Download Genetics: The Science of Heredity

Genetics: The Science of Heredity
Table of Contents
Mendel’s Work
Probability and Heredity
The Cell and Inheritance
The DNA Connection
Genetics: The Science of Heredity - Mendel’s Work
Outlining
As you read, make an outline
about Mendel’s work. Use the
red headings for the main
ideas and the blue headings
for the supporting ideas.
Mendel’s Work
I.
II.
Mendel’s Experiments
A. Crossing Pea Plants
B. The F1 Offspring
C. The F2 Offspring
D. Experiments With Other
Traits
Dominant and Recessive
Alleles
A. Genes and Alleles
B. Alleles in Mendel’s
Crosses
C. Symbols for Alleles
D. Significance of Mendel’s
Contribution
Genetics: The Science of Heredity
Mendel’s Work
Introduction Pg. 218
1.
Gregor Mendel experimented with hundreds of pea plants
to understand the process of ______.
heredity
2. Heredity
C- is the passing of traits from parents to offspring
3. Genetics
A- is the scientific study of heredity.
4.
Traits
B- are physical characteristics.
Genetics: The Science of Heredity - Mendel’s Work
Crossing Pea Plants
Gregor Mendel crossed pea plants that had different traits.
The illustrations show how he did this.
Genetics: The Science of Heredity - Mendel’s Work
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.
Genetics: The Science of Heredity
Mendel’s Work
Mendel’s Experiments Pg. 219-220
5.
In a flower, the female sex cells, or eggs, are produced by
the ____. Pollen, which contains the male sex cells, is
produced by the _____.
pistil
stamens
6. What are purebred organisms?
They are the offspring of many generations that have
the same trait.
Genetics: The Science of Heredity
Mendel’s Work
7.
Complete the flowchart:
Purebred tall plants are crossed with purebred ____plants.
short
F1 offspring are all ____.
tall
F1 offspring are allowed to self pollinate.
F2 offspring are ___and ____.
tall and short
8. Traits in garden peas that Mendel studied:
• pod, color, seed shape, and flower position.
Genetics: The Science of Heredity - Mendel’s Work
Dominant and Recessive Alleles
Mendel studied several traits in pea plants.
Genetics: The Science of Heredity
Mendel’s Work
9.
Two forms of the trait of seed shape in pea plants are ___
and ____.
round and wrinkled
Dominate and Recessive Alleles Pg. 221-223
10. Sentences that are true about alleles.
• Alleles are different forms of a gene.
• Dominant alleles always show up in the organism when the
allele is present.
11. Only pea plants that have two recessive alleles for short
stems will be short.
True
Genetics: The Science of Heredity
Mendel’s Work
12.
Purebred short
C- two alleles for short stems
13. Purebred tall
A- two alleles for tall stems
14. Hybrid tall
B- one allele for tall stems and one allele for
short stems
15. A dominant allele is represented by a(n) _____.
capital letter
Genetics: The Science of Heredity
Mendel’s Work
16.
A recessive allele is represented by a(n) _____.
lowercase letter
17. How would a geneticist write the alleles to show that a tall
pea plant has one allele for tall stems and one allele for short
stems?
Tt
18. Some scientists during Mendel’s time thought Mendel
should be called the Father of Genetics.
False
Genetics: The Science of Heredity
End of Section:
Mendel’s Work
Genetics: The Science of Heredity - Probability and Heredity
Building Vocabulary
After you read the section, reread the paragraphs that
contain definitions of Key Terms. Use all the information you
have learned to write a definition of each Key Term in your
own words.
Key Terms:
Examples:
probability
homozygous
An organisms
Probability
is that
a number
has two
that
identical
describes
alleles
howfor
likely
a trait
it isis
that an
said
to be
event
homozygous.
will occur.
Punnett square
heterozygous
AnPunnett
A
organisms
square
that has
is a two
chartdifferent
that shows
alleles
all for
thea trait is
possible combinations
heterozygous
for that of
trait.
alleles that can result from a
genetic cross.
In codominance, the alleles are neither dominant nor
An organism’s phenotype is its physical appearance,
recessive.
or visible traits.
codominance
phenotype
genotype
An organism’s genotype is its genetic makeup, or
allele combinations.
Genetics: The Science of Heredity
Probability and Heredity
Principles of Probability Pg. 226-227
1.
2.
•
•
•
A number that describes how likely it is that an event will
occur is called _____.
probability
Circle the following that equals the probability that a
tossed coin will land heads up.
one in two
½
50 Percent
3. When you toss a coin 20 times, you will always get 10 heads
and 10 tails.
False
Genetics: The Science of Heredity
Probability and Heredity
4.
If you toss a coin five times and it lands heads up each
time, can you expect the coin to land heads up on the
sixth toss?
No, the results of the first five tosses do not affect the
results of the sixth toss.
Probability and Genetics Pg. 228-229
5. When Mendel crossed two hybrid plants for stem height (Tt),
what results did he always get?
He always found that about three fourths of the plants
had tall stems and one fourth of the plants had short stems.
Genetics: The Science of Heredity
Probability and Heredity
6.
Mendel realized that the principles of probability could be
used to _____ the results of genetic crosses.
predict
7. A chart that shows all the possible combinations of alleles
that can result from a genetic cross is called a(n) _____.
Punnett Square
8. Work on your own using a combination of alleles Tt and Tt.
Genetics: The Science of Heredity
Probability and Heredity
8. Results of the cross
Tt
T
t
T
TT
Tt
t
Tt
tt
Tt
Genetics: The Science of Heredity - Probability and 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.
Genetics: The Science of Heredity - Probability and Heredity
Probability and Genetics
In a genetic cross, the allele that each parent will pass on to
its offspring is based on probability.
Genetics: The Science of Heredity - Probability and Heredity
Phenotypes and Genotypes
An organism’s phenotype is its physical appearance, or
visible traits, and an organism’s genotype is its genetic
makeup, or allele combinations.
Genetics: The Science of Heredity
Probability and Heredity
Phenotypes and Genotypes Pg. 230
9.
Phenotype
B- an organism’s physical appearance or visible traits
10. Genotype
C- an organism’s genetic makeup or allele
combinations
11. Homozygous
A- describes an organism with two identical alleles for
a trait
Genetics: The Science of Heredity
Probability and Heredity
12.
Heterozygous
D- Describes an organism that has two different
alleles for a trait
13. Mendel used the term ____ to describe heterozygous pea
plants.
hybrid
Codominance Pg. 231
14. In codominance, the alleles are neither dominant nor
recessive.
True
Genetics: The Science of Heredity
Probability and Heredity
15. In cattle, red hair and white hair are codominant. Cattle
with both white hair and red hair are _____.
heterozygous
Genetics: The Science of Heredity - Probability and Heredity
Codominance
In codominance, the alleles are neither dominant nor
recessive. As a result, both alleles are expressed in the
offspring.
Genetics: The Science of Heredity - Probability and 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.
Genetics: The Science of Heredity - Probability and Heredity
Percentages
Practice Problem
Suppose 3 out of 12 coins landed with tails up. How can you
express this as a percent?
25%
Genetics: The Science of Heredity - Probability and 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%
Genetics: The Science of Heredity - Probability and 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
Genetics: The Science of Heredity - Probability and 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.
Genetics: The Science of Heredity - Probability and 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.
Genetics: The Science of Heredity
End of Section:
Probability and
Heredity
Genetics: The Science of Heredity - The Cell and Inheritance
Identifying Supporting Evidence
As you read, identify the evidence that supports the
hypothesis that genes are found on chromosomes. Write
the evidence in a graphic organizer.
Grasshoppers:
24 chromosomes in body
cells, 12 in sex cells.
Chromosomes are
important in
inheritance.
Fertilized egg has
24 chromosomes.
Alleles exist in
pairs in
organisms.
Genetics: The Science of Heredity
The Cell and Inheritance
Chromosomes and Inheritance Pg. 235
1. Sentences that are true about what Sutton observed about
chromosome number.
• Grasshopper sex cells have half the number of
chromosomes as body cells.
• When grasshopper sex cells join, the fertilized egg has the
same number of chromosomes as the body cells of the
parents.
2.
What is the chromosomes theory of inheritance?
Genes are carried from parents to their offspring on
chromosomes.
Genetics: The Science of Heredity - The Cell and Inheritance
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.
Genetics: The Science of Heredity
The Cell and Inheritance
Meiosis Pg. 236-237
3.
What is Meiosis?
It is the process by which the number of chromosomes
is reduced by half to form sex cells--sperm and eggs.
4. Complete the cycle diagram:
• Parent cell has four chromosomes arranged in ____ pairs.
two
• Chromosome pairs ______and are distributed to sex cells,
Each sex cell has ____ chromosomes.
separate
Four
Genetics: The Science of Heredity
The Cell and Inheritance
4. The cycle continued:
• Sex cells combine to produce offspring. Each offspring has
____ chromosomes, one pair from each parent.
two
5. A Punnett square is a shorthand way to show the events
that occur during _____.
meiosis
6. During meiosis, the two alleles for each gene stay together.
False- separate
Genetics: The Science of Heredity - The Cell and Inheritance
Punnett Square
A Punnett square is actually a way to show the events that
occur at meiosis.
Genetics: The Science of Heredity
The Cell and Inheritance
7.
If the male parent cell is heterozygous for a trait, Tt, what
alleles could the sperm cells possible have?
Half the sperm cells will have the T allele and the other
half will have the t allele.
A Lineup of Genes Pg. 238
8. How many pairs of chromosomes do human body cells
contain?
23 pairs of chromosomes
9. How are the genes lined up in a pair of chromosomes?
Genes are lined up in the same order on both
chromosomes.
Genetics: The Science of Heredity - The Cell and Inheritance
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.
Genetics: The Science of Heredity
End of Section:
The Cell and
Inheritance
Genetics: The Science of Heredity - The DNA Connection
Sequencing
Sequence is the order in which the steps in a process occur.
As you read, make a flowchart that shows protein synthesis.
Put each step in the flowchart in the order in which it occurs.
Protein Synthesis
DNA provides code to form messenger RNA.
Messenger RNA attaches to ribosome.
Transfer RNA “reads” the messenger RNA.
Amino acids are added to the growing protein.
Genetics: The Science of Heredity
The DNA Connection
The Genetic Code Pg. 240
1.
Sentences that are true about genes, chromosomes, and
proteins.
• Genes control the production of proteins in an organism’s
cells.
• Proteins help determine the size, shape, and other traits of
an organism.
2.
a.
b.
c.
d.
A DNA molecule is made up of four nitrogen bases:
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
Genetics: The Science of Heredity
The DNA Connection
3.
What is the genetic code?
The genetic code is the order of nitrogen bases along a
gene that specifies what type of protein will be produced.
4. One group of three nitrogen codes for one _____.
amino acid
Genetics: The Science of Heredity - The DNA Connection
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.
Genetics: The Science of Heredity - The DNA Connection
How Cells Make Proteins
During protein synthesis, the cell uses information from a
gene on a chromosome to produce a specific protein.
Genetics: The Science of Heredity
The DNA Connection
How cells Make Protein Pg. 241-243
5.
During protein synthesis, the cell uses information from a
____ on a chromosome to produce a specific _____.
gene
protein
6. Proteins are made on _____ in the cytoplasm of the cell.
ribosomes
Genetics: The Science of Heredity
The DNA Connection
7. Complete the Venn Diagram:
In DNA:
Thymine stays inside the nucleus.
In RNA:
Uracil goes out into the cytoplasm.
In both DNA and RNA:
Cytosine, adenine, and guanine.
8. List two kinds of RNA and tell their jobs.
a. Messenger RNA copies the coded message from the DNA
in the nucleus and carries the message to the ribosomes in
the cytoplasm.
Genetics: The Science of Heredity
The DNA Connection
8.
b. Transfer RNA carries amino acids to the ribosome and
adds them to the growing protein.
9. Circle the letter of the first step in the protein synthesis.
• DNA “unzips” to direct the production of a strand of
messenger RNA.
10. Circle the letter of the last step in protein synthesis.
• The protein chain grows longer as each transfer RNA
molecule adds an amino acid.
Genetics: The Science of Heredity
The DNA Connection
Mutations Pg. 244-245
11. What is a mutation?
A mutation is any change in a gene or chromosome.
12. How can mutations affect protein synthesis in cells?
Mutations can cause a cell to produce an incorrect
protein during protein synthesis.
13. Sentences that are true about mutations.
• Some mutations occur when one nitrogen base is
substituted for another.
• Some mutations occur when chromosomes don’t separate
correctly during meiosis.
Genetics: The Science of Heredity
The DNA Connection
14. Mutations can be a source of genetic _____.
variety
15. All mutations are harmful.
False
16. Mutation that are ____ improve an organism’s chances
for survival and reproduction.
helpful
17. Whether a mutation is harmful or helpful depends partly
on an organism’s _____.
environment
Genetics: The Science of Heredity - The DNA Connection
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.
Genetics: The Science of Heredity
The DNA Connection
Key Terms
1. Meiosis
2. Punnett Square
3. Phenotype
4. Messenger RNA
5. Heterozygous
6. Probability
7. Dominant Allele
8. Trait
9. Gene
10. Genetics
11. Purebred
Genetics: The Science of Heredity
End of Section:
The DNA
Connection
Genetics: The Science of Heredity
Graphic Organizer
RNA
includes
Messenger RNA
Transfer RNA
functions to
functions to
Copy the coded
message from the
DNA
Carry the message
to the ribosome in
the cytoplasm
Carry amino acids
Add amino acids
to the growing
protein
Genetics: The Science of Heredity
End of Section:
Graphic Organizer