Domanda del libro di testo
How do mammals, including humans, solve the 'dosage problem' caused by the presence of an X and Y chromosome in one sex and two X chromosomes in the other sex?
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Ch. 5 - Sex Determination and Sex Chromosomes
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
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TOC.tableOfContents
- Ch. 1 - Introduction to Genetics16
- Ch. 2 - Mitosis and Meiosis28
- Ch. 3 - Mendelian Genetics37
- Ch. 4 - Modification of Mendelian Ratios53
- Ch. 5 - Sex Determination and Sex Chromosomes32
- Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement37
- Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes36
- Ch. 8 - Genetic Analysis and Mapping in Bacteria and Bacteriophages24
- Ch. 9 - DNA Structure and Analysis38
- Ch. 10 - DNA Replication29
- Ch. 11 - Chromosome Structure and DNA Sequence Organization22
- Ch. 12 - The Genetic Code and Transcription36
- Ch. 13 - Translation and Proteins27
- Ch. 14 - Gene Mutation, DNA Repair, and Transposition34
- Ch. 15 - Regulation of Gene Expression in Bacteria22
- Ch. 16 - Regulation of Gene Expression in Eukaryotes37
- Ch. 17 - Recombinant DNA Technology27
- Ch. 18 - Genomics, Bioinformatics, and Proteomics30
- Ch. 19 - The Genetics of Cancer21
- Ch. 20 - Quantitative Genetics and Multifactorial Traits37
- Ch. 21 - Population and Evolutionary Genetics45
Klug10th EditionEssentials of GeneticsISBN: 9780135588789Non è quello che usi tu?Cambia libro di testo
Capitolo 5, Problema 8
What specific observations (evidence) support the conclusions about sex determination in Drosophila and humans?
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Identify the key differences in sex determination mechanisms between Drosophila and humans. In Drosophila, sex is determined by the ratio of X chromosomes to sets of autosomes (X:A ratio), whereas in humans, sex is determined by the presence or absence of the Y chromosome.
Examine experimental evidence in Drosophila, such as the observation that flies with two X chromosomes and two sets of autosomes (X:A = 1) develop as females, while those with one X chromosome and two sets of autosomes (X:A = 0.5) develop as males. This supports the role of the X:A ratio in sex determination.
Consider genetic studies in humans showing that individuals with XY chromosomes develop as males due to the presence of the SRY gene on the Y chromosome, which triggers male development, while individuals with XX chromosomes develop as females. This highlights the importance of the Y chromosome in human sex determination.
Look at cases of sex reversal or intersex conditions in both species, such as XX males or XY females in humans, and how these cases provide evidence for the genetic basis of sex determination (e.g., translocation of SRY gene). In Drosophila, changes in the X:A ratio can lead to intersex phenotypes, further supporting the ratio model.
Summarize that the specific observations supporting sex determination conclusions include chromosome counts, phenotypic sex outcomes, and genetic manipulations or mutations that alter expected sex development patterns in both Drosophila and humans.
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Chromosomal Basis of Sex Determination
Sex determination in both Drosophila and humans is governed by specific chromosomes, known as sex chromosomes. In humans, the presence of XX chromosomes typically results in females, and XY in males. In Drosophila, the ratio of X chromosomes to sets of autosomes determines sex, with XX being female and XY male. Observations of chromosome patterns in offspring support these mechanisms.
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Percorso guidato
04:24
Sex Determination
Genetic Evidence from Mutant and Aneuploid Individuals
Studies of individuals with abnormal numbers or structures of sex chromosomes, such as Turner syndrome (XO) or Klinefelter syndrome (XXY) in humans, and similar chromosomal variants in Drosophila, provide evidence for how sex chromosomes influence sexual development. These genetic anomalies help clarify the role of specific chromosomes in sex determination.
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09:05Aneuploidy
Experimental Crosses and Phenotypic Ratios
Controlled breeding experiments in Drosophila and pedigree analyses in humans reveal patterns of inheritance and sex ratios that support chromosomal sex determination. For example, observing the sex ratios in offspring from specific crosses or families helps confirm the role of sex chromosomes and the mechanisms by which they determine sex.
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10:20Monohybrid Cross
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Describe the major difference between sex determination in Drosophila and in humans.
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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.
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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.
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