Download Intro to Genetics

Trait – A physical characteristic encoded by a
gene
• Ex: Eye color, hair color, freckles
Allele – One possible version of one specific
gene
• Represented by letters
• Ex: F = freckles
f = no freckles
Dominant – Type of allele that may mask the
effect of others
• Represented by capital letters
• Ex: B for brown eyes
Recessive – Type of allele that may be
masked by others
• Represented by lowercase letters
• Ex: b for blue eyes
Homozygous – Two alleles of the same
type are present
Ex: BB
bb
Heterozygous – Two different alleles are
present
Ex: Bb
Phenotype – Physical appearance of trait
• Described with words: Purple flower, white flower
Genotype – Genetic makeup (alleles)
• Represented by letters: PP, Pp, pp
• Represented by words: Homozygous dominant, homozygous
recessive, heterozygous
For a parrot with feathers, green feathers
are dominant (G) and blue feathers are
recessive (g).
What genotype is a homozygous recessive parrot?
What genotype is a homozygous dominant parrot?
What genotype is a heterozygous parrot?
Punnett Square – method used to predict
outcomes of simple genetic crosses
Monohybrid cross – genetic cross for a
single trait
is dominant to
Red hair (R) is dominant over blond hair (r). Make a cross
between a heterozygous red head and a blond.
R
r
r
r
Rr
rr
Rr
rr
What percentage of the offspring will have red hair? 50%
Let’s try some more…
In pea plants, tall pea plants (T) are dominant
over short pea plants (t). Construct a Punnett
Square for a heterozygous tall pea plant and a short
pea plant.
t
t
T
Tt
Tt
t
tt
tt
What are the
percentage of
phenotypes?
50% tall
50% short
FLASHCARDS
For each key term, write the definition and
draw a picture to help you remember.
Get them checked off by me for a grade!
 Genotype
Allele
Dominant
Heterozygous
Phenotype
Trait
Recessive
Homozygous
TRAIT BROCHURES
Pretend you are writing a pamphlet explaining the
difference between the following terms:
Genotype
Phenotype
Allele
Trait
Dominant
Recessive
Heterozygous
Homozygous
Use any three sets of terms, please include
definitions and pictures!
If you want to do a comic, set of memes, or
anything else, please let me know. 
 One allele completely masks the other
 Use uppercase and lowercase versions of the same
letter
 Neither allele is dominant
 Heterozygotes show a blended phenotype
 Use different, lowercase letters
 Both alleles are dominant
 Heterozygotes show a mixed or patterned phenotype
(both alleles show equally)
 Use different, uppercase letters