Free Mendel's Laws of Inheritance MCQs with Answers

• A. maize
• B. the garden pea
• C. Drosophila
• D. the snapdragon

Explanation: Pisum sativum was an ideal choice because it has clearly contrasting characters, is normally self pollinating so pure lines are easy to…

• A. independent assortment
• B. dominance
• C. segregation
• D. linkage

Explanation: The law of segregation follows from the separation of homologous chromosomes in anaphase I of meiosis, so a heterozygote produces two…

• A. 1:1
• B. 9:3:3:1
• C. 1:2:1
• D. 3:1

Explanation: Crossing two heterozygotes gives one homozygous dominant, two heterozygotes and one homozygous recessive, and since the first three all…

• A. 9:3:3:1
• B. 3:1
• C. 1:1:1:1
• D. 12:3:1

Explanation: Each gene independently gives a three to one ratio, so combining two of them multiplies out to nine both dominant, three of each single…

• A. another tall plant of unknown genotype
• B. a dwarf plant
• C. a known heterozygous tall plant
• D. itself only

Explanation: A test cross uses the homozygous recessive parent, here the dwarf, because such a parent contributes only recessive alleles and so the…

• A. 1:2:1
• B. 3:1
• C. 9:3:3:1
• D. 1:1

Explanation: Of four F2 offspring one is homozygous dominant, two are heterozygous and one is homozygous recessive.

• A. codominance
• B. incomplete dominance
• C. epistasis
• D. multiple alleles

Explanation: In incomplete dominance the heterozygote shows a blend, because one dose of the functional allele makes too little pigment for full…

• A. incomplete dominance
• B. sex linkage
• C. codominance
• D. epistasis

Explanation: A person of group AB makes both the A antigen and the B antigen on the red cell surface, so neither allele is diluted or masked and both…

• A. a single pair of alleles at one locus
• B. two separate genes on two chromosomes
• C. sex linked inheritance
• D. multiple alleles, three of which exist at one locus

Explanation: The gene has three alleles in the population, I A, I B and i, though any one individual carries only two of them, and this is the…

• A. has many easily distinguished contrasting characters
• B. has an unusually long life cycle
• C. cannot self pollinate
• D. blends its characters in every generation

Explanation: Peas offer clear alternatives such as tall versus dwarf, self pollinate to give pure lines and produce many offspring quickly.

• A. genotype
• B. phenotype
• C. karyotype
• D. pedigree

Explanation: Phenotype is what can be seen or measured, while genotype is the allele combination behind it.

• A. homozygous dominant
• B. homozygous recessive
• C. heterozygous
• D. hemizygous

Explanation: Heterozygous means two unlike alleles at a locus, and such individuals are often called carriers when the recessive allele is hidden.

• A. dihybrid cross
• B. test cross
• C. back cross
• D. monohybrid cross

Explanation: Mono means one character, such as height, and the classic F2 ratio of 3 to 1 comes from it.

• A. 3/4
• B. 1/4
• C. 1/2
• D. All of them

Explanation: The cross gives TT, Tt, Tt and tt, so three of four genotypes contain a dominant allele and appear tall.

• A. dominant alleles always mask recessive ones
• B. the alleles of one pair separate into gametes independently of the alleles of other pairs
• C. genes on the same chromosome always recombine
• D. opposite traits blend together in the F1 generation

Explanation: During meiosis each pair of homologues lines up independently, so the allele a gamete gets for one character does not influence the other…

• A. 2
• B. 3
• C. 4
• D. 8

Explanation: Each gene pair contributes two choices, so 2 times 2 gives four gamete types: AB, Ab, aB and ab.

• A. complete dominance
• B. linkage
• C. crossing over
• D. codominance

Explanation: Both alleles express themselves side by side in the heterozygote, producing distinct red and white hairs rather than a blended colour.

• A. only when present in the homozygous condition
• B. in both the heterozygous and homozygous conditions
• C. only in males
• D. only in the F1 generation

Explanation: In a heterozygote the dominant allele masks the recessive one, so the recessive trait appears only when both alleles are recessive.

• A. one
• B. two
• C. three
• D. four

Explanation: Each person inherits one allele from each parent, so only two can be present, one on each homologue.

• A. genome
• B. gene pool
• C. linkage group
• D. gene family

Explanation: A linkage group is everything that travels together on one chromosome during meiosis unless crossing over intervenes.