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SECTION
MENDEL AND HEREDITY
6,3
Study Guide
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KEY CONCEPT
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Mendel's research showed that traits
are inherited as discrete units'
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MAIN IDEA: Mendel laid the groundwork for
genetics'
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What is gerietics?
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our current understanding of genetics?
whose early work is the basis for much of
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from the views of many scientists of
How did Mendel's views on inheritance difrer
his time?
of inheritance'
MAIN IDEA: Mendel's data revealed patterns
choices that
helped him see
three important
In designing hts experiments, Mendel made
list Mendel's three choices and wnte an exampie
patterns of inheritanca ln the tabie below.
ofno* he put each ofthese choices into action'
Mendel's Choices
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7. Why did Mendel use
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Unit 3 Resource Book
McDougai Lrttell BioiogY
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STUDY GUIDE, CONTINUED
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8' Fill in the sequence diagram below
to summarize Mendel's experimental process
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Bred fiowers resulting
in F, generation with
dominant phenotype.
Hesulted in F, generation
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recessive phenotypes.
Mendel concluded that traits are inherited as "discrete units."
What do we cali these
discrete units today?
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1O. What two conclusions make up Mendel,s law of segregation?
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Vocabulary Check
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11' segregarion means "separation." what is "segregated" in
Mendel s law of segregation?
12. What
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10 Study Guide
Unit 3 Besource Book
McDougal Lrttell Biology
TRAITS, GENES, AND ALLELES
Study Guide
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KEY CONCEPT
VOCABULARY
Genes encode proteins that
produce a diverse range of
gene
heterozygous
phenotype
allele
genome
dominant
homozygous
genotype
recessive
traits.
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MAIN IDEA:
The same gene can have many versions.
1. What is the relationship between a gene and a protein?
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What is an allele?
3.
What term describes
4.
Wnte a definition of homologous chromosomes using the terms o'gene" and "allele."
a
pair of alleles that are the same? that are different?
In the space below, draw a pair of homologous chromosomes. Label the chromosomes with
two sets of genes, one with homozygous alleles (Gene A, Gene A) and one with heterozygous
alleles (Gene B, Gene b).
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Unit 3 Resource Book
McDougal Littell Biology
Study Guide 13
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MAIN IDEA: Genes influence the development of traits.
5. write an analogy to show the difference between genotype and phenotype.
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6. How are alleles
represented on paper?
Fill in the table below with the missing genotype, phenotype (dominant or recessive),
or
alleles (TT, Tt, tt).
Genotype
Phenotype
Alleles
homozygous dominant
recessive
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8. If an organism has a recessive
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trait, can you determine its genotype for that trait?
What factors besides alleles affect phenotype?
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Vocabulary Check
1O. What type of alleles are present in an organism with a
Qe genotype?
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11. What is an alternative form of a gene?
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12. What is the opposite of homozygous? of dominant?
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Unit 3 Resource Book
McDougal Littell Biology
Name
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STUDY GUIDE, CONTINUED
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MAIN IDEA: A dihybrid cross involves two traits.
8. What is a dihybrid cross?
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9. Why does each parent organism in the F1 generation
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Suppose an organism had the genotype
from this allele combination?
have four alleles listed in Figure
AABb. What two types of gametes could result
11. What is the phenotypic ratio that results from a dihybrid cross between two organisms
that are heterozygous for both traits? See Figure 6. 17 for heip.
MAIN IDEA: Heredity patterns can be calculated with probability.
12. Probability predicts the
number ofoccurrences. not the
number of occurrences.
13. To caiculate
the probability that two independent events
will
happen together,
the probability of each individual event.
14- In Figure 6.18, the probability of getting one coin that is heads up and one
coin that is
tails up is
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15. What is a testcross?
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16. What is independent in the iaw of independent assortment?
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Study Guide
Unit 3 Resource Book
McDougal Littell Biology
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SECTION
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TRAITS AND PROBABILITY
Study Guide
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KEY CONCEPT
VOCABULARY
The inheritance of traits
Punnett square
follows the rules of
probability.
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law of independent
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assortment
dihybrid cross
monohybrid cross
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MAIN IDEA: Punnett
squares illustrate genetic crosses.
Identifu what each of the numbered parts represents in the Punnett square below. Then draw
lines from each of the parents' alleles to the corresponding alleies in the offspring.
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Why does each parent contribute only one allele to the offspring?
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MAIN IDEA: A monohybrid cross involves one trait.
5. You know a ratio is a comparison that tells how two or more
things relate. What is
a
genotypic ratio? a phenotypic ratio?
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What is the genotypic ratio of the offspring in Figure 6.15?
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7. What is the phenotypic ratio of the offspring in Figure 6.15?
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Unit 3 Resource Book
McDougal Littell Biology
study Guide 17
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SECTION
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MEIOSIS AND GENETIC VARIATION
Study Guide
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KEY CONCEPT
VOCABULARY
Independent assortment and crossing over during meiosis
result in genetic diversity.
crossing
MAIN IDEA:
over
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genetic linkage
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Sexual reproduction creates unique gene combinations.
1. What are two ways that sexual reproduction helps create and maintain genetic diversity?
2.
Which does sexual reproduction create, new alleles or new combinations of alleles?
3.
How is the production of unique genetic combinations an advantage to organisms and
species?
MAIN IDEA: Crossing over during
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meiosis increases genetic diversity.
Are chromosomes in a duplicated or an unduplicated state when crossing over occurs?
Use sketches to illustrate how crossing over contributes to genetic diversity. Use Figure 6.20
for reference. 1. Draw a celi with four chromosomes in the first box. Make one pair of
chromosomes large and the other par small. Color in one large chromosome and one small
chromosome. Leave the other two chromosomes white. 2. In the next box, draw the cell in
prophase I. Have each pair of homologous chromosomes line up together-large with iarge,
small with small. 3. In the third box, show crossing over between each pair of homologous
chromosomes. 4. In the last box, show what the chromosomes look like as a result of crossing
over. \bu will use this sketch in the next exercise.
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Unit 3 Resource Book
McDougal Littell Biology
Study Guide 21
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Refer to your cell sketch in the last box on the previous page. AIso refer to Figure 6.5 if
necessary. 1. In the first box below, show what your cell would look like at the end of meiosis
I. Remember, the result will be two cells that have one duplicated chromosome from each
horirologous pair. 2.In the second box, show what your cell would look like at the end of
meiosis II. Remember, the result will be four cells that have one (arduplicated) chromosome
from each homologous pair.
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5. If
genes A and B are iocated on separate, nonhomologous chromosomes, will they
follow Mendel's law of independent assortrnent? Explain.
lr. Ifgenes A and B are located at opposite ends on the same chromosome, are they likely
to follow Mendel's law of rndependent assortment? Explain.
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If
genes A and B are located very ciose together on the same chromosome,
are they
likeiy to follow Mendel's law of independent assortment? Explain.
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Vocabulary Check
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The exchange of chromosome segments between homologous chromosomes is called
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The tendency for two genes that are iocated close together on a chromosome to be
inherited together is called
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study Guide
Unit 3 Resource Book
McDougal Linell Biology