Embedded Files
Objectives
Objectives
Quiz 1:
1. Understand the relationship between chromosome, gene, allele, trait, genotype, and phenotype.
2. Be able to determine phenotypes and genotypes in genetics problems based on Mendel's Laws, including classifying as homozygous recessive, heterozygous (a.k.a. carrier), or homozygous dominant.
3. Use a Punnett Square to determine phenotype and genotype probabilities in a monohybrid cross.
4. Be able to construct, label genotypes in, and interpret a pedigree.
5. Be able to determine if a pedigree displays autosomal dominant or autosomal recessive inheritance.
Quiz 2:
6. Use a Punnett Square to determine phenotype and genotype probabilities in a dihybrid cross.
7. Recognize inheritance patterns indicating codominance, incomplete dominance, sex-linkage, multiallelic traits, and polygenic traits.
8. Be able to construct monohybrid crosses for codominance and incomplete dominance scenarios.
9. Explain Mendel's three laws and how they can be observed in a dihybrid cross.
10. Identify whether a pedigree displays an autosomal or sex-linked, and dominant or recessive pattern of inheritance.
Vocabulary
Vocabulary
Quiz 1:
Allele
Dominant
F1 generation
F2 generation
Gamete
Gene
Generation
Genotype
Heterozygous
Homozygous
Mendel's Laws (Law of Dominance, Law of Segregation, Law of Independent Assortment)
P generation
Pedigree
Phenotype
Punnett Square
Recessive
Test cross
Trait
Zygote
Quiz 2:
Autosomal chromosome
Autosomal trait
Codominance
Environmental influence
Incomplete dominance
Multiallelic trait or gene
Polygenic trait
Sex chromosome
Sex-linked trait
X-linked, Y-linked
Textbook Reference
Textbook Reference
Quiz 1:
5.12: Mendel deduced the basic principles of genetics by breeding pea plants
5.13: A Punnett square can be used to predict the results of a genetic cross
5.14: Mendel's law of independent assortment accounts for the inheritance of multiple traits
5.15: Pedigrees can be used to trace traits in human families
Quiz 2:
5.16: The inheritance of many traits is more complex than Mendel's laws
5.17: Linked genes may not obey the law of independent assortment
5.18: Sex-linked genes display unusual inheritance patterns
Relevant Files
Relevant Files
Many websites have practice problems, though not necessarily of MCAS caliber. Here is one and here are more...
Sample MCAS Questions
Sample MCAS Questions
Quiz 1:
1. In sheep, the allele for white wool (W) is dominant, and the allele for black wool (w) is recessive. A farmer has mated two Suffolk sheep for a few years. These matings have resulted in six offspring, four with white wool and two with black wool. One parent has white wool and the other has black wool. Which of the following could be the genotypes of the parent sheep?
A. WW and Ww
B. WW and ww
C. Ww and Ww
D. Ww and ww
2. In pigeons, the allele B produces ash-red feathers. The allele b produces blue feathers. The B allele is dominant to the b allele.
A pigeon with the genotype Bb is crossed with a pigeon with the genotype bb. What percentage of the offspring are expected to have ash-red feathers?
A. 0%
B. 25%
C. 50%
D. 100%
3. A gene in horses controls whether the horse has a white coat or a colored coat. A white female horse and a white male horse are the parents of a total of five female offspring. Three of these offspring have white coats. The other two offspring have colored coats.
The phenotypes of the horses suggest which of the following as the most likely pattern of inheritance for coat color?
A. The allele for a white coat is dominant
B. The allele for a white coat is recessive
C. The allele for a white coat is sex-linked
D. The allele for a white coat is codominant
4. A cow and bull have a calf with the same coat color as they have. This calf developed from a zygote. During the development of this zygote, a mutation occurred in a coat color gene.
Which of the following best explains why the calf's phenotype is the same as its parents?
A. The mutation is not present in the parent animals.
B. The mutated gene is passed on during reproduction.
C. The mutated allele is dominant over the parental allele.
D. The mutation does not affect the expression of the coat color trait.
5. Hawaiian happy face spiders from the island of Maui can have different markings, as shown below. A single gene determines the markings on the spiders.
A plain spider is crossed with a patterned spider. The patterned spider is homozygous. The pattern allele is dominant to the plain allele.
What percentage of the offspring from this cross are expected to be patterned rather than plain?
A. 0%
B. 25%
C. 50%
D. 100%
6. A partial Punnett square is shown below.
AA AA
Aa Aa
Which of the following statements describes the parental genotypes that would result in this Punnett square?
A. Both parents are heterozygous.
B. Both parents are homozygous dominant.
C. One parent is homozygous recessive and the other parent is heterozygous.
D. One parent is homozygous dominant and the other parent is heterozygous.
7. Shelly and Jason are siblings, but Shelly looks like their father while Jason looks like their mother. Which of the following statements best explains the different in Shelly and Jason's features?
A. Shelly inherited a greater number of chromosomes from their father than Jason did.
B. Shelly inherited a smaller number of X chromsomes from their mother than Jason did.
C. Shelly and Jason had different mutations occur in the 46 chromosomes they inherited from their mother and father.
D. Shelly and Jason inherited different combinations of 23 chromosomes from their mother and 23 chromosomes from their father.
8. In mussels, brown (B) coloring is dominant, and blue (b) coloring is recessive. If a blue mussel has two brown parents, what percentage of the total offspring of these brown parents are expected to be blue?
A. 100%
B. 75%
C. 50%
D. 25%
9. A mutation in which of the following types of cells could be passed on to an organism's offspring?
A. blood
B. egg
C. muscle
D. nerve
10. In cats, the allele for short hair (H) is dominant to the allele for long hair (h). If a heterozygous short-hair cat is crossed with a long-hair cat, what percentage of the offspring is expected to be heterozygous for hair length?
A. 0%
B. 25%
C. 50%
D. 75%
11. When looking at a child, many people make statements such as "She has her mother's eyes" and "She has her father's hair color."
a. Describe the roles of the following in sexual reproduction:
meiosis
gametes
fertilization
zygote
b. Explain in detail why children's features may be similar to, but not exactly the same as, their parents' features.
12. An inherited metabolic disorder called phenylketonuria (PKU) can result in serious problems in infancy. The chance that two parents who are heterozygous will have a child with PKU is 25%.
Which of the following terms best applies to the inheritance pattern for PKU?
A. codominant
B. dominant
C. recessive
D. sex-linked
13. Individual Y has two Hb A alleles and therefore produces normal red blood cells. Individual Z has two Hb S alleles and therefore produces sickle-shaped red blood cells.
Which of the following statements best compares individual Y and individual Z in terms of genotype and phenotype?
A. The individuals have the same genotype and the same phenotype.
B. The individuals have the same genotype but different phenotypes.
C. The individuals have different genotypes but the same phenotype.
D. The individuals have different genotypes and different phenotypes.
14. Which of the following statements best explains why offspring produced by sexual reproduction often look similar to, but not exactly the same as, their parents?
A. The offspring have genetic material from both the mother and the father.
B. The cells of the offspring contain all the dominant genes from the parents.
C. The cells of the offspring undergo mitosis many times as the offspring grow and develop.
D. The offspring have a period of embryonic development, rather than being born immediately after fertilization.
Quiz 2:
15. In a certain variety of chicken, some offspring have a feather pattern that is black-and-white checkered. Chickens with this checkered feather pattern result from the cross of a black chicken with a white chicken. Which of the following types of inheritance is most likely responsible for the checkered feather pattern?
A. Codominant
B. Dominant
C. Polygenic
D. Sex-linked
16. In fruit flies, a single gene controls wing phenotype. Wing phenotypes are long wings, or short vestigial wings.
Two fruit flies with long wings are crossed. Of the 95 offspring produced, 73 have long wings. The others have vestigial wings. Which of the following conclusions about the inheritance of long wings and vestigial wings is best supported by the results of the experiment?
A. The alleles for long wings and vestigial wings are sex-linked.
B. The alleles for long wings and vestigial wings are codominant.
C. The allele for long wings is dominant and the allele for vestigial wings is recessive.
D. The allele for vestigial wings is dominant and the allele for long wings is recessive.
17. Corn snakes show variety in their skin color pattern. While the complete genetics of corn snake color are complex, the most common colors on normal corn snakes - red and black - are each coded by one gene.
For the red gene, the allele for the presence of red pigment (R) is dominant and the allele for the absence of red pigment (r) is recessive. Likewise, for the black gene, the allele for the presence of black pigment (B) is dominant and the allele for the absence of black pigment (b) is recessive.
a. Draw the Punnett Square for the cross of a snake that is homozygous dominant for the red color with a snake that is heterozygous for the red color. What percentage of the offspring is expected to have red pigment in their skin?
b. Draw the Punnett Square for the cross of two snakes that are heterozygous for the black color. What percentage of the offspring are expected to have black pigment in their skin?
c. The parent snakes in part (b) that are heterozygous for black color are both homozygous recessive for the red gene. Each parent has genotype rr for the red gene. Based on this information, what percentage of their offspring are expected to lack both the red and black pigments in their skin? Explain your reasoning.
18. In pea plants, the genes for seed color and seed shape are on different chromosomes. Which of the following explains why the genes for these traits are not inherited together?
A. Natural selection
B. Artificial selection
C. The law of segregation
D. The law of independent assortment
19. The pedigree below shows the occurrence of Becker muscular dystrophy in a family. Becker muscular dystrophy causes muscle weakness.
Based on this pedigree, it is most reasonable to conclude that Becker muscular dystrophy is which of the following?
A. A polygenic trait
B. A codominant trait
C. A sex-linked recessive trait
D. An autosomal dominant trait
20. Human blood types are genetically determined. The table below shows the symbols used to represent two of the alleles for blood types and gives a description of each allele.
In homozygous individuals, two IA alleles result in blood type A and two IB alleles result in blood type B. The IA and IB alleles are codominant, resulting in blood type AB in individuals heterozygous for the two alleles.
A male and a female both have blood type AB. If they have a child, what is the probability that the child will also have blood type AB?
A. 1/4
B. 1/2
C. 3/4
D. 1/1
21. The diagram below shows the positions of the genes for flower color and stem length in a pea plant. The chromosomes represented below will replicate before meiosis.
For these two genes, what is the maximum number of different allele combinations that can be formed normally in gametes produced from this cell?
A. 2
B. 4
C. 6
D. 8
22. Which of the following terms applies to traits, such as human eye color, that are controlled by more than one gene?
A. Codominant
B. Polygenic
C. Recessive
D. Sex-linked
23. In some pea plant experiments, Mendel studied the inheritance patterns of two characteristics at one, such as seed shape and seed color. He did this to determine which of the following?
A. The process by which mutations occur
B. Where genes are located within the chromosomes
C. Whether characteristics are inherited together or separately
D. The number of crosses necessary to cause physical changes in inheritance patterns
(Questions 24-28) Earlobes may be free or attached, as shown in the image below. The type of earlobe for a person is genetically determined. The allele for free earlobes (E) is dominant, the allele for attached earlobes (e) is recessive.
24. Which of the following encodes the genetic information for the earlobe trait?
A. ATP
B. DNA
C. hormones
D. carbohydrates
25. If female #3 and male #4 were to have another child, what would be the probability of that child having attached earlobes?
A. 1/4
B. 1/2
C. 3/4
D. 1/1
26. If female #11 has a child with a male who has attached earlobes, which of the following genotypes is possible for the child?
A. ee only
B. Ee only
C. EE or Ee
D. EE or ee
27. Female #10 is heterozygous for the earlobe trait. Suppose she has five children with a male who is also heterozygous for the earlobe trait.
Which of the following describes the most likely phenotypes of the five children?
A. All of the children have free earlobes
B. All of the children have attached earlobes
C. Some of the children have free earlobes and some have attached earlobes
D. The female children all have free earlobes and the male children all have attached earlobes
28. On a pedigree, it may not be possible to determine the genotype of every individual.
a. Can the genotype of male #1 be conclusively determined based on the information given in the pedigree? Explain your answer.
b. Can the genotype of female #2 be conclusively determined based on the information given in the pedigree? Explain your answer.
You may use Punnett squares to support your answers to parts (a) and (b).
29. According to Mendel's law of segregation, which of the following statements describes what happens to the alleles of a gene pair?
A. The alleles are moved to different chromosomes.
B. The alleles are mutated in the process of mitosis.
C. The alleles are separated during fertilization.
D. The alleles are separated during gamete formation.
30. Leaves from two white clover plants, each with a different pattern, are shown below.
The leaf patterns are genetically determined by alleles of a single gene. Plant 1 is homozygous for the chevron allele. Plant 2 is homozygous for the oval allele. The chevron and oval alleles are codominant.
If plant 1 and plant 2 are crossed, the codominance of the alleles will most likely result in which of the following leaf patterns on the offspring plants? Options are presented in the order of A, B, C, D.
31. People who are tune deaf are unable to follow a rhythm. Scientists have evidence that tune deafness can be genetic. The pedigree below traces the inheritance of tune deafness in a family. Individuals in the pedigree are numbered.
Scientists have analyzed the inheritance patterns for tune deafness and have concluded that tune deafness is caused by an autosomal dominant allele, T.
a. Provide evidence from the pedigree that conclusively shows that the tune deafness allele is autosomal dominant, not autosomal recessive. Explain your reasoning.
b. Identify the genotypes of individuals 5 and 6, and then draw the Punnett square for the cross of these two individuals.
c. Compare the expected percentage of each phenotype of the offspring from the cross in part (b) with the actual percentage of each phenotype observed in the children of individuals 5 and 5.
32. A pedigree showing the inheritance of a gold dorsal stripe pattern in ball pythons is shown below.
According to the pedigree, what type of trait is this stripe pattern in ball pythons?
A. codominant
B. polygenic
C. recessive
D. sex-linked
33. Two chromosome pairs from a diploid organism are shown below.
Assuming meiosis and fertilization occur normally, which of the following parts of alleles can an offspring receive from this parent?
A. A and A
B. A and a
C. A and f
D. F and F
34. In rabbits, a single gene controlling coat color has four alleles. The inheritance pattern for coat color in rabbits is therefore best described as which of the following?
A. multiple allele
B. polygenic
C. recessive
D. sex-linked
35. Gregor Mendel developed an understanding of heredity through his experiments with pea plants. The diagram below shows a cell with two pairs of homologous chromosomes and a genotype of AaBb.
a. Identify all the possible allele combinations that could be formed if this cell undergoes meiosis.
b. Identify one of Mendel’s laws that is illustrated when you write out these allele combinations. Explain this law.
36. In fruit flies, the gene for eye color is located on the X chromosome, and the red eye allele (R) is dominant to the white eye allele (r). A female fly with genotype XRXr is mated with a male fly with genotype XrY.
Which of the following statements best describes the expected outcome of the cross?
A. The chance of an offspring having red eyes is 75%.
B. The chance of an offspring having white eyes is 50%.
C. The chance that a male offspring will have white eyes is 0%.
D. The chance that a female offspring will have red eyes is 100%.
37. A pedigree is a diagram that traces the inheritance of a trait through a family. Which of the following patterns is typical in a pedigree for an autosomal dominant trait?
A. The trait affects only males.
B. The trait appears in every generation.
C. The trait appears in only one-fourth of the individuals.
D. The trait affects all the individuals of the second generation.
Answers
1. D
2. C
3. A
4. D
5. D
6. D
7. D
8. D
9. B
10. C
11.
12. C
13. D
14. A
15. A
16. C
17. Sample responses here.
18. D
19. C
20. B
21. B
22. B
23. C
24. B
25. B
26. A
27. C
28.
29. D
30. C
31. Sample responses here.
32. C
33. C
34. A
35. Sample responses can be found here.
36. B
37. B
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