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Introduction to Genetics
ANSWER KEY
Genetics
#1 Study of how traits are passed on from one
generation to another.
#2 Traits from 1st paragraph:
– Hair color, eye color,
– Flower color,
– Hair type; long, short, curly, straight
One Trait = Two Genes
4) Blue Eyes
– 1 TRAIT
– 2 GENES (one from each parent)
5) Short plant with Red flowers
– 2 TRAITS
– 4 GENES
6) Blond, Curly, Blue Eyes
– 3 TRAITS
– 6 GENES
#7) Symbols represent traits:
Trait
Allele
Symbol
Allele
Symbol
Seed Shape
Round
R
Wrinkled
r
Flower Color Purple
P
White
p
Pod Color
Green
G
Yellow
g
Pod Shape
Inflated
I
Constricted
i
Flower
position
Axial
A
Terminal
a
Genotype vs. Phenotype
8) Round seed shape:
– Genotype = RR or Rr
– Phenotype = round
9) Genotype of purple
flower?
– PP or Pp
 Phenotype of short
plant?
 Short
 Genotype of short
plant?
– tt
10) Dominant vs. Recessive
• Dominant flower color?
– Purple
• Dominant flower position?
– Axial
• Recessive flower position?
– terminal
11) Dominant vs. recessive
• DOMINANT traits are symbolized with
CAPITAL letters. (T, R, B)
• Recessive traits are symbolized with lower
case letters (t, r, b).
• The letter selected for the symbol comes from
the DOMINANT trait.
#12--Tall plant x Short plant
Male
TT
X
Offspring = Tt
Tall
Female
tt
#13- Green pods (GG) x yellow pods (gg)
GG
X
Offspring = Gg
Green Pods
gg
#14) Purple Flower x White flower
PP
X
Offspring = Pp
Purple
Flowers
pp
#15) Homozygous vs. Heterozygous
• BB
– Homozygous
• Rr
– Heterozygous
• rr
– Homozygous
• Aa
– Heterozygous
• YY
– Homozygous
#17- Essential Vocab
• Genotype – the symbolized form; gene formula (ex: BB)
• Phenoypte – physical appearance/description (ex: brown)
• Homozygous – 2 genes that are the same (ex: BB or bb) ; Pure
Bred
• Heterozygous – 2 genes that are different (ex: Bb) ; Hybrid
• Dominant – the stronger gene; appears in the phenotype if
present
• Recessive – the weaker gene; appears in the phenotype only
when homozygous
#18- Vocab Check
• Notice blue eyes:
– Phenotype
• Symbol for a trait:
– Genotype
• Genotype for short pea plant:
– Homozygous
#19- Application: Hair example
• Genotype of Curly parent:
– CC
• Genotype of straight haired parent:
– cc
• Offspring:
– Genotype: Cc
– Phenotype: curly haired
• Curly and straight always produce curly.
• Which trait is dominant?
– Curly