Free resources for Genetics in Biology: lessons, PDFs and video courses. Genetics study material for SAT, ACT, AP, GED, PSAT 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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