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

15. Genomes and Genomics

Genomics and Human Medicine

Genetics

15. Genomes and Genomics

Genomics and Human Medicine

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2:09 minutes

Problem 32

Textbook Question

The CRISPR–Cas9 complex directs the Cas9 endonuclease to a specific genomic locus. If the endonuclease domain is inactivated and replaced with a transcriptional activator (or repressor) domain, what would be the functional consequence of directing such a complex to a specific chromosomal location?

Verified step by step guidance

Understand the CRISPR–Cas9 system: The CRISPR–Cas9 system is a gene-editing tool where the Cas9 protein acts as an endonuclease, cutting DNA at a specific location guided by a complementary RNA sequence (guide RNA).

Recognize the modification described: In this scenario, the endonuclease activity of Cas9 is inactivated, meaning it can no longer cut DNA. Instead, a transcriptional activator or repressor domain is fused to the Cas9 protein.

Determine the functional role of the modified complex: The modified CRISPR–Cas9 complex can still bind to the target DNA sequence guided by the guide RNA, but instead of cutting the DNA, it will influence gene expression at that locus.

Analyze the effect of the activator or repressor domain: If a transcriptional activator domain is attached, the complex will enhance the transcription of the target gene. Conversely, if a repressor domain is attached, the complex will suppress the transcription of the target gene.

Conclude the functional consequence: Directing such a modified CRISPR–Cas9 complex to a specific chromosomal location allows for precise regulation of gene expression, enabling activation or repression of specific genes without altering the DNA sequence itself.

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Key Concepts

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

CRISPR-Cas9 Mechanism

CRISPR-Cas9 is a revolutionary gene-editing technology that utilizes a guide RNA to direct the Cas9 endonuclease to a specific DNA sequence. The Cas9 protein then introduces double-strand breaks at the targeted site, allowing for gene modification. Understanding this mechanism is crucial for grasping how modifications can be made to the genome.

Transcriptional Activators and Repressors

Transcriptional activators and repressors are proteins that enhance or inhibit the transcription of specific genes. When a transcriptional activator is fused to the CRISPR-Cas9 complex, it can promote gene expression at the targeted locus, while a repressor would decrease expression. This concept is essential for understanding how gene regulation can be manipulated using CRISPR technology.

Gene Regulation

Gene regulation refers to the processes that control the timing and amount of gene expression. By directing a modified CRISPR-Cas9 complex to specific chromosomal locations, researchers can either upregulate or downregulate gene expression, thereby influencing cellular functions and phenotypes. This concept is fundamental for exploring the functional consequences of targeted gene modulation.

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Craig Venter and others have constructed synthetic copies of viral genomes. For example, the genome for poliovirus and the 1918 influenza strain responsible for the pandemic flu have been assembled this way. The United States currently has a moratorium on federal funding for 'gain-of-function' experiments which increase the virulence or transmission potential of viruses. What concerns might ethicists have about synthetic biology studies involving potential pandemic pathogens?

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Textbook Question

What techniques can scientists use to determine if a particular transgene has been integrated into the genome of an organism?

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Textbook Question

Gene targeting and gene editing are both techniques for removing or modifying a particular gene, each of which can produce the same ultimate goal. What is the main technical difference in how DNA is modified that differs between these approaches?

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How would you edit a specific nucleotide in a genome?

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Textbook Question

How might you use CRISPR–Cas9 to create a large deletion?

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Multiple Choice

The human genome project discovered that protein coding regions make up what percent of the human genome?