/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 24 Hairlessness in American rat ter... [FREE SOLUTION] | 91影视

91影视

Log out

Learning Materials

Features

Discover

Chapter 3: Problem 24

Hairlessness in American rat terriers is recessive to the presence of hair. Suppose that you have a rat terrier with hair. How can you determine whether this dog is homozygous or heterozygous for the hairy trait?

Short Answer

Expert verified
Perform a test cross with a homozygous recessive \((hh)\) to see if any offspring are hairless, indicating heterozygosity. If all offspring have hair, the dog is likely homozygous dominant.

Step by step solution

01

Define the Genotypes

First, we need to understand the genetics behind hair presence. Having hair is the dominant trait, represented by the allele \(H\), and hairlessness is the recessive trait, represented by the allele \(h\). The genotypes for a rat terrier with hair can either be homozygous dominant \((HH)\) or heterozygous \((Hh)\).
02

Construct a Test Cross

To determine if the dog is homozygous \((HH)\) or heterozygous \((Hh)\), we perform a test cross. This involves breeding the dog with a rat terrier that is homozygous recessive \((hh)\) for hairlessness.
03

Analyze Potential Offspring Outcomes

If the dog is homozygous \((HH)\), all offspring will have the genotype \(Hh\) and will exhibit the trait of having hair. However, if the dog is heterozygous \((Hh)\), the possible offspring genotypes will be 50% \(Hh\) (having hair) and 50% \(hh\) (hairless).
04

Interpret the Test Cross Results

After performing the test cross, observe the offspring. If any of the offspring are hairless \((hh)\), the dog must be heterozygous \((Hh)\). If all offspring have hair, then it is likely the dog is homozygous \((HH)\).

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Recessive Trait
In genetics, a **recessive trait** is a characteristic that appears only when an individual inherits two identical alleles for that trait. These alleles are typically denoted with lowercase letters. In our exercise, hairlessness in American rat terriers is a recessive trait, represented by the allele \( h \).
This means a rat terrier will only be hairless if it possesses two \( h \) alleles, meaning its genotype must be \( hh \). If an individual carries at least one dominant allele, it will exhibit the dominant trait (in this case, having hair).

  • Only visible when two recessive alleles are present
  • Masked by dominant traits in heterozygous conditions
Understanding recessive traits allows us to predict potential outcomes in genetic crosses, such as determining the genotype of a rat terrier with hair.
Test Cross
A **test cross** is a helpful genetic tool to determine whether an individual exhibiting a dominant trait is homozygous dominant or heterozygous. This involves crossing the individual with a partner known to be homozygous recessive.
In our exercise, to determine if the rat terrier with hair is \( HH \) or \( Hh \), we perform a test cross with a hairless terrier (\( hh \)).

  • If the terrier is \( HH \), all offspring will have hair (\( Hh \) genotype).
  • If the terrier is \( Hh \), about half the offspring may be hairless (\( hh \) genotype).
This method is reliable because the appearance of a recessive trait in any offspring indicates the presence of the recessive allele in the parent.
Genotype Analysis
**Genotype analysis** is crucial in understanding the genetic makeup and potential variety of offspring. By analyzing genotypes, we can predict the probability of inheriting specific traits.
In our rat terrier scenario, understanding genotype allows us to predict the outcome of a cross. A hairy terrier could either be homozygous dominant \( (HH) \) or heterozygous \( (Hh) \).

The analysis begins with identifying possible genotype combinations in offspring.
  • If \( HH \), no recessive trait shows in offspring.
  • If \( Hh \), there's a 50% chance for both hairy (\( Hh \)) and hairless (\( hh \)) offspring.
Through observing offspring phenotypes, we can conclude whether the hairy terrier is homozygous or heterozygous, providing a practical application of genotype analysis in genetics.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

What is the principle of segregation? Why is it important?

In guinea pigs, the allele for black fur \((B)\) is dominant over the allele for brown \((b)\) fur. A black guinea pig is crossed with a brown guinea pig, producing five \(\mathrm{F}_{1}\) black guinea pigs and six \(\mathrm{F}_{1}\) brown guinea pigs. a. How many copies of the black allele (B) will be present in each cell of an \(\mathrm{F}_{1}\) black guinea pig at the following stages: \(\mathrm{G}_{1}, \mathrm{G}_{2},\) metaphase of mitosis, metaphase I of meiosis, metaphase II of meiosis, and after the second cytokinesis following meiosis? Assume that no crossing over takes place. b. How many copies of the brown allele \((b)\) will be present in each cell of an \(\mathrm{F}_{1}\) brown guinea pig at the same stages as those listed in part \(a\) ? Assume that no crossing over takes place.

A geneticist discovers an obese mouse in his laboratory colony. He breeds this obese mouse with a normal mouse. All the \(\mathrm{F}_{1}\) mice from this cross are normal in size. When he interbreeds two \(\mathrm{F}_{1}\) mice, eight of the \(\mathrm{F}_{2}\) mice are normal in size and two are obese. The geneticist then intercrosses two of his obese mice, and he finds that all the progeny from this cross are obese. These results lead the geneticist to conclude that obesity in mice results from a recessive allele. A second geneticist at a different university also discovers an obese mouse in her laboratory colony. She carries out the same crosses as the first geneticist and obtains the same results. She also concludes that obesity in mice results from a recessive allele. One day the two geneticists meet at a genetics conference, learn of each other's experiments, and decide to exchange mice. They both find that, when they cross two obese mice from the different laboratories, all the offspring are normal; however, when they cross two obese mice from the same laboratory, all the offspring are obese. Explain their results.

Suppose that you are raising Mongolian gerbils. You notice that some of your gerbils have white spots, whereas others have solid coats. What type of crosses could you carry out to determine whether white spots are due to a recessive or a dominant allele?

Phenylketonuria (PKU) is a disease that results from a recessive gene. Suppose that two unaffected parents produce a child with PKU. a. What is the probability that a sperm from the father will contain the PKU allele? b. What is the probability that an egg from the mother will contain the PKU allele? c. What is the probability that their next child will have PKU? d. What is the probability that their next child will be heterozygous for the PKU gene?
See all solutions

Recommended explanations on Biology Textbooks

Biological Molecules

Read Explanation

Ecosystems

Read Explanation

Microbiology

Read Explanation

Heredity

Read Explanation

Responding to Change

Read Explanation

Cell Cycle

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.