Skip to main content
Pearson+ LogoPearson+ Logo
Ch. 20 - Recombinant DNA Technology
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
All textbooksKlug 12th EditionCh. 20 - Recombinant DNA TechnologyProblem 33a
Chapter 20, Problem 33a

The U.S. Department of Justice has established a database that catalogs PCR amplification products from short tandem repeats of the Y chromosome (Y-STRs) in humans. The database contains polymorphisms of five U.S. ethnic groups (African-Americans, European Americans, Hispanics, Native Americans, and Asian-Americans) as well as the worldwide population.
Given that STRs are repeats of varying lengths, for example (TCTG)₉₋₁₇ or (TAT)₆₋₁₄, explain how PCR could reveal differences (polymorphisms) among individuals. How could the Department of Justice make use of those differences?

Verified step by step guidance
1
Step 1: Understand the concept of Short Tandem Repeats (STRs). STRs are sequences of DNA consisting of repeating units of 2-6 base pairs. The number of repeats in these sequences can vary among individuals, creating polymorphisms (genetic variations). For example, one person might have (TCTG)₉ repeats, while another might have (TCTG)₁₇ repeats.
Step 2: Learn how PCR (Polymerase Chain Reaction) works. PCR is a technique used to amplify specific DNA sequences. Primers are designed to flank the STR regions, allowing the amplification of these regions. The size of the amplified product will depend on the number of repeats in the STR region.
Step 3: Understand how differences in STR lengths are detected. After PCR amplification, the products are typically analyzed using gel electrophoresis or capillary electrophoresis. These techniques separate DNA fragments based on size, revealing the length of the STR region for each individual.
Step 4: Explore how STR polymorphisms can be used for identification. Since STR lengths vary greatly among individuals, they serve as a genetic fingerprint. Comparing STR profiles can help identify individuals or determine familial relationships.
Step 5: Consider the application by the Department of Justice. The database of Y-STR polymorphisms can be used in forensic investigations to match DNA samples from crime scenes to suspects or to identify unknown individuals. Y-STRs are particularly useful in tracing paternal lineage, as they are inherited from father to son without recombination.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2m
Was this helpful?

Key Concepts

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

Short Tandem Repeats (STRs)

Short Tandem Repeats (STRs) are repeating sequences of DNA, typically 2-6 base pairs in length, that vary in number among individuals. These variations, or polymorphisms, can be used as genetic markers for identification purposes. STRs are particularly useful in forensic science and population genetics because they are highly variable and can provide a unique genetic profile for individuals.
Recommended video:
Guided course
04:18
Duplications

Polymerase Chain Reaction (PCR)

Polymerase Chain Reaction (PCR) is a molecular biology technique used to amplify specific DNA sequences, making millions of copies of a targeted region. This process involves repeated cycles of denaturation, annealing, and extension, allowing for the analysis of small amounts of DNA. In the context of STRs, PCR can selectively amplify these regions, enabling the detection of variations that distinguish individuals.
Recommended video:
Guided course
07:39
Genetic Cloning

Forensic Applications of Y-STRs

Y-STRs are specific to the Y chromosome and are inherited paternally, making them particularly useful in forensic investigations involving male lineage. The U.S. Department of Justice can utilize the polymorphisms found in Y-STRs to create genetic profiles that help identify suspects or victims in criminal cases. By comparing Y-STR profiles from crime scene evidence to those in the database, investigators can establish familial relationships or link individuals to specific populations.
Recommended video:
Guided course
07:56
Sex-Linked Genes
Related Practice
Textbook Question

In humans, congenital heart disease is a common birth defect that affects approximately 1 out of 125 live births. Using reverse transcription PCR (RT-PCR), Samir Zaidi and colleagues [(2013) Nature 498:220.223] determined that approximately 10 percent of the cases resulted from point mutations, often involving histone function. To capture products of gene expression in developing hearts, they used oligo(dT) in their reverse transcription protocol.

How would such a high %T in a primer influence annealing temperature?

671
views
Textbook Question

In humans, congenital heart disease is a common birth defect that affects approximately 1 out of 125 live births. Using reverse transcription PCR (RT-PCR), Samir Zaidi and colleagues [(2013) Nature 498:220.223] determined that approximately 10 percent of the cases resulted from point mutations, often involving histone function. To capture products of gene expression in developing hearts, they used oligo(dT) in their reverse transcription protocol.

Compared with oligo(dT) primers, a pool of random sequence primers requires a trickier assessment of annealing temperature. Why?

486
views
Textbook Question

In humans, congenital heart disease is a common birth defect that affects approximately 1 out of 125 live births. Using reverse transcription PCR (RT-PCR), Samir Zaidi and colleagues [(2013) Nature 498:220.223] determined that approximately 10 percent of the cases resulted from point mutations, often involving histone function. To capture products of gene expression in developing hearts, they used oligo(dT) in their reverse transcription protocol.

If one were interested in comparing the quantitative distribution of gene expression in, say, the right and left sides of a developing heart, how might one proceed using RT-PCR?

605
views
Textbook Question

The U.S. Department of Justice has established a database that catalogs PCR amplification products from short tandem repeats of the Y chromosome (Y-STRs) in humans. The database contains polymorphisms of five U.S. ethnic groups (African-Americans, European Americans, Hispanics, Native Americans, and Asian-Americans) as well as the worldwide population.

Y-STRs from the nonrecombining region of the Y chromosome (NRY) have special relevance for forensic purposes. Why?

514
views
Textbook Question

The U.S. Department of Justice has established a database that catalogs PCR amplification products from short tandem repeats of the Y chromosome (Y-STRs) in humans. The database contains polymorphisms of five U.S. ethnic groups (African-Americans, European Americans, Hispanics, Native Americans, and Asian-Americans) as well as the worldwide population.

What would be the value of knowing the ethnic population differences for Y-STR polymorphisms?

536
views
Textbook Question

The U.S. Department of Justice has established a database that catalogs PCR amplification products from short tandem repeats of the Y chromosome (Y-STRs) in humans. The database contains polymorphisms of five U.S. ethnic groups (African-Americans, European Americans, Hispanics, Native Americans, and Asian-Americans) as well as the worldwide population.

For forensic applications, the probability of a 'match' for a crime scene DNA sample and a suspect's DNA often culminates in a guilty or innocent verdict. How is a 'match' determined, and what are the uses and limitations of such probabilities?

461
views