Download Heredity

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.
Genotype
The inherited combination of
alleles (Represented by letters)
• Example: DD or Dd or dd
Can you see an
organism’s 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
 2.heterozygous
 3.homozygous
 4.heterozygous
 5.homozygous
 6.
homozygous