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 Rearrangements: Duplications

Genetics

6. Chromosomal Variation

Chromosomal Rearrangements: Duplications

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1:26 minutes

Problem 13

Textbook Question

Discuss Ohno's hypothesis on the role of gene duplication in the process of evolution. What evidence supports this hypothesis?

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Ohno's hypothesis, proposed by Susumu Ohno, suggests that gene duplication is a major driver of evolutionary innovation. When a gene is duplicated, one copy retains the original function while the other copy is free to accumulate mutations, potentially leading to new functions or regulatory patterns.

Explain that gene duplication can occur through mechanisms such as unequal crossing over during meiosis, retrotransposition, or whole-genome duplication events. These processes create additional copies of genes in the genome.

Discuss the potential fates of duplicated genes: (1) nonfunctionalization, where one copy becomes a pseudogene; (2) subfunctionalization, where the two copies divide the original function; or (3) neofunctionalization, where one copy evolves a new function.

Provide evidence supporting Ohno's hypothesis, such as the presence of gene families (e.g., the globin gene family) that arose through duplication and subsequent divergence. These gene families often show functional specialization, supporting the idea of evolutionary innovation.

Highlight examples of whole-genome duplication events in evolutionary history, such as those in plants (e.g., polyploidy in wheat) and vertebrates, which have contributed to increased genetic complexity and the emergence of novel traits.

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Key Concepts

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

Ohno's Hypothesis

Ohno's hypothesis, proposed by Susumu Ohno in 1970, suggests that gene duplication is a key mechanism in evolution, allowing for genetic redundancy. This redundancy enables one copy of a gene to maintain its original function while the other can acquire mutations that may lead to new functions, contributing to evolutionary innovation and complexity.

Gene Duplication

Gene duplication is a process where a segment of DNA is copied, resulting in two identical or similar genes. This can occur through various mechanisms, such as unequal crossing over during meiosis or retrotransposition. The duplicated genes can diverge over time, leading to functional specialization, which is crucial for the evolution of new traits and adaptations.

Evidence Supporting Ohno's Hypothesis

Evidence supporting Ohno's hypothesis includes comparative genomic studies that show higher rates of gene duplication in species with complex traits. Additionally, examples of gene families, such as the globin gene family, illustrate how duplicated genes can evolve new functions. Phylogenetic analyses also reveal patterns of gene duplication and subsequent divergence across different lineages, reinforcing the role of duplication in evolutionary processes.

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Related Practice

Multiple Choice

A person has a WT chromosome with the following segments. A B C • D E F G H. Which of the following shows how the chromosome would look after an tandem duplication?

How do we know that the mutant Bar-eye phenotype in Drosophila is due to a duplicated gene region rather than to a change in the nucleotide sequence of a gene?

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Textbook Question

From the following list, identify the types of chromosome changes you expect to show phenotypic consequences. duplication

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Textbook Question

A pair of homologous chromosomes in Drosophila has the following content (single letters represent genes):

Chromosome 1RNMDHBGKWU

Chromosome 2RNMDHBDHBGKWU

What term best describes the unusual structure that forms during pairing of these chromosomes?

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Textbook Question

Dr. Ara B. Dopsis has an idea he thinks will be a boon to agriculture. He wants to create the 'pomato,' a hybrid between a tomato (Lycopersicon esculentum) that has 12 chromosomes and a potato (Solanum tuberosum) that has 48 chromosomes. Dr. Dopsis is hoping his new pomato will have tuber growth like a potato and the fruit production of a tomato. He joins a haploid gamete from each species to form a hybrid and then induces doubling of chromosome number. Will this hybrid be infertile?

Describe at least two mechanisms by which duplicate genes arise. What are the possible fates of duplicate genes? Does the mode of duplication affect possible fates?

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Multiple Choice

A person has a WT chromosome with the following segments. A B C • D E F G H. Which of the following shows how the chromosome would look after an insertional duplication?

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