Introduction to Genetics

Vocabulary:

  1. Trait: A characteristic that an organism can pass on to its offspring
    through its genes.
  2. Genetics: The study of heredity (how genes and traits are
    passed from parents to offspring).
  3. Gene: The set of information that controls a trait; a segment of DNA on
    a chromosome that codes for a specific trait.
  4. Dominant allele: An allele whose trait always shows up in the organism
    when the allele is present.
  5. Recessive allele: An allele that does not show up when a dominant allele
    is present.
  6. Phenotype: An organism’s physical appearance, or visible traits.
  7. Genotype: The alleles an organism has. For example, Bb or bb.
  8. Homozygous: Having two identical alleles for a trait.
  9. Heterozygous: Having two different alleles for a trait
  10. Punnett square: A chart that shows all the possible combinations of
    alleles from a genetic cross.

Punnett Square example:

DNA Basics Chapter 8: Genotypes and Phenotypes - MyHeritage Blog
https://blog.myheritage.com/

The homozygous blue-eyed parent can only pass down a blue allele.

The heterozygous brown-eyed parent can pass down a blue allele or a brown allele.

The children who inherit a blue allele and a brown allele, i.e., a blue-brown genotype, will have a brown-eye phenotype and have brown eyes.

Similarly, the children who inherit two blue alleles, i.e., a blue-blue genotype, will have a blue-eye phenotype and have blue eyes.

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