Slide 1

Genetics and Evolution

Molecular Basis of Inheritance - Chromosomal Mutation

• Introduction to chromosomal mutation
• Types of chromosomal mutations
• Examples of chromosomal mutations
• Importance of chromosomal mutations in evolution

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Slide 2

Introduction to Chromosomal Mutation

• Chromosomal mutation refers to changes in the structure or number of chromosomes.
• These mutations can occur due to errors during DNA replication or as a result of environmental factors.
• Chromosomal mutations can have a significant impact on an organism’s phenotype.

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Slide 3

Types of Chromosomal Mutations

1. Deletion: A segment of the chromosome is lost.
2. Duplication: A segment of the chromosome is duplicated.
3. Inversion: A segment of the chromosome is reversed.
4. Translocation: A segment of one chromosome is transferred to another non-homologous chromosome.

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Slide 4

Deletion

• Deletion occurs when a segment of the chromosome is lost.
• It can lead to a loss of genetic information and cause various genetic disorders.
• Example: Cri-du-chat syndrome, which is characterized by a high-pitched cry and developmental delays.

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Slide 5

Duplication

• Duplication occurs when a segment of the chromosome is duplicated.
• Extra copies of genes can lead to genetic disorders or the evolution of new genes.
• Example: Charcot-Marie-Tooth disease, which affects the peripheral nerves and causes muscle weakness.

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Slide 6

Inversion

• Inversion occurs when a segment of the chromosome is reversed.
• This can disrupt gene function and potentially lead to genetic disorders.
• Example: Hemophilia, a bleeding disorder caused by a gene inversion on the X chromosome.

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Slide 7

Translocation

• Translocation occurs when a segment of one chromosome is transferred to another non-homologous chromosome.
• This can result in gene fusion or disruption of gene regulation.
• Example: Chronic myelogenous leukemia (CML), which is caused by a translocation between chromosomes 9 and 22.

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Slide 8

Examples of Chromosomal Mutations

• Down syndrome (trisomy 21): An individual has three copies of chromosome 21 instead of the usual two.
• Turner syndrome (monosomy X): Females have only one X chromosome instead of the usual two.
• Klinefelter syndrome (XXY): Males have an extra X chromosome.

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Slide 9

Importance of Chromosomal Mutations in Evolution

• Chromosomal mutations provide a source of genetic variation.
• They can lead to the evolution of new species or the adaptation of existing ones.
• Changes in chromosome structure can affect gene expression and potentially drive speciation.

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Slide 10

Recap

• Chromosomal mutations refer to changes in the structure or number of chromosomes.
• Types of chromosomal mutations include deletion, duplication, inversion, and translocation.
• Examples of chromosomal mutations include Down syndrome, Turner syndrome, and Klinefelter syndrome.
• Chromosomal mutations play an important role in evolution by providing genetic variation.

Slide 11

Chromosomal Mutations - Effects on Gene Expression

• Chromosomal mutations can disrupt normal gene expression patterns.
• Changes in chromosomal structure can alter the regulation of genes.
• Imbalances in gene dosage can lead to disease or developmental abnormalities.
• Example: Down syndrome is caused by an extra copy of chromosome 21, which leads to overexpression of certain genes.

Slide 12

Genetic Disorders Resulting from Chromosomal Mutations

• Many genetic disorders are caused by chromosomal mutations.
• These disorders can be inherited or arise spontaneously.
• Examples: Turner syndrome, Klinefelter syndrome, Prader-Willi syndrome, Angelman syndrome, etc.
• These disorders have characteristic symptoms and affect various aspects of development and health.

Slide 13

Effects of Chromosomal Mutations on Sex Chromosomes

• Chromosomal mutations can affect the number or structure of sex chromosomes.
• Such mutations can impact an individual’s sexual development and fertility.
• Examples: Turner syndrome, Klinefelter syndrome, XYY syndrome, etc.

Slide 14

Impact of Chromosomal Mutations on Evolutionary Processes

• Chromosomal mutations play a significant role in evolution.
• They contribute to genetic variation, which is the raw material for natural selection.
• Certain chromosomal mutations can enhance an organism’s ability to adapt to its environment.
• Examples: Duplications can create gene families that provide new functions and selective advantages.

Slide 15

Chromosomal Mutations and Cancer

• Certain chromosomal mutations are associated with cancer development.
• Translocations, deletions, or amplifications of specific genes can lead to uncontrolled cell growth.
• Examples: Philadelphia chromosome in chronic myelogenous leukemia, oncogene amplification in breast cancer.

Slide 16

Prenatal Testing and Chromosomal Mutations

• Chromosomal mutations can be detected through prenatal testing.
• Techniques such as amniocentesis or chorionic villus sampling (CVS) can reveal chromosomal abnormalities in fetuses.
• This information can help parents make informed decisions about their pregnancy and potential medical interventions.

Slide 17

Chromosomal Mutations and Plant Breeding

• Chromosomal mutations can be harnessed in plant breeding to create improved cultivars.
• Induced mutations through radiation or chemical treatments can lead to new traits or traits not found in the original population.
• Examples: Seedless fruits, disease resistance, improved yield.

Slide 18

Chromosome Painting and Fluorescence In Situ Hybridization (FISH)

• Chromosome painting and FISH are techniques that allow visualization and localization of specific chromosomes or genomic regions.
• These techniques are useful in chromosomal aberration analysis, evolutionary studies, and genetic research.
• FISH involves labeling DNA probes with fluorescent tags that bind to complementary DNA sequences on the target chromosomes.

Slide 19

Chromosomal Mutations and Evolutionary Relationships

• Examination of chromosomal mutations can provide insights into evolutionary relationships between species.
• Similar or distinct chromosomal rearrangements can suggest common ancestry or divergence.
• This information is used in phylogenetic studies and understanding speciation processes.

Slide 20

Summary

• Chromosomal mutations can impact gene expression, cause genetic disorders, and influence evolutionary processes.
• Effects on sex chromosomes can lead to sexual development abnormalities.
• Chromosomal mutations are associated with cancer development and can be detected through prenatal testing.
• In plant breeding, induced mutations can lead to new traits and improved cultivars.
• Techniques like chromosome painting and FISH allow visualization and analysis of chromosomal aberrations.

Slide 21

Chromosomal Mutations and Genetic Disorders

• Chromosomal mutations can result in various genetic disorders that affect human health.
• Some examples of genetic disorders caused by chromosomal mutations include:
  • Down syndrome
  • Turner syndrome
  • Klinefelter syndrome
  • Cri-du-chat syndrome
• These disorders can have significant impacts on an individual’s physical and cognitive development.

Slide 22

Down Syndrome

• Down syndrome is caused by an extra copy of chromosome 21.
• It leads to characteristic physical features, intellectual disability, and an increased risk of certain health conditions.
• Examples of health conditions associated with Down syndrome include heart defects, hearing loss, and thyroid problems.

Slide 23

Turner Syndrome

• Turner syndrome occurs in females and is characterized by the absence or partial absence of one X chromosome.
• It leads to short stature, infertility, and specific physical features such as a webbed neck and lymphedema.
• Hormone therapy can help manage some of the symptoms associated with Turner syndrome.

Slide 24

Klinefelter Syndrome

• Klinefelter syndrome affects males and is characterized by the presence of one or more extra X chromosomes (XXY or XXXY).
• It can cause infertility, reduced facial and body hair, and developmental difficulties.
• Testosterone replacement therapy can help manage some of the symptoms associated with Klinefelter syndrome.

Slide 25

Cri-du-Chat Syndrome

• Cri-du-chat syndrome is caused by a deletion of a portion of chromosome 5.
• Individuals with this syndrome have a high-pitched cry in infancy and may experience intellectual disability, developmental delays, and distinct facial features.
• Early interventions and therapies can help support the development and well-being of individuals with Cri-du-chat syndrome.

Slide 26

Chromosomal Mutations and Evolutionary Processes

• Chromosomal mutations can have significant impacts on evolutionary processes.
• Certain mutations can lead to the creation of new genes or change the expression of existing genes, providing potential advantages in different environments.
• The accumulation of genetic variations through chromosomal mutations can drive speciation and the formation of new species.

Slide 27

Gene Duplication and Evolution

• Gene duplication is a type of chromosomal mutation that can have significant evolutionary implications.
• When a section of a chromosome is duplicated, it creates an extra copy of a gene.
• This duplicated gene can undergo further changes, leading to the evolution of new functions or the acquisition of novel traits.

Slide 28

Example: Hemoglobin Genes

• The human genome contains two clusters of globin genes, alpha and beta, which encode different types of hemoglobin.
• Gene duplications in the past have resulted in the evolution of different globin genes with specialized functions, such as fetal hemoglobin.
• These gene duplications have allowed for adaptations to different stages of life and modes of oxygen delivery.

Slide 29

Chromosomal Rearrangements and Divergence

• Chromosomal rearrangements, such as inversions and translocations, can contribute to speciation and the divergence of species.
• These rearrangements can lead to changes in gene expression, disrupt gene flow between populations, and create reproductive barriers.
• Over time, these evolutionary changes can result in the formation of distinct species.

Slide 30

Recap

• Chromosomal mutations can result in various genetic disorders, such as Down syndrome, Turner syndrome, Klinefelter syndrome, and Cri-du-chat syndrome.
• These mutations have significant impacts on an individual’s physical and cognitive development.
• Chromosomal mutations can also shape evolutionary processes by creating new genes through duplication and contributing to speciation through rearrangements.
• Understanding the relationship between chromosomal mutations, genetic disorders, and evolution is crucial in studying the molecular basis of inheritance.