Free resources for Genetics in Biology: lessons, PDFs and video courses. Genetics study material for GCSE, A-Level, AS-Level, 11+ with Khan Academy, Wikipedia and video solutions.
Genetics studies how traits pass from parents to offspring. The basic unit of heredity is the gene, a segment of DNA located on chromosomes. Gregor Mendel's pea experiments established the laws of segregation and independent assortment, the foundation of classical genetics.
Key vocabulary: dominant alleles mask recessive ones; genotype is the genetic makeup (e.g., Aa) while phenotype is the observable trait. A monohybrid cross between two heterozygotes (Aa × Aa) yields a 3:1 phenotype ratio; a dihybrid cross yields 9:3:3:1. Beyond Mendel, incomplete dominance, codominance, multiple alleles (ABO blood groups), and X-linked inheritance (color blindness, hemophilia) are standard exam topics.
Genetics appears heavily in AP Biology, GCSE/A-Level Biology, and MCAT prep. Pedigree analysis and Punnett square problems are the most common question formats — practicing crosses until the ratios become automatic is the fastest path to full marks.
Pick the correct answer — instant feedback!
1. In a cross Aa × Aa, what fraction of offspring show the dominant phenotype?
2. The observable expression of a trait is called the:
3. Color blindness is typically inherited via which chromosome?
Genotype is the allele combination an organism carries (e.g., Aa); phenotype is the trait actually expressed (e.g., purple flowers).
A 3:1 phenotype ratio and a 1:2:1 genotype ratio.
Males have only one X chromosome, so a single recessive allele on it is always expressed.
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