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Quizzes > Science

Alternate forms of a gene quiz: what are they called?

Quick, free quiz to test your genetics basics on different forms of a gene. Instant results.

Editorial: Review CompletedCreated By: Costa DemosUpdated Aug 25, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
paper art dna helix chromosome cutouts punnett squares question marks on teal background for heredity genetics quiz

This quiz helps you learn what the alternate forms of a gene are called (alleles) and practice key heredity rules. Try quick questions on traits, Punnett squares, and chromosomes, then go deeper with our genotype vs phenotype quiz and molecular genetics quiz, or sharpen skills with a brief genotype practice quiz.

What is the term for alternate forms of a gene located at the same position on homologous chromosomes?
Phenotypes
Chromatids
Genotypes
Alleles
Alleles are alternate versions of a gene that occupy the same locus on homologous chromosomes, leading to variation in traits like flower color or blood type. They determine the specific form a gene can take and influence the phenotype when expressed. This foundational concept in genetics explains how different traits are inherited. .
The observable physical or biochemical characteristics of an organism are referred to as its what?
Phenotype
Genotype
Chromosome
Allele
Phenotype describes the observable traits of an organism, such as height, eye color, or enzyme activity. It results from the interaction of the genotype with the environment. Unlike genotype, which is the genetic makeup, phenotype is what you can actually see or measure. .
The genetic makeup of an organism, representing the alleles present, is called its what?
Karyotype
Phenotype
Allele
Genotype
Genotype refers to the specific set of alleles an organism carries, which underlies its potential traits. Unlike phenotype, genotype is not observable directly but can be inferred from crosses or genetic testing. It determines how alleles are combined and inherited. .
An individual with two identical alleles for a gene is described as what?
Heterozygous
Hemizygous
Polygenic
Homozygous
Homozygous individuals carry two identical alleles at a gene locus, such as AA or aa. This means there is no allelic variation at that locus within the individual. Homozygosity often leads to consistent trait expression if alleles are either both dominant or both recessive. .
An organism with two different alleles for a gene is known as what?
Homozygous
Hemizygous
Heterozygous
Polyploid
Heterozygous individuals have two different alleles at a gene locus, such as Aa. This genetic variation often leads to expression of the dominant allele in the phenotype while the recessive allele remains hidden. Heterozygosity contributes to genetic diversity in populations. .
A dominant allele is best described as which of the following?
Is expressed in the phenotype when only one copy is present
Suppresses meiosis
Is always harmful
Is only expressed when two copies are present
A dominant allele exerts its effect and determines the phenotype even if only one copy is present (heterozygous condition). It masks the presence of a recessive allele in a heterozygote. Dominant alleles are not necessarily more common or beneficial than recessive ones. .
A recessive allele is characterized by which statement?
Determines the wild-type trait
Is always more common in a population
Is expressed only when two copies are present
Is expressed in a heterozygote
A recessive allele only influences the phenotype when two copies are present (homozygous recessive condition). In a heterozygote, its effect is masked by the dominant allele. Recessive alleles can be common or rare and are not inherently wild-type or mutant. .
When crossing red-flowered and white-flowered snapdragons results in pink flowers, this is an example of what inheritance pattern?
Incomplete dominance
Recessive epistasis
Pleiotropy
Codominance
Incomplete dominance occurs when neither allele is completely dominant, resulting in a blending of traits, such as pink flowers from red and white parents. Neither allele masks the other, producing an intermediate phenotype. This contrasts with codominance where both alleles are fully expressed side by side. .
In the human ABO blood group system, the A and B alleles are considered what type of interaction?
Incompletely dominant
Codominant
Dominant and recessive
Recessive to O
In the ABO system, both A and B alleles are codominant, meaning they are each fully expressed when present together in genotype AB. Neither allele masks the other, so both antigens appear on red blood cells. The O allele is recessive to both A and B. .
When more than two alleles for a gene exist in a population, this phenomenon is called what?
Gene linkage
Pleiotropy
Polygenic inheritance
Multiple alleles
Multiple alleles refer to the existence of more than two allele forms of a gene within a population, even though an individual carries only two copies. Classic examples include the ABO blood group system. This increases genetic diversity without changing the two-allele limit per individual. .
One gene influencing multiple, seemingly unrelated phenotypic traits describes which genetic phenomenon?
Polygenic inheritance
Epistasis
Pleiotropy
Genetic linkage
Pleiotropy occurs when a single gene affects two or more distinct phenotypic traits, such as a gene causing both coat color and vision defects. It highlights the interconnected nature of biological pathways. Mutations in pleiotropic genes often have wide-ranging effects. .
One gene masking the expression of another gene is referred to as what?
Complementation
Independent assortment
Epistasis
Codominance
Epistasis occurs when the allele of one gene hides or masks the expression of alleles of a different gene. This interaction modifies classic Mendelian ratios, such as producing a 9:3:4 ratio in dihybrid crosses. Epistatic interactions are common in biochemical pathways. .
The most common form of a gene in a natural population is called the what?
Wild-type allele
Recessive allele
Null allele
Mutant allele
The wild-type allele is the form of a gene most frequently observed in natural populations, typically associated with standard or healthy phenotypes. Other alleles that deviate from this norm are considered mutants. Wild-type status can vary between populations and environments. .
A change in the DNA sequence of a gene that produces a different form of that gene is called a what?
Mutant allele
Recessive allele
Allelic series
Wild-type allele
A mutant allele arises from a DNA sequence alteration, which may alter gene function or expression, leading to different phenotypes. Mutations can be beneficial, neutral, or harmful and occur in many forms such as point mutations or insertions. This contrasts with the wild-type allele. .
A trait controlled by two or more genes, each contributing to the phenotype, is known as what?
Pleiotropy
Epistasis
Polygenic inheritance
Multiple alleles
Polygenic inheritance involves multiple genes (polygenes) collectively influencing a single trait, often resulting in a continuous distribution of phenotypes such as height or skin color. Each gene adds a small effect to the overall phenotype. This mechanism explains quantitative trait variation. .
The proportion of individuals with a particular genotype that actually display the corresponding phenotype is called what?
Penetrance
Expressivity
Codominance
Linkage
Penetrance refers to the percentage of individuals carrying a particular genotype who express the expected phenotype. When penetrance is less than 100%, some individuals with the genotype do not show the trait. Environmental factors and modifier genes often influence penetrance. .
The degree to which a genotype is expressed in the phenotype is referred to as what?
Epistasis
Dominance
Expressivity
Penetrance
Expressivity describes the extent or severity of phenotype expression among individuals with the same genotype. Variable expressivity can result in a range of trait manifestations from mild to severe. It differs from penetrance, which measures occurrence. .
Which of the following is NOT a condition required for Hardy-Weinberg equilibrium?
Non-random mating
No mutation
No selection
Random mating
Hardy-Weinberg equilibrium requires random mating, absence of mutation, large population size, no selection, and no migration. Non-random mating violates one of these key assumptions, disrupting allele frequencies over generations. This condition is critical for predicting genetic variation in idealized populations. .
In the Hardy-Weinberg equation p² + 2pq + q² = 1, what does 2pq represent?
Homozygous dominant frequency
Heterozygote genotype frequency
Recessive phenotype frequency
Allele frequency
In p² + 2pq + q² = 1, p² is frequency of homozygous dominant, q² is homozygous recessive, and 2pq is frequency of heterozygotes. This part of the equation calculates how often two different alleles pair in a population at equilibrium. It is foundational for population genetics. .
If the frequency of allele A is 0.7 and allele a is 0.3, what is the expected frequency of heterozygotes under Hardy-Weinberg?
0.09
0.49
0.42
0.21
Under Hardy-Weinberg, heterozygote frequency is calculated as 2pq. Here p=0.7 and q=0.3, so 2 × 0.7 × 0.3 = 0.42. This gives the proportion of Aa genotypes expected in the population. It assumes equilibrium conditions. .
Genes located close together on the same chromosome that tend to be inherited together are said to be what?
Epistatic
Linked
Polygenic
Pleiotropic
Linked genes are physically close on the same chromosome and exhibit reduced recombination, so they are often inherited together. Their linkage can be mapped by measuring recombination frequencies. This concept contrasts with independent assortment of unlinked genes. .
A recombination frequency of 5% between two genes indicates they are how many map units apart?
On different chromosomes
5 map units
5 megabases
Very loosely linked
Recombination frequency between two genes corresponds directly to map distance in centimorgans or map units, where 1% recombination equals 1 map unit. Thus 5% recombination indicates 5 map units apart. This method is fundamental for constructing genetic linkage maps. .
In a male human, genes on the X chromosome that have no homologous allele on the Y chromosome are described as what?
Homozygous
Heterozygous
Hemizygous
Monosomic
In males (XY), genes present on the X chromosome without a counterpart on the Y are hemizygous, meaning there is only one allele copy in the diploid genome. This makes recessive X-linked alleles directly expressed. Hemizygosity is key in understanding X-linked inheritance. .
An ordered series of alleles at a gene locus arranged by their dominance hierarchy is known as what?
Genetic linkage group
Allelic series
Epistatic network
Complementation group
An allelic series is a set of multiple alleles at a single locus, ranked by their dominance relationships, from most dominant to least. This hierarchy explains how different mutations can yield a range of phenotypes. Allelic series are common in studies of gene function. .
Recessive epistasis often produces which phenotypic ratio in the F2 generation of a dihybrid cross?
9:6:1
12:3:1
9:3:4
9:7:3
In recessive epistasis, a homozygous recessive genotype at one locus masks the expression of alleles at a second locus, producing a 9:3:4 phenotypic ratio in F2 progeny. Classic examples include coat color in Labrador retrievers. This ratio deviates from Mendel's 9:3:3:1. .
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Study Outcomes

  1. Identify Alternate Gene Forms -

    Understand what alternate forms of a gene are called and how alleles contribute to trait variation.

  2. Analyze Inheritance Patterns -

    Differentiate between dominant, recessive, and codominant inheritance using quiz-based scenarios to reinforce learning.

  3. Apply Mendelian Principles -

    Use the laws of segregation and independent assortment to predict genotypic and phenotypic ratios in offspring.

  4. Evaluate Mutation Effects -

    Assess how various mutations impact gene function and phenotype to deepen your genetics understanding.

  5. Interpret Genetics Trivia -

    Use your knowledge to tackle genetics trivia questions and brainpop heredity quiz answers with confidence.

  6. Recall Key Genetics Terms -

    Master essential terminology such as allele, genotype, phenotype, and mutation to enhance your biology vocabulary.

Cheat Sheet

  1. Alleles: The Alternate Forms of a Gene -

    Alleles are what are alternate forms of a gene called, and they determine variants like eye color or blood type. For example, the B and b alleles in pea plants control purple versus white flowers (Mendel's classic experiments). Mnemonic: "A is for Allele, Alternative A - Z."

  2. Genotype vs. Phenotype -

    Your genotype is the pair of alleles you carry (e.g., Bb), while your phenotype is the physical trait you express (purple flowers). Understanding this distinction is key for any heredity and genetics quiz or genetics inheritance quiz. Remember: "Genotype = Genetic code; Phenotype = Physical show."

  3. Mendel's Laws of Inheritance -

    Gregor Mendel's Law of Segregation states that allele pairs separate during gamete formation, and the Law of Independent Assortment explains how different genes independently pass to offspring. These principles form the backbone of many genetics trivia questions and brainpop heredity quiz answers. A quick tip: "S-I pattern - Segregation then Independence."

  4. Punnett Squares for Predicting Ratios -

    Punnett squares provide a simple grid to visualize all possible allele combinations from each parent and predict genotypic and phenotypic ratios. For instance, a monohybrid cross (Bb x Bb) yields a 1:2:1 genotype ratio and a 3:1 phenotype ratio. Practice with a genetics inheritance quiz to boost confidence!

  5. Non-Mendelian Patterns: Beyond Simple Dominance -

    Not all traits follow one dominant and one recessive allele - explore incomplete dominance (e.g., red x white snapdragons yield pink) and codominance (e.g., AB blood type). Multiple alleles, like the ABO blood group system, demonstrate more complexity. Keep these examples in mind for your heredity and genetics quiz and brainpop heredity quiz answers.

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