Genetics Study Notes

Genetics Study Notes

• Genetics is the study of variation and inheritance of genes.
• DNA: A chemical that carries genetic instructions (a code) formed by the sequence of bases. Stored as chromosomes in the nucleus of a cell.
• Gene: A section of DNA that codes for a protein which determines a particular trait.
• Allele: An alternative form of a gene.
• Chromosome: An organised structure of DNA found in the nucleus of a cell.
• Genes vs Alleles: Genes code for a protein determining a trait while alleles are alternative versions of a gene. Members of a species have the same genes, but different alleles.
• DNA Structure: A double helix made of nucleotides.
• Nucleotide: A sub-unit made of a phosphate, sugar (deoxyribose)and a base.
• Complementary Base Pairing Rule: A-T, C-G
• Rosalind Franklin: Her X-ray diffraction work, particularly Photo 51, was crucial to determining the double-helix structure of DNA.
• Homologous Chromosomes: Pairs of chromosomes that are the same length and carry the same genes at the same locations (loci). Individuals inherit one chromosome from each parent.
• Genetic Code: The base sequence (order of bases A, T, C, and G) in DNA.
• Genetic Code is read in triplets: Triplets code for specific amino acids.
• Amino Acids form Proteins and Phenotypes: Amino acids arranged according to the base sequence form different proteins and therefore different phenotypes.

Homologous Pair of Chromosomes

• Homologous Chromosomes are pairs of chromosomes with the same length.
• They have the same location (loci) for genes.
• Individuals inherit one chromosome from each parent.
• Homologous chromosomes may not carry the same alleles.

Inheritance of Genetic Variation

• Inheritance: Passing of genetic information from parents to offspring.
• Monohybrid Inheritance: Inheritance of characteristics controlled by one gene.
• Alleles: Alternative versions of a gene.

Genotype vs Phenotype

• Genotype: The alleles an individual carries for a gene.
• Phenotype: The physical expression or appearance of the genotype.

Punnett Squares

• Punnett squares are used to predict the possible genotypes and phenotypes of offspring from a cross.
• Genotypes of parents must be known to predict outcomes.
• Expected phenotype ratio: The percentages of different phenotype outcomes for each cross.
• Expected results may differ from observed outcomes due to random chance.

Pedigree Charts

• Pedigree charts are used to track the inheritance of genetic traits across generations.
• Allow determination of genotypes and phenotypes involved

DNA Sequencing

• DNA sequencing is a technique to determine the exact order of bases in a DNA strand.
• Advantages over Punnett squares and pedigree charts as gives exact genetic code and mutations/variations compared to normal alleles
• Disadvantage: Punnett squares and Pedigrees may only predict traits

Selective Breeding

• Inbreeding depression: Loss of fitness and strength in a population from inbreeding and inheriting harmful alleles.
• Inbreeding: Producing offspring from mating related individuals.
• Reduced genetic diversity: Reduced variation due to selective breeding.
• Unintended traits: Focusing on desirable traits could increase undesirable ones.

Cloning

• Cloning: Creating a genetically identical copy of a DNA, cell, or organism.
• Reproductive cloning: Deliberate production of genetically identical individuals. (e.g. for medical or agriculture)
• Help balance ecosystems: Reviving endangered species.
• Increase livestock output: Increase in productivity, health and reducing risks of outbreaks.

Transgenesis

• Transgenesis: Introducing a gene from one organism to another.
• Purpose: Create organisms with desired traits (e.g., disease resistance, pest resistance) or produce specific proteins (e.g,. insulin).

DNA Profiling

• DNA profiling: Technique to identify individuals and compare their genetic markers.
• DNA profiling in Forensics -comparing DNA from a crime scene with DNA from suspects.
• DNA profiling for parentage testing - determining the biological relationship.

DNA Barcoding

• DNA barcoding: Method of species identification using DNA sequences of standardized DNA segments.
• Used in identifying food fraud and monitoring species (especially identifying invasive species).

Explore the crucial concepts of genetics, including DNA structure, gene functions, and the differences between genes and alleles. This quiz will help you understand key terms like nucleotides and homologous chromosomes, as well as the contributions of important figures like Rosalind Franklin. Test your knowledge on the foundations of inheritance and variation in living organisms.