Title: Trait Inheritance
Course: Question Banks

Q: Which is one of the seven characteristics that Mendel observed in pea plants?
- flower size (Incorrect. Mendel did not study flower size in his pea plants.)
- stem color (Incorrect. Mendel did not study stem color in his pea plants.)
- seed texture (Correct. Mendel studied seven traits total, including seed texture, in his pea plants.)
A: seed texture

Q: ________ originated before the discovery of DNA
- Darwinian genetics (Incorrect. There is no Darwinian genetics.)
- Linnaean genetics (Incorrect. There is no Linnaean genetics.)
- Mendelian genetics (Correct. Mendel developed his basic understanding of genetics without knowing about DNA.)
A: Mendelian genetics

Q: A key feature of Mendel’s experiments that allowed him to identify genetic principles was that he ________.
- allowed self-fertilization to occur (Incorrect. While some of Mendel’s plants were allowed to self-fertilize, he also had to perform a number of directed crosses.)
- chose traits with continuous variation to study (Incorrect. Mendel’s studies were successful because he chose traits with discontinuous variation, or distinct classes.)
- studied a large number of plants through the F_2 generation (Correct. Mendel could not have reached his conclusions without studying through the F_2 generation; scientists would not have accepted his studies without his large sample size.)
A: studied a large number of plants through the F_2 generation

Q: True-breeding individuals are ________ for a characteristic.
- heterozygous (Incorrect. Heterozygous individuals are not true-breeding for a characteristic.)
- dominant (Incorrect. True-breeding individuals are not necessarily dominant.)
- recessive (Incorrect. True-breeding individuals are not necessarily recessive.)
- homozygous (Correct. True-breeding individuals have two copies of the same allele of a gene.)
A: homozygous

Q: If parents differ in ________ during a testcross, it is a monohybrid cross.
- two characteristics (Incorrect. “Di” indicates two; so a dihybrid cross is focused on two characteristics.)
- three characteristics (Incorrect. “Tri” indicates three; so a trihybrid cross is focused on three characteristics.)
- one characteristic (Correct. “Mono” indicates only one; so a monohybrid cross is focused on a single characteristic.)
A: one characteristic

Q: An individual’s genetic composition is its ________.
- phenotype (Incorrect. Phenotype is the outward appearance of a trait (or entire organism).)
- ploidy (Incorrect. Ploidy refers to how many copies of each chromosome an organism has.)
- genotype (Correct. Genotype is the genetic composition of an organism.)
A: genotype

Q: A ________ is designed to identify the dominant trait.
- Punnett square (Incorrect. A Punnett square is a laboratory tool for predicting genotypes and phenotypes in offspring.)
- pedigree analysis (Incorrect. A pedigree analysis is used to study traits in humans when the genes controlling the trait are unknown.)
- testcross (Correct. A testcross will indicate which allele is dominant (and by extension, which is recessive).)
A: testcross

Q: If tall stems is dominant to short stems in pansies, what type of stem will the offspring of a tall plant and a short plant have?
- Average (Incorrect. In the case of dominant and recessive traits, the “intermediate” phenotype is not in the middle.)
- Short (Incorrect. Short stems would be recessive in this case, and only present if both parents had short stems.)
- Tall (Correct. Dominant traits express exclusively whenever they are present, regardless of the number of copies.)
A: Tall

Q: If you cross a true-breeding purple flower pea plant with a true-breeding white flower pea plant, which generation will tell you what trait is dominant?
- P_0 (Incorrect. This generation is the one used in the true-breeding cross.)
- F_2 (Incorrect. All the offspring of this generation will not show the same phenotype, though the dominant phenotype will be the most common.)
- F_1 (Correct. The offspring of two true-breeding parents will all display the dominant phenotype.)
A: F_1

Q: Mendel’s law of segregation tells us that ________.
- genes will display preferential segregation so that the dominant gene is inherited more often (Incorrect. A dominant gene is not necessarily inherited more often, it is just more commonly seen in phenotypes.)
- genes do not influence each other with regards to sorting into alleles and every possibility of allele combinations is equally likely (Incorrect. This is Mendel’s Law of Independent Assortment, best illustrated by a dihybrid or larger cross.)
- paired genes must segregate equally into gametes so that offspring have an equal likelihood of inheriting either gene (Correct. This is Mendel’s Law of Segregation, which is best illustrated by a simple monohybrid cross.)
A: paired genes must segregate equally into gametes so that offspring have an equal likelihood of inheriting either gene

Q: To test Mendel’s law of independent assortment, at a minimum you need to perform a ________ cross.
- monohybrid (Incorrect. A monohybrid cross is needed to test the law of segregation but is not sufficient for the law of independent assortment.)
- trihybrid (Incorrect. A trihybrid cross will let you test the independent inheritance of three traits, which is beyond the simplest test needed to assess the law of independent assortment.)
- dihybrid (Correct. A dihybrid cross will let you test the independent inheritance of two traits.)
A: dihybrid

Q: Use the following image to answer the question. If you performed the cross indicated to the F_2 generation, how many smooth, yellow peas would you expect to see in 100 offspring?
- 19 (Incorrect. This would be the number of smooth, green and the number of wrinkled, yellow peas.)
- 6 (Incorrect. This would the number of wrinkled, green peas.)
- 57 (Correct. This would be the number of smooth, yellow peas.)
A: 57

Q: Mendel’s law of independent assortment tells us that ________.
- paired genes must segregate equally into gametes so that offspring have an equal likelihood of inheriting either gene (Incorrect. This is Mendel’s Law of Segregation, which is best illustrated by a simple monohybrid cross.)
- genes will display preferential segregation so that the dominant gene is inherited more often (Incorrect. A dominant gene is not necessarily inherited more often, it is just more commonly seen in phenotypes.)
- genes do not influence each other with regards to sorting into alleles and every possibility of allele combinations is equally likely (Correct. This is Mendel’s Law of Independent Assortment, best illustrated by a dihybrid or larger cross.)
A: genes do not influence each other with regards to sorting into alleles and every possibility of allele combinations is equally likely

Q: Identify the phenotype combinations that indicate incomplete dominance.
- MN blood types in humans (Incorrect. This is a case of codominance.)
- Calico kittens from tortoiseshell and white parents (Incorrect. Coat colors, especially calico, in cats is a bit more complicated than just variations on dominance patterns.)
- Pink flowers from red and white parents (Correct. Pink is intermediate, or a blending, between the red and white colors of the parents.)
A: Pink flowers from red and white parents

Q: Incomplete dominance is ________
- equal expression of both alleles for a gene (Incorrect. This is codominance.)
- the term used when more than two alleles exist for a gene. (Incorrect. This is simply known as a multiple allele trait.)
- expression of two contrasting alleles that results in an intermediate phenotype (Correct. Incomplete dominance appears to match the old theories of ‘blending’ of phenotypes. But it doesn’t because both alleles are still present and given the right combinations in offspring, can result in the original ‘pure’ phenotype.)
A: expression of two contrasting alleles that results in an intermediate phenotype

Q: The genotype C^RC^W is an example of a(n) ________ trait.
- dominant (Incorrect. This is not how dominant traits are notated.)
- mixed dominant (Incorrect. There are no mixed dominant traits.)
- incomplete dominant (Correct. This is how traits that display incomplete dominance are notated.)
A: incomplete dominant

Q: In codominant inheritance, how many distinct phenotypes are there?
- one (Incorrect. There is actually never a single phenotype. The simplest of genetic traits has at least two.)
- two (Incorrect. Two phenotypes are the results of simple dominance.)
- three (Correct. There are three phenotypes in codominance: the homozygous phenotype of one version of the allele, the homozygous phenotype of the other allele version, and the heterozygous phenotype.)
A: three

Q: In phenotypes with ________ inheritance, the parental traits have equal expression in a single offspring.
- incomplete dominant (Incorrect. The parental traits are not equally expressed in incomplete dominance.)
- dominant-recessive (Incorrect. The parental traits are not equally expressed in dominant-recessive in a single offspring.)
- codominant (Correct. The heterozygous phenotype shows equal expression of the parental traits..)
A: codominant

Q: Identify the phenotype combinations that indicate codominance.
- Pink flowers from red and white parents (Incorrect. Pink is intermediate, or a blending, between the red and white colors of the parents, which is incomplete dominance.)
- Calico kittens from tortoiseshell and white parents (Incorrect. Coat colors, especially calico, in cats is a bit more complicated than just variations on dominance patterns.)
- MN blood types in humans (Correct. This is a case of codominance: both alleles are expressed equally.)
A: MN blood types in humans

Q: Human (and fly) males are said to be ________ for a sex-linked trait.
- homozygous (Incorrect. Homozygous individuals have two identical copies of the allele for the gene under question.)
- Heterozygous (Incorrect. Heterozygous individuals have two different alleles for the gene under question.)
- hemizygous (Correct. Males will have only one copy of the X chromosome that carries the X-linked characteristic.)
A: hemizygous

Q: A female carrier of a sex-linked trait will pass the disease on to ________ of her daughters.
- 25% (Incorrect. Remember: she is just a carrier.)
- 50% (Incorrect. Remember: she is just a carrier.)
- 0% (Correct. Since the mother is just a carrier, she will not pass on a dominant disease allele to her daughters.)
A: 0%

Q: In order for all of a woman’s sons to have a particular X-linked disease, the woman must be ________ for the disease.
- heterozygous (Incorrect. If she is heterozygous, then only half her eggs will have the disease allele. Therefore there is a 50% chance her sons will inherit a normal allele.)
- a carrier (Incorrect. A carrier is a woman who has one disease allele but does not have the disease herself.)
- homozygous (Correct. If a woman has the disease, then she has two disease alleles on her X-chromosome. Therefore all her sons will inherit the single defect X-linked allele (and half her daughters will be carriers).)
A: homozygous

Q: The ABO blood groups in humans are expressed as the I^A, I^B, and i alleles. The I^A allele encodes the A blood group antigen, IB encodes B, and i encodes O. Both A and B are dominant to O. If a heterozygous blood type A parent (I^Ai) and a heterozygous blood type B parent (I^Bi) mate, one quarter of their offspring will have AB blood type (I^AI^B) in which both antigens are expressed equally. Therefore, ABO blood groups are an example of ________.
- multiple alleles and incomplete dominance (Incorrect. There is no intermediate phenotype in this case because both the I^A and I^B alleles are expressed when present.)
- codominance and incomplete dominance (Incorrect. There is no intermediate phenotype in this case because both the I^A and I^B alleles are expressed when present.)
- multiple alleles and codominance (Correct. This is a case of multiple alleles because there are three alleles possible. It is a case of codominance between the I^A and I^B alleles, which will both be equally expressed when present.)
A: multiple alleles and codominance

Q: When many alleles exist for the same gene, the ________ phenotype is the wild type.
- most rare (Incorrect. The wild type phenotype is not the most rare.)
- most unique (Incorrect. The wild type phenotype is not the most unique.)
- most common (Correct. The most common phenotype is the one found most often in the ‘wild’ = the wild type.)
A: most common

Q: When many alleles exist for the same gene, the less common types are ________.
- dominant (Incorrect. The less common alleles are not necessarily dominant.)
- recessive (Incorrect. The less common alleles are not necessarily recessive.)
- variants (Correct. The less common alleles may be dominant or recessive to the wild-type, which is the most common. The wild-type phenotype is not necessarily a dominant one.)
A: variants

Q: Choose the best example of expressivity.
- A disorder that causes opposite effects in the sexes (Incorrect. Effects in the sexes is not a component of expressivity.)
- A disorder that may or may not show up in a carrier (Incorrect. This describes penetrance.)
- A disorder that has varying levels of severity (Correct. Expressivity refers to the variation in phenotypic expression when an allele is present.)
A: A disorder that has varying levels of severity

Q: Choose the best example of complete penetrance.
- A disorder that causes opposite effects in the sexes (Incorrect. This is not a case of complete penetrance.)
- A disorder that has varying levels of severity (Incorrect. This would depend on a gene’s expressivity.)
- A gene that is expressed in all of a population with the gene (Correct. Penetrance refers to the probability of a gene being expressed; expression in all of a population equals complete penetrance.)
A: A gene that is expressed in all of a population with the gene

Q: Reduced penetrance and variable expressivity are both likely due to ________.
- genetic effects (Incorrect. Genetic effects alone do not explain penetrance or expressivity.)
- environmental and lifestyle factors (Incorrect. Environmental and lifestyle factors, even together, are unlikely to be the causes of changes in penetrance or expressivity.)
- genetic, environmental, and lifestyle factors (Correct. Most likely reduced penetrance and variable expressivity are due to a combination of these three factors.)
A: genetic, environmental, and lifestyle factors

Q: When investigating the genetics of a disease with no known cause, medical teams use ________ to track the disease in families.
- bloodlines (Incorrect. Bloodlines is not a term generally applied to humans.)
- lineages (Incorrect. While lineages are what is looked at in families, this is not the tool used by medical.)
- pedigrees (Correct. Pedigrees are used by medical personnel to examine the history of a disease in families.)
A: pedigrees

Q: A family history can be used as ________ tool to asses a person’s risk for certain diseases.
- diagnostic (Incorrect. A disease is not diagnosed in an individual based on family history. This simply contributes to the final diagnostic.)
- treatment (Incorrect. Treatment plans are individualized, not based on family histories.)
- screening (Correct. Family histories can indicate the possibility or prevalence of certain diseases within a family, and hence individual members of that family.//reading https://courses.lumenlearning.com/wm-biology1/chapter/reading-pedigrees-and-disease/)
A: screening

Q: In a pedigree, females are indicated by ________.
- squares (Incorrect. Males are indicated by squares in pedigrees.)
- diamonds (Incorrect. Diamonds are used to indicate a specific number of children but when the sexes of each child is unknown. For example: 8 children would be represented by a diamond with the number ‘8’ inside it.)
- circles (Correct. Females are indicated by circles in pedigrees.)
A: circles

Q: Among medical screening tools, ________ are the most readily updated.
- blood tests (Incorrect. Blood tests are not the most readily updated screening tools.)
- genetic screening (Incorrect. Genetic tests are not the most readily updated screening tools.)
- pedigrees (Correct. The simple visual features of a pedigree make it easily updated when new information is obtained or new family members added to the analysis.)
A: pedigrees

Q: In a pedigree, individuals with the condition under investigation are indicated by a ________.
- open shape (Incorrect. An open shape indicates an unaffected individual.)
- diamond (Incorrect. Diamonds are used to indicate a specific number of children but when the sexes of each child is unknown. For example: 8 children would be represented by a diamond with the number ‘8’ inside it.)
- colored-in shape (Correct. Impacted individuals are indicated by the sex-specific shape which has been colored (or shaded) in.)
A: colored-in shape

Q: A ________ trait will be observed only in individuals that are homozygous for that trait.
- dominant (Incorrect. Dominant traits will be observable in heterozygous individuals as well.)
- codominant (Incorrect. Codominant traits will be observable in heterozygous individuals as well.)
- recessive (Correct. Recessive traits only display in homozygous individuals.)
A: recessive

Q: A disorder that displays dominant inheritance will appear in ________.
- male children only (Incorrect. A dominant trait does not display different expression due to sex.)
- female children only (Incorrect. A dominant trait does not display different expression due to sex.)
- all children (Correct. A dominant trait will appear in all individuals with the trait, regardless of sex.)
A: all children

Q: Only female individuals can ________ sex-linked disorders.
- have (Incorrect. In humans, few females have sex-linked disorders.)
- be immune to (Incorrect. Females are not immune from sex-linked disorders; they just occur much more rarely in females.)
- be carriers of (Correct. In humans, only females may be carriers of sex-linked disorders because they have two chromosomes.)
A: be carriers of

Q: Human sex-linked disorders in which male children are affected and female children are carriers are carried on the ________ chromosome.
- Y (Incorrect. Female children do not have a Y chromosome at all so they cannot be carriers of a Y-linked trait.)
- 22nd (Incorrect. Chromosome 22 is an autosome so it cannot carry sex-linked traits.)
- X (Correct. Male children only have one of each sex chromosome. Female children do not have a Y chromosome at all but do have two X chromosomes. So if females are carriers, then the sex-linked trait must be on the X chromosome.)
A: X

Q: Y-linked disorders appear in ________.
- female children (Incorrect. Females do not have a Y-chromosome, so they cannot have a Y-linked disorder.)
- male and female children (Incorrect. Females do not have a Y-chromosome, so they cannot have a Y-linked disorder.)
- male children (Correct. A disorder Y-linked disorder only appears in male children.)
A: male children

Q: In ________, the expression of one gene may be masked by the expression of another.
- continuous variation (Incorrect. Continuous variation refers to a range of possible phenotypes for a trait, such as height in humans.)
- pleiotropy (Incorrect. Pleiotropic genes affect multiple, seemingly unrelated aspects of phenotype.)
- epistasis (Correct. Epistatic interactions are antagonistic, in which one gene masks the expression of another.)
A: epistasis

Q: If the product of one gene is masked by another, the ________ is said to be hypostatic.
- subservient gene (Incorrect. This is not the term for the masked gene.)
- masking gene (Incorrect. This is not the term for the masked gene.)
- hidden gene (Correct. The masked gene is termed ‘hypostatic’ in an epistatic relationship.)
A: hidden gene

Q: The basis for epistatic gene relationships is often ________.
- one gene serves as a transcription factor for the hypostatic gene (Incorrect. This is not the foundation of most epistatic relationships.)
- one gene physically inhibits activity of another (Incorrect. This is not the foundation of most epistatic relationships.)
- the function of one gene being required for the expression of another in the same biochemical pathway (Correct. The biochemical basis of epistasis is often a gene pathway in which the expression of the hypostatic gene is dependent on the function of a gene in proximity to it within the pathway.)
A: the function of one gene being required for the expression of another in the same biochemical pathway

Q: ________ inheritance can often be identified by complex inheritance patterns and a wide range of phenotypes.
- Continuous variation (Incorrect. Continuous variation describes a wide range of phenotypes but does not indicate inheritance patterns.)
- Pleiotropic (Incorrect. Pleiotropic genes affect multiple, seemingly unrelated aspects of phenotype.)
- Polygenic (Correct. Polygenic inheritance involves multiple genes interacting and results in a wide range of phenotypes.)
A: Polygenic

Q: Eye color is known to be controlled through ________.
- pleiotropic inheritance (Incorrect. Eye color is not a pleiotropic trait.)
- epistatic inheritance (Incorrect. Eye color is not an epistatic trait.)
- polygenic inheritance (Correct. In humans eye color is controlled by two major genes and at least 14 additional genes that influence exact eye color.)
A: polygenic inheritance

Q: When studying a polygenic trait, the ________ are often difficult to determine.
- combined gene impacts (Incorrect. The combined impacts of the genes can be easy to recognize, such as the actual eye color a person has.)
- environmental impacts (Incorrect. Environmental impacts can be easily determined, such as when looking at base skin color versus skin color after sun exposure.)
- effects and inheritance patterns of each gene (Correct. The effect of each individual gene and the inheritance of gene alleles can be hard to distinguish.)
A: effects and inheritance patterns of each gene

Q: Traits with ________ will often display a bell curve-shaped distribution when graphed.
- codominant inheritance (Incorrect. Codominant traits have distinct phenotypes, so are easily categorized.)
- dominant-recessive inheritance (Incorrect. Dominant-recessive traits have distinct phenotypes, so are easily categorized.)
- continuous variation (Correct. Continuous variation traits graph to a bell curve-shaped distribution pattern.)
A: continuous variation

Q: When traits vary in small gradations and span a spectrum of possibilities, they are displaying ________.
- pleiotropy (Incorrect. Pleiotropic genes affect multiple, seemingly unrelated aspects of phenotype.)
- epistasis (Incorrect. Epistasis occurs when one gene product masks the expression of another.)
- continuous variation (Correct. The hallmark of continuous variation is a spectrum of phenotypes that can be difficult to distinguish from each other.)
A: continuous variation

Q: Continuous variation traits are often ________.
- epistatic (Incorrect. Epistasis occurs when one gene product masks the expression of another. It does not generate continuous variation.)
- multiple allele traits (Incorrect. Multiple allele traits are controlled by single genes that just have more than two alleles in the population.)
- polygenic (Correct. Traits that show continuous variation are often polygenic, meaning multiple genes contribute to the final phenotype.)
A: polygenic

Q: The range of ________ is known as the norm of reaction.
- traits, which trend towards an average state over several generations, (Incorrect. This would be regression to the mean.)
- genotypic possibilities in a given trait (Incorrect. This is not the norm of reaction.)
- phenotypic possibilities influenced by environment (Correct. The range of phenotypic possibilities is known as the norm of reaction.)
A: phenotypic possibilities influenced by environment

Q: The norm of reaction is ultimately determined by ________ but is set by ________.
- the basic genotype; environmental exposure (Incorrect. The final phenotype in a norm of reaction state is not determined by the genotype.)
- epistatic interactions; pleiotropic interactions (Incorrect. Epistatic and pleiotropic interactions may play a role in some, but certainly not all, final phenotypes that show a norm of reaction.)
- environmental exposures; the basic genotype (Correct. The basic genotype establishes the possible phenotypes but the final range of phenotypes is determined by environmental influences on that genotype.)
A: environmental exposures; the basic genotype

Q: Environmental effects are important to assess because ________.
- they determine occurrence of diseases (Incorrect. Environmental effects and exposures may result in some diseases, but certainly not all.)
- they always overwhelm genetic factors (Incorrect. Some disorders or phenotypes are wholly controlled by genetics, such as Huntingdon’s.)
- they can modify gene expression (Correct. Understanding the effects of environment and environmental exposures can help in mitigating some disease possibilities, such as PKU.)
A: they can modify gene expression

Q: Which of the following is true of pleiotropic genes?
- The expression of one gene may be masked by the expression of another. (Incorrect. This is epistasis.)
- Traits vary in small gradations and span a spectrum of possibilities. (Incorrect. This is continuous variation, which are not necessarily pleiotropic genes.)
- Genes may affect multiple, seemingly unrelated aspects of phenotype. (Correct. Pleiotropic genes affect what appear to be unrelated aspects of phenotype, though usually there is a biochemical or regulatory explanation to be found.)
A: Genes may affect multiple, seemingly unrelated aspects of phenotype.

Q: The flower color gene studied by Mendel affected three traits. This is an example of ________.
- codominant inheritance (Incorrect. One gene affecting three traits in not codominant inheritance.)
- polygenic inheritance (Incorrect. Polygenic inheritance involves more than one gene.)
- pleiotropic genes (Correct. The “flower color” gene actually affected flower color, color of the seed coat, and color of the axils.)
A: pleiotropic genes

Q: Alleles of pleiotropic genes are inherited ________.
- in a sex-linked fashion (Incorrect. Pleiotropic genes are not necessarily sex-linked though they can be.)
- in set combinations (Incorrect. Pleiotropic genes are not necessarily linked in any fashion; they display independent assortment.)
- just as single trait alleles are (Correct. Alleles of pleiotropic genes are transmitted in the same way as alleles of genes that affect single traits.)
A: just as single trait alleles are