Skip to main content
Pearson+ LogoPearson+ Logo
Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 14 - Analysis of Gene Function via Forward Genetics and Reverse GeneticsProblem 30
Chapter 14, Problem 30

How would you edit a specific nucleotide in a genome?

Verified step by step guidance
1
Understand the concept of genome editing: Genome editing involves making precise changes to the DNA sequence of an organism. The most common tool for this is CRISPR-Cas9, which allows for targeted modifications at specific locations in the genome.
Identify the target nucleotide: Determine the exact location of the nucleotide you want to edit within the genome. This requires knowledge of the gene sequence and the specific base pair to be altered.
Design a guide RNA (gRNA): Create a short RNA sequence that is complementary to the DNA sequence near the target nucleotide. This gRNA will guide the Cas9 enzyme to the correct location in the genome.
Introduce the CRISPR-Cas9 system into the cell: Deliver the gRNA, Cas9 enzyme, and a repair template (if needed) into the cell. The repair template is a DNA sequence that contains the desired nucleotide change and serves as a template for the cell's repair machinery.
Allow the cell to repair the DNA: The Cas9 enzyme creates a double-strand break at the target site. The cell's natural repair mechanisms, such as homology-directed repair (HDR), use the repair template to fix the break, incorporating the desired nucleotide change into the genome.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
3m
Was this helpful?

Key Concepts

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

CRISPR-Cas9

CRISPR-Cas9 is a revolutionary gene-editing technology that allows for precise modifications of DNA sequences. It utilizes a guide RNA to direct the Cas9 enzyme to a specific location in the genome, where it creates a double-strand break. This break can then be repaired by inserting, deleting, or replacing nucleotides, enabling targeted edits in the genome.
Recommended video:
Guided course
06:38
Regulation

Nucleotide Structure

Nucleotides are the building blocks of DNA and RNA, consisting of a sugar, a phosphate group, and a nitrogenous base. The sequence of these nucleotides encodes genetic information. Understanding the structure and function of nucleotides is essential for editing specific sites in the genome, as it allows for the identification of target sequences for modification.
Recommended video:
Guided course
06:25
DNA Structure

Homology-Directed Repair (HDR)

Homology-Directed Repair (HDR) is a cellular mechanism that repairs double-strand breaks in DNA using a homologous template. This process is crucial for precise genome editing, as it allows for the incorporation of specific nucleotide changes when a donor DNA template is provided. HDR is often utilized in conjunction with CRISPR-Cas9 to achieve accurate edits in the genome.
Recommended video:
Guided course
05:44
Repair Pathways
Related Practice
Textbook Question

Most organisms display a circadian rhythm, a cycling of biological processes that is roughly synchronized with day length (e.g., jet lag occurs in humans when rapid movement between time zones causes established circadian rhythms to be out of synch with daylight hours). In Drosophila, pupae eclose (emerge as adults after metamorphosis) at dawn.

In most plants, such as Arabidopsis, genes whose encoded products have roles related to photosynthesis have expression patterns that vary in a circadian manner. Using this knowledge, how would you screen for Arabidopsis mutants that have an impaired circadian rhythm?

580
views
Textbook Question

Most organisms display a circadian rhythm, a cycling of biological processes that is roughly synchronized with day length (e.g., jet lag occurs in humans when rapid movement between time zones causes established circadian rhythms to be out of synch with daylight hours). In Drosophila, pupae eclose (emerge as adults after metamorphosis) at dawn.

In each case, how would you clone the genes you identified by mutation?

541
views
Textbook Question

Mutations in the Drosophila Ultrabithorax (Ubx) gene result in wings developing from two thoracic segments, rather than just one as in wild-type flies. In the mouse genome there are two Ubx orthologs . How would you determine whether the two mouse genes have distinct or redundant functions?

476
views
Textbook Question

Through a forward genetics screen in Arabidopsis you have identified a mutation that results in leaves curling upward, rather than being flat as in wild type. You have cloned the corresponding gene and note that it is a member of a small gene family composed of three additional members in Arabidopsis. How will you determine if the other three members of the gene family have similar or distinct functions as compared with the gene you first identified?

424
views
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?

661
views
Textbook Question

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

628
views