Textbook Question
Write a short essay that discusses the difference between the more traditional Mendelian and neo-Mendelian modes of inheritance (qualitative inheritance) and quantitative inheritance.
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Ch. 20 - Quantitative Genetics and Multifactorial Traits
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
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Table of contents
- 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
Chapter 20, Problem 1d
How do we know that monozygotic twins are not identical genotypically as adults?
Verified step by step guidance1
Understand that monozygotic twins originate from a single fertilized egg, so they start with identical genotypes at conception.
Recognize that as twins develop and age, various genetic and epigenetic changes can occur, such as mutations and DNA methylation, which can alter gene expression without changing the DNA sequence.
Consider that environmental factors and random cellular events can lead to differences in gene regulation and expression between the twins, contributing to phenotypic differences.
Learn about studies that compare the DNA sequences of adult monozygotic twins, which have found small genetic differences due to somatic mutations accumulated over time.
Conclude that these genetic and epigenetic changes explain why monozygotic twins are not completely identical genotypically as adults, despite originating from the same zygote.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Monozygotic Twins and Genetic Identity
Monozygotic twins originate from a single fertilized egg that splits, resulting in two individuals with nearly identical DNA at conception. However, despite their initial genetic identity, differences can arise over time due to various biological processes.
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03:59
Twin Studies
Somatic Mutations and Genetic Variation
As monozygotic twins develop and age, somatic mutations—random changes in DNA occurring in body cells—can accumulate differently in each twin. These mutations contribute to genetic differences that make their genomes not perfectly identical in adulthood.
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09:28Genomic Variation
Epigenetic Modifications
Epigenetic changes, such as DNA methylation and histone modification, alter gene expression without changing the DNA sequence. Environmental factors and life experiences cause distinct epigenetic patterns in each twin, leading to phenotypic and functional differences despite similar genotypes.
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Related Practice
Textbook Question
How can we ascertain the number of polygenes involved in the inheritance of a quantitative trait?
Textbook Question
What findings led geneticists to postulate the multiple-factor hypothesis that invoked the idea of additive alleles to explain inheritance patterns?
Textbook Question
How do we assess environmental factors to determine if they impact the phenotype of a quantitatively inherited trait?
Textbook Question
Define the following:
(a) Polygenic
(b) Additive alleles
(c) Correlation
(d) Monozygotic and dizygotic twins
(e) Heritability
(f) QTL
(g) Continuous variation
Textbook Question
A dark-red strain and a white strain of wheat are crossed and produce an intermediate, medium-red F₁. When the F₁ plants are interbred, an F₂ generation is produced in a ratio of 1 dark-red: 4 medium-dark-red: 6 medium-red: 4 light-red: 1 white. Further crosses reveal that the dark-red and white F₂ plants are true breeding
Based on the ratios in the F₂ population, how many genes are involved in the production of color?