Genetics Essentials Cheat Sheet

Genetics explores how traits are inherited from parents to offspring through DNA, influencing everything from physical appearance to susceptibility to disease. Understanding DNA structure, replication, transcription, translation, and inheritance patterns is key to comprehending life's diversity.

Core Principles

• DNA structure: Double helix composed of nucleotides (sugar, phosphate, nitrogenous base).
• DNA replication: Semi-conservative process where DNA makes exact copies of itself.
• Transcription: DNA sequence is copied into mRNA.
• Translation: mRNA sequence is used to build proteins at ribosomes.
• Genes: Segments of DNA that code for specific proteins and traits.
• Mutations: Changes in DNA sequence that can be harmful, helpful, or neutral.
• Inheritance: Traits are passed from parents to offspring via alleles.
• Mendelian Genetics: Dominant and recessive alleles determine phenotypes.
• Non-Mendelian Genetics: Includes incomplete dominance, codominance, and sex-linked traits.
• Asexual Reproduction: One parent, offspring are clones.
• Sexual Reproduction: Two parents, offspring have genetic variation.
• Meiosis: Produces haploid gametes for sexual reproduction.
• Mitosis: Produces diploid somatic cells for growth and repair.

Action Steps

• Identify parent genotypes.
• Determine possible gametes (alleles) from each parent.
• Use a Punnett square to predict offspring genotypes.
• Determine offspring phenotypes based on genotypes and dominance.
• Analyze inheritance patterns (Mendelian, non-Mendelian).

Formulas

• A pairs with T ($A=T$)
• G pairs with C ($G=C$)
• DNA bases: Adenine (A), Thymine (T), Guanine (G), Cytosine (C)
• RNA bases: Adenine (A), Uracil (U), Guanine (G), Cytosine (C)
• Codon: 3 mRNA bases = 1 amino acid

Key Terms

• DNA: Deoxyribonucleic acid; the molecule that carries genetic instructions.
• Gene: A segment of DNA that codes for a specific protein or trait.
• Chromosome: Tightly coiled DNA found in the nucleus, carrying genetic information.
• Nucleotide: The building block of DNA and RNA, consisting of a sugar, phosphate, and nitrogenous base.
• Replication: The process of duplicating DNA.
• Transcription: The process of creating an mRNA copy from a DNA template.
• Translation: The process of synthesizing a protein from an mRNA sequence.
• Allele: Different versions of the same gene (e.g., dominant or recessive).
• Genotype: The genetic makeup of an organism (e.g., BB, Bb, bb).
• Phenotype: The observable physical characteristics of an organism (e.g., blue eyes, tall).
• Homozygous: Having two identical alleles for a trait (e.g., TT or tt).
• Heterozygous: Having two different alleles for a trait (e.g., Tt).
• Dominant: An allele that masks the effect of a recessive allele.
• Recessive: An allele whose effect is masked by a dominant allele.
• Mutation: A change in the DNA sequence.
• Mitosis: Cell division resulting in two identical diploid daughter cells.
• Meiosis: Cell division resulting in four haploid gametes.

Timeline

• Ancient Greece: Early ideas about heredity proposed (e.g., Hippocrates).
• Mid-1800s: Gregor Mendel conducts experiments with pea plants, establishing basic laws of inheritance.
• Late 1800s: Friedrich Miescher discovers 'nuclein' (DNA) in white blood cells.
• Early 1900s: Chromosomal theory of inheritance proposed; genes are located on chromosomes.
• 1920s-1940s: Experiments by Griffith, Avery, MacLeod, McCarty, Hershey, and Chase identify DNA as the genetic material.
• 1953: Watson and Crick propose the double helix structure of DNA, aided by data from Franklin and Wilkins.
• 1960s: The genetic code is deciphered, linking DNA sequences to amino acids.
• 1970s-1980s: Development of recombinant DNA technology and gene sequencing.
• 1990-2003: Human Genome Project maps the entire human genetic code.

People

• Gregor Mendel: Father of Genetics; established laws of inheritance.
• James Watson: Co-discoverer of the DNA double helix structure.
• Francis Crick: Co-discoverer of the DNA double helix structure.
• Rosalind Franklin: Provided crucial X-ray diffraction images of DNA, aiding structure discovery.
• Maurice Wilkins: Provided DNA X-ray diffraction data to Watson and Crick.
• Oswald Avery: Demonstrated that DNA is the genetic material.
• Alfred Hershey: Confirmed DNA as the genetic material through bacteriophage experiments.
• Barbara McClintock: Discovered transposons ('jumping genes').