Elite Private School
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Biology Student’s
Subject: =
Name: 10
7.3 Gene Linkage and Grade
Unit/Topic: Section: Date:
Mapping Level: Student’s
Student ID
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Fill in the blank or circle the word or phrase that best completes the statement.
1. Gene linkage describes genes that are on the same chromosome and tend to be
inherited separately / together.
2. Fruit flies were useful in Morgan’s research, because many generations of fruit
flies could be grown slowly / quickly, and fruit flies had traits that were easy /
difficult to observe.
3. A wild type differs from a mutant type. A wild type is the least common / most
common phenotype, and a mutant type is a much less / much more common
phenotype.
4. Morgan made several conclusions from his research on fruit flies:
Linked genes are on the same _________________.
Chromosomes, not genes, assort ________________ during meiosis.
Homologous genes can be exchanged through _________________ during
meiosis.
5. The sequence diagram on the following page shows how scientific work
progressed in the discovery of gene linkage.
Place the statements below into appropriate boxes in the diagram on the next
page. Some statements may go into more than one box.
a. Studied fruit flies.
b. Studied pea plants.
c. Suggested that genes assort independently of one another.
d. Suggested that chromosomes assort independently.
e. Suggested that some genes are linked.
f. Concluded that linked genes were on the same chromosome.
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Worksheets
Study Guide A continued
Mendel: Punnett, Bateson: Morgan:
MAIN IDEA: Linkage maps estimate distances between genes.
Circle the word or phrase that best completes the statement.
6. The distance between two genes is related to the chance that they are inherited
together. The closer / farther apart genes are, the more likely they will be
inherited together. The closer / farther apart they are, the more likely they are
to be separated.
7. The basis of Sturtevant’s research was the hypothesis that the frequency of
cross-overs during meiosis / mitosis is related to the distance between genes.
8. What is a linkage map?
a. A map of each gene’s phenotype relative to other genes.
b. A map of each gene’s shape relative to other genes.
c. A map of the relative locations of genes on a chromosome.
d. A map of the relative sizes of genes on a chromosome.
9. How are cross-over frequencies related to linkage maps?
a. The percentage of cross-overs is added to the map linkages.
b. The percentage of cross-overs is converted into map units.
c. The percentage of cross-overs is generated by map units.
d. The percentage of cross-overs is subtracted from the percentage of linkages.
10. What two things do linkage maps show about genes on a chromosome?
a. An estimate of physical distance between genes.
b. The actual physical distance between genes.
c. The relative locations of genes.
d. The relative sizes of genes.
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Study Guide A continued
11. Use the cross-over frequencies given below to draw a linkage map for the four
genes listed. Think about the relationship between cross-over frequency and
distance in linkage map units. Use Figure 3.3 to help you make the linkage
map. Put gene A on the far left of the map, then work through the distances
between the gene pairs.
Cross-over Frequencies: Linkage Map
A-B 20%
B-C 5%
A-C 25%
A-D 7%
D-B 13%
D-C 18%
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STUDY GUIDE B:
MAIN IDEA: Gene linkage was explained through fruit flies.
1. What is gene linkage?
______________________________________________________________
2. Why were fruit flies useful in Morgan’s research?
______________________________________________________________
3. What is the difference between a wild type and a mutant type?
______________________________________________________________
3. What did Morgan conclude from his research on fruit flies?
______________________________________________________________
______________________________________________________________
Complete the sequence below to take notes about the discovery of gene linkage.
Mendel: Punnett, Bateson: Morgan:
Genes assort
independently of one
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Study Guide B continued
MAIN IDEA: Linkage maps estimate distances between genes.
5. How is the distance between two genes related to the chance they are
inherited together?
______________________________________________________________
6. What hypothesis was the basis of Sturtevant’s research?
______________________________________________________________
7. What is a linkage map?
______________________________________________________________
8. How are cross-over frequencies related to linkage maps?
______________________________________________________________
______________________________________________________________
9. What do linkage maps show about genes on a chromosome?
______________________________________________________________
______________________________________________________________
Use the cross-over frequencies given below to draw a linkage map for the four genes listed.
Think about the relationship between cross-over frequency and distance in linkage map
units. Use Figure 3.3 to help you make the linkage map. Put gene A on the far left of the map,
then work through the distances between the gene pairs.
Cross-over Frequencies: Linkage Map
A-B 20%
B-C 5%
A-C 25%
A-D 7%
D-B 13%
D-C 18%
