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