IB Biology HL D3.2 Inheritance Questions

Practise IB Biology HL D3.2 with inheritance diagrams and data questions on alleles, pedigrees, linkage, variation, probability and genetic disorders.

Exam points

Identify haploid gametes, genotype, phenotype and homozygous or heterozygous alleles.
Solve monohybrid crosses with Punnett grids; infer genotypes and dominant or recessive outcomes.
Explain recessive PKU from PAH deficiency to phenylalanine accumulation and treatment.
Explain environment-driven gene-expression changes that alter phenotype, not genotype.
Explain SNPs as single-base variants and identify multiple-allele crosses from a Punnett grid.
Deduce ABO inheritance and transfusion compatibility from IA, IB, i, antigens and antibodies.
Explain codominance and incomplete dominance and interpret their phenotype ratios in genetic crosses.
Explain XX/XY inheritance and the Y-chromosome SRY/TDF signal in testis development.
Infer X-linked or autosomal inheritance, genotypes and risks from haemophilia and pedigree data.
Interpret continuous height data using polygenic effects, environment and trait distributions.
Compare box plots by median and IQR; identify outliers with the 1.5 × IQR rule.
Explain allele segregation and independent assortment through meiosis I and random bivalent orientation.
Use 9:3:3:1 or 1:1:1:1 ratios to solve and interpret dihybrid crosses.
Infer linkage from parental and recombinant offspring; relate recombination to crossing over.
Use expected counts, degrees of freedom and p-values to test genetic ratios with χ².

Covered syllabus points

D3.2.1—Haploid gametes + fusion = diploid zygote D3.2.2—Genetic crosses in flowering plants D3.2.3—Genotype D3.2.4—Phenotype D3.2.5—Dominant and recessive alleles D3.2.6—Phenotypic plasticity D3.2.7—Phenylketonuria (PKU)D3.2.8—SNPs and multiple alleles D3.2.9—ABO blood groups D3.2.10—Incomplete dominance and codominance D3.2.11—Sex determination D3.2.12—Haemophilia D3.2.13—Pedigree charts D3.2.14—Continuous variation D3.2.15—Box-and-whisker plots D3.2.16 (HL)—Segregation and independent assortment D3.2.17 (HL)—Dihybrid crosses D3.2.18 (HL)—Human gene loci D3.2.19 (HL)—Autosomal gene linkage D3.2.20 (HL)—Recombinants D3.2.21 (HL)—Chi-squared test

[Maximum number: 1]

What is always passed to the next generation as a result of sexual reproduction?

Homologous chromosomes from the mother

A chromatid from every chromosome of the father

A haploid set of chromosomes from the mother

All alleles from each parent

[Maximum number: 1]

A pea plant that is homozygous for purple flowers is crossed with a pea plant having white flowers and the descendants are all plants with purple flowers. One of these $\mathrm{F}_{1}$ plants is then crossed with a pea plant having white flowers. In the resulting offspring, what can be expected?

100 % of plants with purple flowers

100 % of plants with white flowers

75 % of plants with purple flowers, 25 % with white flowers

50 % of plants with purple flowers, 50 % with white flowers

[Maximum number: 5]

In a strain of soybeans, high oil content (H) in seeds is dominant to low oil content (h) and four seeds in a pod (F) is dominant to two seeds in a pod (f). A farmer crosses two soybean plants, both with high oil content and four seeds in a pod. The offspring have a phenotypic ratio of 9: 3: 3: 1.

(a)

Identify the genotypes of the soybean plants with high oil content and four seeds in a pod that were used in the cross.

[ 1 ]

$\mathrm{HhFf} \times \mathrm{HhFf} /($ both ) HhFf;

(b)

For the soybean cross HhFf × HhFf, determine the genotypes of the gametes and offspring using a Punnett grid.

[ 2 ]

gametes	HF	Hf	hF	hf
HF	HHFF	HHFf	HhFF	HhFf
Hf	HHFf	HHff	HhFf	Hhff
hF	HhFF	HhFf	hhFF	hhFf
hf	HhFf	Hhff	hhFf	hhff

(c)

Identify the phenotypes of each part of the phenotypic ratio.

Table with Ratio and Phenotypes columns. The ratio entries are 9, 3, 3 and 1; all four phenotype cells are blank for completion.

[ 2 ]

ratio	phenotypes
9	high oil four seeds;
3	high oil two seeds;
3	low oil four seeds;
1	low oil two seeds;

[Maximum number: 1]

Identify the genotypes of the soybean plants with high oil content and four seeds in a pod that were used in the cross.

$\mathrm{HhFf} \times \mathrm{HhFf} /($ both ) HhFf;

[Maximum number: 2]

Identify the phenotypes of each part of the phenotypic ratio.

ratio	phenotypes
9	high oil four seeds;
3	high oil two seeds;
3	low oil four seeds;
1	low oil two seeds;

[Maximum number: 1]

Huntington's disease is an autosomal dominant genetic disease. What are the chances of two parents that are heterozygous for the gene having a child with Huntington's disease?

25 %

50 %

75 %

100 %

[Maximum number: 1]

Scientists incubated larvae of the moth Utetheisa ornatrix at either $15^{\circ} \mathrm{C}$ or $22^{\circ} \mathrm{C}$ until they hatched. They found the hatched moths had different wing colour patterns due to phenotypic plasticity.

$Moth from larvae incubated at \(15^{\circ$

Moth from larvae incubated at \(15^{\circ

$Moth from larvae incubated at \(22^{\circ$

Moth from larvae incubated at \(22^{\circ

Which of the following explains the observed differences in wing colour?

Colder temperatures induce mutations in genes for wing colour.

The expression of genes for wing colour is affected by temperature.

A mutation makes moths less visible to predators in cold climates.

Wing colour is the result of polygenic inheritance.

[Maximum number: 1]

The table summarizes the relative content of essential amino acids in different foods. Cysteine and tyrosine are classified as being "conditionally essential". The quantity of each amino acid in a hen egg is set as 1.0 and all other values are relative to the hen egg standard.

Phenylalanine is converted to tyrosine by the enzyme phenylalanine hydroxylase.

When infants with the condition phenylketonuria (PKU) are left untreated, they have a build-up of phenylalanine in the blood and high levels of phenylalanine in the urine. State the cause of this condition.

[Maximum number: 1]

Which Punnett grid provides evidence of multiple alleles?

Table for Question 9 — IB Biology HL — Option A

Table for Question 9 — IB Biology HL — Option B

Table for Question 9 — IB Biology HL — Option C

Table for Question 9 — IB Biology HL — Option D

[Maximum number: 4]

Variation in genetically inherited characteristics is the basis for evolution.

Outline the inheritance of blood types in the ABO blood system in humans.

a. i and I ${ }^{\mathrm{A}}$ and $\mathrm{I}^{\mathrm{B}}$ are alleles (of the blood group gene)
b. $I^{A}$ is dominant and i is recessive $/ I^{B}$ is dominant and i is recessive
c. Group O (only) with ii and Group A with $\mathrm{I}^{\mathrm{A}} \mathrm{i}$ or $\mathrm{I}^{\mathrm{A}} \mathrm{I}^{\mathrm{A}} /$ Group B with $\mathrm{I}^{\mathrm{B}} \mathrm{i}$ or $\mathrm{I}^{\mathrm{B}} \mathrm{I}^{\mathrm{B}}$
d. $\mathrm{I}^{\mathrm{A}}$ and $\mathrm{I}^{\mathrm{B}}$ are co-dominant so Group AB with $\mathrm{I}^{\mathrm{A}} \mathrm{I}^{\mathrm{B}}$
e. one allele/copy of the gene inherited from each parent/Punnett square showing this

[Maximum number: 1]

A variety of Pelargonium has yellow leaves. When plants of this variety are crossed, the resulting seeds produce green, yellow and white seedlings in the ratio 1: 2: 1. If plants with yellow leaves are crossed with plants with green leaves, what would the expected ratio of phenotypes in the offspring be?

Green

Yellow

White

[Maximum number: 1]

What causes gonads to develop as testes in humans?

Effect of placental hormones

Initiation of testosterone secretion in puberty

Development of secondary sexual characteristics

Activation and transcription of a gene on the Y chromosome

[Maximum number: 1]

Hemophilia is a sex-linked disease that affected some members of royal families in Europe during the 19th and 20th centuries.

Deduce the genotype of Queen Victoria's daughter Alice.

$\mathrm{X}^{\mathrm{H}} \mathrm{X}^{\mathrm{h}}$ ;

[Maximum number: 3]

In late-onset Tay-Sachs disease, neurological disorders slowly appear in adults. The pedigree chart shows four generations of a family affected by the disease.

(a)

Determine the type of inheritance shown in the pedigree chart.

[ 1 ]

(b)

At the gene locus for the disease, the alleles are N and n . Deduce the genotype of the person identified as

[ 2 ]

(i)

At the gene locus for late-onset Tay-Sachs disease, the alleles are N and n. Deduce the genotype of the person identified as A.

[ 1 ]

(ii)

At the gene locus for late-onset Tay-Sachs disease, the alleles are N and n. Deduce the genotype of the person identified as B.

[ 1 ]

[Maximum number: 2]

Male and female human skeletons obtained from different archaeological sites in Greece were studied in order to find trends in human height evolution in Europe. The box-and-whisker plots show heights of skeletons dating from two historical periods: Neolithic (6500-3000 BC) and Roman (146-324 AD).

Box-and-whisker plots compare male and female skeletal heights in cm for Neolithic and Roman periods. Grey boxes denote males, white boxes females; median lines, whiskers and outlier circles are shown.

Using the data, discuss the hypothesis that variation in human height is due to polygenic inheritance.

[Maximum number: 3]

(a)

Using the graph,

[ 3 ]

(i)

Using the box-and-whisker plot, estimate the median height of females in the Roman period.

[ 1 ]

(ii)

Using the box-and-whisker plot, estimate the maximum height of males in the Neolithic period.

[ 1 ]

(iii)

State the reason that some of the data points were plotted outside the whiskers.

[ 1 ]

[Maximum number: 2]

The micrograph shows a plant cell of Lilium grandiflorum during meiosis.

Outline the law of independent assortment.

[Maximum number: 3]

In cats, the allele for curled ears (C) is dominant over the allele for normal ears (c). The allele for black colour (B) is dominant over the allele for grey colour (b). A cross occurs between two cats that are both heterozygous for these unlinked traits.

Using a Punnett grid, predict the ratio of phenotypes of offspring in the next generation.

[Maximum number: 2]

Hemophilia is a sex-linked disease that affected some members of royal families in Europe during the 19th and 20th centuries.

Explain gene linkage and its effects on inheritance.

[Maximum number: 1]

The diagram shows one of Thomas Hunt Morgan's crosses of Drosophila in the early 20th century.

Identify the recombinants.

[Maximum number: 2]

The diagram shows one of Thomas Hunt Morgan's crosses of Drosophila in the early 20th century.

The chi-squared value was calculated as shown. Deduce, with reasons, whether the observed ratio differed significantly from the expected Mendelian ratio.

c^{2}=\Sigma \frac{(\text { Observed }- \text { Expected })^{2}}{\text { Expected }}=1002.6

All question bank results loaded

Covered syllabus points

Question 1

Question 2

Question 3

Question (a)

Question (b)

Question (c)

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question (a)

Question (b)

Question (i)

Question (ii)

Question 15

Question 16

Question (a)

Question (i)

Question (ii)

Question (iii)

Question 17

Question 18

Question 19

Question 20

Question 21