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Chapter 5 Genetics: The Science of Heredity
Table of Contents
Chapter Preview
5.1 Mendel’s Work
5.2 Probability and Heredity
5.3 The Cell and Inheritance
5.4 Genes, DNA, and Proteins
Chapter 5 Genetics: The Science of Heredity
Chapter Preview Questions
1. What carries the instructions that cells need to carry out all
the functions of life?
a. amino acids
b. enzymes
c. nucleic acids
d. proteins
Chapter 5 Genetics: The Science of Heredity
Chapter Preview Questions
1. What carries the instructions that cells need to carry out all
the functions of life?
a. amino acids
b. enzymes
c. nucleic acids
d. proteins
Chapter 5 Genetics: The Science of Heredity
Chapter Preview Questions
2. Which of the following elements can be found in
nucleic acids?
a. carbon
b. oxygen and hydrogen
c. nitrogen and phosphorus
d. all of the above
Chapter 5 Genetics: The Science of Heredity
Chapter Preview Questions
2. Which of the following elements can be found in
nucleic acids?
a. carbon
b. oxygen and hydrogen
c. nitrogen and phosphorus
d. all of the above
Chapter 5 Genetics: The Science of Heredity
Chapter Preview Questions
3. Which kind of nucleic acid carries information about
an organism?
a. RNA
b. cytoplasm
c. protein
d. DNA
Chapter 5 Genetics: The Science of Heredity
Chapter Preview Questions
3. Which kind of nucleic acid carries information about
an organism?
a. RNA
b. cytoplasm
c. protein
d. DNA
Chapter 5 Genetics: The Science of Heredity
Chapter Preview Questions
4. Where is most DNA found?
a. in the chromatin in the nucleus of a cell
b. in the cytoplasm of a cell
c. in proteins
d. in amino acids
Chapter 5 Genetics: The Science of Heredity
Chapter Preview Questions
4. Where is most DNA found?
a. in the chromatin in the nucleus of a cell
b. in the cytoplasm of a cell
c. in proteins
d. in amino acids
Chapter 5 Genetics: The Science of Heredity
How are traits passed from parents to offspring?
In a litter of puppies, some of the
puppies have a black and white
coat, and others have a red and
white coat. What can you infer
about how their parents look?
What can you infer about the
parents’ DNA?
Chapter 5 Genetics: The Science of Heredity
Use Suffixes
Suffix
Meaning of Suffix
Example and
Meaning of Example
-ance, -ence
state of; quality of
importance State of being
important
Chapter 5 Genetics: The Science of Heredity
Use Suffixes
Suffix
-ant, -ent
Meaning of Suffix
Example and
Meaning of Example
inclined to; likely to
dependent Likely to rely on
something or someone else
Chapter 5 Genetics: The Science of Heredity
Use Suffixes
Suffix
-ity
Meaning of Suffix
Example and
Meaning of Example
state of; quality of
simplicity State of being
simple or easy
Chapter 5 Genetics: The Science of Heredity
Use Suffixes
Suffix
-tion
Meaning of Suffix
Example and
Meaning of Example
process of; state of
production Process
of making
Chapter 5 Genetics: The Science of Heredity
Apply It!
1. What is the suffix in the word dominant? If the verb dominate
means “to have control over,” what do you think dominant means?
What does dominance probably mean?
–ant, likely to have control over, the state of having control over
2. The word probable means “likely to happen.” What does
probability mean?
the state of something that is likely to happen
Chapter 5 Genetics: The Science of Heredity
End of Chapter
Preview
Chapter 5 Genetics: The Science of Heredity
Section 1:
Mendel’s Work
What were the results of Mendel’s
experiments, or crosses?
What controls the inheritance of traits in
organisms?
Chapter 5 Genetics: The Science of Heredity
Crossing Pea Plants
Gregor Mendel crossed pea plants that had different traits.
The illustrations show how he did this.
Chapter 5 Genetics: The Science of Heredity
Mendel’s Experiments
In all of Mendel’s crosses, only one form of the trait appeared
in the F1 generation. However, in the F2 generation, the “lost”
form of the trait always reappeared in about one fourth of the
plants.
Chapter 5 Genetics: The Science of Heredity
Dominant and Recessive Alleles
Mendel studied several traits in pea plants.
Chapter 5 Genetics: The Science of Heredity
End of Section:
Mendel’s Work
Chapter 5 Genetics: The Science of Heredity
Section 2: Probability
and Heredity
What is probability and how does it help
explain the results of genetic crosses?
What is meant by genotype and phenotype?
What is codominance?
Chapter 5 Genetics: The Science of Heredity
Percentages
One way you can express a probability is as a percentage. A
percentage (%) is a number compared to 100. For example,
50% means 50 out of 100.
Suppose that 3 out of 5 tossed coins landed with heads up.
Here’s how you can calculate what percent of the coins
landed with heads up.
1. Write the comparison as a fraction.
3 out of 5 = 3/5
2. Multiply the fraction by 100% to express it as a
percentage.
3/5 x 100%/1 = 60%
Chapter 5 Genetics: The Science of Heredity
Percentages
Practice Problem
Suppose 3 out of 12 coins landed with tails up. How can you
express this as a percent?
25%
Chapter 5 Genetics: The Science of Heredity
A Punnett Square
The diagrams show how to make a Punnett square. In this
cross, both parents are heterozygous for the trait of seed
shape. R represents the dominant round allele, and r
represents the recessive wrinkled allele.
Chapter 5 Genetics: The Science of Heredity
Probability and Genetics
In a genetic cross, the allele that each parent will pass on to
its offspring is based on probability.
Chapter 5 Genetics: The Science of Heredity
What Are the Genotypes?
Mendel allowed several F1 pea
plants with yellow seeds to selfpollinate. The graph shows the
approximate numbers of the F2
offspring with yellow seeds and
with green seeds.
Chapter 5 Genetics: The Science of Heredity
What Are the Genotypes?
Reading Graphs:
How many F2 offspring had
yellow seeds? How many had
green seeds?
Yellow–6,000; green–2,000
Chapter 5 Genetics: The Science of Heredity
What Are the Genotypes?
Calculating:
Use the information in the
graph to calculate the total
number of offspring that
resulted from this cross. Then
calculate the percentage of
the offspring with yellow peas,
and the percentage with
green peas.
8,000; 75% have yellow peas
and 25% have green peas.
Chapter 5 Genetics: The Science of Heredity
What Are the Genotypes?
Inferring:
Use the answers to Question
2 to infer the probable
genotypes of the parent
plants. (Hint: Construct Punnett
squares with the possible
genotypes of the parents.)
Both parents probably had
the genotype Bb.
Chapter 5 Genetics: The Science of Heredity
Phenotypes and Genotypes
An organism’s phenotype is its physical appearance, or
visible traits. An organism’s genotype is its genetic makeup,
or allele combinations.
Chapter 5 Genetics: The Science of Heredity
Codominance
In codominance, the alleles are neither dominant nor
recessive. As a result, both alleles are expressed in the
offspring.
Chapter 5 Genetics: The Science of Heredity
Links on Probability and Genetics
Click the SciLinks button for links on probability and genetics.
Chapter 5 Genetics: The Science of Heredity
End of Section:
Probability and Heredity
Chapter 5 Genetics: The Science of Heredity
Section 3: The Cell
and Inheritance
What role do chromosomes play in inheritance?
What events occur during meiosis?
What is the relationship between chromosomes and
genes?
Chapter 5 Genetics: The Science of Heredity
Meiosis
During meiosis, the chromosome pairs separate and are
distributed to two different cells. The resulting sex cells have
only half as many chromosomes as the other cells in the
organism.
Chapter 5 Genetics: The Science of Heredity
Punnett Square
A Punnett square is actually a way to show the events that
occur at meiosis.
Chapter 5 Genetics: The Science of Heredity
A Lineup of Genes
Chromosomes are made up of many
genes joined together like beads on a
string. The chromosomes in a pair may
have different alleles for some genes
and the same allele for others.
Chapter 5 Genetics: The Science of Heredity
Links on Meiosis
Click the SciLinks button for links on meiosis.
Chapter 5 Genetics: The Science of Heredity
Chromosomes
Click the Video button to watch a movie about chromosomes.
Chapter 5 Genetics: The Science of Heredity
End of Section: The
Cell and Inheritance
Chapter 5 Genetics: The Science of Heredity
Section 4: Genes, DNA,
and Proteins
What forms the genetic code?
How does a cell produce proteins?
How can mutations affect an organism?
Chapter 5 Genetics: The Science of Heredity
The DNA Code
Chromosomes are made of DNA. Each chromosome
contains thousands of genes. The sequence of bases in a
gene forms a code that tells the cell what protein to produce.
Chapter 5 Genetics: The Science of Heredity
How Cells Make Proteins
During protein synthesis, the cell uses information from a
gene on a chromosome to produce a specific protein.
Chapter 5 Genetics: The Science of Heredity
Protein Synthesis Activity
Click the Active Art button to open a browser window and
access Active Art about protein synthesis.
Chapter 5 Genetics: The Science of Heredity
Mutations
Mutations can cause a cell to produce an incorrect protein
during protein synthesis. As a result, the organism’s trait, or
phenotype, may be different from what it normally would
have been.
Chapter 5 Genetics: The Science of Heredity
Protein Synthesis
Click the Video button to watch a movie
about protein synthesis.
Chapter 5 Genetics: The Science of Heredity
End of Section: Genes,
DNA, and Proteins
Chapter 5 Genetics: The Science of Heredity
QuickTake Quiz
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