Fundamentals of Genetics, DNA, and Inheritance Principles

Genetics: The Study of Gene Inheritance

Genes are transmitted according to defined rules or laws. Genes are located on chromosomes, which are cellular structures. Sex is determined by specific genes or chromosomes in most living organisms.

Key Genetic Terms

• Genotype: The genetic constitution of an individual, referring to a specific character or the entire set of genes.
• Phenotype: The external expression of the genotype; the observable characteristics of an individual.
• Alleles: Variants that a gene may present. For each gene, an individual has a pair of alleles, often represented by letters.
• Homozygous: An individual having two identical alleles for a specific gene.
• Heterozygous: An individual carrying two different alleles for a specific gene.

Mendelian Genetics

The Mendelian model proposes that each genetic trait is determined by a pair of factors (alleles).

Mendel's Laws of Inheritance

1. Law of Uniformity: The first filial generation (F1), resulting from crossing two purebred lines, is uniform, expressing the dominant trait of one parent.
2. Law of Segregation: Traits reappear in the second generation (F2) that were not manifest in the F1 generation because the allele pairs segregate during gamete formation and recombine in the offspring.
3. Law of Independent Assortment: Alleles for different traits segregate independently of one another during gamete formation, provided the genes are on different chromosomes.

DNA: The Molecule of Heredity

Every living cell contains DNA (Deoxyribonucleic Acid), primarily located in the nucleus. DNA holds the genetic information, like a library containing instructions for the development and characteristics of organisms. DNA is composed of:

• Nitrogenous bases
• A pentose sugar (deoxyribose)
• A phosphate group

RNA and Protein Synthesis

RNA (Ribonucleic Acid) plays a crucial role in protein synthesis. There are three main types: Messenger RNA (mRNA), Transfer RNA (tRNA), and Ribosomal RNA (rRNA). Protein synthesis involves two main steps:

1. Transcription: Information stored in DNA is transcribed into mRNA. mRNA is synthesized using one DNA strand as a template.
2. Translation: The mRNA sequence dictates the order of amino acids in a protein chain. After transcription, mRNA moves to the cytoplasm and binds to ribosomes, where translation occurs with the help of tRNA.

Amino Acids: Building Blocks of Proteins

Amino acids are the fundamental units that build proteins. There are 20 common types of amino acids that combine in long chains to form diverse proteins.

Recombinant DNA Technology

Genetically modified organisms (GMOs), such as modified viruses or bacteria, are created using recombinant DNA techniques.

Assisted Reproductive Technologies

These technologies assist with conception:

• Artificial Insemination (AI): Introduction of semen into the uterus using a cannula. Sperm may be from the partner or an anonymous donor if male infertility is a factor.
• In Vitro Fertilization (IVF): Fertilization occurs outside the body ('in vitro') in a laboratory. The resulting embryo is then implanted into the mother's uterus.