Genetics Quiz: Genetic Terminology

What this quiz covers

This quiz focuses on Genetic Terminology, giving you a quick way to practice the rules, question types, and explanations that matter most for Genetics.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. locus, because it is a specific location but lacks a protein product.
2. gene, because it codes for a functional, non-protein product. (correct answer)
3. phenotype, because it has an observable regulatory effect on the cell.
4. allele, because it represents a non-protein-coding variant of a gene.

Explanation: The correct answer is B. The contemporary definition of a gene is a region of DNA that codes for a functional product, which can be either a protein or a functional RNA molecule. Since the described DNA segment is transcribed into a functional miRNA, it fits the definition of a gene. A is incorrect because a locus is merely the location; the segment itself, having a function, is a gene. C is incorrect because the DNA segment is part of the genotype; its regulatory effect is what contributes to the phenotype. D is incorrect because an allele is a variant of a gene. The segment itself is the fundamental unit, the gene.

Question 2

1. genes for the same phenotype.
2. loci for the same gene.
3. alleles of the same gene. (correct answer)
4. genotypes of the same allele.

Explanation: The correct answer is C. The question describes two different versions (red-eye and white-eye) of a single gene that controls eye color. Different versions or variants of the same gene are known as alleles. A is incorrect because they are variations of one gene, not two different genes. B is incorrect because these alleles are found at the same locus (location) on the X chromosome, they are not different loci. D is incorrect as it confuses the terms; a genotype is a combination of alleles, and an allele is a variant of a gene. One cannot have different genotypes of the same allele.

Question 3

1. genotype.
2. phenotype.
3. karyotype.
4. genome. (correct answer)

Explanation: The correct answer is D. The genome is defined as the complete set of genetic material or instructions in an organism. The question asks for the term that describes the 'entire set of genetic instructions' for a species, which is the definition of a genome. A, genotype, refers to the specific combination of alleles an individual possesses, which is a more narrow term than genome. B, phenotype, refers to the observable traits of an organism, not its genetic code. C, karyotype, refers to the number and appearance of chromosomes in the nucleus, which is a component of the genome but not the entire set of instructions.

Question 4

1. genes that interact to determine a single phenotype.
2. genotypes that result from the combination of two loci.
3. loci on chromosome 9 that control the blood group trait.
4. alleles of a single gene that influence the blood group phenotype. (correct answer)

Explanation: The correct answer is D. The passage states that the ABO blood group is determined by a single gene with three common variants ($I^A$, $I^B$, and i). Different versions or variants of a single gene are called alleles. These alleles combine to form a genotype (e.g., $I^A$ i), which in turn determines the phenotype (e.g., Type A blood). A is incorrect because I^A, I^B, and i are variants of the same gene, not different genes. The interaction of multiple genes to determine a single trait is known as polygenic inheritance. B is incorrect because I^A, I^B, and i are alleles, not genotypes. A genotype is the combination of two alleles in a diploid individual (e.g., $I^A$ $I^B$). C is incorrect because these are all variants found at the same specific location (locus) on chromosome 9.

Question 5

1. genome for kernel development.
2. phenotype for kernel color and shape.
3. alleles for two different traits.
4. genotype at two unlinked loci. (correct answer)

Explanation: The correct answer is D. This notation describes the combination of alleles (e.g., R and r, Su and Su) that an individual possesses for specific genes, which is the definition of a genotype. Since two different genes are specified, it is a genotype at two loci. 'Alleles' (C) is too narrow, as it refers to the individual variants, not the combination. 'Phenotype' (B) refers to the observable traits (e.g., 'purple, starchy kernels'), not the genetic symbols. 'Genome' (A) is too broad, as it refers to all genetic material, not just these two genes.

Question 6

1. Gene
2. Allele
3. Genotype
4. Phenotype (correct answer)

Explanation: The correct answer is D. The phenotype is the observable trait or set of traits of an organism, which includes physical, biochemical, and physiological characteristics like a medical condition. The gene (A) is the entire 1,480 bp DNA sequence. The allele (B) is the specific version with the base substitution. The genotype (C) is the pair of alleles an individual possesses (e.g., homozygous for the sickle-cell allele).

Question 7

1. genotype; phenotypes
2. phenotype; genes (correct answer)
3. genome; alleles at a single locus
4. phenotype; alleles at a single locus

Explanation: The correct answer is B. Height is the observable trait, which is the phenotype. The scenario describes this trait as being influenced by hundreds of different genetic factors. Each of these genetic factors is a gene. Therefore, the phenotype (height) results from the combined effect of many genes. A incorrectly swaps the terms; genotype determines phenotype, not the other way around. C and D are incorrect because they refer to alleles at a single locus, which describes a Mendelian trait, not a complex, polygenic trait like height that involves many genes at many different loci.

Question 8

1. phenotype; genotype (correct answer)
2. genotype; phenotype
3. allele; genome
4. genome; locus

Explanation: The correct answer is A. Phenotype refers to the observable characteristics of an organism, which includes molecular traits like the amount of a specific protein. A Western blot measures protein levels, thus assessing a molecular phenotype. Genotype refers to the genetic makeup of an organism, specifically the sequence of its alleles. DNA sequencing directly reads this genetic information. B is incorrect as it reverses the correct association. C is incorrect because while the sequence reveals a specific allele, the broader concept is genotype. The genome refers to the entire set of genetic material, not just one gene. D is incorrect because the genome is the entire genetic library, and a locus is just a gene's address. DNA sequencing provides the specific genetic code (genotype), not just its location.

Question 9

1. The cells have different genomes because they express different sets of genes.
2. The cells have different alleles at key loci, leading to their distinct phenotypes.
3. The cells share an identical genome, but their distinct phenotypes arise from differential gene expression. (correct answer)
4. The cells contain the same genes, but their genotypes differ to allow for specialized functions.

Explanation: The correct answer is C. All somatic cells within a single individual contain the same complete set of genetic material, which is the genome. The specialization of cells like skin cells and neurons into different types with different functions (phenotypes) is not due to differences in their DNA content, but rather to differential gene expression—meaning different sets of genes are turned 'on' or 'off' in each cell type. A is incorrect because the genome is identical. Gene expression patterns differ, but this does not change the underlying genomic sequence. B is incorrect because the alleles at all loci are the same in both cells. D is incorrect because the genotype (the specific combination of alleles) is identical in both cells.

Question 10

1. A new allele has been created, leading to a change in genotype, but the phenotype remains unchanged. (correct answer)
2. A new gene has been formed, altering the organism's genome and resulting in a new phenotype.
3. The locus of the gene has shifted, which changes the genotype without affecting the allele.
4. The phenotype has been altered at the molecular level, while the genotype and the allele remain the same.

Explanation: The correct answer is A. A mutation, by definition, creates a new version of a gene, which is called an allele. This change in the DNA sequence means the organism's genotype for that gene is now different. However, because the mutation is silent (the amino acid sequence is unchanged), the resulting protein and the observable traits (the phenotype) are not altered. B is incorrect because a point mutation creates a new allele, not an entirely new gene. The overall genome is largely unaffected. C is incorrect because a point mutation does not change the physical location (locus) of a gene on the chromosome. D is incorrect because the genotype and allele have changed due to the mutation. The phenotype is what remains the same.

Question 11

1. a single phenotype can be determined by multiple different genotypes.
2. the environment is the primary determinant of the genome's expression.
3. the genotype at a single locus can influence multiple phenotypic traits. (correct answer)
4. multiple alleles at a single locus are required to produce a complex phenotype.

Explanation: The correct answer is C. The scenario describes a single gene mutation (FBN1) leading to multiple, seemingly unrelated, observable traits (tall stature, long limbs, heart issues). This demonstrates that the genetic information at one specific location (the genotype at the FBN1 locus) can have widespread effects on the body's overall structure and function (the phenotype). A describes polygenic inheritance, which is the opposite of pleiotropy. B is incorrect because while the environment can modify phenotype, Marfan syndrome is a clear example of a genetically determined disorder. D is incorrect because the condition is caused by a single mutant allele; it doesn't require multiple alleles to be present simultaneously, but rather one specific allele in the genotype.

Question 12

1. Their phenotype consists of two different alleles at the HEXA locus.
2. Their genotype for the HEXA gene is heterozygous. (correct answer)
3. Their genotype is determined by a single recessive allele.
4. Their phenotype is homozygous, but their genotype is heterozygous.

Explanation: The correct answer is B. A carrier for a recessive disorder has one normal (dominant) allele and one disease-causing (recessive) allele. A genotype consisting of two different alleles for a particular gene is defined as heterozygous. A is incorrect because phenotype refers to observable traits (the individual is healthy), not the alleles themselves. C is incorrect because a genotype in a diploid organism is determined by two alleles, not one. D is incorrect because phenotype is a description of a trait (e.g., 'healthy'), not a genetic state like homozygous. While the individual's healthy phenotype resembles that of a homozygous dominant individual, the term 'homozygous phenotype' is imprecise.

Question 13

1. different genomes, which may contain functionally homologous genes. (correct answer)
2. the same genome, but with different alleles expressed in each organism.
3. different genotypes, which result in identical phenotypes for metabolic traits.
4. the same loci for all genes, but vastly different gene sequences.

Explanation: The correct answer is A. The genome is the complete set of genetic material for an organism. Since humans and yeast are different species, they have vastly different genomes. However, due to shared evolutionary history, they can have genes with similar functions (homologous genes), such as those for glycolysis. B is incorrect because the genomes are fundamentally different, not the same. C is incorrect because genotype typically refers to the alleles within an individual of a species, not a comparison between species. Also, the metabolic phenotypes are similar, not identical. D is incorrect because the loci (gene positions) and overall chromosomal organization are completely different between yeast and humans.

Question 14

1. phenotype composed of two alleles; phenotype composed of one allele
2. genotype composed of two alleles; genotype composed of one allele (correct answer)
3. locus composed of two genes; locus composed of one gene
4. genome composed of two phenotypes; genome composed of one phenotype

Explanation: The correct answer is B. Genotype refers to the set of alleles an organism possesses for a gene. Since a diploid organism has two copies of each chromosome, it has two copies of the gene and thus its genotype is composed of two alleles (which can be the same or different). A haploid organism has only one copy of the chromosome, so its genotype for that gene consists of only one allele. A is incorrect because phenotype is the observable trait, not the composition of alleles. C is incorrect because a locus is a location, not a composition of genes. D is incorrect because a genome is the entire set of genetic material, and it does not consist of phenotypes.

Question 15

1. phenotype; dominant
2. locus; heterozygous
3. allele; Tt
4. genotype; heterozygous (correct answer)

Explanation: The correct answer is D. A test cross involves crossing an organism with a dominant phenotype to a homozygous recessive organism. The 1:1 ratio of tall to short offspring reveals that the tall parent must have been carrying the recessive allele to pass it on to half its offspring. Therefore, its genetic makeup, or genotype, was heterozygous (Tt). A is incorrect because phenotype describes the observable trait ('tall'), not the underlying genetics, and 'dominant' describes an allele, not a phenotype. B is incorrect because a locus is a location, which cannot be heterozygous. C is incorrect because an allele is a single version of a gene (e.g., 'T' or 't'), not the pair ('Tt'), and an allele itself cannot be described as 'Tt'.

Question 16

1. A new gene into the mouse genome.
2. A new allele at a pre-existing locus. (correct answer)
3. A new locus on a specific chromosome.
4. A new phenotype into the mouse genotype.

Explanation: The correct answer is B. Altering a single nucleotide within an existing gene creates a new version of that gene. This new version is defined as a new allele. The location of the gene (the locus) remains unchanged. The researcher has directly manipulated the DNA sequence to create this new allele. A is incorrect because the researcher modified an existing gene, not introduced a completely new one. C is incorrect because the location (locus) of the gene was not changed, only its internal sequence. D is incorrect because it confuses the terms phenotype and genotype. A phenotype is an observable trait, while a genotype is the genetic constitution. One cannot introduce a phenotype into a genotype.

Question 17

1. The plants have different genotypes for height, leading to their different observable traits.
2. The plants possess different alleles at the height locus, which are expressed differently under stress.
3. The plants share an identical genotype, but exhibit different phenotypes due to environmental influence. (correct answer)
4. The plants have the same phenotype for height initially, but their genomes diverge in response to the environment.

Explanation: The correct answer is C. The plants are described as genetically identical, meaning they have the same set of genes and alleles (genotype). The observed difference in height (100 cm vs. 50 cm) is a difference in their physical characteristics (phenotypes). This variation is caused by environmental factors (sunlight, nutrients), illustrating the principle that phenotype is a result of the interaction between genotype and environment. A is incorrect because the plants are genetically identical, so they have the same genotype. B is incorrect because being genetically identical means they have the same alleles at every locus. D is incorrect because the phenotype (height) is different between the mature plants, not the same. Furthermore, the core genome of an organism does not change in response to environmental conditions in this manner.

Question 18

1. Its phenotype is pink flowers, resulting from its heterozygous genotype. (correct answer)
2. Its genotype is pink flowers, which is an expression of its $C^RC^W$ phenotype.
3. Its phenotype is $C^RC^W$, which leads to an intermediate physical trait.
4. Its genotype and phenotype are both described as heterozygous.

Explanation: The correct answer is A. The phenotype is the observable characteristic (pink flowers), which is the physical expression of the genetic makeup, or genotype (in this case, $C^RC^W$, which is heterozygous). Choices B and C incorrectly swap the definitions of genotype and phenotype. Choice D is incorrect because phenotype is a description of a trait, not a genetic state; 'heterozygous' is a term that applies only to the genotype.

Question 19

1. The phenotype for coat color.
2. The expression of the pigment gene.
3. The genotype at the pigment locus. (correct answer)
4. The function of the pigment enzyme.

Explanation: The correct answer is C. The rabbit's genotype, its underlying genetic makeup for the pigment gene, does not change due to environmental temperature. The phenotype (observable coat color, choice A), gene expression (choice B), and enzyme function (choice D) are all shown to be variable and dependent on temperature. The experiment's entire purpose is to demonstrate how a constant genotype can result in a variable phenotype due to environmental influence.

Question 20

1. It alters the loci of the genes within the translocated segment. (correct answer)
2. It creates new alleles for all genes on both chromosomes 14 and 21.
3. It changes the entire genome of the individual into a new species.
4. It modifies the genotypes of the genes in the segment but not their phenotypes.

Explanation: The correct answer is A. A locus is the specific physical location of a gene on a chromosome. A translocation is a large-scale mutation that moves a segment of one chromosome to another. Therefore, all the genes within the translocated segment from chromosome 14 now have new physical locations (loci) on chromosome 21. B is incorrect because translocation moves genes; it does not change their internal DNA sequence to create new alleles. C is incorrect because while this is a significant chromosomal abnormality, it does not change the fundamental set of genes to the extent that it creates a new species. The genome is altered, but this choice is an overstatement. D is incorrect because moving a gene to a new location can drastically alter its expression (a change in phenotype) due to new regulatory environments, a phenomenon known as a position effect. Furthermore, the genotypes (allelic composition) of the genes themselves are not altered.