Exam - Genetics - Inheritance Patterns

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Exam - Genetics - Inheritance Patterns - Quiz

Questions and Answers
  • 1. 

    In humans, pigmented skin is dominant to non-pigmented skin (albinism). What is the genotype of an individual with albinism?

    • A.

      Carrier

    • B.

      Heterozygous

    • C.

      Homozygous dominant

    • D.

      Homozygous recessive

    Correct Answer
    D. Homozygous recessive
    Explanation
    An individual with albinism has a genotype of homozygous recessive. This means that both of their alleles for the pigmentation gene are recessive, resulting in the absence of pigmentation in their skin.

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  • 2. 

    Adrenoleukodystrophy (ALD) is a sex-linked recessive trait that affects the nervous system. In one family, the father, mother, daughter, and elder son do not have ALD, while the younger son has ALD. Who must be a carrier of the ALD allele?

    • A.

      Father

    • B.

      Mother

    • C.

      Daughter

    • D.

      Elder son

    Correct Answer
    B. Mother
    Explanation
    Since ALD is a sex-linked recessive trait, it is carried on the X chromosome. The father cannot be a carrier because he does not have ALD, and the elder son cannot be a carrier because he does not have ALD either. The daughter cannot be a carrier because she would have inherited the X chromosome without the ALD allele from her mother. Therefore, the only possible carrier of the ALD allele is the mother, who can pass it on to her affected younger son.

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  • 3. 

    Cystic fibrosis is a genetic disease in which excess mucus accumulates in the lungs and digestive system of affected individuals. Males and females must inherit 2 of the same alleles with this mutation to have the disease. What is the mode of inheritance of cystic fibrosis?

    • A.

      Autosomal dominant

    • B.

      Autosomal recessive

    • C.

      Sex-linked dominant

    • D.

      Sex-linked recessive

    Correct Answer
    B. Autosomal recessive
    Explanation
    Cystic fibrosis is a genetic disease that follows an autosomal recessive mode of inheritance. This means that both copies of the gene responsible for cystic fibrosis must be mutated for an individual to develop the disease. In this case, males and females must inherit two copies of the same allele with the mutation to have cystic fibrosis. If they inherit only one mutated allele, they will be carriers of the disease but will not show symptoms.

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  • 4. 

    Which event of meiosis reveals the mechanism for understanding Mendel’s laws of segregation and independent assortment?

    • A.

      Chromosome number is reduced during telophase I so gametes have half the standard number of chromosomes.

    • B.

      The arrangement of homologous chromosomes during metaphase I varies from cell to cell.

    • C.

      Centromeres break apart during anaphase II so that sister chromatids can move to opposite poles of the cell.

    • D.

      DNA is replicated during interphase before chromosomes condense and become attached to kinetochores.

    Correct Answer
    B. The arrangement of homologous chromosomes during metaphase I varies from cell to cell.
    Explanation
    The arrangement of homologous chromosomes during metaphase I varies from cell to cell. This event in meiosis is known as independent assortment, where homologous chromosomes align randomly along the metaphase plate. This process allows for different combinations of alleles to be present in the resulting gametes, which is the basis for Mendel's law of independent assortment. By observing the different arrangements of homologous chromosomes, scientists can understand how genetic traits are inherited and passed on to offspring.

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  • 5. 

    Two black guinea pigs bred and produced 3 black offspring and 2 albino offspring. Assuming no mutations, which guinea pigs must be heterozygous?        

    • A.

      All 3 black offspring

    • B.

      Exactly 2 of the black offspring Exactly 2 of the black offspring Exactly 2 of the black offspring Exactly 2 of the black offspring

    • C.

      Both albino offspring

    • D.

      Both parents

    Correct Answer
    D. Both parents
    Explanation
    The fact that two black guinea pigs produced both black and albino offspring suggests that both parents must be heterozygous for the black coat color gene. This means that each parent carries both a dominant allele for black coat color and a recessive allele for albino coat color. When these alleles are passed on to their offspring, there is a chance that the recessive allele for albino coat color will be expressed in some of the offspring. Therefore, both parents must be heterozygous in order to produce both black and albino offspring.

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  • 6. 

    The genotype of F1 individuals from a dihybrid cross is AaBb x AaBB. What is the expected ratio of AaBb individuals in the F2 generation?

    • A.

      8/16

    • B.

      4/16

    • C.

      2/16

    • D.

      1/16

    Correct Answer
    B. 4/16
    Explanation
    In a dihybrid cross, the F1 individuals have the genotype AaBb x AaBB. When these individuals are crossed in the F2 generation, the possible genotypes of the offspring are AaBb, AaBB, AABb, and AABB. Out of these four possible genotypes, only one is AaBb. Therefore, the expected ratio of AaBb individuals in the F2 generation is 1/4, which is equivalent to 4/16.

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  • 7. 

    Alkaptonuria is a genetic disorder of protein metabolism.  The disorder is determined by 2 alleles at 1 locus. What is the genotype for Individual 1 in the diagram?

    • A.

      AA or Aa

    • B.

      AA

    • C.

      Aa

    • D.

      Aa

    Correct Answer
    C. Aa
    Explanation
    The genotype for Individual 1 in the diagram is Aa. This is because the disorder Alkaptonuria is determined by 2 alleles at 1 locus, which means that an individual can have either two copies of the dominant allele (AA), one copy of the dominant allele and one copy of the recessive allele (Aa), or two copies of the recessive allele (aa). Since the answer options are AA or Aa, Individual 1 must have one copy of the dominant allele (A) and one copy of the recessive allele (a), making their genotype Aa.

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  • 8. 

    A trisomy of chromosome 21 causes what condition?

    • A.

      Albinism

    • B.

      Dwarfism

    • C.

      Down syndrome

    • D.

      Color blindness

    Correct Answer
    C. Down syndrome
    Explanation
    A trisomy of chromosome 21 refers to the presence of an extra copy of chromosome 21 in a person's cells. This genetic abnormality is the cause of Down syndrome, a condition characterized by intellectual disability, distinct facial features, and certain medical conditions such as heart defects and digestive problems. Albinism is a genetic condition characterized by a lack of pigment in the skin, hair, and eyes. Dwarfism refers to a condition of short stature. Color blindness is a condition where individuals have difficulty distinguishing certain colors.

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  • 9. 

    Keisha passes a local dairy farm that has many brown cows, but only a few white cows. A dominant allele produces brown hair in cows and a recessive allele produces white hair. Which characteristic of any brown cow can Keisha identify?

    • A.

      The genotype of both of the cow’s parents

    • B.

      The genotype of the cow’s hair color

    • C.

      The phenotype of both of the cow’s parents

    • D.

      The phenotype of the cow’s hair color

    Correct Answer
    D. The phenotype of the cow’s hair color
    Explanation
    Keisha can identify the phenotype of the cow's hair color because the question states that the dominant allele produces brown hair in cows and the recessive allele produces white hair. The phenotype refers to the observable characteristics of an organism, in this case, the color of the cow's hair. Therefore, by observing the cow's hair color, Keisha can determine whether it is brown or white, indicating the phenotype of the cow's hair color.

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  • 10. 

    Jeanine inherited 2 alleles for round eye shape and has round eye shape. Her brother inherited 1 allele for round eye shape and 1 allele for almond eye shape and has almond eye shape. What type of trait is round eye shape?

    • A.

      Co-dominant

    • B.

      Dominant

    • C.

      Recessive

    • D.

      Sex-linked

    Correct Answer
    C. Recessive
    Explanation
    Round eye shape is a recessive trait. This is because Jeanine inherited 2 alleles for round eye shape and has round eye shape, while her brother inherited 1 allele for round eye shape and 1 allele for almond eye shape and has almond eye shape. In this case, the presence of even one allele for almond eye shape in Jeanine's brother is enough to determine his eye shape, indicating that the almond eye shape allele is dominant over the round eye shape allele. Therefore, round eye shape must be the recessive trait in this scenario.

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  • 11. 

    In humans, red-green color blindness is a recessive, sex-linked trait. The chromosomes and alleles associated with color blindness are represented in this chart. Which child could NOT be born to these parents; a female (XBXb) and a male (XBY)?

    • A.

      Color-blind daughter

    • B.

      Color-blind son

    • C.

      Daughter with normal color vision

    • D.

      Son with normal color vision

    Correct Answer
    A. Color-blind daughter
    Explanation
    In humans, red-green color blindness is a recessive, sex-linked trait. This means that it is carried on the X chromosome. Since the mother is a carrier (XBXb) and the father is not color blind (XBY), there is a 50% chance that a daughter will be a carrier (XBXb) and a 50% chance that a son will not be color blind (XBY). However, it is not possible for a daughter to be color blind because she would need to inherit the recessive allele from both parents (XbXb), which is not possible in this case. Therefore, a color-blind daughter could not be born to these parents.

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  • 12. 

    The pedigree shows 3 generations of a family and the family’s incidences of color blindness, a sex-linked, recessive trait. Which pair of females must have the same genotype?

    • A.

      3 and 5

    • B.

      7 and 11

    • C.

      8 and 13

    • D.

      10 and 14

    Correct Answer
    C. 8 and 13
    Explanation
    In the given pedigree, females 8 and 13 must have the same genotype. This can be concluded because both females have a color-blind father (individual 6) and a carrier mother (individual 9). Since color blindness is a sex-linked recessive trait, females can only be affected if they inherit the color-blind allele from both parents. Therefore, females 8 and 13 must both be carriers of the color-blind allele, making their genotypes the same.

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  • 13. 

    Which example best illustrates Mendel’s law of independent assortment?

    • A.

      Two short-haired cats produce a litter of 4 kittens including 1 long-haired and 3 short-haired.

    • B.

      A color-blind man and a woman with normal vision produce a son with normal vision and a color-blind daughter.

    • C.

      A tall purple-flowered pea plant and a short white-flowered pea plant are crossed, producing offspring including tall white-flowered pea plants.

    • D.

      A red-flowered snapdragon and a white-flowered snapdragon are crossed, producing offspring with pink flowers.

    Correct Answer
    C. A tall purple-flowered pea plant and a short white-flowered pea plant are crossed, producing offspring including tall white-flowered pea plants.
    Explanation
    This example best illustrates Mendel's law of independent assortment because it shows the inheritance of two different traits (height and flower color) that are independently inherited. The fact that the offspring include tall white-flowered pea plants shows that the traits are not linked or influenced by each other, as they are inherited independently.

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  • 14. 

    Horses born to 2 palomino (golden-coated) horses have a 25% chance of having a white coat, a 25% chance of having a chestnut (brown) coat, and a 50% chance of having a palomino coat. Which description of inheritance best explains the coat-color trait in these horses?

    • A.

      Palomino coat color is a recessive trait.

    • B.

      Palomino coat color is a dominant trait.

    • C.

      Coat color is an incompletely dominant trait.

    • D.

      Coat color is a sex-linked trait.

    Correct Answer
    C. Coat color is an incompletely dominant trait.
  • 15. 

    The X and Y chromosomes are called the

    • A.

      Extra chromosomes.

    • B.

      Phenotypes.

    • C.

      Sex chromosomes.

    • D.

      All of the above.

    Correct Answer
    C. Sex chromosomes.
    Explanation
    The X and Y chromosomes are referred to as sex chromosomes because they determine the sex of an individual. In humans, females have two X chromosomes (XX) and males have one X and one Y chromosome (XY). These chromosomes carry genes that are responsible for the development of sexual characteristics and reproductive functions. The other options, extra chromosomes and phenotypes, are incorrect as they do not specifically describe the X and Y chromosomes.

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  • 16. 

    Which of the following is the best explanation for the observation that females rarely get the disease hemophilia?

    • A.

      Large quantities of male hormones are necessary in order for the allele carrying the disease to be expressed.

    • B.

      Female fetuses that carry the allele for the disease die before birth.

    • C.

      A female could get the disease only by having a mother who is a carrier and a father who has the disease. Since most males with the disease do not survive to reproductive age, this is an extremely unlikely event.

    • D.

      A female could get the disease only by having parents who are both carriers of the disease. Because females cannot be carriers, this is an impossible event.

    Correct Answer
    C. A female could get the disease only by having a mother who is a carrier and a father who has the disease. Since most males with the disease do not survive to reproductive age, this is an extremely unlikely event.
    Explanation
    Hemophilia is a sex-linked recessive disorder, which means it is carried on the X chromosome. Since females have two X chromosomes, they would need to inherit the disease-causing allele from both parents to have the disease. The given answer states that a female could get the disease only if her mother is a carrier and her father has the disease. However, it also mentions that most males with the disease do not survive to reproductive age, making this scenario extremely unlikely. This explains why females rarely get the disease hemophilia.

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  • 17. 

    In a mating between two parental types, one of which is homozygous dominant for two linked traits and one of which is homozygous recessive for the same two linked traits, evidence of crossing-over would be apparent in which of the following generations?

    • A.

      Parents

    • B.

      F1

    • C.

      F2

    • D.

      All of the above

    Correct Answer
    C. F2
    Explanation
    In the F2 generation, evidence of crossing-over would be apparent. This is because crossing-over occurs during meiosis, specifically during the formation of gametes. In the F1 generation, the offspring would have one dominant and one recessive allele for each trait, but they would not show evidence of crossing-over. However, in the F2 generation, the alleles from the F1 generation can recombine through crossing-over, resulting in new combinations of traits that were not present in the parental generation. Therefore, the F2 generation would show evidence of crossing-over.

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  • 18. 

    Which of the following traits is controlled by multiple alleles in humans?

    • A.

      Sickle cell anemia

    • B.

      Blood type

    • C.

      Hemophilia

    • D.

      Pattern baldness

    Correct Answer
    B. Blood type
    Explanation
    Blood type is controlled by multiple alleles in humans. The ABO blood group system is determined by three alleles: A, B, and O. These alleles determine the presence or absence of specific antigens on the surface of red blood cells. A person can have blood type A (AA or AO), blood type B (BB or BO), blood type AB (AB), or blood type O (OO), depending on the combination of alleles inherited from their parents. This multiple allele inheritance pattern allows for the existence of different blood types in the human population.

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  • 19. 

    What would be the blood type of a person who inherited an A allele from one parent and an O allele from the other?

    • A.

      Type A

    • B.

      Type B

    • C.

      Type AB

    • D.

      Type O

    Correct Answer
    A. Type A
    Explanation
    A person who inherited an A allele from one parent and an O allele from the other would have a blood type A. This is because the A allele is dominant over the O allele, so even though they have one O allele, the presence of the A allele will determine their blood type as A.

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  • 20. 

    While studying several generations of a particular family, a geneticist observed that a certain disease was found equally in males and females and that all children who had the disease had parents who also had the disease. The gene coding for this disease is probably

    • A.

      Sex-linked recessive.

    • B.

      Sex-linked dominant.

    • C.

      Autosomal recessive.

    • D.

      Autosomal dominant.

    Correct Answer
    D. Autosomal dominant.
    Explanation
    Based on the information provided, the geneticist observed that the disease was found equally in males and females, which suggests that it is not sex-linked. Additionally, the fact that all children who had the disease had parents who also had the disease indicates that it is inherited from both parents, ruling out a recessive pattern. Therefore, the most likely explanation is that the gene coding for this disease is autosomal dominant.

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  • 21. 

    If both parents carry the recessive allele that causes cystic fibrosis, the chance that their child will develop the disease is

    • A.

      One in two.

    • B.

      One in four.

    • C.

      Two in five.

    • D.

      100%.

    Correct Answer
    B. One in four.
    Explanation
    If both parents carry the recessive allele for cystic fibrosis, there is a one in four chance that their child will develop the disease. This is because both parents must pass on the recessive allele for the child to inherit the disease. If only one parent passes on the allele, the child will be a carrier but not develop the disease. Therefore, the chance of the child developing the disease is one in four.

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  • 22. 

    If a characteristic is sex-linked, it

    • A.

      Occurs most commonly in males.

    • B.

      Occurs only in females.

    • C.

      Can never occur in females.

    • D.

      Is always fatal.

    Correct Answer
    A. Occurs most commonly in males.
    Explanation
    Sex-linked characteristics are traits that are determined by genes located on the sex chromosomes, specifically the X chromosome. Since males have one X and one Y chromosome, while females have two X chromosomes, any gene on the X chromosome will have a greater chance of being expressed in males. This is because males only need one copy of the gene to show the trait, while females need two copies. Therefore, a sex-linked characteristic is more likely to occur in males, although it can still occur in females if they inherit the gene from both parents.

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  • 23. 

    Since the allele for colorblindness is located on the X chromosome, colorblindness

    • A.

      Cannot be inherited.

    • B.

      Occurs only in adults.

    • C.

      Is sex-linked.

    • D.

      None of the above.

    Correct Answer
    C. Is sex-linked.
    Explanation
    Colorblindness is a genetic disorder that is caused by a mutation in the genes located on the X chromosome. Since males have only one X chromosome, they are more likely to inherit colorblindness if their mother carries the mutated gene. Females, on the other hand, have two X chromosomes, so they have a lower chance of inheriting colorblindness. This pattern of inheritance, where the gene is located on the sex chromosome, is known as sex-linked inheritance. Therefore, the correct answer is that colorblindness is sex-linked.

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  • 24. 

    The sex of an offspring is determined by

    • A.

      The mother.

    • B.

      The father.

    • C.

      Both parents.

    • D.

      The offspring.

    Correct Answer
    B. The father.
    Explanation
    The sex of an offspring is determined by the father because the father contributes both an X or Y chromosome to the fertilization process. The mother only contributes an X chromosome. If the father's sperm carries an X chromosome, the offspring will be female, and if it carries a Y chromosome, the offspring will be male. Therefore, the father's contribution determines the sex of the offspring.

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  • 25. 

    When Gregor Mendel crossed true-breeding tall plants with true-breeding short plants, all the offspring were tall because

    • A.

      The allele for tall plants is recessive.

    • B.

      The allele for short plants is dominant.

    • C.

      The allele for tall plants is dominant.

    • D.

      They were true-breeding like their parents.

    Correct Answer
    C. The allele for tall plants is dominant.
    Explanation
    When Gregor Mendel crossed true-breeding tall plants with true-breeding short plants, all the offspring were tall because the allele for tall plants is dominant. This means that the presence of the allele for tall plants will result in the expression of the tall phenotype, overriding the presence of the allele for short plants. As a result, even though the short plants were true-breeding, their offspring inherited the dominant allele for tall plants from one parent, leading to the expression of the tall phenotype in all the offspring.

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  • 26. 

    A tall plant is crossed with a short plant. If the tall F1 pea plants are allowed to self-pollinate,

    • A.

      The offspring will be of medium height.

    • B.

      All of the offspring will be tall.

    • C.

      All of the offspring will be short.

    • D.

      Some of the offspring will be tall, and some will be short.

    Correct Answer
    D. Some of the offspring will be tall, and some will be short.
    Explanation
    When a tall plant is crossed with a short plant, the resulting F1 generation will all be tall because the tall trait is dominant over the short trait. However, when the tall F1 plants self-pollinate, the offspring will inherit a mix of alleles from both parents. This means that some of the offspring will receive the dominant tall allele and be tall, while others will receive the recessive short allele and be short. Therefore, the correct answer is that some of the offspring will be tall, and some will be short.

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  • 27. 

    A heterozygous tall pea plant is crossed with a short plant. The probability that an F1 plant will be tall is

    • A.

      25%.

    • B.

      50%.

    • C.

      75%.

    • D.

      100%.

    Correct Answer
    B. 50%.
    Explanation
    When a heterozygous tall pea plant is crossed with a short plant, the genotype of the heterozygous tall pea plant is Tt (T for tall and t for short). In this case, the T allele is dominant over the t allele. Therefore, there is a 50% chance that the offspring will inherit the T allele and be tall, and a 50% chance that the offspring will inherit the t allele and be short. Hence, the probability that an F1 plant will be tall is 50%.

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  • 28. 

    In the Punnett square shown in Figure 11–1, which of the following is true about the offspring resulting from the cross?

    • A.

      About half are expected to be short.

    • B.

      All are expected to be short.

    • C.

      About half are expected to be tall.

    • D.

      All are expected to be tall.

    Correct Answer
    D. All are expected to be tall.
    Explanation
    The Punnett square in Figure 11-1 shows that both parents are homozygous dominant for the tall trait. Therefore, all of the offspring resulting from the cross will inherit the dominant allele for tallness from both parents, resulting in all offspring being tall.

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  • 29. 

    How many different allele combinations would be found in the gametes produced by a pea plant whose genotype was RrYY?

    • A.

      2

    • B.

      4

    • C.

      8

    • D.

      16

    Correct Answer
    A. 2
    Explanation
    The correct answer is 2 because the pea plant genotype is RrYY, which means it has two different alleles for each gene. During gamete formation, each gamete will receive one allele from each gene, resulting in two different allele combinations.

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  • 30. 

    A cross of a black chicken (BB) with a white chicken (WW) produces all speckled offspring (BBWW). This type of inheritance is known as

    • A.

      Incomplete dominance.

    • B.

      Polygenic inheritance.

    • C.

      Codominance.

    • D.

      Multiple alleles.

    Correct Answer
    C. Codominance.
    Explanation
    When a cross between a black chicken (BB) and a white chicken (WW) produces all speckled offspring (BBWW), it indicates that both the black and white alleles are expressed equally in the offspring. This type of inheritance, where both alleles are fully expressed and neither is dominant over the other, is known as codominance.

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