Ch. 2 - Transmission Genetics

Sanders - Genetic Analysis: An Integrated Approach 3rd Edition

Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook

Sanders 3rd Edition

Ch. 2 - Transmission Genetics

Problem 45a

Chapter 2, Problem 45a

Domestic dogs evolved from ancestral gray wolves. Wolves have coats of short, straight hair and lack 'furnishings,' a growth pattern marked by eyebrows and a mustache found in some domestic dogs. In domestic dogs, coat variation is controlled by allelic variation in three genes. Recessive mutant alleles in the FGF5 gene result in long hair, while dogs carrying the dominant ancestral allele have short hair. Likewise, recessive mutant alleles in the KRT71 gene result in curly hair, whereas dogs with an ancestral dominant allele have straight hair. Dominant mutant alleles in the RSPO2 gene cause the presence of furnishings, while dogs homozygous for the ancestral recessive allele have no furnishings. A pure-breeding curly- and long-haired poodle with furnishings was crossed to a pure-breeding short- and straight-haired border collie lacking furnishings

What are the genotypes and phenotypes of the puppies?

Verified step by step guidance

Step 1: Identify the genetic traits and their inheritance patterns. The problem describes three traits controlled by three genes: FGF5 (hair length), KRT71 (hair texture), and RSPO2 (presence of furnishings). FGF5 has a recessive mutant allele for long hair and a dominant ancestral allele for short hair. KRT71 has a recessive mutant allele for curly hair and a dominant ancestral allele for straight hair. RSPO2 has a dominant mutant allele for furnishings and a recessive ancestral allele for no furnishings.

Step 2: Determine the genotypes of the parent dogs. The pure-breeding curly- and long-haired poodle with furnishings must be homozygous recessive for FGF5 (long hair, ff), homozygous recessive for KRT71 (curly hair, kk), and homozygous dominant for RSPO2 (furnishings, FF). The pure-breeding short- and straight-haired border collie lacking furnishings must be homozygous dominant for FGF5 (short hair, FF), homozygous dominant for KRT71 (straight hair, KK), and homozygous recessive for RSPO2 (no furnishings, ff).

Step 3: Predict the genotypes of the offspring. Since the parents are pure-breeding, the offspring will inherit one allele from each parent for each gene. For FGF5, the offspring will inherit one dominant allele (F) from the border collie and one recessive allele (f) from the poodle, resulting in heterozygous genotypes (Ff). For KRT71, the offspring will inherit one dominant allele (K) from the border collie and one recessive allele (k) from the poodle, resulting in heterozygous genotypes (Kk). For RSPO2, the offspring will inherit one dominant allele (F) from the poodle and one recessive allele (f) from the border collie, resulting in heterozygous genotypes (Ff).

Step 4: Determine the phenotypes of the offspring based on their genotypes. For FGF5, heterozygous (Ff) results in short hair because the dominant allele (F) masks the recessive allele (f). For KRT71, heterozygous (Kk) results in straight hair because the dominant allele (K) masks the recessive allele (k). For RSPO2, heterozygous (Ff) results in furnishings because the dominant allele (F) is expressed.

Step 5: Summarize the genotypes and phenotypes of the puppies. The genotypes of the puppies are FfKkFf, and their phenotypes are short, straight hair with furnishings. This is due to the dominance of the ancestral alleles for hair length and texture, and the dominance of the mutant allele for furnishings.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

Key Concepts

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

Genotype and Phenotype

Genotype refers to the genetic makeup of an organism, specifically the alleles it carries for a particular trait. Phenotype, on the other hand, is the observable physical or biochemical characteristics of an organism, which result from the interaction of its genotype with the environment. Understanding the relationship between genotype and phenotype is crucial for predicting the traits of offspring in genetic crosses.

Alleles and Dominance

Alleles are different forms of a gene that can exist at a specific locus on a chromosome. In genetics, dominance describes the relationship between alleles, where a dominant allele can mask the expression of a recessive allele in a heterozygous individual. This concept is essential for determining the expected phenotypes of the offspring based on the parental genotypes in the given cross.

Punnett Square

A Punnett square is a diagram used to predict the genotypes and phenotypes of offspring from a genetic cross. By organizing the alleles of the parents, it allows for a visual representation of all possible combinations of alleles in the offspring. This tool is particularly useful in this scenario to determine the potential genotypes and phenotypes of the puppies resulting from the cross between the curly- and long-haired poodle and the short- and straight-haired border collie.

Recommended video:

Guided course

18:27

Chi Square Analysis

Related Practice

Textbook Question

A pure-breeding fruit fly with the recessive mutation cut wing, caused by the homozygous cc genotype, is crossed to a pure-breeding fly with normal wings, genotype CC. Their F₁ progeny all have normal wings. F₁ flies are crossed, and the F₂ progeny have a 3:1 ratio of normal wing to cut wing. One male F₂fly with normal wings is selected at random and mated to an F₂ female with normal wings. Using all possible genotypes of the F₂ flies selected for this cross, list all possible crosses between the two flies involved in this mating, and determine the probability of each possible outcome.

670

views

Textbook Question

Situs inversus is a congenital condition in which the major visceral organs are reversed from their normal positions. Investigations into the genetics of this abnormality revealed that individuals with at least one dominant allele (SI) of an autosomal gene are normal but, surprisingly, of individuals that are homozygous for a recessive allele (si), 1/2 are situs inversus and 1/2 are normal.

What genotypes and phenotypes are expected in progeny from a cross of two si si individuals?

415

views

Textbook Question

What genotypes and phenotypes are expected in progeny from a cross of two SI si individuals?

565

views

Textbook Question

Domestic dogs evolved from ancestral gray wolves. Wolves have coats of short, straight hair and lack 'furnishings,' a growth pattern marked by eyebrows and a mustache found in some domestic dogs. In domestic dogs, coat variation is controlled by allelic variation in three genes. Recessive mutant alleles in the FGF5 gene result in long hair, while dogs carrying the dominant ancestral allele have short hair. Likewise, recessive mutant alleles in the KRT71 gene result in curly hair, whereas dogs with an ancestral dominant allele have straight hair. Dominant mutant alleles in the RSPO2 gene cause the presence of furnishings, while dogs homozygous for the ancestral recessive allele have no furnishings. A pure-breeding curly- and long-haired poodle with furnishings was crossed to a pure-breeding short- and straight-haired border collie lacking furnishings

If dogs of the F₁ generation are interbred, what proportions of genotypes and phenotypes are expected in the F₂?

510

views

Textbook Question

Alleles of the IGF-1 gene in dogs, encoding insulin-like growth factor, largely determine whether a domestic dog will be large or small. Dogs with an ancestral dominant allele are large, whereas dogs homozygous for the mutant recessive allele are small. Chondrodysplasia, a short-legged phenotype (as in dachshunds and basset hounds), is caused by a dominant gain-of-function allele of the FGF4 gene. The MSTN gene encodes myostatin, a regulator of muscle development. Dogs with a dominant ancestral allele of the MTSN gene have normal muscle development, while dogs homozygous for recessive mutants in the MTSN gene are 'double muscled' and have trouble running quickly. However, dogs heterozygous for the mutant allele run faster than either of the homozygotes.

You breed a pure-breeding small basset hound of normal musculature with a pure-breeding 'bully' whippet, a double-muscled large dog with normal legs.

What are the genotypes and phenotypes of the F₁ puppies?

656

views

Textbook Question

You breed a pure-breeding small basset hound of normal musculature with a pure-breeding 'bully' whippet, a double-muscled large dog with normal legs.

If the F₁ of this cross is interbred, what proportion of the F₂ are expected to be fast runners and what proportion normal-speed runners?

439

views