Introduction to Molecular Biology and Genetics

Posted on Oct 9, 2024 in Biology

DNA: Deoxyribonucleic Acid

Structure and Function

DNA carries hereditary information, making it the genetic material of life. It is composed of nucleotides, each containing a sugar, a nitrogenous base, and a phosphate group. The core structure of DNA is a double helix.

Nitrogenous Bases

The nitrogenous bases in DNA are Adenine, Guanine, Cytosine, and Thymine.

RNA: Ribonucleic Acid

Structure and Function

RNA is found in the nucleus and cytoplasm. It carries the genetic message from DNA and aids in its decoding. There are different types of RNA, including messenger RNA (mRNA).

Structure and Composition

RNA is single-stranded and composed of nucleotides, each containing a nitrogenous base, a sugar, and a phosphate group.

Nitrogenous Bases

The nitrogenous bases in RNA are Uracil, Adenine, Guanine, and Cytosine.

Central Dogma of Molecular Biology

The central dogma describes the flow of genetic information:

  • Replication: DNA replicates itself.
  • Transcription: DNA is transcribed into mRNA.
  • Translation: mRNA is translated into protein.

In summary:

  • Genetic information in DNA is preserved through replication.
  • Information is transferred from DNA to mRNA through transcription.
  • The mRNA message enables protein synthesis in ribosomes through translation.

Changes in Hereditary Material

Changes in hereditary material, while infrequent, can be influenced by physical and chemical factors.

Chromosomal Mutations

Structural Alterations

These changes result from breaks and rejoining of chromosome fragments.

  • Deletions: Loss of a chromosome fragment.
  • Inversions: Reversal of a chromosome segment.
  • Translocations: A chromosome segment moves to a non-homologous chromosome.

Numerical Alterations

These changes affect the number of chromosomes.

  • Haploidy: The number of chromosomes matches that of gametes.
  • Polyploidy: More than two complete chromosome sets.
  • Nullisomy: Missing a pair of homologous chromosomes.
  • Monosomy: Missing one chromosome from a homologous pair.
  • Trisomy: An extra chromosome in a homologous pair.

Gene Mutations

Small, specific alterations in DNA nucleotides can cause changes in mRNA and the resulting protein. These often affect a few nucleotides. A change in a single amino acid may not always prevent the protein from functioning, but it can lead to phenotypic effects.

Genetic Engineering

Genetic engineering involves manipulating and transferring genes between organisms.

Tools

  • Enzymes: Exonucleases, endonucleases (restriction enzymes), polymerases, ligases, transferases.

Techniques

  • Cloning: Using vectors like plasmids or bacteriophages.
  • Sequencing: Determining the order of nitrogenous bases in DNA.

Genetic Engineering in Higher Organisms

GMOs are plants and animals with introduced genes from other organisms.

  • Animals: Modifications are made in germ cells.
  • Plants: Ti plasmids are often used.

Genetic engineering also enables cloning, creating genetically identical organisms.

Biotechnology

Biotechnology applies scientific and engineering principles to biological systems for producing goods and services.

Key Elements

  • Biocatalysts: Biological systems (bacteria, yeast, algae, animal/plant cells) used to catalyze reactions.
  • Bioreactors: Tanks where biotechnological processes occur.

Biotechnology and Medicine

Biotechnology has led to new drugs and gene therapy, which aims to repair genetic defects. Forensic science utilizes DNA sequencing for identification.

Bioethics

Bioethics addresses ethical concerns related to biotechnology.

  • Eugenics: Improving the human race.
  • Positive Eugenics: Preserving gametes from exceptional individuals.
  • Gene Therapy: Correcting genetic diseases.

UNESCO aims to ensure biotechnological advancements respect human rights.

UNESCO Objectives

  • Provide a framework for ethical laws.
  • Respect human dignity, rights, life, and liberty.
  • Support ethical scientific research.
  • Promote dialogue on bioethics.

Ethical Considerations

  • Assisted Reproduction: Ethical concerns regarding surrogate mothers.
  • Prenatal Diagnosis: Ethical considerations of abortion in cases of disease.
  • Preimplantation Genetic Diagnosis: Analyzing embryos from in vitro fertilization.
  • Freezing of Human Embryos: Ethical implications of freezing and thawing embryos.
  • Therapeutic Cloning: Cloning for organs and tissues.
  • Stem Cells: Therapeutic potential and ethical considerations.