Genetic Engineering and Inheritance: A Comprehensive Guide
Gene Therapy and Genetic Engineering
Gene Therapy Techniques
Gene therapy aims to replace faulty genes causing genetic diseases with healthy ones. There are two main approaches:
- Germline gene therapy: Replacing genes in gametes (sperm or egg cells).
- Somatic cell gene therapy: Introducing healthy genes into the patient’s body cells.
Somatic cell gene therapy is more complex due to the need for transcription and translation to produce the correct protein. Challenges include delivering the gene into cells using vectors like viruses or liposomes.
Cystic Fibrosis Gene Therapy
Cystic fibrosis is caused by a faulty CFTR gene, leading to thick, sticky mucus that causes blockages in the respiratory system. Gene therapy for cystic fibrosis involves introducing a healthy CFTR gene into the epithelial cells of the respiratory system using liposomes. This treatment requires ongoing administration as new epithelial cells will still have the faulty gene.
Recombinant DNA Technology
Recombinant DNA technology involves incorporating foreign DNA into a bacterial plasmid. Key steps include:
- Identifying and cutting out the desired gene using restriction enzymes.
- Cutting the bacterial plasmid with the same restriction enzyme to create complementary “sticky ends.”
- Splicing the gene and plasmid together using DNA ligase.
This technology is used to produce human insulin and other complex proteins in large quantities.
Genetically Modified (GM) Crops
GM crops are engineered for desirable characteristics like disease resistance or longer shelf life. While they offer benefits such as higher yields and reduced pesticide use, concerns exist regarding potential long-term health impacts and reduced biodiversity.
Inheritance and Genetic Variation
Linkage and Genetic Fingerprinting
Linkage refers to the tendency of alleles on the same chromosome to be inherited together. Genetic fingerprinting utilizes non-coding DNA sections with repeating nucleotide blocks to identify individuals. Techniques like electrophoresis and Southern blotting are used to create unique DNA profiles.
Mutations and Their Effects
Mutations are changes in the DNA sequence that can lead to altered protein structure and function. Sickle-cell anemia is an example of a disease caused by a single nucleotide mutation. Mutagens, such as radiation and certain chemicals, increase the risk of mutations.
Meiosis and Genetic Diversity
Meiosis is a cell division process that produces gametes with half the number of chromosomes as the parent cell. Crossing over and independent assortment during meiosis contribute to genetic diversity in offspring.
Mendelian Inheritance
Mendel’s laws of inheritance describe how traits are passed from parents to offspring. Key concepts include:
- Alleles: Different forms of the same gene.
- Genotype: An individual’s genetic makeup.
- Phenotype: An individual’s observable traits.
- Dominant and recessive alleles: Dominant alleles mask the expression of recessive alleles.
Other inheritance patterns include codominance and sex-linked inheritance.
Human Reproduction and Development
Male and Female Reproductive Systems
The male reproductive system includes the testes, epididymis, vas deferens, and prostate gland. The female reproductive system includes the ovaries, oviducts, uterus, and vagina.
Spermatogenesis and Oogenesis
Spermatogenesis is the process of sperm cell production in the testes. Oogenesis is the process of egg cell production in the ovaries. Both processes involve meiosis.
Fertilization and Pregnancy
Fertilization occurs when a sperm cell penetrates an egg cell, forming a zygote. The zygote undergoes cleavage and develops into a blastocyst, which implants in the uterus lining. The hormone hCG is produced during pregnancy and can be detected in pregnancy tests.
Plant Reproduction and Pollination
Pollination Mechanisms
Pollination is the transfer of pollen from the anther to the stigma of a flower. Plants have evolved various mechanisms for pollination, including:
- Insect pollination: Flowers attract insects with bright colors, nectar, and scent.
- Wind pollination: Flowers produce large amounts of lightweight pollen that can be carried by the wind.
- Self-pollination: Pollen from the same flower fertilizes the egg.
- Cross-pollination: Pollen from one flower fertilizes the egg of another flower.
Cross-pollination promotes genetic diversity, while self-pollination can lead to the expression of harmful recessive traits.