This document provides an introduction to genetics concepts including: 1) Genes located on chromosomes are segments of DNA that code for proteins which determine traits. Traits are physical characteristics influenced by alleles which are different versions of genes. 2) Genotype refers to the alleles an organism receives from its parents, while phenotype describes the physical traits that are expressed. 3) Dominant alleles will always be expressed over recessive alleles in determining an organism's phenotype, with the exception of traits only expressed in the homozygous recessive genotype.

1. INTRO TO
GENETICS
NOTES
UNIT 7: GENETICS
DAY 1
REEBOPS!

2. I CAN…
• I CAN explain the relationship
between
chromosomes, DNA, genes, alleles, pr
oteins, and traits
• I CAN explain the difference between
genotype and phenotype
• I CAN differentiate between
homozygous and heterozygous
• I CAN determine phenotype based on
dominant and recessive alleles.

3. WHAT CONTROLS WHAT I LOOK LIKE?
ANSWER: GENES!
Genes – sections of DNA that
code for proteins. Proteins
determine your traits. B=brown b=blue
Traits – physical
characteristics
(color, height, size, personalit
y etc.)
Alleles – different types of
genes
Ex: alleles for eyes could be
brown, blue, green, hazel, etc.

4. CFU
What might be two different allele types of hair color?
What macromolecule plays an important role in determining
your traits?
Arrange from smallest to biggest:
DNA, gene, chromosome, nucleotide

5. WHERE DO MY GENES COME FROM?
Review: you get one set of 23 chromosomes from your
mom and another set of 23 chromosomes from your dad
– sexual reproduction
• You can get different types of genes from your
mom and dad  different alleles
• Ex: Allele for blue eyes from dad, brown eyes
from mom

6. WHAT IS A WHAT IS A
GENOTYPE? PHENOTYPE?
• genotype - letter showing each • Phenotype –physical
allele we get from our parents characteristic
• Ex: brown eyes from dad • Ex: brown
(B) + blue eyes from mom eyes, curly
(b) = Bb hair, widow’s
• If the alleles are the same (BB peak, sickle cell
or bb) the organism is disease, etc.
homozygous for the trait • Different alleles
code for different
• If the alleles are different (Bb) phenotypes!
the organism is heterozygous
for the trait

7. CHECK FOR
UNDERSTANDING
For the following examples, write down if the person is
homozygous or heterozygous for a specific trait
EE
Ee
ee

8. SO HOW DO YOU DECIDE
WHICH TRAIT TO SHOW?
There is a battle going on…
between your Mom and Dad’s alleles!

9. DOMINANT VS. RECESSIVE
• dominant allele always wins over the
recessive allele. It’s the phenotype that
shows up.
• It’s always the capital letter
• recessive allele is the loser. It’s always
overshadowed if a dominant allele is
present
• Phenotype is only expressed if the
organism’s genotype is homozygous
recessive ex: bb, hh, tt, etc.
• Always the lowercase letter CU Buffs
DOMINATING, as per
usual.
“DOMINANT TRAIT...I'll overpower you!
RECESSIVE TRAIT...I will hide!”

10. CHECK FOR UNDERSTANDING
B is the allele for brown hair and b is the allele for
blonde hair. What will be the phenotype of a
reebop with the genotype Bb?
Is the person homozygous or heterozygous for
this trait?
STEP UP: Widow’s peak (w) is a dominant trait. If
a dad is homozygous for widow’s peak and the
mom has no widow’s peak, what are the parents
genotypes?
Will their kid have a widow’s peak?
Widow’s peak

11. PRACTICE MAKES PERFECT!
homozygous or heterozygous?
TT = _________________
tt = __________________
Tt = __________________
dominant or recessive trait expressed?
TT = _________________
tt = __________________
Tt = __________________