Genetic Inheritance, Natural Selection, and Hormonal Regulation

Sickle Cell Anaemia and Malaria Resistance

Sickle cell anaemia is a genetic mutation in humans characterized by a disorder in the amino acid sequence of the haemoglobin molecule. This results in red blood cells taking on a sickle shape. Malaria is caused by a parasite that thrives in red blood cells; consequently, individuals with sickle-shaped cells possess immunity to malaria. This explains why the condition is more prevalent in tropical regions where malaria is common. However, individuals with sickle cell anaemia typically have a significantly shorter life expectancy.

Artificial and Natural Selection

Artificial selection is utilized to produce varieties of animals and plants with increased economic importance.

Defining Natural Selection

Natural selection is defined as the greater chance of passing on genes by the best-adapted organisms. Following natural variation, organisms compete; only the most capable reach reproductive age, producing offspring best fitted to their environment.

Natural selection serves as a mechanism for evolution. Because only the most adapted survive to reproduce, offspring become increasingly better adapted to their environment over time as negative traits are eliminated.

Antibiotic Resistance Example

An example of natural selection is observed in bacteria surviving antibiotics. If a new antibiotic is introduced to kill a strain of bacteria (Q), most will die. However, survivors reproduce, and the entire subsequent generation develops immunity to the antibiotic.

Genetic Engineering Principles

Genetic engineering is defined as the process of taking a gene from one species and inserting it into another.

Insulin Production via Bacteria

Genetic engineering has been used to insert human insulin genes into bacteria to produce insulin for diabetes treatment. The process involves:

• Extracting plasmids (circular DNA) from bacteria.
• Cutting the plasmids using specific enzymes.
• Cutting a section of human DNA using the same enzymes.
• Inserting the human DNA into the plasmids.
• Cloning the modified bacteria to produce insulin.

Hormonal Regulation of the Menstrual Cycle

FSH (Follicle-Stimulating Hormone)

• Stimulates follicle development.
• Causes maturation of the egg.

Oestrogen

• Repairs and thickens the lining of the uterus.
• Promotes the development of blood vessels.
• Prepares the uterus for implantation.
• Stimulates the release of LH.
• Inhibits the release of FSH and stops the production of eggs.

LH (Luteinizing Hormone)

• Stimulates the release of the ovum from the ovary.

Progesterone

• Maintains the lining of the uterus.
• Prevents menstruation.
• Prepares the lining for implantation.
• Prevents the development of blood cells.
• Inhibits the secretion of LH and FSH.