Name:
Date:
Subject:
Theory of Heredity
Objectives
Objective 1: ASWBAT describe what heredity is.
Objective 2: ASWBAT describe what both genes and traits are and how they are
connected.
Objective 3: ASWBAT describe Mendel’s 4 hypotheses that lead to the Theory of Heredity.
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)
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Objective: 3
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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)
Gregor Mendel
Heredity
Dominant Gene
Genes
Traits
Recessive Gene
Alleles
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Pre-quiz
Do your best to answer the following questions.
1. How many parents are required for sexual reproduction?
Answer:
2. What are sex cells?
Answer:
3. How much of the parent’s chromosomes does a sex cell have?
Answer:
4. How do the offspring compare to the parents in sexual reproduction?
Answer:
Gregor Mendel
Gregor Mendel is considered the father of genetics. This is because he was the first person
to realize some very important concepts about how organisms get their traits from their
parents. During the 1800’s he lived his life as a monk, but he was also a scientist at heart.
He grew up on a farm and learned a great deal on how to grow food. As a monk he was in
charge of the monastery garden. In this garden he did some experiments on pea plants. He
bred pea plants with certain traits and observed the results. These observations lead him
to some very important discoveries. These discoveries lead to the theory of heredity. The
Theory of Heredity is the foundation for the study of genetics.
Pea Plant Traits
Gregor Mendel
Video: Gregor Mendel – Heredity
1. Why do they call Gregor Mendel the “father of genetics”?
Answer:
Genes and Traits
Do you ever wonder why you look the way you do? The reason is because you inherited
your traits from your parents. They gave you these traits by giving you your genes. A trait
is any distinguishing quality that an organism has. They are the way an organism looks or
behaves. For example a trait of a giraffe is its long neck or the color of your hair is one of
your traits. Genes are segments of DNA that are in your chromosomes. These segments of
DNA are like instructions for your cells. They “control” organism’s traits.
Gene
Trait
Video: Genetics 101 - Genes
1. What is a gene?
Answer:
2. What is a trait? Give an example of one of your traits.
Answer:
3. How are genes and traits connected?
Answer:
Theory of Heredity
Heredity is the passing of traits from parents to their offspring. The Theory of Heredity
explains how this happens. Gregor Mendel’s work provided a framework the basics of
heredity.
1. What is heredity?
Answer:
Critical Thinking Break! – Mendel’s Peas
Mendel made the following observations when he grew his pea plants.
Action! – Discuss the following question with your partner. What do you conclude based
on these observations?
Gregor Mendel’s Four Hypotheses
Long before scientists knew about DNA or genes, Gregor Mendel made some profound
discoveries. His experiments on pea plants lead him to come up with four conclusions
about how traits are passed from parent to offspring. These conclusions today are the
foundation to the Theory of Heredity.
Hypothesis 1
Mendel’s first hypothesis is that offspring get two of every gene. For example, there is
gene that gives you your hair color. But, you don’t just get one of them you actually get two.
Hypothesis 2
Not all genes for a trait are the same. Genes can have different versions. We call these
different versions alleles. For example, there is a gene for how your hair looks, but there
are a couple of versions or alleles for your hair. One that gives you strait hair, one that
gives you wavy hair, and one that give you curly hair.
Hypothesis 3
Of the different alleles that a gene can have, they can be either dominant or recessive. This
means that if you have two different alleles for the same gene one might “dominate” over
the other and it will be expressed in the offspring. For example, the allele for brown eyes is
dominant and the allele for blue eyes is recessive. So if you have both a brown eye allele
and a blue eye allele you will have brown eyes. The brown eye allele “dominates” the blue
eye allele.
Hypothesis 4
As you now know you get two of every one of your genes. Mendel’s final theory states that
we get 1 of each gene from each parent. For example, you have two genes for your skin
color. You got one from you mom and one from your dad.
Action! - Lets look back at his observations and see how he came up with these
conclusions.
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Describe Mendel’s four hypotheses in one sentence each.
1:
2:
3:
4:
Quiz
Directions: Answer the following questions to see if you met the objectives.
1. What is heredity?
Answer:
2. What is a gene?
Answer
3. What is a trait?
Answer:
4. How are your traits connected to your genes?
Answer:
5. Describe Mendel’s four hypotheses.
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2:
3:
4: