Name:
Date:
Subject:
Genetics
Objectives
Objective 1: ASWBAT identify and describe what a genotype, phenotype and alleles are.
Objective 2: ASWBAT identify whether an organism is heterozygous or homozygous for a
given trait.
Objective 3: ASWBAT identify the phenotype of an offspring when given the genotype.
On a scale of 1 – 3 how well you can do on this objective now.
(1 – Not at all
2 – I know it a little bit
3 – I know it very well)
Objective: 1
Objective: 2
Objective: 3
1
1
1
2
2
2
3
3
3
Key Vocabulary Words
On a scale of 1 – 3 how well you know the vocabulary words below.
(1 – Not at all 2 – I know it a little bit 3– I know it very well)
Phenotype
Genotype
Allele
Homozygous
Heterozygous
1
1
1
1
1
2
2
2
2
2
Pre-quiz
Do your best to answer the following questions.
1. What is a gene?
Answer:
2. What is a Trait?
Answer:
3. How are genes and traits connected?
Answer:
4. What is heredity?
Answer:
3
3
3
3
3
Allele
As you now know, genes are segments of DNA that give you your inherited traits. For
example, you have a gene that gives you your natural hair color. You also know that there
are different hair colors. You can have brown, blonde, black, and everything in between.
These different hair colors come from different versions of the gene. The different
versions of the same gene are called alleles.
Alleles for Eye Color
Examples of Alleles
Gene = Eye Color
Allele = Brown Eye Gene
Allele = Blue Eye Gene
Allele = Green Eye Gene
Genotype
As you now know, you inherit two of every gene. This means that you might have two
different alleles of the same gene. The combination of alleles that you inherit from your
parents is called your genotype. It is the type of genes you inherit. For example, if your
inherited a blue eye gene from you mom and a green eye gene from your dad, then your
genotype is 1 green eyed gene and 1 blue eye gene. Genotypes can be homozygous or
heterozygous. A homozygous genotypes means the organism inherited two of the same
allele. A heterozygous genotype means the organism inherited two different alleles.
Phenotype
Genes control your traits. If you have two genes for brown eyes you will have brown eyes.
This is the expression of the trait or what is called a phenotype. The phenotypes are the
traits the organism has.
Chromosomes
(Contain the Genes)
Genotype
(Two white fur genes)
Phenotype
(White Fur)
1. What is an allele?
Answer:
2. What is an organism’s genotype?
Answer:
3. What is an organism’s phenotype?
Answer:
4. What does a homozygous genotype tell you about an organism?
Answer:
5. What does a heterozygous genotype tell you about an organism?
Answer:
Dominant or Recessive?
Not all alleles are created equal. In fact some of them can “dominate” over others.
Sometimes genes can simply be dominant or recessive. This means that if you possess the
dominant gene in your genotype then your phenotype will be to have the dominant trait. It
only takes one dominant allele to have the dominant trait. In order to have a recessive
trait your genotype must have two recessive alleles.
In order for you to know which allele is dominant and which allele is recessive you always
assign dominant alleles an upper case letter and recessive alleles a lower case letter.
Example: Black or White Fur in rabbits?
Gene: Fur Color in rabbits
Dominant Allele = Black Fur = F
Recessive Allele = White Fur = f
Genotype: FF
(Homozygous Dominant)
Phenotype = Black Fur
Genotype: Ff
(Heterozygous)
Phenotype = Black Fur
1. What does it mean when a gene is dominant?
Answer:
2. What does it mean when a gene is recessive?
Answer:
Genotype: ff
(Homozygous Recessive)
Phenotype = White Fur
Action! – Let’s see what traits we have that are dominant or recessive.
Worksheet: Dominant and Recessive Traits
Use the following example to answer the following questions.
Example: Pea Plant Flower Color
Gene: Flower Color
Dominant Allele: Purple Flower = B
Recessive Allele: White Flower = b
Organism 1
Organism 2
Organism 3
?
BB
Bb
1. What is the genotype of organism 1?
Answer:
2. What is the phenotype of organism 1?
Answer:
3. What is the phenotype of organism 2?
Answer:
4. What is the genotype of organism 3?
Answer:
Action! – Let’s make a baby! (Not what your thinking)
Worksheet: Coin-flip genetics
?
Quiz
Directions: Answer the following questions to see if you met the objectives.
1. What is an allele?
Answer:
2. Explain what a genotype is.
Answer
3. Explain what a phenotype is.
Answer:
4. What does it mean if a gene is dominant?
Answer:
5. What does it mean if a gene is recessive?
Answer:
Use the following example to answer the following questions.
Example: Human Eye Color
Gene: Eye color
Dominant Allele: Brown Eyes = B
Recessive Allele: Blue Eyes = b
Organism 1
Organism 2
Organism 3
?
BB
?
6. What is the genotype of organism 1?
Answer:
7. What is the phenotype of organism 1?
Answer:
8. What is the phenotype of organism 3? How do you know?
Answer:
9. What is the genotype of organism 2? How do you know?
Answer:
10. Is organism 1 heterozygous or homozygous for eye color?
Answer:
11. Is organism 2 heterozygous or homozygous for eye color?
Answer:
12. Is organism 3 heterozygous or homozygous for eye color?
Answer:
Bb