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

MaleTT X

Femalett

Offspring = Tt

Tall

#13- Green pods (GG) x yellow pods (gg)

GG X gg

Offspring = Gg

Green Pods

#14) Purple Flower x White flower

PP X pp

Offspring = Pp

Purple Flowers

#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