Genetics, Human Genome, and Biotechnology: Study Notes for General Biology

Genetics and Inheritance of Traits

Patterns of Inheritance

Inheritance patterns describe how genetic traits are transmitted from parents to offspring. These patterns can vary depending on the interaction between alleles and the number of genes involved.

• Incomplete Dominance: A form of inheritance where the heterozygote displays a phenotype that is intermediate between the two homozygotes. Example: In snapdragons, crossing red and white flowers produces pink offspring.

• Codominance: Both alleles in a heterozygote are fully expressed, resulting in a phenotype that shows both traits. Example: Human blood type AB, where both A and B antigens are present.

• Multiple Alleles: More than two possible alleles exist for a gene, but an individual inherits only two. Example: The ABO blood group system in humans.

• Polygenic Traits: Traits controlled by two or more genes, often showing a range of phenotypes. Example: Human skin color and height.

Environmental Effects on Gene Expression

The environment can influence the expression of genes, affecting the phenotype of an organism.

• Key Point: Environmental factors such as temperature, nutrition, and exposure to chemicals can modify gene expression.

• Example: The fur color of Himalayan rabbits changes with temperature; cooler areas of the body are darker.

The Human Genome Project

Overview and Significance

The Human Genome Project (HGP) was an international scientific effort to map and sequence the entire human genome.

• Advantages:

  • Identification of genes associated with diseases

  • Improved diagnosis and treatment of genetic disorders

  • Advancement in personalized medicine

• Disadvantages:

  • Ethical concerns regarding genetic privacy

  • Potential for genetic discrimination

  • High initial cost and complexity

Chromosomes and Karyotypes

Structure and Function

Chromosomes are thread-like structures made of DNA and proteins, carrying genetic information.

• Karyotype: An organized profile of an individual's chromosomes, used to detect chromosomal abnormalities.

• How to Read Karyotypes: Chromosomes are arranged in pairs by size and shape; abnormalities can be identified by changes in number or structure.

Human Chromosomal Disorders

Chromosomal disorders result from changes in chromosome number or structure.

• Examples:

  • Down syndrome (Trisomy 21): Extra copy of chromosome 21

  • Turner syndrome: Missing one X chromosome in females

  • Klinefelter syndrome: Extra X chromosome in males (XXY)

• Causes: Nondisjunction during meiosis, leading to abnormal chromosome numbers.

Cell Cycle and Cancer

The cell cycle is the series of events that cells go through as they grow and divide. Cancer is caused by uncontrolled cell division due to mutations in genes regulating the cell cycle.

• Consequences: Tumor formation, disruption of normal tissue function.

Evolutionary Advantage of Genetic Variation

Maintaining genetic variation in populations increases the ability to adapt to changing environments.

• Key Point: Heterozygosity can provide a survival advantage under certain conditions (e.g., sickle cell trait and malaria resistance).

Recombinant DNA and Biotechnology

Recombinant DNA Technology

Recombinant DNA involves combining DNA from different sources to create new genetic combinations.

• Polymerase Chain Reaction (PCR): A technique to amplify specific DNA sequences.

• DNA Fingerprinting: Identifies individuals based on unique patterns in their DNA.

• CRISPR: A genome editing tool that allows precise modifications to DNA sequences.

• Gel Electrophoresis: Separates DNA fragments by size for analysis.

Applications of Biotechnology

Biotechnology uses living organisms or their products for practical purposes.

• Medical Applications: Production of insulin, growth hormones, and vaccines using genetically modified organisms.

• Agricultural Applications: Development of genetically modified crops with improved traits.

Ethical Issues in Biotechnology

Biotechnological advances raise important ethical questions.

• Key Issues:

  • Genetic privacy and consent

  • Potential misuse of genetic information

  • Equity in access to biotechnological advances

Summary Table: Key Genetic Concepts

Concept	Definition	Example
Incomplete Dominance	Heterozygote shows intermediate phenotype	Pink snapdragon flowers
Codominance	Both alleles fully expressed	AB blood type
Polygenic Trait	Trait controlled by multiple genes	Human height
Recombinant DNA	DNA from different sources combined	Insulin production in bacteria
CRISPR	Genome editing tool	Gene therapy

Key Equations and Terms

• Genotype Frequency (Hardy-Weinberg):

$p^2 + 2pq + q^2 = 1$

• Allele Frequency:

$p + q = 1$

• Polymerase Chain Reaction (PCR) Steps:

  1. Denaturation

  2. Annealing

  3. Extension

Additional info: Some content was inferred and expanded for academic completeness, including examples and definitions not explicitly listed in the original file.