Ch. 18 - Developmental Genetics

Sanders - Genetic Analysis: An Integrated Approach 3rd Edition

Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172당신이 사용하는 게 아니라요?교과서 변경

Sanders 3rd Edition

Ch. 18 - Developmental Genetics

문제 15

18장, 문제 15

What phenotypes do you expect in flies homozygous for loss-of-function mutations in the following genes: Krüppel, odd-skipped, hedgehog, and Ultrabithorax?

검증된 단계별 안내

Understand that the question is about Drosophila melanogaster (fruit fly) development and the role of specific genes in this process.

Recognize that Krüppel, odd-skipped, hedgehog, and Ultrabithorax are genes involved in the segmentation and patterning of the Drosophila embryo.

Krüppel is a gap gene, and loss-of-function mutations typically result in the absence of certain segments in the middle of the embryo.

Odd-skipped is a pair-rule gene, and its loss-of-function mutations often lead to the absence of alternate segments, affecting the even-numbered parasegments.

Hedgehog is a segment polarity gene, and its loss-of-function mutations can cause defects in segment patterning, leading to a 'lawn of denticles' phenotype.

Ultrabithorax is a homeotic gene, and its loss-of-function mutations can result in the transformation of the third thoracic segment into a second thoracic segment, leading to the development of an extra pair of wings.

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

영상 길이:

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Homozygous Loss-of-Function Mutations

Homozygous loss-of-function mutations occur when both alleles of a gene are non-functional, leading to a complete loss of the gene's normal activity. In the context of Drosophila (fruit flies), these mutations can significantly affect development and phenotype, as the affected genes often play crucial roles in processes like segmentation and pattern formation.

Gene Function in Development

The genes mentioned—Krüppel, odd-skipped, hedgehog, and Ultrabithorax—are essential for proper embryonic development in Drosophila. Each gene is involved in specific developmental pathways that dictate body segmentation, organ formation, and overall morphology. Understanding the normal function of these genes helps predict the phenotypic consequences of their loss.

Phenotypic Expression

Phenotypic expression refers to the observable traits or characteristics of an organism resulting from the interaction of its genotype with the environment. In the case of flies with mutations in the specified genes, the expected phenotypes can include altered body segments, misplacement of structures, or even lethality, depending on the gene's role in development and the severity of the mutation.

관련 실천

교과서 질문

The bicoid gene is a coordinate maternal–effect gene. A female that is homozygous for a loss-of-function bicoid allele is mated to a wild-type male. What are the phenotypes of their progeny?

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교과서 질문

In contrast to Drosophila, some insects (e.g., centipedes) have legs on almost every segment posterior to the head. Based on your knowledge of Drosophila, propose a genetic explanation for this phenotype, and describe the expected expression patterns of genes of the Antennapedia and bithorax complexes.

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교과서 질문

The pair-rule gene fushi tarazu is expressed in the seven even-numbered parasegments during Drosophila embryogenesis. In contrast, the segment polarity gene engrailed is expressed in the anterior part of each of the 14 parasegments. Since both genes are active at similar times and places during development, it is possible that the expression of one gene is required for the expression of the other. This can be tested by examining expression of the genes in a mutant background—for example, looking at fushi tarazu expression in an engrailed mutant background, and vice versa. Given the hierarchy of gene action during Drosophila embryogenesis, what might you predict to be the result of these experiments?

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교과서 질문

The pair-rule gene fushi tarazu is expressed in the seven even-numbered parasegments during Drosophila embryogenesis. In contrast, the segment polarity gene engrailed is expressed in the anterior part of each of the 14 parasegments. Since both genes are active at similar times and places during development, it is possible that the expression of one gene is required for the expression of the other. This can be tested by examining the expression of the genes in a mutant background—for example, looking at fushi tarazu expression in an engrailed mutant background, and vice versa. Based on your prediction, can you predict the phenotype of the fushi tarazu and engrailed double mutant?

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교과서 질문

The bicoid gene is a coordinate maternal–effect gene. If loss of bicoid function in the egg leads to lethality during embryogenesis, how are females homozygous for bicoid produced? What is the phenotype of a male homozygous for bicoid loss-of-function alleles?

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교과서 질문

Given that maternal Bicoid activates the expression of hunchback, what would be the consequence of adding extra copies of the bicoid gene by transgenic means to a wild-type female with two copies, thus creating a female fly with three or four copies of the bicoid gene? How would the hunchback expression be altered? What about the expression of other gap genes and pair-rule genes?

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