Understanding Allergy, Immunity, and Genetics

Posted on Feb 28, 2025 in Biology

Allergy and Immune Response

Allergy

Anti-allergen interacts with mast cells, leading to histamine production and other cellular blood circulation effects.

Humoral Response

B lymphocytes produce antibodies (AC) that bind to antigens. AC functions include:

  • Neutralizing antigens
  • Agglutination
  • Precipitation
  • Activation of the complement system (a group of inactive proteins in plasma)

Cellular Response

Macrophages present antigens on their surface along with Major Histocompatibility Complex (MHC) proteins. This antigen-presenting cell (APC) binds to T helper cells. Macrophages produce interleukin, stimulating T lymphocyte production. T lymphocytes can produce neutralizing viruses.

Key cells involved: Macrophages, T lymphocytes, B lymphocytes, granulocytes (neutrophils, basophils, eosinophils), and mast cells.

Autoimmunity

Occurs when the body’s immune system mistakenly identifies its own cells as foreign and attacks them.

Lymphocytes

A deficiency in lymphocytes can compromise the immune system, increasing susceptibility to infectious diseases.

Genetic Variation

Genetic Drift

Changes in gene frequencies within populations due to chance events.

Gene Flow (Gene Migration)

The transfer of alleles from one population to another.

Cellular Processes

Somatic Cells

Autosomes and sex chromosomes.

Mitosis

Allows daughter cells to have the same genetic information as the mother cell. Stages include:

  • Prophase (nuclear envelope breaks down)
  • Metaphase (chromosomes align in the equatorial plane)
  • Anaphase (sister chromatids separate)
  • Telophase (cell wall formation in plants via the phragmoplast)

Meiosis

Reduces the number of chromosomes, converting diploid cells into haploid cells. It introduces genetic variability through recombination. Stages include:

  • Meiosis I: Homologous chromosome separation
  • Meiosis II: Sister chromatid separation

Prophase I Stages

  • Leptotene
  • Zygotene: Synapsis begins between homologous chromosomes, forming bivalents.
  • Pachytene: Crossing over occurs, exchanging DNA fragments between homologous chromosomes (genetic recombination).
  • Diplotene: Chromosomes begin to separate, with chiasmata marking crossover points.
  • Diakinesis

Other stages: Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II

Cellular Biology

Prokaryotes

  • No histones
  • 106 base pairs
  • RNA polymerase
  • 70S ribosome (30S, 50S)
  • Not colinear (DNA length ≠ RNA length)
  • Simultaneous transcription and translation
  • Polycistronic mRNA (encodes multiple proteins)

Eukaryotes

  • DNA + Protein = Chromatin
  • 109 base pairs
  • RNA polymerase (I, II, III)
  • Genes with introns (removed via splicing)
  • RNA maturation
  • Monocistronic

Mutations

Can be genic or chromosomal (structural or numerical). Structural mutations include deletion, duplication, inversion (pericentric, paracentric), and translocation.

Causes include spontaneous errors (DNA polymerase), mutagenic agents, and transposons.