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Genetics Problem Set 3B
Genetics Problem Set 3C
Last Updated 3/15/06
Check out the Mendelian Genetics Site at The Biology Project, developed at The University of Arizona.

Genetics Problem Set 3A -- Simple Mendelian Inheritance [Do the more complicated problems in problem set 3B and problem set 3C, when you are finished with these.]

True/False, Multiple Choice, etc.
1) Name the "Father of Genetics".

2) Which of the following statements are true?
A) Dominant alleles always mask the effect of recessive allele in the heterozygous condition. B) A hybrid is a pair of homozygous alleles. C) The probability of independent events occurring together is the product of the probabilities of the individual events occurring separately. D) Mitosis results in the production of daughter cells with half the number of genes of the original cell. E) Characters and traits are the same thing. F) Pure breeding lines are homozygous for most alleles. G) The parental generation of a cross is designated as P.

3) (circle the correct answer) Mendel's second law states that...
A) Alleles at a locus segregate from each other into separate gametes. B) During gamete formation the segregation of the alleles of one locus is independent of the segregation of the alleles of another locus. C) Mendel's first law is violated when genes are on the same chromosome. D) DNA is the genetic material. E) The information for making proteins is found in genes.

Genetics Problems (Crosses)
1) Coleus plants with hairy (dominant phenotype), red (dominant phenotype) leaves are crossed with plants with smooth (recessive phenotype), green (recessive phenotype) leaves. The cross produces 108 plants with hairy red leaves and 5 plants with smooth red leaves. What is the likely genotype of the parental hairy, red leafed plant?

2) In dragons there are alleles for fire breathing (B) and for nonfire breathing (N) as well as alleles for Red scales (R), Green scales (G), short tail (S), and long tail (L). You are interested in breeding these dragons to save the species which is endangered. You cross pure breeding, red, fire breathing dragons with short tails to pure breeding green, nonfire breathers with long tails. The F2 generation of this cross shows the phenotypes in the following table. The loci are not linked.

Phenotypes [Number]
Green, fire breathing, short tail [6], Green, fire breathing, long tail [30], Green, nonfire breathing, short tail [20], Green, nonfire breathing, long tail [70], Red, fire breathing, short tail [23], Red, fire breathing, long tail [65], Red, nonfire breathing, short tail [75], Red, nonfire breathing, long tail [210]

A) Which alleles are dominant and which are recessive?
B) You want to testcross a dragon with the THREE DOMINANT TRAITS, what genotype dragon would you use to testcross this dragon? (show the alleles).

3) The rare Cheshire cat has alleles for large grins (l) and for small grins (s) as well as alleles for striped (a), unstriped (b), curly tail (cur), and straight tail (str) [Carol, Lewis. Journal of Strange Critters. Vol. 1. pp. 1-7.] You are interested in breeding these cats and selling them as pets but first you must understand their genetics. You cross pure breeding large grinned, striped, straight tailed cats with small grinned, unstriped, curly tailed cats. The F2 generation of this cross shows the phenotypes in the following table. The loci are not linked.

Phenotypes [Number]
Large grin, striped, curly tail [14], Large grin, striped, straight tail [6], Large grin, unstriped, curly tail [42], Large grin, unstriped, straight tail [18], Small grin, striped, curly tail [40], Small grin, striped, straight tail [19], Small grin, unstriped, curly tail [130], Small grin, unstriped, straight tail [50]

A) Which alleles are dominant and which are recessive?
B) A cat has the three dominant phenotypes for the grin, stripe and tail loci. What cat would you use to testcross the dominant phenotype cat?

4) One genotype of a diploid fungus which parasitizes fish can use glycogen as an energy source but can not use galactose as an energy source. Another genotype can use galactose but not glycogen. These two fungal genotypes are crossed and the resultant spores are placed on nutrient poor medium containing either galactose or glycogen. All the F1 fungal spores germinate and grow on either medium. The loci are not linked. A) A fungus heterozygous for the galactose utilizing locus and homozygous recessive for the glycogen utilizing locus is crossed with the F1 generation of the previous cross. What fraction of the fungal spores are expected to germinate on nutrient poor medium containing both glycogen and galactose? B) What fraction of the fungal spores above are expected to germinate on nutrient poor medium containing glycogen?

Genetics Problems (Mode of Inheritance)
1) In 1978, Dr. Iris Rhizome reported data from a dihybrid experiment with sunflowers. One parent had hairy leaves and yellow colored petals. The other parent had smooth leaves and rust petals. All the F1 plants had hairy leaves and rust colored petals. The F2 progeny phenotypes were as follows:

Phenotype [Number of plants]
Hairy leaves and rust petals [201], Hairy leaves and yellow petals [89], Smooth leaves and yellow petals [74], Smooth leaves and rust petals [27]

What is the likely mode of inheritance for the four phenotypes ?

Genetics Problems (Pedigrees)
1) The following pedigree is for Arabian horses which have a dominant allele Hee and a recessive allele haw. What are the genotypes of all the horses in the pedigree? Write your answers on the DOTTED LINES under each horse.

 

2) The following pedigree is for dogs which have a dominant allele Bow and a recessive allele wow. What are the genotypes of all the dogs in the pedigree? Write your answers on the DOTTED LINES under each dog. You may use a slash if one of the two alleles is unknown.

3) The following pedigree is for Frogs which have a dominant allele Rib and a recessive allele bit.
A) What are the genotypes of all the frogs in the pedigree? Write your answers on the DOTTED LINES under each frog. B) (fill in the blank) What is the probability that the individual marked with a * is homozygous? ________________

5) A human female with a blood type of A has a child with a blood type of B. Which of the following statements below HAS to be true?
A) The genotype of the father is IBIB. B) The genotype of the mother is IAIA. C) The father of the child has type O blood. D) The father of the child can not have type AB blood. E) The father of the child can not have type A blood.

===================== ANSWERS =======================

True/False, Multiple Choice, etc.
1) The "Father of Genetics" is Gregor Mendel.

2) The following are true statements.
A) Dominant alleles always mask the effect of recessive allele in the heterozygous condition. C) The probability of independent events occurring together is the product of the probabilities of the individual events occurring separately. E) Characters and traits are the same thing. F) Pure breeding lines are homozygous for most alleles. G) The parental generation of a cross is designated as P.

3) Mendel's second law states that...B) During gamete formation the segregation of the alleles of one locus is independent of the segregation of the alleles of another locus.

Genetics Problems (Crosses)

1) Results of the testcross: 108 Hairy Red (Hh Rr) & 5 Smooth Red (hhRr).
Therefore the hairy red parent is heterozygous hairy, homozygous red

2) A) N is dominant to B. R is dominant to G. L is dominant to S. B) BB GG SS.

3) A) s is dominant to l. b is dominant to a. cur is dominant to str. B) A cat of genotype ll aa strstr.

4) A) Cross: Galgal glygly X Gal gal Glygly

Everything, but the genotype galgal glygly, will grow = 1 - galgal glygly

probability of being galgal = 1/2 X 1/2 = 1/4
probability of being glygly = 1 X 1/2 = 1/2

probability of being galgal glygly = 1/4 X 1/2 = 1/8

Probability of growing on one of the two media = 1 - 1/8 = 7/8

B) Fungi of genotype Gly___ will grow on only the glycogen medium.
Probability of being Gly___ = Glygly + GlyGly = 1/2 + 0 = 1/2

 

Genetics Problems (Mode of Inheritance)
1) In 1978, Dr. Iris Rhizome reported data from a dihybrid experiment with sunflowers. One parent had hairy leaves and yellow colored petals. The other parent had smooth leaves and rust petals. All the F1 plants had hairy leaves and rust colored petals. The F2 progeny phenotypes were as follows:

Phenotype [Number of plants]
Hairy leaves and rust petals [201], Hairy leaves and yellow petals [89], Smooth leaves and yellow petals [74], Smooth leaves and rust petals [27]

Hairy leaves are dominant to smooth leaves at one locus, and rust petals are dominant to yellow petals at a second unlinked locus.

Genetics Problems (Pedigrees)
1)

2)

3) A)

B) The individual marked with a * has a 1/3 chance of being homozygous?

5) E) The father of the child can not have type A blood.