Learning Outcomes:
i. Define and explain the concept of gene linkage.
ii. Understand how genes on the same chromosome tend to be inherited together.
iii. Describe the phenomenon of crossing over during meiosis.
iv. Appreciate how crossing over contributes to genetic diversity in offspring.
Introduction:
Imagine a bustling train station where genes, like passengers, board chromosomes, their designated trains. In the world of genetics, genes located close together on the same chromosome often travel together, like families on a long journey. This tendency of linked genes to be inherited together is called gene linkage. But wait, the journey isn't always predictable! Sometimes, during a special process called crossing over, genes on the same train can switch partners, leading to unexpected combinations in the offspring. Get ready to embark on a fascinating exploration of gene linkage and crossing over, where the rules of inheritance get a little twist!
i. The Chain Reaction: Understanding Gene Linkage
Think of genes as beads strung together on a chromosome necklace. Linked genes, like close friends, are positioned very near each other on this necklace. During the formation of reproductive cells (sperm and egg), chromosomes pair up and undergo a dance called meiosis. This dance separates the chromosomes, ensuring each gamete receives one copy from each parent. However, because linked genes are close neighbors, they often end up on the same chromosome during this separation, leading to their inheritance together. This is why, for example, children with parents who have both blue eyes are more likely to inherit blue eyes themselves, as the genes for blue eye color tend to be linked.
ii. The Grand Swap: Unveiling Crossing Over
But here's where the story takes a turn! During meiosis, something magical can happen. Imagine two train tracks running parallel, representing the paired chromosomes. During the dance, a section of one chromosome can break and exchange material with the other chromosome. This is crossing over, a process where genes literally switch partners, creating new combinations on the chromosomes. This means that even if linked genes are initially inherited together, crossing over can shuffle them up, leading to offspring with different combinations of traits than their parents. Crossing over, like a talented magician, adds a layer of unpredictability to the inheritance of linked genes, creating a wider variety of phenotypes in the next generation.
iii. Beyond the Basics: A World of Diversity
Gene linkage and crossing over are not just theoretical concepts; they have real-world implications. Understanding these mechanisms helps us explain:
Why some traits, like certain blood types or disease susceptibility, often appear together in families.
How genetic maps are constructed by tracking the inheritance patterns of linked genes.
The remarkable diversity of offspring even within siblings, thanks to the shuffling of genes during crossing over.
Gene linkage and crossing over are like hidden threads woven into the tapestry of inheritance, influencing the traits we inherit and the diversity we see in the world around us. By appreciating these fascinating phenomena, we gain a deeper understanding of the intricate dance of life and the remarkable power of our genetic code. So next time you look at your family or marvel at the variety of life forms, remember the invisible train tracks of chromosomes, the magical swap of crossing over, and the fascinating story of how genes travel and combine to create the unique individuals we all are.
Class Sessions
1- Lesson 01: Respiratory Surface and Properties
2- Lesson 02: Components of Human Respiratory System
3- Lesson 03: Ventilation Mechanism in Humans
4- Lesson 04: Lung Volumes and Capacities
5- Lesson 05: Control of Breathing
6- Lesson 06: Transport of Oxygen and Carbon Dioxide
7- Lesson 07: Role of Respiratory Pigments
8- Lesson 08: Respiratory Tract Infections
9- Lesson 09: Disorders of Lungs
10- Lesson 10: Effects of Smoking on Respiratory System
11- Lesson 01: Elements of Homeostatic Mechanisms
12- Lesson 02: Homeostatic Mechanisms and Feedback Systems
13- Lesson 03: Osmoconformers and Osmoregulators
14- Lesson 04: Osmoregulation
15- Lesson 05: Problems Faced by Osmoregulators
16- Lesson 06: Osmoregulation in Different Habitats
17- Lesson 07: Nitrogenous Compounds in Excretion
18- Lesson 08: Excretory Products and Habitat
19- Lesson 09: Organs of the Urinary System
20- Lesson 10: Structure of Kidney and its Function
21- Lesson 11: Structure of Nephron
22- Lesson 12: Kidney Functioning - Glomerular Filtration, Selective Reabsorption, and Tubular Secretion
23- Lesson 13: Regulation of Urine Concentration
24- Lesson 14: Kidneys as Excretion and Osmoregulation Organs
25- Lesson 15: Comparison of Glomerular and Peritubular Capillaries
26- Lesson 16: Urinary Tract Infections and Responsible Bacteria
27- Lesson 17: Causes and Treatments of Kidney Stones
28- Lesson 18: Causes of Kidney Failure
29- Lesson 19: Dialysis - Mechanism and Problems
30- Lesson 20: Kidney Transplant - Principles and Problems
31- Lesson 21: Thermoregulation and its Needs
32- Lesson 22: Classification of Animals Based on Heat Source
33- Lesson 23: Classification of Animals Based on Thermoregulation Ability
34- Lesson 24: Regulatory Strategies in Human Thermoregulation
35- Lesson 01: Structure of Bone and Comparison with Cartilage
36- Lesson 02: Functions of Osteoblasts, Osteoclasts, and Osteocytes
37- Lesson 03: Divisions of the Human Skeleton
38- Lesson 04: Bones of Appendicular and Axial Skeleton
39- Lesson 05: Types of Joints - Fibrous, Cartilaginous, and Synovial
40- Lesson 06: Disorders of the Human Skeleton
41- Lesson 07: Types of Fractures and Repair Process
42- Lesson 08: First-Aid Treatment for Fracture
43- Lesson 09: Comparison of Smooth Muscles, Cardiac Muscles, and Skeletal Muscles
44- Lesson 10: Ultra-structure of Skeletal Muscle
45- Lesson 11: Sliding Filaments Model of Muscle Contraction
46- Lesson 12: Antagonistic Muscles in Knee Joint Movement
47- Lesson 13: Muscle Fatigue, Cramps, and Tetany
48- Lesson 14: Tetanus vs. Muscle Tetany
49- Lesson 01: Receptors as Stimulus Transducers
50- Lesson 02: Path of Message Transmission to the CNS
51- Lesson 03: Three Neurons in Nervous Transmission
52- Lesson 04: Muscles and Glands as Effectors
53- Lesson 05: Structure of Sensory, Associative, and Motor Neurons
54- Lesson 06: Myelinated vs. Non-myelinated Neurons
55- Lesson 07: Function of Three Types of Neurons with Reflex Arc
56- Lesson 08: Nerve Impulse Definition
57- Lesson 09: Generation and Transmission of Nerve Impulse
58- Lesson 10: Factors for Resting Membrane Potential of Neuron
59- Lesson 11: Graphical Representation of Membrane Phenomena
60- Lesson 12: Velocities of Nerve Impulse
61- Lesson 13: Role of Local Circuits in Saltatory Conduction
62- Lesson 14: Structure of Synapse
63- Lesson 15: Synaptic Transmission of Nerve Impulse
64- Lesson 16: Classification of Neurotransmitters
65- Lesson 17: Main Components of the Nervous System
66- Lesson 18: Functions of Major Divisions of the Brain
67- Lesson 19: Architecture of Human Brain
68- Lesson 20: Cranial and Spinal Nerves
69- Lesson 21: Autonomic Nervous System
70- Lesson 22: Receptors for Smell, Taste, and Touch/Pain
71- Lesson 23: Narcotic Drugs and their Interaction with the Nervous System
72- Lesson 24: Use and Abuse of Drugs
73- Lesson 25: Drug Addiction and Tolerance
74- Lesson 26: Effects of Drug Addiction and Tolerance on the Nervous System
75- Lesson 27: Withdrawal Symptoms of Alcohol
76- Lesson 28: Classification of Nervous Disorders
77- Lesson 29: Causes, Symptoms, and Treatment of Various Nervous Disorders
78- Lesson 30: Diagnostic Tests for Nervous Disorders - EEG, CT Scan, and MRI
79- Lesson 01: Role of Hormones as Chemical Messengers
80- Lesson 02: Chemical Nature of Hormones and Important Examples
81- Lesson 03: Path of Chemical Message from Release to Action
82- Lesson 04: Two Modes of Hormone Action at Target Cells
83- Lesson 05: Location of Endocrine Glands in the Human Body
84- Lesson 06: Hormonal Secretions of Endocrine Glands
85- Lesson 07: Major Functions and Imbalances of Hormones
86- Lesson 08: Neurosecretory Role of Hypothalamus
87- Lesson 09: Functions of Hormones Secreted by Other Endocrine Tissues
88- Lesson 10: Feedback Mechanism of Hormones
89- Lesson 11: Positive and Negative Feedback with Reference to Hormones
90- Lesson 01: Definition of Behavior
91- Lesson 02: Relationship Between Stimuli and Behavior
92- Lesson 03: Relationship Between Heredity and Behavior
93- Lesson 04: Biological Rhythms and Examples
94- Lesson 05: Definition of Innate (Inborn) Behavior
95- Lesson 06: Examples of Innate Behavior (Taxis and Tropism)
96- Lesson 07: Justification of Reflexes as Innate Behavior
97- Lesson 08: Definition of Instincts as Innate Behavior
98- Lesson 09: Examples of Species-Specific Instinctive Behavior
99- Lesson 10: Definition of Learning and Distinction from Innate Behavior
100- Lesson 11: Definition and Example of Habituation
101- Lesson 12: Explanation of Imprinting Through Lorenz's Work
102- Lesson 13: Differentiation of Habituation and Imprinting
103- Lesson 14: Classical Conditioning and Pavlov's Work
104- Lesson 15: Instrumental Conditioning and Skinner's Work
105- Lesson 16: Latent Learning and Example of a Rat in a Maze
106- Lesson 17: Interpretation of Kohler's Work on Chimpanzee's Insight Learning
107- Lesson 18: Differentiation Between Animal Aggregations and Animal Societies
108- Lesson 19: Description of Hostile and Helpful Interactions in Social Behavior
109- Lesson 20: Explanation of Agonistic Behavior and Its Role in Social Order
110- Lesson 21: Explanation of Territorial Behavior Through Monkey and Gorilla Examples
111- Lesson 22: Explanation of Dominance Hierarchy Through Chicken Example
112- Lesson 23: Definition of Altruism and Illustration Through Honeybee Society
113- Lesson 01: Structures of Male Reproductive System and Their Functions
114- Lesson 02: Principal Reproductive Hormones in Human Males
115- Lesson 03: Structures of Female Reproductive System and Their Functions
116- Lesson 04: Menstrual Cycle and Hormonal Regulation
117- Lesson 05: Causes of Female and Male Infertility
118- Lesson 06: In-Vitro Fertilization (IVF) as a Solution to Infertility
119- Lesson 07: Definition and Causes of Miscarriage
120- Lesson 08: Relationship Between Miscarriage and Abortion
121- Lesson 09: Causes, Symptoms, and Treatment of Gonorrhea and Syphilis
122- Lesson 10: Explanation of AIDS as a Worldwide Sexually Transmitted Disease
123- Lesson 01: Cleavage and Its Relation to Yolk Amount
124- Lesson 02: Events of Gastrulation
125- Lesson 03: Tissues and Organs Formed from Germ Layers
126- Lesson 04: Events of Neurulation
127- Lesson 05: Formation of Neural Crest and Derivatives
128- Lesson 06: Definition of Organogenesis
129- Lesson 07: Role of Nucleus and Cytoplasm in Development
130- Lesson 08: Overview of Hans Spemann's Work in the Discovery of Induction
131- Lesson 09: Definition of Organizers and Differentiation Between Primary and Secondary Induction
132- Lesson 10: Events of Development in Human Trimesters
133- Lesson 11: Development of Twins and Quadruplets
134- Lesson 12: Structural Details of Placenta and Umbilical Cord
135- Lesson 13: Differentiation Between Gestation and Pregnancy
136- Lesson 14: Role of Fetal and Maternal Hormones in Labor
137- Lesson 15: Definition of Premature Birth and Correlation with Growth Phases
138- Lesson 16: Definition of Afterbirth and Detachment of Umbilical Cord
139- Lesson 17: Definition of Colostrum and Hormonal Role in Milk Production
140- Lesson 18: Hormonal Regulation at the End of Milk Production
141- Lesson 19: Comparison of Breastfeeding and Bottle-feeding
142- Lesson 20: Maternal Derived Abnormalities and Developmental Issues
143- Lesson 21: Genetic Abnormalities in Embryos and Spontaneous Abortion
144- Lesson 22: Fetal Surgery to Correct Developmental Problems
145- Lesson 23: Definition of Allometric Growth and Correlation with Postnatal Development
146- Lesson 24: Definition of Aging
147- Lesson 25: Rationalizing Aging as a Part of Normal Development
148- Lesson 26: Factors Responsible for Aging (Genetic and Extrinsic)
149- Lesson 27: Changes in Primary Aging
150- Lesson 28: Changes in Secondary Aging
151- Lesson 29: Changes at System and Cellular Levels During Aging
152- Lesson 01: Association of Inheritance with Mendel's Laws
153- Lesson 02: Explanation of the Law of Independent Assortment
154- Lesson 03: Expression of Limitations in the Law and Its Usefulness
155- Lesson 04: Statement of the Scope of Independent Assortment in Variation
156- Lesson 05: Evaluation of Inheritance and Mixing During Fertilization as Probabilistic
157- Lesson 06: Description of Exceptions to Mendel's Laws
158- Lesson 07: Explanation of Incomplete Dominance and Example in 4 O’clock Plant
159- Lesson 08: Differentiation Between Incomplete Dominance and Co-dominance
160- Lesson 09: Description of Multiple Alleles and Alleles for ABO Blood Groups
161- Lesson 10: Explanation of Two Alleles with Equal Dominance and Genetics of AB Blood Group
162- Lesson 11: Naming Various Human Blood Group Systems
163- Lesson 12: Association of Multiple Alleles with the ABO Blood Group System
164- Lesson 13: Investigation of Reasons for O-negative as Universal Donor and AB-positive as Universal Recipient
165- Lesson 14: Description of Occurrence of Other Blood Group Systems
166- Lesson 15: Association of Positive and Negative Blood Groups with the Presence and Absence of Rh Factor
167- Lesson 16: Justification of Rh Incompatibility Danger to Fetus and Mother
168- Lesson 17: Explanation of Erythroblastosis Fetalis in Light of Antigen-Antibody Reaction
169- Lesson 18: Measures to Counter Erythroblastosis Fetalis Before Occurrence
170- Lesson 19: Explanation of Polygenic and Epistasis
171- Lesson 20: Description of Polygenic Inheritance with Examples from Plants and Animals
172- Lesson 21: Listing Five Polygenic Traits Discovered in Humans
173- Lesson 22: Relating Polygenic Inheritance with Epistasis
174- Lesson 23: Example of Epistasis in Mammals and Plants with Justification of Modified Mendelian Ratios
175- Lesson 24: Description of Gene Linkage and Crossing Over
176- Lesson 25: Explanation of How Gene Linkage Counters Independent Assortment and Crossing-Over Modifies Progeny
177- Lesson 26: Exemplification of Gene Linkage with Drosophila Example
178- Lesson 27: Suggestion of Large Progeny Size for Linkage Observations
179- Lesson 28: Explanation of XX-XY Mechanism of Sex Determination in Drosophila and Mammals
180- Lesson 29: Description of XX-XO and ZZ-ZW Sex Determination Systems and Karyotype Evaluation
181- Lesson 30: Identification of Differences Between Homogametic and Heterogametic Conditions in Human Karyotype
182- Lesson 31: Identification of Male and Female Individuals in Drosophila and Man Karyotypes
183- Lesson 32: Solving Genetics Problems Related to Sex Determination
184- Lesson 33: Description of the Concept of Sex-Linkage
185- Lesson 34: Explanation of the Inheritance of Sex-Linked Traits in Drosophila
186- Lesson 35: Description of Sex-Linked Inheritance of Male Characters and the Effect of Hollandric Genes
187- Lesson 36: Description of Sex-Influenced and Sex-Limited Traits with Examples from Human Genetics
188- Lesson 37: Description of X-Linked Disorders with Reference to Patterns of Inheritance
189- Lesson 38: Naming Some Sex-Linked Disorders of Man and Drosophila
190- Lesson 39: Critical Analysis of the Inheritance of Haemophilia, Colour Blindness, and Muscular Dystrophy
191- Lesson 01: Critical Analysis of the History of Chromosomal Theory with Reference to Correns’ Work
192- Lesson 02: Critical Analysis of the Experiments of T.H. Morgan Supporting Chromosomal Theory
193- Lesson 03: Annotation of the Detailed Structure of a Chromosome
194- Lesson 04: Description of the Concept of Gene and Gene Locus
195- Lesson 05: Explanation of Alleles as Alternative Forms of a Gene
196- Lesson 06: Narration of Griffith and Hershey-Chase Experiments on DNA as Hereditary Material
197- Lesson 07: Description of Three Models Proposed for DNA Replication Mechanism
198- Lesson 08: Narration of Meselson and Stahl's Work on Semi-conservative DNA Replication
199- Lesson 09: Description of Events in the Process of DNA Replication
200- Lesson 10: Explanation of DNA Stability and Variability as Characteristics of Replicating DNA
201- Lesson 11: Description of the Central Dogma of Gene Expression
202- Lesson 12: Definition of Gene and Genetic Code
203- Lesson 13: Differentiation Between Genetic Code and Codon
204- Lesson 14: Explanation of the Mechanism of Transcription
205- Lesson 15: Explanation of the Shortening of Transcribed mRNA Molecule in Eukaryotes
206- Lesson 16: Differentiation of Protein Synthesis in Prokaryotes and Eukaryotes
207- Lesson 17: Suggestion of Possible Uses of Synthesized Proteins Within or Outside a Cell
208- Lesson 18: Importance of Gene Expression Regulation
209- Lesson 19: Description of Negative Control of Gene Expression by Repressor Proteins
210- Lesson 20: Description of Positive Control of Gene Expression by Activator Proteins
211- Lesson 21: Relation of Gene Expression with Introns and Exons
212- Lesson 22: Definition of Mutation and Identification of Various Sources
213- Lesson 23: Differentiation Between Natural and Induced Mutations and Mutagens
214- Lesson 24: Justification That Most Mutations Are Harmful
215- Lesson 25: Rationalization That Mutations Might Contribute to Evolution
216- Lesson 26: Description of Symptoms, Causes, and Treatments of Chromosomal Mutations
217- Lesson 27: Description of Symptoms, Causes, and Treatments of Gene Mutations
218- Lesson 01: Description of Creationism and the Theory of Evolution
219- Lesson 02: Differentiation Between Convergent and Divergent Evolution
220- Lesson 03: Description of Theories on the Evolution of Eukaryotes from Prokaryotes
221- Lesson 04: Description of Lamarck's Theory of Inheritance of Acquired Characters
222- Lesson 05: Description of Darwin's Observations During HMS Beagle Voyage
223- Lesson 07: Description of Ideas by Charles Lyell, James Hutton, and Thomas Malthus
224- Lesson 08: Description of Alfred Wallace's Role in the Development of Darwinism
225- Lesson 09: Justification for Attribution of the Theory to Darwin
226- Lesson 10: Explanation of Hardy-Weinberg Theorem and Its Assumptions
227- Lesson 11: Explanation of Genetic Drift (Neutral Selection)
228- Lesson 12: Explanation of the Concept of Speciation and Its Mechanisms
229- Lesson 13: Listing Vestigial Structures in Humans and Categorizing Them
230- Lesson 06: Explanation of Darwin's Theory of Natural Selection
231- Lesson 14: Description and Analysis of Technological Contributions to Evolutionary Understanding
232- Lesson 01: Definition of Biogeochemical Cycles and Primary Reservoirs
233- Lesson 02: Detailed Description of Water Cycle
234- Lesson 03: Definition of Aquifers and Water Table
235- Lesson 04: Detailed Description of Nitrogen Cycle
236- Lesson 05: Explanation of Productivity (Gross and Net Primary Productivity)
237- Lesson 06: Explanation of Energy Flow in Trophic Levels
238- Lesson 07: Interpretation of Pyramids of Number, Biomass, and Energy
239- Lesson 08: Definition of Ecological Succession and Description of Types
240- Lesson 09: Differentiation Between Xerarch and Hydrarch Succession
241- Lesson 10: Explanation of Xerarch Succession on a Bare Rock
242- Lesson 11: Description of Population Characteristics
243- Lesson 12: Explanation of Demographic Principles and Population Growth Issues
244- Lesson 13: Analysis of the Role of Population Welfare Department, Government of Pakistan
245- Lesson 14: Relating Nuclear Power to Fossil Fuel Scarcity
246- Lesson 15: Discussing Problems of Nuclear Power
247- Lesson 16: Identifying Causes of Increasing Carbon Dioxide Concentration
248- Lesson 17: Correlating CO2 Concentration with Global Warming
249- Lesson 18: Explaining Causes and Effects of Acid Rain
250- Lesson 19: Describing Composition and Role of Ozone Layer
251- Lesson 20: Stating Sources of Chlorofluorocarbons and Ozone Depletion
252- Lesson 21: Explaining Effects of Ultraviolet Radiation
253- Lesson 22: Narrating the Chernobyl Nuclear Disaster
254- Lesson 23: Distinguishing Between Renewable and Non-Renewable Resources
255- Lesson 24: Describing Human Responsibility for Depleting Environmental Resources
256- Lesson 25: Discussing Conventional and Non-Conventional Energy Resources
257- Lesson 26: Analyzing Environmental Education Efforts
258- Lesson 01: Defining Gene Cloning
259- Lesson 02: Describing Gene Cloning Techniques
260- Lesson 03: Explaining Restriction Endonucleases and DNA Ligases
261- Lesson 04: Describing Gene Selection and Isolation
262- Lesson 05: Explaining Vectors in Recombinant DNA Technology
263- Lesson 06: Stating Steps for DNA Insert Integration into Vectors
264- Lesson 07: Describing Vector Selection for DNA Insert Uptake
265- Lesson 08: Explaining Polymerase Chain Reaction (PCR) for Gene Amplification
266- Lesson 09: Describing Genomic Library Construction
267- Lesson 10: Explaining DNA Sequencing Methods
268- Lesson 11: Describing Gel Electrophoresis for Gene Sequencing
269- Lesson 12: Introducing Automated DNA Sequencing
270- Lesson 13: Describing DNA Analysis Mechanisms
271- Lesson 14: Defining Genome Analysis, Genome Map, and Genetic Markers
272- Lesson 15: Stating the History of the Human Genome Project
273- Lesson 16: Describing the Goals of the Human Genome Project
274- Lesson 17: Predicting Benefits of the Human Genome Project
275- Lesson 18: Defining Terms in Plant Tissue Culture
276- Lesson 19: Explaining Tissue Culture and Differentiating Organ and Cell Culture
277- Lesson 20: Differentiating Callus and Suspension Culture Techniques
278- Lesson 21: Describing Various Plant Tissue Culture Techniques
279- Lesson 22: Explaining Animal Tissue Culture Techniques
280- Lesson 23: Stating Objectives of Transgenic Organisms
281- Lesson 24: Describing Methods for DNA Introduction into Cells/Embryos
282- Lesson 25: Describing Biotechnology's Role in Plant Resistance
283- Lesson 26: Stating Human Gene Transfers in Animals
284- Lesson 27: Describing the Role of Transgenic Bacteria
285- Lesson 28: Discussing Ecological Concerns with Transgenic Bacteria
286- Lesson 29: Describing Genetic Engineering in Farm Animals
287- Lesson 30: Describing Biotechnological Production of Vaccines
288- Lesson 31: Stating Biotechnology's Role in Disease Diagnosis
289- Lesson 32: Describing Products Obtained for Disease Treatment
290- Lesson 33: Explaining Methods for Gene Therapy
291- Lesson 34: Describing Gene Therapies in Detection and Treatment
292- Lesson 35: Explaining Gene Therapy for Cystic Fibrosis
293- Lesson 36: Describing Scope and Importance in Human Welfare
294- Lesson 37: Listing Hazards and Ethical Implications of Gene Technology
295- Lesson 01: Explaining Integrated Disease Management
296- Lesson 02: Describing Vaccination and Its Importance
297- Lesson 03: Listing Common Viral Diseases Requiring Vaccination
298- Lesson 04: Describing the Role of Vaccines in Disease Prevention
299- Lesson 05: Stating Vaccination Schedules
300- Lesson 06: Describing Animal Husbandry and Its Economic Role
301- Lesson 07: Listing Outstanding Milk Producing Breeds
302- Lesson 08: Describing Methods for Plant Improvements
303- Lesson 09: Explaining Home Gardening and Its Importance
304- Lesson 10: Identifying Seasonal Vegetable and Fruit Plants for Home Gardening
305- Lesson 11: Explaining the Role of Microbes in Various Applications