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Edexcel IGCSE Biology B Inheritance Questions

Practise inheritance questions on DNA, genes, chromosomes, alleles, protein synthesis and genetic diagrams using tables, sequences and ratios.

Syllabus
First assessment 2019
Course
Biology 4BI1

Exam points

  • state and compare genome, gene and allele definitions from short prompts
  • interpret DNA or mRNA sequences, codons and protein synthesis descriptions
  • complete genotype tables or genetic diagrams and give phenotype ratios

Covered syllabus points

3.14 Genome and genes3.15 Chromosomes and genes3.16B DNA structure3.17B RNA structure3.18B Protein synthesis3.19 Alleles3.20 Genetic terminology3.21B Codominance3.22 Polygenic inheritance3.23 Monohybrid inheritance3.24 Interpreting family pedigrees3.25 Monohybrid cross probabilities3.26 Sex chromosomes3.27 Sex determination at fertilisation3.28 Mitosis and identical diploid cells3.29 Roles of mitosis3.30 Meiosis and haploid gametes3.31 Random fertilisation and variation3.32 Human diploid and haploid chromosome numbers3.33 Variation within a species3.34 Mutation3.35B DNA mutations and phenotype3.36B Effects of genetic mutations3.37B Mutagens3.38 Darwin’s theory of evolution by natural selection3.39 Antibiotic resistance

Question 1

[Maximum number: 12]

Question (a)

(a)

Inheritance involves genomes, genes and alleles.

[ 3 ]

Question (i)

(i)

State what is meant by the term genome.

[ 1 ]

Question (ii)

(ii)

Explain the difference between a gene and an allele.

[ 2 ]

Question (b)

(b)

In horses, black hair is caused by a dominant allele, B . The recessive allele, b, codes for brown hair.

A heterozygous black-haired male horse breeds with a heterozygous black-haired female horse.

[ 6 ]

Question (i)

(i)

Draw a genetic diagram to show the genotypes of the parents, the gametes they can produce and the genotypes and ratio of phenotypes of their possible offspring.

[ 4 ]

Question (ii)

(ii)

Calculate the probability that the first offspring will be male and have black hair.

probability =

[ 2 ]

Question (c)

(c)

In horses, eye colour is also controlled by a single gene with two alleles.

The dominant allele causes brown eyes and the recessive allele codes for blue eyes.

A farmer has a male horse with brown eyes.
Explain how the farmer could determine the genotype of this male horse.

[ 3 ]

Question 2

[Maximum number: 1]

An Amoeba is a microscopic single-celled organism that lives in pond water.
The diagram shows an Amoeba with some structures labelled.

Figure for Question 2 — Edexcel IGCSE Biology

Which structure contains chromosomes?

A

P

B

Q

C

R

D

S

Question 3

[Maximum number: 7]

The sequence of bases on one strand of a section of DNA is

TAC CGT AAT TAT

Question (a)

(a)

Which of these is the complementary sequence of DNA on the other strand of the double helix?

A

ATG GCA TTA ATA

B

AUG GCA UUA AUA

C

CGT TAC GGC CGC

D

CGU UAC GGC CGC

[ 1 ]

Question (b)

(b)

Which of these is the correct summary of the processes occurring during protein synthesis?

Figure for Question (b) — Edexcel IGCSE Biology
[ 1 ]

Question (c)

(c)

The table shows different mRNA codons for some amino acids.

Table for Question (c) — Edexcel IGCSE Biology
[ 5 ]

Question (i)

(i)

UUU-AUG-UGU is one combination of codons that codes for the sequence of amino acids W-X-Y.

Give the number of other combinations that code for the same amino acid sequence.
number of other combinations =……

[ 1 ]

Question (ii)

(ii)

Explain why most genetic mutations have no effect on the phenotype of an organism.

Use the information in the table and your own knowledge in your answer.

[ 3 ]

Question (iii)

(iii)

State one way that the incidence of mutations can be increased.

[ 1 ]
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