MCQ Unit 3 [30 marks]

1. [1 mark]

A woman with blood type A has three children with a man who has blood type AB. The first child has blood type B. What
is the probability that the second child born to the couple will have blood type AB?

A. 0.75

B. 0.50

C. 0.25

D. 0.00

2. [1 mark]

What benefit is derived from the use of Bt crops?

A. It can lead to an increase in genetic diversity of crop species.

B. Genetically modified species can interbreed with native species.

C. The numbers of monarch butterflies can be permanently reduced.

D. It can lead to a reduction in the use of pesticides.

3. [1 mark]

What are all the possible phenotypes of children born to a mother with blood group AB and a father with blood group A?

A. AB only

B. A and B

C. AB, A and B

D. AB, A and O

4. [1 mark]

A pregnant woman had fetal cells removed by chorionic villus sampling and tested. The following karyogram was
produced.

What does this show?

A. The child is female with Down syndrome.

B. The child is female without Down syndrome.

C. The child is male with Down syndrome.

D. The child is male without Down syndrome.

5. [1 mark]

A pair of alleles controls the secretion of antigens corresponding to blood group in saliva. Examine the pedigree chart.

[Source: © International Baccalaureate Organization 2019]

Based on this pedigree chart, which best describes the allele conferring antigen secretion in saliva?

A. Dominant

B. Recessive

C. Sex-linked

D. Co-dominant

6. [1 mark]
The system of sex determination in chimpanzees (Pan troglodytes) is the same as in other mammals. A chimpanzee has
48 chromosomes in the nuclei of its body cells.

What can be deduced from this information?

A. The sex of the chimpanzee

B. The number of genes in each chromosome

C. Whether non-disjunction has occurred

D. The number of autosomes in a diploid cell

7. [1 mark]

At which stage of meiosis are bivalents formed?

A. Interphase

B. Prophase I

C. Prophase II

D. Metaphase II

8. [1 mark]

Which pedigree chart is consistent with the inheritance of red-green colour blindness?

[Source: © International Baccalaureate Organization 2019]

9. [1 mark]

Which statement correctly describes genome and proteome?

A. Only the genome but not the proteome can be analysed using gel electrophoresis.

B. The genome and the proteome are the same in all tissues in an organism.

C. In cells of different tissues, the genome is the same while the proteome varies.

D. Only mutations in the proteome but not in the genome cause any variability.

10. [1 mark]

The image shows the results of Griffith’s experiment with S and R strains of Streptococcus pneumoniae in mice (Mus
musculus).
What is an explanation for the results?

A. Mice vary in their resistance to bacteria.

B. The R strain and S strain mated.

C. R strain bacteria are more heat-stable than S strain.

D. DNA was transferred from heat-killed S cells to R cells.

11. [1 mark]

What is the same in all parts of homologous chromosomes?

A. Base pair sequence

B. Alleles

C. Sequence of genes

D. Deletions

12. [1 mark]

What helps make the genome of each human unique?

Some yeast genes can be replaced by human genes that then continue to produce the same human proteins in the yeast
cells. Which statement helps to explain this evidence?

A. The DNA of yeast and humans is identical.

B. Yeast and humans have the same number of chromosomes.

C. The genetic code is universal.

D. Yeast and humans are both eukaryotes.

14. [1 mark]

What determines the genomic size of a species?

A. The total amount of DNA

B. The total number of genes

C. The total number of alleles

D. The total number of chromosomes

15. [1 mark]

What happens during meiosis I and meiosis II?

16. [1 mark]
HindIII is an endonuclease that recognizes the sequence A A G C T T, cutting between the two adenines.

Into how many DNA fragments would the strand shown be cut by HindIII?

A. 2

B. 3

C. 4

D. 5

17. [1 mark]

An allele for lactase persistence allows humans to digest milk as adults. People who lack this allele are lactose intolerant
in adulthood.

What is the pattern of inheritance?

A. Lactase persistence is sex-linked recessive.

B. Lactase persistence is autosomal recessive.

C. Lactase persistence is sex-linked dominant.

D. Lactase persistence is autosomal dominant.

18. [1 mark]

A child has blood group A. The father of the child has blood group B. What are the possible genotypes of the mother?

I. IAIA

II. IAIB

III. IAi

A. I only. C. II and III only

B. I and II only D. I, II and III

19. [1 mark]

Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is based on DNA
sequences and the cladogram on the right is based on comparing protein sequences.
What is the reason that cladograms based on DNA sequences are more reliable predictors of the phylogenetic
relationship of species than cladograms based on protein sequences?

A. Amino acids are not as chemically stable as DNA nucleotides.

B. DNA mutates but amino acids do not.

C. Several different triplets of bases can code for the same amino acid.

D. There are 20 different amino acids but only 4 nucleotides.

20. [1 mark]

What distinguishes an allele from a gene?

A. An allele is made of RNA.

B. An allele is shorter.

C. An allele is a variety of a gene.

D. An allele cannot be transferred during genetic modification.

21. [1 mark]

Which is a characteristic of the pairs of sister chromatids that are visible during meiosis?

A. They result from the replication of DNA before meiosis.

B. They are only present in meiosis I.

C. They split apart during metaphase I in meiosis.

D. They are only present in meiosis II.

22. [1 mark]

Some breeds of dogs are characterized by the presence of a melanistic mask, which is a darkening of the fur near the
nose, as shown by the arrow in this photograph.
Which outcome is matched with a valid conclusion if dogs that were pure breeding for melanistic masks were crossed
with dogs without melanistic masks?

A. If 0 % of the puppies have a mask, the character is recessive.

B. If 25 % of the puppies have a mask, the character is dominant.

C. If 75 % of the puppies have a mask, the character is dominant.

D. If 100 % of the puppies have a mask, the character is recessive.

23. [1 mark]

The diagram shows a pedigree of cystic fibrosis, in which the black colour indicates the presence of cystic fibrosis.

What is the probability that the individual labelled X is a carrier of cystic fibrosis?

A. 1.00

B. 0.50

C. 0.25

D. 0.00

24. [1 mark]

What is produced by somatic-cell nuclear

A. Adult sheep
B. Cloned embryos
C. Rooted stem-cuttings
D. Genetically modified food

25. [1 mark]

The diploid number of chromosomes in humans (Homo sapiens) is 46 and the diploid number of chromosomes in rice
(Oryza sativa) is 24. What does this indicate about diploid chromosome numbers?

A. Plant species have a lower diploid number of chromosomes than animals.

In a person who is heterozygous for sickle-cell anemia, where is the mutation found?

A. In every gamete produced

B. Only in gametes carrying an X chromosome

C. In all brain cells

D. In blood plasma

27. [1 mark]

What is the chromosome number in a human gamete with non-disjunction?

A. 46

B. 45

C. 24

D. 23

28. [1 mark]

In a human with type A blood, what determines the blood group?

A. Sex chromosomes

B. One or two alleles

C. Multiple alleles

D. Codominant alleles

29. [1 mark]

A colour blind man and a woman carrier for colour blindness have a son. What is the probability that their son will be
colour blind?

A. 25 %

B. 50 %

C. 75 %

D. 100 %

30. [1 mark]

Laboratory analysis of DNA from a 40 000 year old woolly mammoth used the polymerase chain reaction (PCR). What
role did the PCR have in the analysis?

A. DNA denaturation

B. DNA comparison

C. DNA separation

D. DNA amplification