Introduction to Genetics
Genetics
– The scientific study of heredity.• Example: Geneticist,
Genetic counselor, Genetics researcher
HeredityThe 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
GenesThe 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 TraitA 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 TraitWhen 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
PhenotypeThe 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.SS2.Bb3.pp4.Tt5.RR6.ff
1.homozygous1.homozygous 2.heterozygous2.heterozygous 3.homozygous3.homozygous 4.heterozygous4.heterozygous 5.homozygous5.homozygous 6. homozygous6. homozygous