BIO 101
Topic: Heredity and evolution: Introduction to Darwinism and Lamarkism, Mendelian
laws, explanation of key genetic terms
By Dr. A. T. Anifowoshe
Department of Zoology
University of Ilorin, Ilorin, Nigeria
----------------------------------------------------------------------------------------------------------------
Hereditary and Evolution
Heredity
Heredity refers to the process through which genetic information is passed from one generation
to the next. It is mediated through genes, which are segments of DNA that code for specific
traits.
Types of Heritable Characters:
1. Physical Traits:
These traits are controlled by genes and influenced by alleles inherited from
both parents. Examples: Eye color, height, skin color, hair texture etc
2. Physiological Traits:
Such traits are encoded by specific genes that regulate biochemical and
physiological processes. Examples: Blood type, metabolic rates, and immune
responses.
3. Behavioral Traits:
Examples: Certain instinctual behaviors and predispositions to learning or
temperament. Often influenced by both genetic and environmental factors.
4. Disease Susceptibility:
Such traits are often controlled by one or multiple genes. Examples: Inherited
disorders like sickle cell anemia, cystic fibrosis, or predisposition to conditions
like diabetes or heart disease.
, Role of Chromosomes in Heredity and Heritable Characters
Introduction:
Chromosomes are vital structures within cells that carry genetic material in the form of DNA.
They play a fundamental role in heredity, serving as the medium through which genetic
information is passed from parents to offspring. Chromosomes house genes, the functional
units of heredity, which determine an organism's traits, or heritable characters.
Role of Chromosomes in Heredity
1. Carriers of Genetic Information:
Chromosomes are made up of DNA and proteins. The DNA contains sequences called
genes, which encode the instructions for the development and functioning of living
organisms. In the nucleus of each cell, DNA molecule is packaged into thread-like
structures called Chromosomes. It was first described by Straubberg (1875) and was
coined by Waldeyer in 1888. Each chromosome is made up of DNA tightly coiled by
proteins called Histones.
2. Transmission During Cell Division:
i. Mitosis: Ensures that genetic information is faithfully copied and distributed
to daughter cells, maintaining genetic consistency within an organism.
ii. Meiosis: Halves the chromosome number in gametes (sperm and egg cells),
ensuring that offspring inherit the correct number of chromosomes when
gametes fuse during fertilization.
3. Chromosome Structure and Function:
i. Chromosome Number: Each species has a specific chromosome number
(e.g., humans have 46 chromosomes arranged in 23 pairs). This number is
critical for maintaining the integrity of an organism's genetic code.
ii. Homologous Chromosomes: Chromosomes come in pairs, one from each
parent, and contain alleles of the same genes, which may differ in their
expression.
Organisms No. of Chromosomes (2n)
Human 46
Dog 78
Chimpanzee 48
Horse 64
Chicken 78
Fruit-fly 8
Mosquito 6
Nematode 11(m), 12(f)
Rice, Tomatoes 24
Maize, Carrot 20
Topic: Heredity and evolution: Introduction to Darwinism and Lamarkism, Mendelian
laws, explanation of key genetic terms
By Dr. A. T. Anifowoshe
Department of Zoology
University of Ilorin, Ilorin, Nigeria
----------------------------------------------------------------------------------------------------------------
Hereditary and Evolution
Heredity
Heredity refers to the process through which genetic information is passed from one generation
to the next. It is mediated through genes, which are segments of DNA that code for specific
traits.
Types of Heritable Characters:
1. Physical Traits:
These traits are controlled by genes and influenced by alleles inherited from
both parents. Examples: Eye color, height, skin color, hair texture etc
2. Physiological Traits:
Such traits are encoded by specific genes that regulate biochemical and
physiological processes. Examples: Blood type, metabolic rates, and immune
responses.
3. Behavioral Traits:
Examples: Certain instinctual behaviors and predispositions to learning or
temperament. Often influenced by both genetic and environmental factors.
4. Disease Susceptibility:
Such traits are often controlled by one or multiple genes. Examples: Inherited
disorders like sickle cell anemia, cystic fibrosis, or predisposition to conditions
like diabetes or heart disease.
, Role of Chromosomes in Heredity and Heritable Characters
Introduction:
Chromosomes are vital structures within cells that carry genetic material in the form of DNA.
They play a fundamental role in heredity, serving as the medium through which genetic
information is passed from parents to offspring. Chromosomes house genes, the functional
units of heredity, which determine an organism's traits, or heritable characters.
Role of Chromosomes in Heredity
1. Carriers of Genetic Information:
Chromosomes are made up of DNA and proteins. The DNA contains sequences called
genes, which encode the instructions for the development and functioning of living
organisms. In the nucleus of each cell, DNA molecule is packaged into thread-like
structures called Chromosomes. It was first described by Straubberg (1875) and was
coined by Waldeyer in 1888. Each chromosome is made up of DNA tightly coiled by
proteins called Histones.
2. Transmission During Cell Division:
i. Mitosis: Ensures that genetic information is faithfully copied and distributed
to daughter cells, maintaining genetic consistency within an organism.
ii. Meiosis: Halves the chromosome number in gametes (sperm and egg cells),
ensuring that offspring inherit the correct number of chromosomes when
gametes fuse during fertilization.
3. Chromosome Structure and Function:
i. Chromosome Number: Each species has a specific chromosome number
(e.g., humans have 46 chromosomes arranged in 23 pairs). This number is
critical for maintaining the integrity of an organism's genetic code.
ii. Homologous Chromosomes: Chromosomes come in pairs, one from each
parent, and contain alleles of the same genes, which may differ in their
expression.
Organisms No. of Chromosomes (2n)
Human 46
Dog 78
Chimpanzee 48
Horse 64
Chicken 78
Fruit-fly 8
Mosquito 6
Nematode 11(m), 12(f)
Rice, Tomatoes 24
Maize, Carrot 20
