Domanda del libro di testo
Describe how nondisjunction in human female gametes can give rise to Klinefelter and Turner syndrome offspring following fertilization by a normal male gamete.
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Ch. 7 - Sex Determination and Sex Chromosomes
Klug12th EditionConcepts of GeneticsISBN: 9780135564776
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TOC.tableOfContents
- Ch. 1 - Introduction to Genetics17
- Ch. 2 - Mitosis and Meiosis36
- Ch. 3 - Mendelian Genetics51
- Ch. 4 - Extensions of Mendelian Genetics74
- Ch. 5 - Chromosome Mapping in Eukaryotes51
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages46
- Ch. 7 - Sex Determination and Sex Chromosomes33
- Ch. 8 - Chromosome Mutations: Variation in Number and Arrangement40
- Ch. 9 - Extranuclear Inheritance31
- Ch. 10 - DNA Structure and Analysis43
- Ch. 11 - DNA Replication and Recombination44
- Ch. 12 - DNA Organization in Chromosomes30
- Ch. 13 - The Genetic Code and Transcription54
- Ch. 14 - Translation and Proteins47
- Ch. 15 - Gene Mutation, DNA Repair, and Transposition41
- Ch. 16 - Regulation of Gene Expression in Bacteria29
- Ch. 17 - Transcriptional Regulation in Eukaryotes41
- Ch. 18 - Post-transcriptional Regulation in Eukaryotes33
- Ch. 19 - Epigenetics33
- Ch. 20 - Recombinant DNA Technology44
- Ch. 21 - Genomic Analysis36
- Ch. 22 - Applications of Genetic Engineering and Biotechnology36
- Ch. 23 - Developmental Genetics37
- Ch. 24 - Cancer Genetics34
- Ch. 25 - Quantitative Genetics and Multifactorial Traits54
- Ch. 26 - Population and Evolutionary Genetics45
Klug12th EditionConcepts of GeneticsISBN: 9780135564776Non è quello che usi tu?Cambia libro di testo
Capitolo 7, Problema 10a
An insect species is discovered in which the heterogametic sex is unknown. An X-linked recessive mutation for reduced wing (rw) is discovered. Contrast the F1 and F2 generations from a cross between a female with reduced wings and a male with normal-sized wings when the female is the heterogametic sex.
Guida verificata passo dopo passo1
Step 1: Identify the sex determination system and the genotypes of the parents. Since the female is heterogametic, the sex chromosomes are likely ZW for females and ZZ for males (opposite to the XY system). The mutation is X-linked recessive, but here it corresponds to the Z chromosome, so the allele for reduced wings (rw) is on the Z chromosome.
Step 2: Assign genotypes to the parents. The female with reduced wings is heterogametic (ZW), so she must carry the rw allele on her Z chromosome (Z^rw W). The male with normal wings is homogametic (ZZ) and must have normal alleles (Z^+ Z^+).
Step 3: Determine the possible gametes from each parent. The female can produce gametes Z^rw and W, while the male produces gametes Z^+ only (since both chromosomes are Z^+).
Step 4: Predict the F1 offspring genotypes by combining the gametes. The F1 males will be Z^+ W (normal wings), and the F1 females will be Z^rw Z^+ (carriers or affected depending on dominance).
Step 5: For the F2 generation, cross F1 individuals considering their genotypes and sex chromosomes. Analyze the expected phenotypic ratios by tracking the inheritance of the rw allele on the Z chromosome, remembering that females are ZW and males are ZZ.
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Heterogametic and Homogametic Sex Determination
Heterogametic sex produces two different types of sex chromosomes (e.g., XY in males), while homogametic sex produces identical sex chromosomes (e.g., XX in females). Identifying which sex is heterogametic is crucial for predicting inheritance patterns of sex-linked traits, as it affects how alleles on sex chromosomes are transmitted.
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04:24
Sex Determination
X-linked Recessive Inheritance
X-linked recessive traits are caused by mutations on the X chromosome and typically manifest in the heterogametic sex if they carry the mutant allele, since they have only one X chromosome. In homogametic individuals, two copies of the recessive allele are needed for expression. This pattern influences phenotypic ratios in offspring.
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09:30X-Inactivation
Genetic Crosses and Generational Analysis (F1 and F2)
F1 generation results from the initial parental cross, while F2 is produced by interbreeding F1 individuals. Analyzing phenotypes and genotypes across these generations helps reveal inheritance patterns, especially when sex linkage and heterogamety are involved, allowing prediction of offspring ratios under different genetic assumptions.
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02:48Chi Square Analysis
Pratica correlata
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What specific observations (evidence) support the conclusions about sex determination in Drosophila and humans?
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When cows have twin calves of unlike sex (fraternal twins), the female twin is usually sterile and has masculinized reproductive organs. This calf is referred to as a freemartin. In cows, twins may share a common placenta and thus fetal circulation. Predict why a freemartin develops.
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Domanda del libro di testo
An attached-X female fly, XXY, expresses the recessive X-linked white-eye mutation. It is crossed to a male fly that expresses the X-linked recessive miniature-wing mutation. Determine the outcome of this cross in terms of sex, eye color, and wing size of the offspring.
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Domanda del libro di testo
An insect species is discovered in which the heterogametic sex is unknown. An X-linked recessive mutation for reduced wing (rw) is discovered. Contrast the F1 and F2 generations from a cross between a female with reduced wings and a male with normal-sized wings when the male is the heterogametic sex.
467
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Domanda del libro di testo
The phenotype of an early-stage human embryo is considered sexually indifferent. Explain why this is so even though the embryo's genotypic sex is already fixed.
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