Study Notes
Inheritance is the transmission of genetic information from generation to generation.
- Chromosome — a coil, or thread of DNA (made up of strings of genes) Example: Humans have 23 pairs of chromosomes.
- Gene — a short length of DNA found on a chromosome that codes for a specific protein Example: A gene might code for collagen in skin cells.
- Diploid — containing full pairs of chromosomes Example: Human cells with 46 chromosomes.
- Haploid — containing half pairs of chromosomes Example: Human gametes with 23 chromosomes.
- Allele — different form of a gene Example: Blue and brown eye color alleles.
- Dominant allele — an allele that is always expressed when present Example: Denoted by an uppercase letter like B.
- Recessive allele — an allele that is only expressed when a dominant allele is not present Example: Denoted by a lowercase letter like b.
- Homozygous — when a gene has two identical alleles Example: BB or bb.
- Heterozygous — when a gene has two different alleles Example: Bb.
- Genotype — the genetic makeup of an organism in terms of alleles Example: BB, Bb, or bb.
- Phenotype — the physical characteristic of an organism due to its genotype and environment Example: Blue eyes from a BB genotype.
Exam Tips
Key Definitions to Remember
- Chromosome
- Gene
- Allele
- Dominant allele
- Recessive allele
- Homozygous
- Heterozygous
- Genotype
- Phenotype
Common Confusions
- Mixing up the sequences of amino acids and bases in DNA and RNA.
- Differences between mitosis and meiosis.
Typical Exam Questions
- What is a chromosome? A coil of DNA made up of genes.
- How do alleles affect phenotype? Dominant alleles are expressed over recessive ones.
- What is the difference between genotype and phenotype? Genotype is the genetic makeup; phenotype is the physical expression.
What Examiners Usually Test
- Understanding of key terms like chromosome, gene, and allele.
- Ability to predict inheritance patterns using Punnett squares.
- Differences between mitosis and meiosis.