Da VIP Academy / GED / Science / Life Science
Cells & Heredity
Describe cell structures and predict inheritance using dominant and recessive traits.
How it works
Cells do jobs
The nucleus stores DNA, mitochondria release energy from food, the cell membrane controls what enters and leaves, and chloroplasts (plants only) capture light for photosynthesis.
Genes come in pairs
Each parent contributes one allele. A dominant allele (B) shows whenever present; a recessive trait (bb) appears only when both alleles are recessive. A Punnett square crosses the parents to show the possible combinations.
Worked examples
Cross Bb × Bb. What fraction of offspring show the recessive trait?
- Possible pairs: BB, Bb, Bb, bb.
- Only bb shows the recessive trait.
- 1 out of 4, or 25%.
Words to know
- Allele
- One version of a gene.
- Genotype
- The allele pair an organism carries.
- Phenotype
- The trait you can observe.
Test-day tips
- • Recessive traits need two copies — that single fact answers many heredity questions.