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Chapter Analysis
Advanced25 pages • EnglishQuick Summary
The chapter 'Principles of Inheritance and Variation' delves into Mendel's laws of inheritance, including the laws of dominance, segregation, and independent assortment. It explores genetic concepts such as genotype and phenotype, linkage and recombination, and polygenic inheritance. The chapter also covers chromosomal theory, mutation, genetic disorders, and sex determination in humans. It provides a comprehensive understanding of how traits are inherited and expressed across generations.
Key Topics
- •Mendel's Laws of Inheritance
- •Genotype and Phenotype
- •Law of Dominance and Segregation
- •Linkage and Recombination
- •Polygenic Inheritance
- •Sex Determination in Humans
- •Pleiotropy
- •Genetic Disorders
Learning Objectives
- ✓Understand the basic principles of Mendelian inheritance.
- ✓Describe the processes of dominance, segregation, and independent assortment.
- ✓Explain the concepts of linkage and recombination.
- ✓Differentiate between Mendelian and non-Mendelian traits.
- ✓Identify how genetic disorders are inherited.
- ✓Analyze sex determination mechanisms in humans.
Questions in Chapter
Mention the advantages of selecting pea plant for experiment by Mendel.
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Differentiate between the following – (a) Dominance and Recessive (b) Homozygous and Heterozygous (c) Monohybrid and Dihybrid.
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A diploid organism is heterozygous for 4 loci, how many types of gametes can be produced?
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Explain the Law of Dominance using a monohybrid cross.
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Define and design a test-cross.
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Using a Punnett Square, workout the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus.
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When a cross is made between tall plant with yellow seeds (TtYy) and tall plant with green seed (Ttyy), what proportions of phenotype in the offspring could be expected to be (a) tall and green, (b) dwarf and green.
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Two heterozygous parents are crossed. If the two loci are linked, what would be the distribution of phenotypic features in F1 generation for a dihybrid cross?
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Briefly mention the contribution of T.H. Morgan in genetics.
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What is pedigree analysis? Suggest how such an analysis can be useful.
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Additional Practice Questions
What role did the discovery of chromosomes play in the validation of Mendel's laws?
mediumAnswer: The discovery of chromosomes was crucial in validating Mendel's laws as it provided a physical basis for the existence and behavior of genes. Chromosomal movements during meiosis explained the segregation and independent assortment of genes, aligning with Mendel's findings.
Explain the significance of co-dominance and provide an example.
mediumAnswer: Co-dominance is the phenomenon where both alleles in a gene pair are fully expressed, resulting in offspring with a phenotype that is neither dominant nor recessive. An example of co-dominance is the ABO blood group system, where both A and B alleles are expressed in AB blood type.
Describe how polygenic inheritance differs from Mendelian inheritance.
hardAnswer: Polygenic inheritance involves multiple genes contributing to a single trait, resulting in a continuous range of phenotypes, such as height or skin color. In contrast, Mendelian inheritance involves single genes controlling distinct traits, producing discrete phenotype categories.
How is a test cross used to determine an organism's genotype?
mediumAnswer: A test cross involves breeding an organism exhibiting a dominant phenotype with a homozygous recessive organism. The phenotypic ratio of the offspring can indicate whether the original organism was homozygous dominant or heterozygous.
What is the chromosomal basis for sex determination in humans?
easyAnswer: In humans, sex determination is based on the presence of sex chromosomes: XX for females and XY for males. The Y chromosome carries specific genes that determine male characteristics, making the genetic makeup of sperm crucial in determining sex.
Provide an explanation for pleiotropy with an example.
hardAnswer: Pleiotropy occurs when a single gene affects multiple phenotypic traits. An example is phenylketonuria, where a mutation in the gene coding for the enzyme phenylalanine hydroxylase affects mental development and pigmentation.