Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement

Klug - Essentials of Genetics 10th Edition

Klug10th EditionEssentials of GeneticsISBN: 9780135588789Not the one you use?Change textbook

Klug 10th Edition

Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement

Problem 6

Chapter 6, Problem 6

Contrast the fertility of an allotetraploid with an autotriploid and an autotetraploid.

Verified step by step guidance

Step 1: Define the terms to understand the types of polyploids involved. An allotetraploid has two different sets of chromosomes from two different species (2n from species A + 2n from species B), an autotriploid has three sets of chromosomes all from the same species (3n), and an autotetraploid has four sets of chromosomes all from the same species (4n).

Step 2: Consider how chromosome pairing occurs during meiosis in each type. In an allotetraploid, homologous chromosomes from each species pair properly because they come in sets of two, allowing for regular bivalent formation.

Step 3: Analyze the autotriploid situation. With three sets of chromosomes, homologous chromosomes cannot pair evenly during meiosis, leading to unbalanced gametes and reduced fertility.

Step 4: Examine the autotetraploid case. Since there are four homologous chromosomes from the same species, pairing can occur as multivalents or bivalents, which can lead to some irregular segregation but generally better fertility than triploids.

Step 5: Summarize the fertility outcomes based on chromosome pairing and segregation: allotetraploids tend to have high fertility due to stable bivalent pairing, autotriploids have low fertility due to irregular segregation, and autotetraploids have intermediate to high fertility depending on how chromosomes pair during meiosis.

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.

Polyploidy and Types of Polyploids

Polyploidy refers to organisms having more than two sets of chromosomes. Autopolyploids arise from chromosome duplication within a single species, while allopolyploids result from hybridization between different species followed by chromosome doubling. Understanding these distinctions is crucial for comparing fertility among different polyploid types.

Chromosome Pairing and Meiosis in Polyploids

Fertility in polyploids depends on proper chromosome pairing during meiosis. Autopolyploids often have multivalent pairing due to homologous chromosomes, leading to irregular segregation and reduced fertility. Allopolyploids typically form bivalents because their chromosomes come from different species, promoting regular meiosis and higher fertility.

Fertility Differences Among Autotriploids, Autotetraploids, and Allotetraploids

Autotriploids usually have low fertility due to unbalanced gametes from uneven chromosome segregation. Autotetraploids may have moderate fertility but can suffer from multivalent formation causing some meiotic irregularities. Allotetraploids generally exhibit higher fertility because their chromosomes pair as homologous sets, ensuring balanced gametes.

Recommended video:

Guided course

04:03

Autopolyploidy

Related Practice

Textbook Question

Describe the origin of cultivated American cotton.

views

Textbook Question

Define these pairs of terms, and distinguish between them.

aneuploidy/ euploidy

monosomy/ trisomy

Patau syndrome/ Edwards syndrome

autopolyploidy/ allopolyploidy

autotetraploid/ amphidiploid

paracentric inversion/ pericentric inversion

Textbook Question

What evidence suggests that Down syndrome is more often the result of nondisjunction during oogenesis rather than during spermatogenesis?

views

Textbook Question

For a species with a diploid number of 18, indicate how many chromosomes will be present in the somatic nuclei of individuals that are haploid, tetraploid, trisomic, and monosomic.

views

Textbook Question

Predict how the synaptic configurations of homologous pairs of chromosomes might appear when one member is normal and the other member has sustained a deletion or duplication.

views