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Title: Inheritance
Description: International Baccalaureate Biology HL Topic 10.2 2016 Clear and detailed notes of topic 10.2 from the book and lecture
Description: International Baccalaureate Biology HL Topic 10.2 2016 Clear and detailed notes of topic 10.2 from the book and lecture
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Inheritance
Topic 10
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H
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2
Biology HL
Horizontal bars = homologous chromosomes
■
Show that the locus of G is on the same chromosome as L
➢ Sometimes crossing over can interfere with the linkage
➢ Outcomes of genetic crosses should typically follow Mandelian ratios of 3:1 for an
F2 monohybrid cross and 9:3:3:1 for a dihybrid cross
➢ There is nothing alarming about a slight variation, but if there is a significant
deviation it suggests that independent assortment is not happening and instead
the genes of the traits being observed are linked
Chi-squared tests (x2)
➢ A sample size is far smaller than the whole population studied and therefore the
ratios found in experiments are rarely equal to the theoretical ratios
➢ Chi-squared test is a statistical test that biologists use to see whether the
difference between an observed result and an expected result is statistically
significant
➢ The chi-squared value is compared to a table
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The degrees of freedom is the number of data classes minus 1
In biology the probability 0
...
2
Biology HL
➢ Partly explains the difficulty in finding out which genes are responsible for traits
whose genetic components are not understood
Continuous and discrete variation
➢ Monogenic traits show d
iscrete variation
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The different characteristics can easily be distinguished from each other
■
○
Either this or that
Examples:
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Cystic fibrosis
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Haemophilia
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Sickle cell anaemia
➢ Polygenic traits show continuous variation
○
A gradual change of the characteristic can be seen in a population
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An array of possible phenotypes can be produced
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A discontinuous variation can be displayed as bar charts
○
Examples:
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Height
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Body shape
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Eye colour
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Skin colour
➢ These characteristics can be influenced by environmental factors, like height and
nutrition
3
Title: Inheritance
Description: International Baccalaureate Biology HL Topic 10.2 2016 Clear and detailed notes of topic 10.2 from the book and lecture
Description: International Baccalaureate Biology HL Topic 10.2 2016 Clear and detailed notes of topic 10.2 from the book and lecture