IB Diploma · Biology D3.2
IB Biology D3.2: Inheritance — Practice Questions & Answers
IB Biology D3.2 study notes: genes and alleles, Mendelian genetics, Punnett squares, dominance, sex linkage and genetic variation.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
How many copies of each autosomal gene does a diploid cell have?
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WhyDiploid cells carry two copies of each autosomal gene, one inherited from each parent.
2
Multiple choice
What is the term for the parental generation in a genetic cross?
- P generation
- F1 generation
- F2 generation
- G generation
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WhyThe original parents in a genetic cross are called the P (parental) generation.
3
Multiple choice
Where are female gametes located in flowering plants?
- Ovary
- Anther
- Stigma
- Filament
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WhyIn flowering plants, female gametes (egg cells within ovules) are located in the ovary.
4
Multiple choice
What type of fertilization occurs when a plant produces both male and female gametes?
- Self-fertilization
- Cross-fertilization
- External fertilization
- Internal fertilization
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WhyWhen one plant provides both gametes, the resulting union is called self-fertilisation.
5
Multiple choice
What term describes the combination of alleles inherited by an organism?
- Genotype
- Phenotype
- Karyotype
- Chromatin
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WhyThe genotype is the specific combination of alleles an organism carries for a trait.
6
Multiple choice
What term describes an organism with two identical alleles for a trait?
- Homozygous
- Heterozygous
- Hemizygous
- Aneuploid
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WhyAn organism with two identical alleles for a trait is homozygous for that gene.
7
Multiple choice
What term describes the observable traits of an organism?
- Phenotype
- Genotype
- Allele
- Gene
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WhyThe phenotype is the set of observable characteristics resulting from genotype and environment.
8
Multiple choice
What is the condition where both homozygous-dominant and heterozygous genotypes produce the same phenotype?
- Dominance
- Recessiveness
- Codominance
- Incomplete dominance
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WhyDominance means one allele masks the other, so homozygous-dominant and heterozygous genotypes look the same.
9
Multiple choice
What is the capacity to develop traits suited to the environment by varying gene expression?
- Phenotypic plasticity
- Genetic drift
- Gene flow
- Mutation
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WhyPhenotypic plasticity is the ability to alter gene expression, producing traits suited to the environment.
10
Multiple choice
What human disease is caused by a recessive allele that affects phenylalanine metabolism?
- Phenylketonuria (PKU)
- Hemophilia
- Sickle cell anemia
- Huntington's disease
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WhyPKU is a recessive disorder in which faulty phenylalanine metabolism lets the amino acid accumulate harmfully.
Key terms in Inheritance
Gene: A length of DNA at a specific locus that codes for a particular characteristic.
Allele: One of the alternative versions of a gene; a diploid organism carries two alleles of each gene.
Genotype: The combination of alleles an organism carries for a gene, such as Bb.
Phenotype: The observable characteristic that results from the genotype and its interaction with the environment.
Dominant allele: An allele that is expressed in the phenotype even when only one copy is present.
Recessive allele: An allele expressed in the phenotype only when two copies are present.
Codominance: A pattern in which both alleles in a heterozygote are fully expressed, as in blood group AB.
Sex linkage: The inheritance of genes carried on the X chromosome, causing some conditions to be more common in males.
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