Unit 5: I Got it From My Momma
Mendel’s Laws
Name _______________________________________________
Date ________________ Period _______ Assignment 56
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Every living thing has a set of characteristics inherited, or
What is genetics in your own words?
passed on, from its parent (asexual reproduction) or
parents (sexual reproduction). This is known as heredity, or
the transmission of characteristics from parent to offspring.
Genetics is the scientific study of heredity, which holds the
key to understanding what makes each species, and
individual, unique.
An Australian monk named Gregor Mendel was one of the Who was Gregor Mendel?
most important contributors in the study of genetics.
Mendel was in charge of the monastery garden and he
began performing simple experiments on some very
famous pea plants.
What type of organism did he use for experiments?
He knew that plants could reproduce sexually or asexually.
If they produced asexually, also called self-pollination, they
were clones of themselves. These pea plants were known What does true breeding mean?
as “true breeding” because they would produce geneticallyidentical offspring if allowed to self pollinate.
Mendel wanted to see what would happen if he forced
different true breeding plants to reproduce sexually.
Mendel studied 7 different pea plant traits that he observed
in his true breeding plants. A trait is a specific characteristic
that varies from one individual to another. Each of the 7
traits had an “either-or” possibility. The 7 traits were: seed
shape, seed color, flower color, pod shape, pod color,
flower position, and plant height.
Mendel crossed plants with each of the 7 contrasting traits
together and observed the offspring. We call the original
pair of parent plants the P (parental) generation and the
offspring are called the F1 generation, or “first filial.” (Filial=
son/daughter).
The offspring of parents with different traits are called
hybrids. Think of a hybrid car as the offspring of a gasoline
car and an electric car- the hybrid has some characteristics
from each! We are also hybrids because we have different
traits from our mother and father!
What is the original generation in crosses called?
What are the offspring called?
What would the offspring of the second generation be called?
Mendel was shocked by his results! After performing this
experiment, all of the F1 offspring inherited the trait from
only one parent! For example, when the smooth seed
plants were crossed with the wrinkly seed plants, all of the
seeds were smooth! In each cross, the other trait had
seemed to disappear!
From this set of experiments, Mendel drew two
conclusions.
The first was that biological inheritance is determined by
factors that are passed from one generation to the next.
Today, we call these genes. The different forms of a gene,
such as wrinkly or smooth, are called alleles.
Using what you know about inheritance, make a prediction
about why this is:
Draw a flow chart to depict the cross that Mendel made
between the smooth seeds and wrinkly seeds. Label each of
the generations!
Generation: ___
Description:
Generation: ___
Description:
His second conclusion is the Principle of Dominance. This
principle states that some alleles are dominant and others
are recessive. An organism with a dominant allele will
always exhibit that form of the trait. An organism with a
recessive allele will only exhibit that trait if it has two copies
of the recessive allele-one from the mother, one from the
father.
What is Mendel’s first conclusion?
Mendel still had another question: Had all of the recessive
alleles disappeared or were they still present, but hidden in
the F1 plants? To find out, he allowed the F1 plants to selfpollinate. When he looked at the results, he found that the
F2 plants showed some recessive traits again!
What did Mendel find in the F2 generation of plants?
Mendel then made his conclusion: each organism has
two copies of each gene- one from each parent.
Mendel realized that the alles for each trait segregated
from each other during the formation of the gametes
(independent assortment…). This would allow different
combinations of dominant and recessive alleles to come
together during fertilization! This is Mendel’s 4th and final
conclusion, the Law of Independent Assortment.
At the right is a diagram showing the possible alleles for
short and tall plants from the P generation to F2. Capital
letters represent dominant alleles and lower case letters
represent recessive alleles.
What is Mendel’s second conclusion?
Is smooth seed or wrinkly seed dominant? __________
Which is recessive? ____________
How do you know?
What is Mendel’s 3rd conclusion?
3rd
Write what each plant will look like, tall or short,
underneath the description:
TT= ________ Tt= _________ tt= _________
What percentage of the F2 generation will be short?
Describe the Law of Independent Assortment in your own
words:
Label the generations