Introduction to Genetics

Genetics – The scientific study of heredity. Example: Geneticist, Genetic counselor, Genetics researcher

Heredity The passing of traits from parent to offspring Example: Both of your parents have brown hair and so do you * Heredity is not always this simple. You might have blue eyes even though both of your parents have brown eyes

Traits Distinguishing qualities that can be passed from one generation to the next Examples: hair color, eye color

Genes The set of instructions that determine what traits an offspring has. There are at least two genes for every trait Example: Some people inherit the genes (instructions) for making dimples. Genes are found in the base sequence of the DNA (the letters)!

Alleles Different versions of the same gene Each person only has two alleles, even if there are more possible Example: alleles for eye color would include brown, blue, green, grey, hazel

Dominant Trait A dominant trait is observed when at least one dominant allele is inherited BB or Bb A dominant allele is written as a CAPITAL letter Example: Brown eye color (B) is dominant over blue eye color (b).

Recessive Trait When a trait is recessive it is only visible when two recessive alleles are inherited (bb) A recessive allele is written as a lower case letter Example: Blonde hair color (b) is recessive.

The dominant trait is stronger, more powerful than the recessive trait. The recessive trait is weaker than the dominant trait. The dominant trait overpowers the weaker recessive trait when the two are together.

The inherited combination of alleles (Represented by letters) Example: DD or Dd or dd Can you see an organism’s genotype? Genotype

Phenotype The organisms inherited appearance Example: straight, wavy, or curly hair Can you see an organism’s phenotype?

Applying what you learned! If T=tall and t=short, what will be the organism’s phenotype? TT Tt tt

Homozygous Having two alleles that are the same for a gene “Purebred” or “true-breeding” Examples: BB or bb

Heterozygous Having two alleles that are different for a gene “hybrid” Example: Bb or Pp

Homozygous or Heterozygous? 1.SS 2.Bb 3.pp 4.Tt 5.RR 6.ff 1.homozygous 1.homozygous 2.heterozygous 2.heterozygous 3.homozygous 3.homozygous 4.heterozygous 4.heterozygous 5.homozygous 5.homozygous 6. homozygous 6. homozygous