Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 4: Problem 30

The specification of the anterior-posterior axis in Drosophila embryos is initially controlled by various gene products that are synthesized and stored in the mature egg following oogenesis. Mutations in these genes result in abnormalities of the axis during embryogenesis, illustrating maternal effect. How do such mutations vary from those involved in organelle heredity that illustrate extranuclear inheritance? Devise a set of parallel crosses and expected outcomes involving mutant genes that contrast maternal effect and organelle heredity.

Short Answer

Expert verified
Short Answer: Maternal effect inheritance is when an organism's phenotype is determined by the genotype of its mother, usually due to gene products in the egg cytoplasm, whereas organelle heredity involves the inheritance of cytoplasmic organelles such as mitochondria and chloroplasts and their DNA. Both inheritance types involve maternal inheritance, but the maternal effect is related to gene products while organelle heredity is related to organelle DNA.

Step by step solution

01

Understand maternal effect and organelle heredity

Maternal effect is a type of inheritance where an organism shows the phenotypic effect of a gene present in its mother, regardless of the organism's own genotype. This is usually due to the presence of the gene products in the egg cytoplasm. Organelle heredity, or extranuclear inheritance, is a type of inheritance where traits are passed from parents to offspring via cytoplasmic organelles such as mitochondria and chloroplasts instead of nuclear genes. These organelles have their own DNA, which is passed to offspring primarily through the maternal line.
02

Devise a set of parallel crosses for maternal effect

Let's consider two homozygous lines of Drosophila, one with a wild-type phenotype for the anterior-posterior axis (A), and the other with a mutant phenotype for the axis (a). Here, A represents the dominant wild type, and a represents the recessive maternal-effect mutation. We can represent the crosses as follows: 1. AA (♀) x AA (♂) - Results in all offspring with a wild-type phenotype 2. aa (♀) x AA (♂) - Results in all offspring with mutant phenotypes due to the maternal effect 3. AA (♀) x aa (♂) - Results in all offspring with wild-type phenotypes
03

Devise a set of parallel crosses for organelle heredity

Now let's consider two homozygous lines of Drosophila, one with healthy mitochondria, represented by (+) and the other with mutant mitochondria, represented by (m). We will represent the crosses as follows: 1. (+) (♀) x (+) (♂) - Results in offspring with healthy mitochondria due to maternal inheritance 2. (m) (♀) x (+) (♂) - Results in offspring with mutant mitochondria due to maternal inheritance 3. (+) (♀) x (m) (♂) - Results in offspring with healthy mitochondria due to maternal inheritance
04

Comparison of Expected Outcomes

In the maternal effect crosses, we notice that the mother's genotype directly affects the offspring's phenotype, while in organelle heredity crosses, offspring inherit their mitochondria only from the mother, leading to the expression of the phenotype associated with the mother's mitochondrial genotype. In both cases, paternal contribution does not affect the offspring's phenotype, which highlights the importance of maternal inheritance. However, they differ in that maternal effect involves gene products stored in the egg cytoplasm, whereas organelle heredity involves inheritance of cytoplasmic organelles and their DNA.

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.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

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

In this chapter, we focused on many extensions and modifications of Mendelian principles and ratios, In the process, we encountered many opportunities to consider how this information was acquired. Answer the following fundamental questions: (a) How were early geneticists able to ascertain inheritance patterns that did not fit typical Mendelian ratios? (b) How did geneticists determine that inheritance of some phenotypic characteristics involves the interactions of two or more gene pairs? How were they able to determine how many gene pairs were involved? (c) How do we know that specific genes are located on the sexdetermining chromosomes rather than on autosomes? (d) For genes whose expression seems to be tied to the sex of individuals, how do we know whether a gene is X-linked in contrast to exhibiting sex-limited or sex-influenced inheritance? (e) How was extranuclear inheritance discovered?

Duchenne muscular dystrophy (DMD), marked by muscular degeneration, results from an \(\mathrm{X}\) - linked recessive gene. Thus, a female who is heterozygous for this gene and does not have the disease can be a carrier. What kind of offspring can you expect from a DMD-affected male and a carrier female? Can there be a carrier male?

Three autosomal recessive mutations in yeast, all producing the same phenotype \((m 1, m 2, \text { and } m 3),\) are subjected to complementation analysis, Of the results shown below, which, if any, are alleles of one another? Predict the results of the cross that is not shown-that is, \(m 2 \times m 3\) Cross \(1: \quad m I \times m 2 \longrightarrow P_{1}=\) all wild-type progeny Cross \(2: \quad m I \times m 3 \longrightarrow P_{1}:\) all mutant progeny

In Dexter and Kerry cattle, animals may be polled (hornless) or horned. The Dexter animals have short legs, whereas the Kerry animals have long legs. When many offspring were obtained from matings between polled Kerrys and horned Dexters, half were found to be polled Dexters and half polled Kerrys. When these two types of \(\mathrm{F}_{1}\) cattle were mated to one another, the following \(\mathrm{P}_{2}\) data were obtained: \(3 / 8\) polled Dexters \(1 / 8\) horned Dexters \(3 / 8\) polled Kerrys \(1 / 8\) horned Kerrys A geneticist was puzzled by these data and interviewed farmers who had bred these cattle for decades. She learned that Kerrys were true-breeding. Dexters, on the other hand, were not true- breeding and never produced as many offspring as Kerrys. Provide a genetic explanation for these observations.

The maternal-effect mutation bicoid (bcd) is recessive. In the absence of the bicoid protein product, embryogenesis is not completed. Consider a cross between a female heterozygous for the bicoid mutation \(\left(b c d^{+} / b c d^{-}\right)\) and a homozygous male \(\left(b c d^{\left.-/ b c d^{-}\right)}\right.\) (a) How is it possible for a male homozygous for the mutation to exist? (b) Predict the outcome (normal vs, failed embryogenesis) in the \(\mathrm{F}_{1}\) and \(\mathrm{F}_{2}\) generations of the cross described.
See all solutions

Recommended explanations on Biology Textbooks

Cell Communication

Read Explanation

Genetic Information

Read Explanation

Cells

Read Explanation

Reproduction

Read Explanation

Biology Experiments

Read Explanation

Control of Gene Expression

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.

Sign-up for free