with blood groups A, B, AB, or O.

What are the genotypes of the parents?

  • AB, AO

  • AO, BO

  • AB, OO

  • AB, AB

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101 mark

A woman is a carrier of haemophilia; her husband does not have haemophilia. 

What are the possible genotypes of their children?

  Sons Daughters
A All sufferers All carriers
B Half healthy All carriers
C Half healthy All healthy
D Half healthy Half carriers

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111 mark

The pedigree diagram shows the inheritance of cystic fibrosis across 3 generations.

biology-3-3-q7-ib-hl-

Identify the genotype of the individuals labelled 1, 2 and 3 in the pedigree diagram.

 

 1 2 3
A Heterozygous Homozygous dominant Heterozygous
B Homozygous recessive Homozygous dominant Heterozygous
C Homozygous recessive Heterozygous Heterozygous
D Heterozygous Homozygous recessive Homozygous dominant

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121 mark

A couple are trying to decide whether their children may be at risk of inheriting Huntington's disease. One parent is heterozygous for Huntingtons and the other is a healthy individual. 

Calculate the % chance that their offspring are likely to suffer from the disease.

  • 50%

  • 25%

  • 100%

  • 75%

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131 mark

The pedigree diagram below shows the inheritance of haemophilia across three generations.

biology-q9-3-3-ib-hl

Identify the genotype of person Y.

  • XhXh

  • XHXH

  • XHXh

  • XHY

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