Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

6. Chromosomal Variation

Chromosomal Mutations: Aberrant Euploidy

Genetics

6. Chromosomal Variation

Chromosomal Mutations: Aberrant Euploidy

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3:11 minutes

Problem 22c

Textbook Question

Two experimental varieties of strawberry are produced by crossing a hexaploid line that contains 48 chromosomes and a tetraploid line that contains 32 chromosomes. Experimental variety 1 contains 40 chromosomes, and experimental variety 2 contains 56 chromosomes.
How many chromosomes from the tetraploid lines are contributed to experimental variety 1? To experimental variety 2?

Verified step by step guidance

Step 1: Understand the ploidy levels and chromosome numbers of the parent lines. The hexaploid line has 48 chromosomes, meaning it has 6 sets of chromosomes (48 ÷ 6 = 8 chromosomes per set). The tetraploid line has 32 chromosomes, meaning it has 4 sets of chromosomes (32 ÷ 4 = 8 chromosomes per set). Both lines share the same base chromosome number (8).

Step 2: Analyze the chromosome numbers in the experimental varieties. Experimental variety 1 has 40 chromosomes, and experimental variety 2 has 56 chromosomes. These numbers are derived from contributions by both the hexaploid and tetraploid parent lines.

Step 3: Determine the contribution from the hexaploid line. Since the hexaploid line contributes chromosomes in multiples of 8 (its base chromosome number), calculate how many sets of chromosomes it could contribute to each experimental variety. For variety 1 (40 chromosomes), the hexaploid line could contribute 24 chromosomes (3 sets of 8). For variety 2 (56 chromosomes), the hexaploid line could contribute 48 chromosomes (6 sets of 8).

Step 4: Calculate the contribution from the tetraploid line. Subtract the hexaploid contribution from the total chromosome number in each experimental variety. For variety 1: 40 - 24 = 16 chromosomes from the tetraploid line. For variety 2: 56 - 48 = 8 chromosomes from the tetraploid line.

Step 5: Verify the results. Ensure that the contributions from both parent lines add up to the total chromosome numbers in each experimental variety. For variety 1: 24 (hexaploid) + 16 (tetraploid) = 40 chromosomes. For variety 2: 48 (hexaploid) + 8 (tetraploid) = 56 chromosomes. This confirms the calculations are correct.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Polyploidy

Polyploidy refers to the condition of having more than two complete sets of chromosomes. In this case, the hexaploid line has six sets (48 chromosomes) and the tetraploid line has four sets (32 chromosomes). Understanding polyploidy is essential for analyzing the genetic contributions of different parent lines in hybrid offspring.

Chromosome Contribution in Hybridization

In hybridization, the offspring inherit a combination of chromosomes from both parent lines. The total number of chromosomes in the hybrids can be calculated by adding the contributions from each parent. This concept is crucial for determining how many chromosomes from the tetraploid line are present in the experimental varieties.

Chromosome Count Calculation

Calculating the chromosome count involves understanding how many chromosomes each parent contributes to the offspring. For experimental variety 1 (40 chromosomes) and variety 2 (56 chromosomes), we can set up equations based on the known contributions from the hexaploid and tetraploid lines to find the specific contributions from the tetraploid line.

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Textbook Question

The primrose, Primula kewensis, has 36 chromosomes that are similar in appearance to the chromosomes in two related species, P. floribunda (2n=18) and P. verticillata (2n=18). How could P. kewensis arise from these species? How would you describe P. kewensis in genetic terms?

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Textbook Question

Certain varieties of chrysanthemums contain 18, 36, 54, 72, and 90 chromosomes; all are multiples of a basic set of nine chromosomes. How would you describe these varieties genetically? What feature do the karyotypes of each variety share? A variety with 27 chromosomes has been discovered, but it is sterile. Why?

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Textbook Question

In Drosophila, seven partial deletions (1 to 7) shown as gaps in the following diagram have been mapped on a chromosome. This region of the chromosome contains genes that express seven recessive mutant phenotypes, identified in the following table as a through g. A researcher wants to determine the location and order of genes on the chromosome, so he sets up a series of crosses in which flies homozygous for a mutant allele are crossed with flies homozygous for a partial deletion. The progeny are scored to determine whether they have the mutant phenotype ('m' in the table) or the wild-type phenotype ('+' in the table). Use the partial deletion map and the table of progeny phenotypes to determine the order of genes on the chromosome.

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Textbook Question

Two experimental varieties of strawberry are produced by crossing a hexaploid line that contains 48 chromosomes and a tetraploid line that contains 32 chromosomes. Experimental variety 1 contains 40 chromosomes, and experimental variety 2 contains 56 chromosomes.

Do you expect both experimental lines to be fertile? Why or why not?

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Textbook Question

How many chromosomes from the hexaploid line are contributed to experimental variety 1? To experimental variety 2?

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Multiple Choice

Which type of chromosomal aberration is most likely to result in a gain of function?

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Multiple Choice

Which of the following diseases is caused by a chromosomal abnormality present before birth?