Question

Mendelian genetics practice

1. What is the ratio of phenotypes in the offspring produced by the cross Aa x Aa? Assume complete dominance for the trait. A) 100% dominance B) 100% recessive C) 75% dominant: 25% recessive D) 50% dominant: 50% recessive E) 25% dominant: 75% recessive

2) If the allele for inflated pea pods (I) is dominant to the allele for constricted (i), the cross Ii x ii is expected to produce A) all with inflated pods. B) all with constricted pods. C) half with inflated and half with constricted pods. D) 3/4 with inflated and 1/4 with constricted pods. E) 3/4 with constricted and 1/4 with inflated pods.

3) According to the Law of Segregation A) each individual carries a single copy of each "factor." B) pairs of factors fuse during the formation of gametes. C) pairs of factors separate during the formation of gametes. D) the sex chromosomes of males and females differ. E) there is an independent assortment of non-homologous chromosomes during meiosis.

4) According to the Law of Segregation, in an organism with the genotype Aa A) all the gametes will have gene A. B) all the gametes will have gene a. C) half the gametes will have A and half will have a. D) 3/4 of the gametes will have A and 1/4 will have a. E) 1/4 of the gametes will have A and 3/4 will have a.

5) Which of the following statements is FALSE? A) Individuals with the same phenotype might have different genotypes. B) Matings between individuals with dominant phenotypes cannot produce offspring with recessive phenotypes. C) Matings between individuals with recessive phenotypes usually do not produce offspring with dominant phenotypes. D) Individuals with the same genotype might have different phenotypes. E) All of the above choices are correct.

6) A cross produced 915 offspring with normal pigment and 310 with albinism. Conclusion? A) One of the parents was homozygous for albinism. B) Both parents were heterozygous. C) One parent was homozygous for normal pigmentation. D) Both parents were albinos. E) 605 albino zygotes must have failed to develop.

7) If a round pea has a wrinkled parent, the round pea is A) RR. B) Rr. C) rr. D) haploid. E) recessive.

8) The results of a test cross reveal that all the offspring resemble the parent being tested. This parent must be A) heterozygous. B) recessive. C) self-pollinated. D) homozygous. E) haploid.

9) In a test cross, what percentage of the offspring will have the same genotype as the tested parent if the parent is homozygous? A) 25% B) 50% C) 75% D) 100% E) 0%

10) A particular genetic cross in which the individual in question is crossed with an individual known to be homozygous for a recessive trait is referred to as a(n) A) parental cross. B) F1 cross. C) F2 cross. D) reciprocal cross. E) test cross. Dihybrid

Use the information below to answer questions 11 and 12. Smurfs live in widely separated groups and rarely interbreed, so geneticists know very little about them. On one occasion, two smurfs from different groups did mate. A big-footed, white smurf mated with a small-footed, blue smurf. Three offspring resulted: one big-footed and blue and two small-footed and blue.

11) Which statement about the inheritance of color in smurfs is most likely to be correct? A) Blue is dominant to white. B) White is dominant to blue. C) White and blue are codominant. D) A and C E) You cannot reach any conclusions.

12) Which statement about the inheritance of footedness in smurfs is most likely to be correct? A) Big is dominant to small. B) Small is dominant to big. C) Big and small are codominant. D) A and C. E) You cannot reach any conclusions

13) Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of the cross BbTt × BBtt will have black fur and long tails?

Key Cross Punnet Answer

14. If you cross two organisms that are heterozygous for two traits what is the resulting ratio of phenotypes.

15. You cross a pea plant with yellow, smooth seeds with one having wrinkled, green seeds. You examine the seeds of 967 offspring, and find some have yellow, smooth seeds and some have yellow, wrinkled seeds, but no green seeds of either type show up. What is the genotype of the yellow-seeded parent? (Y = yellow, y = green; S = smooth, s = wrinkled) Key Cross Punnet Answer

Answer 1

Answer to question 1-Option C is the correct answer

Given that genotypes of two parents are Aa and Aa.

Cross between Aa and Aa

Gametes produced are A and a from both the parents

punnet square

	A	a
A	AA	Aa
a	Aa	aa

AA-homozygous dominant(1/4),Aa-heterozygous dominant(2/4) and aa-homozygous recessive(1/4)

Phenotypic ratio is dominant:recessive=3:1(75% dominant and 25% recessive)

Answer to question 2-Option C is the correct answer

Given that the allele for inflated pea pods,I is dominant to the allele for constricted,i

Cross between Ii and ii

Gametes produced are I and i from first parent and i from second parent

punnet square

	I	i
i	Ii	ii
i	Ii	ii

Ii-inflated(2/4) and ii-constricted(2/4)

Half of the offspring are with inflated pods and other half with constricted pods

Answer to question 3-Option C is the correct answer

According to Mendel's law of segregation,pairs of gametes separate during the formation of gametes.Therefore each gametes receives one of the two alleles.

Answer to question 4-Option C is the correct answer

According to the law of segregation, in an organism with the genotype Aa half the gametes will have allele A and half will have allele a.