*20. A chromosome initially has the following segments:


Draw and label the chromosome that would result from each of the following mutations.

(a) Tandem duplication of DEF

(b) Displaced duplication of DEF

(c) Deletion of FG

(e) Paracentric inversion that includes DEFG

(f) Pericentric inversion of BCDE

21. The following diagram represents two nonhomologous chromosomes:

What type of chromosome mutation would produce the following chromosomes?

*22. A species has 2n = 16 chromosomes. How many chromosomes will be found per cell in each of the following mutants in this species?

(a) Monosomic

(b) Autotriploid

(c) Autotetraploid

(d) Trisomic

(e) Double monosomic

(f) Nullisomic

(g) Autopentaploid

(h) Tetrasomic

*23. The Notch mutation is a deletion on the X chromosome of Drosophila melanogaster. Female flies heterozygous for Notch have an indentation on the margin of their wings; Notch is lethal in the homozygous and hemizygous conditions. The Notch deletion covers the region of the X chromosome that contains the locus for white eyes, an X-linked recessive trait. Give the phenotypes and proportions of progeny produced in the following crosses.

(a) A red-eyed, Notch female is mated with white-eyed male.

(b) A white-eyed, Notch female is mated with a red-eyed male.

(c) A white-eyed, Notch female is mated with a white-eyed male.

24. The green nose fly normally has six chromosomes, two metacentric and four acrocentric. A geneticist examines the chromosomes of an odd-looking green nose fly and discovers that it has only five chromosomes; three of them are metacentric and two are acrocentric. Explain how this change in chromosome number might have occurred.

25. Species I is diploid (2n = 8) with chromosomes AABBCCDD; related species II is diploid (2n = 8) with chromosomes MMNNOOPP. Individuals with the following sets of chromosomes represent what types of chromosome mutations?









*26. A wild-type chromosome has the following segments:


An individual is heterozygous for the following chromosome mutations. For each mutation, sketch how the wild-type and mutated chromosomes would pair in prophase I of meiosis, showing all chromosome strands.

27. An individual that is heterozygous for a pericentric inversion has the following two chromosomes:

(a) Sketch the pairing of these two chromosomes in prophase I of meiosis, showing all four strands.

(b) Draw the chromatids that would result from a single crossover between the E and F segments.

(c) What will happen when the chromosomes separate in anaphase I of meiosis?

28. Answer part b of problem 28 for a two-strand double crossover between E and F.

*29. An individual heterozygous for a reciprocal translocation possesses the following chromosomes:

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