Essential Biology 10.3 Polygenic Inheritance (AHL)
Due Date:
Student Name:
Candidate Number: 002171-
Blog resource: http://tinyurl.com/l363hk
Click4Biology: http://click4biology.info/c4b/10/gene10.htm
Cite all sources using the CSE method (or ISO 690 Numerical in Word. Highlight all objective 1 command terms in yellow
and complete these before class. Highlight all objective 2 and 3 command terms in green – these will be part of the
discussions in class. After class, go back and review them.
Complete the self-assessment rubric before submitting to Moodle. Avoid printing this if possible.
1. Define polygenic inheritance.
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2. Distinguish between polygenic inheritance and multiple alleles.
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3. List one human and one plant example of polygenic inheritance.
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4. Define contributing allele.
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5. Polygenic inheritance gives rise to continuous variation within a population.
Explain what this means, using skin colour as an example.
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6. Assume that two genes (A and B) are responsible for inheritance of skin colour, with two alleles each
and that they are unlinked. The dominant alleles code for melanin production.
a. Calculate the number of possible genotypes.
Stephen Taylor
Bandung International School
http://sciencevideos.wordpress.com
Essential Biology 10.3 Polygenic Inheritance (AHL)
Due Date:
Student Name:
Candidate Number: 002171-
b. Apply the possible genotypes to the range of phenotypes below:
aabb
Aabb
c. Explain why the phenotypes show a normal distribution.
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7. Using a punnet grid, explain why it is possible for children to have skin which is darker or lighter than
both parents.
Mother genotype:
Father genotype:
AB
i.
Ab
aB
ab
AB
Ab
aB
ab
Outcome and explanation.
Stephen Taylor
Bandung International School
http://sciencevideos.wordpress.com
Essential Biology 10.3 Polygenic Inheritance (AHL)
Due Date:
Student Name:
Candidate Number: 002171-
8. Compare the advantages and disadvantages of light and dark skin.
Light Skin
Dark Skin
Lack of exposure to sunlight can
result in vitamin D deficiency
Cold Climate
Hot Climate
9. State precautionary measures that could be taken by:
a. Pale-skinned people to avoid the dangers of hot climates?
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b. Dark-skinned people to reduce the disadvantage of a cold climate?
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10. A characteristic is controlled by two unlinked genes with two alleles. Deduce the number of possible
genotypes and phenotypes.
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11. A characteristic is controlled by three genes with two alleles each. Calculate the number of genotypes
possible in a cross between a homozygous recessive father and a homozygous dominant mother.

12. Wheat kernel colour is controlled by three unlinked genes (A, B and C). The dominant alleles code for
production of a red pigment. Deduce the phenotype ratio expected in a test cross with a wheat plant
that is homozygous dominant for A, heterozygous for B and homozygous recessive for C. Show your
working.
Stephen Taylor
Bandung International School
http://sciencevideos.wordpress.com
Essential Biology 10.3 Polygenic Inheritance (AHL)
Due Date:
Student Name:
Candidate Number: 002171-
Works Cited
1. Allott, Andrew. IB Study Guide: Biology for the IB Diploma. s.l. : Oxford University Press, 2007. 978-0-19915143-1.
2. Mindorff, D and Allott, A. Biology Course Companion. Oxford : Oxford University Press, 2007. 978099151240.
3. Clegg, CJ. Biology for the IB Diploma. London : Hodder Murray, 2007. 978-0340926529.
4. Campbell N., Reece J., Taylor M., Simon. E. Biology Concepts and Connections. San Fransisco : Pearson
Benjamin Cummings, 2006. 0-8053-7160-5.
5. Taylor, Stephen. Science Video Resources. [Online] Wordpress, 2010. http://sciencevideos.wordpress.com.
6. Burrell, John. Click4Biology. [Online] 2010. http://click4biology.info/.
7. IBO. Biology Subject Guide. [Online] 2007. http://xmltwo.ibo.org/publications/migrated/productionapp2.ibo.org/publication/7/part/2/chapter/1.html.
EXTRA LINKS
Youtube: Different Colour Twins?
http://www.youtube.com/watch?v=rWYUYrg1CWo
Black & White Twins – Guardian Article
http://www.guardian.co.uk/lifeandstyle/2011/sep/24/twins-black-white?fb=native&CMP=FBCNETTXT9038
TED Talks: Nina Jablonski breaks the illusion of skin color
http://www.ted.com/talks/lang/en/nina_jablonski_breaks_the_illusion_of_skin_color.html
Stephen Taylor
Bandung International School
http://sciencevideos.wordpress.com