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Chapter 5

CAS BI 206 Chapter Notes - Chapter 5: Null Hypothesis, Genetic Linkage, Centimorgan


Department
Biology
Course Code
CAS BI 206
Professor
Chip Celenza
Chapter
5

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Chapter 5: Linkage, Recombination, and Mapping of Genes on
Chromosomes
Recombination separation of genes on chromosome during meiosis
The further apart 2 genes are the greater chance of separation through recombination
The closer 2 genes are the greater chance they will travel together genetic linkage
Syntenic genes located on the same chromosome
Parental types gametes that have same allele combination as parent
Recombinant type gametes that have different allele combination than parent
Two genes are linked when the number of F2 progeny with parental types exceeds recombinant
types
Genes sort together during crossing over
Chi-square test helps to determine is observed data is significantly different from predicted data
Null hypothesis model that may be refuted by test (ex: genes A and B are not linked)
Alternative hypothesis gives rise to precise prediction (ex: genes A and B are linked)
Results indicate there is a significant difference reject null accept linkage
P value probability that set of results represents chance deviation; high = likely that
hypothesis tested explains the data observed differences are insignificant
Formulas
Σ(number observed umber expected) /(number expected) = n2
OF nD = 1
Chiasmata structures where nonsister
chromatids cross over each other exchange
genetic information
Terminalization movement of chiasmata to
end of chromosome, allowing homologous
chromosomes to separate
Closer 2 chromosomes are less likely
random crossover occurs between 2 genes
Recombination frequency % of total progeny
that are recombinant
Centimorgan one RF % point unit of
measurement along chromosome
also called map unit
Recombination frequencies never
exceed 50% (they are unlinked at that
point and therefore have = probability
of assorting separately/together)
High RF far apart/on different
chromosomes
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