Genetics Course Module - Second Level LMD

Genetics Course Module - Second Level LMD

• Course: Genetics, Module: Genetics Second Level LMD, Academic year: 2024-2025

General Introduction to Genetics

• Traits are passed from generation to generation, considered hereditary; some variations are genotypical, new traits appearing in descendants.
• Genetics is the study of heredity and genotypic variations.
• Genotype = internal structure of an individual
• Phenotype = external appearance of a character (traits)
• Homozygous = two identical alleles for a specific trait
• Heterozygous/Hybrid = two different alleles for a specific trait
• Allele is a form of a gene, which determines a character trait.
• Dominant allele expressed if present on one homologous chromosome.
• Recessive allele expression only occurs with two copies of the allele located on homologous chromosomes. Each character is determined by 2 factors, alleles, of the same gene.

Basic Genetic Concepts

• Gene: A unit of genetic information made up of a DNA sequence, responsible for character expression.
• Allele: A specific form or version of a gene.
• Locus: The location of a gene on a chromosome.
• Pair of alleles: Two variants of the same gene occupying the same locus on homologous chromosomes.
• Homologous chromosomes: Chromosome pairs with the same genes, one inherited from each parent.
• Genome: Complete set of DNA and chromosomes in an organism's genetic material.
• DNA: A double-stranded, helical molecule that carries genetic information. It's made up of nucleotide chains/subunits.
• Chromosome: Structures made up of DNA and protein, organized arrangement of genes. Chromosomes can be linear (most organisms) or circular (some organisms), sometimes associated with proteins and RNA.

Introduction to Mendelian Genetics

• Monohybridism: Cross between two organisms with only one differing trait.
• Dihybridism: Cross between two organisms with two differing traits.
• Polyhybridism: Cross between two organisms with multiple differing traits.
• Mendel's Experiment (Monohybridism): Crossing pure-bred pea plants (one trait difference).
  • Parental generation (P): Smooth vs. Wrinkled seeds.
  • First filial generation (F1): All offspring had smooth seeds.
  • Second filial generation (F2): Ratio of 3 smooth to 1 wrinkled seed.

Gene Alleles Assignment

• Assigning symbols for alleles (e.g., 'S' for smooth seed, 's' for wrinkled seed).
• Dominant alleles written in uppercase.
• Recessive alleles written in lowercase.

Mendel's Law of Segregation

• During gamete formation, each allele pair separates, so each gamete carries only one allele of a trait.

Punnett Square

• Method of predicting gene combinations among offspring.
• Demonstrates various combinations and frequencies of offspring genotypes and phenotypes (visual display of gamete combinations and resulting possibilities).

Conclusion

• The wrinkled trait was present in the F1 but hidden, demonstrated by its reappearance in the F2 generation.
• Smooth seeds are dominant, wrinkled are recessive.