Domanda del libro di testo
Draw all possible conclusions concerning the mode of inheritance of the trait portrayed in the following limited pedigree.
614
views
Ch. 3 - Mendelian Genetics
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
Non è quello che usi tu?Cambia libro di testoScegli un libro di testo diverso
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 3, Problema 23b
Two true-breeding pea plants are crossed. One parent is round, terminal, violet, constricted, while the other expresses the contrasting phenotypes of wrinkled, axial, white, full. The four pairs of contrasting traits are controlled by four genes, each located on a separate chromosome. In the F1 generation, only round, axial, violet, and full are expressed. In the F2 generation, all possible combinations of these traits are expressed in ratios consistent with Mendelian inheritance.
Which phenotype appears most frequently in the F2 results? Write a mathematical expression that predicts the frequency of occurrence of this phenotype.
Guida verificata passo dopo passo1
Identify the dominant and recessive alleles for each trait based on the F1 phenotype. Since the F1 generation shows round, axial, violet, and full phenotypes, these are the dominant traits, and wrinkled, terminal, white, and constricted are recessive.
Assign symbols to each gene, for example: R (round) is dominant over r (wrinkled), A (axial) over a (terminal), V (violet) over v (white), and F (full) over f (constricted). The true-breeding parents would be RR AA VV FF (round, terminal, violet, constricted) and rr aa vv ff (wrinkled, axial, white, full).
Determine the genotype of the F1 generation by crossing the two true-breeding parents. The F1 genotype will be heterozygous for all traits: Rr Aa Vv Ff, expressing all dominant phenotypes.
Understand that the F2 generation results from self-crossing the F1 individuals (Rr Aa Vv Ff × Rr Aa Vv Ff). Each gene segregates independently according to Mendel's law of independent assortment.
Calculate the frequency of the most common phenotype in the F2 generation, which is the phenotype expressing all dominant traits (round, axial, violet, full). For each gene, the probability of the dominant phenotype is \$\(\frac{3}{4}\)\$ (since 1/4 are homozygous recessive and 3/4 show the dominant phenotype). Therefore, the overall frequency is the product of the probabilities for all four traits: \$\(\left\)(\(\frac{3}{4}\)\(\right\))^4\$.
Concetti chiave
Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.
Mendelian Inheritance and Dominance
Mendelian inheritance describes how traits are passed from parents to offspring through dominant and recessive alleles. In this question, each trait has two contrasting forms controlled by separate genes, with dominant alleles expressed in the F1 generation. Understanding dominance helps predict which phenotypes appear in offspring.
Video consigliato:
Percorso guidato
04:37
Variations on Dominance
Dihybrid and Multihybrid Crosses
A multihybrid cross involves multiple gene pairs segregating independently, as seen with four gene pairs here. The F2 generation results from self-crossing F1 heterozygotes, producing phenotypic ratios based on independent assortment. Calculating combined probabilities for multiple traits requires multiplying individual trait ratios.
Video consigliato:
Percorso guidato
15:24Punnet Square
Phenotypic Ratios and Probability Calculations
Phenotypic ratios in the F2 generation follow Mendel’s laws, typically 3:1 for single traits with complete dominance. For multiple traits, the overall frequency of a phenotype is the product of individual trait probabilities. This allows prediction of the most frequent phenotype and its expected frequency mathematically.
Video consigliato:
Percorso guidato
07:41Probability