Quiz: Ch. 8 Answers

Wild type chromosome = AB * CDEFG

- Chromosomal mutation 1: AB *CDEFDEFG = tandem duplication of DEF - Chromosomal mutation 2: AB * DEFCDEFG = displaced duplication of DEF - Chromosomal mutation 3: AB * CDE = deletion of FG - Chromosomal mutation 4: AB *CGFED = paracentric inversion that includes DEFG - Chromosomal mutation 5: AEDC * BFG = pericentric inversion of BCDE

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

- Monosomic mutant = 15 - Autotetraploid mutant = 32 - Double monosomic mutant = 14 - Autopentaploid mutant = 40 - Autotriploid mutant = 40 - Trisomic mutant = 17 - Nullisomic mutant = 14 - Tetrasomic mutant = 18

Match the definitions to the appropriate terms that describe the number of chromosomes

- Triploid = 3 homologues of each chromosome - Trisomic = 1 extra copy of a specific chromosome - n = 3 = a genome composed of 3 unique chromosomes

1. Chromosome duplications and deletions frequently result in abnormal phenotypes or inviable gametes. Which factor is a major contributor to this phenomenon? 2. Why are these effects less noticeable for multisomies & monosomies of the X chromosome in humans?

1. Gene dosage is modified 2. X inactivation only allows one X chromosome to be expressed in any given cell

Which segregation pattern results in viable gametes?

Alternate segregation results in viable gametes

Which statement about chromosome inversions is correct?

Chromosome inversions flip a segment of a chromosome 180 degrees

About 0.3% of human live births are trisomic. In contrast, only 0.02% of human live births are monosomic. Select the best explanation for why the occurrence of trisomics is greater than that of monosomics

Deleterious recessive alleles may be masked by dominant alleles on trisomic chromosomes but not on the monosomic chromosomes

Reciprocal translocations can result in nonviable gametes because adjacent-1 segregation produces

Gametes with some chromosome segments present in 2 copies and other segments missing

A chromosomal translocation refers to

Movement of a chromosome segment to a nonhomologous chromosome

Which chromosome makeup represents the alternate segregation pattern?

N1 and N2; T1 and T2

Which statement about polyploidy is not true?

Polyploidy is possible only between the members of the same species

In which stage of meiosis would the chromosomes form a cross-like configuration?

Prophase I

Additional copies of a gene ___ cause cellular problems

Sometimes

Which statement about chromosome translocation is correct?

Translocation can affect gene expression by moving a gene under the control of a different promoter

Which statement about Down syndrome is ture?

Trisomy of chromosome 21 is well tolerated enough to give rise to fully-developed individuals