Chapter 11 Mendelian Genetics I Genetics book

7/28/2019 Chapter 11 Mendelian Genetics I Genetics book

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Chapter 11Mendelian Genetics

Copyright 2010 Pearson Education Inc.


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Study of

Transmission how is a genetic trait inherited

Structure and function of genes process of

expressin a gene, mechanisms of mutations. Transmission genetics

Trait or character

Characteristics of an

individual Genotype

Phenotype

Visible

Invisible

Internal or

External


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1865 he reported

his studies on

Pisum sativum

Results notacknowledged

until late in the

19th century and

early in the 20thcentury


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Ease of growth

Bears flowers and fruit in the same year a

seed is planted

Produces a large number of seeds True-breeding or pure breeding

Contrasting traits


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Reciprocal crosses


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Principle of uniformity


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Alternative traits are determined by

particulate factors

Particulate factors are transmitted from

parents to offspring Particulate factors remain distinct after a

cross (they do not blend)

Genes

Alleles

distinct form of a gene They each specify a trait


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Particulate factors in true breeding are the

same whereas those in F1 are different

Homozygosity

HeterozygosityOne particulate factor masks the other

Dominance

S vs s


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Reginald Punnett


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All reciprocal


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Dominant or wild type alleles encode for a

normal product (protein)

Recessive alleles usually encodes for a

mutated gene which produces a partiallyfunctional or non-functional gene product


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The factors for different pairs of traits assort

independently of one another


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27:9:9:9:3:3:3:1


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Published his results in 1866

Botanists

Carl Correns maize and peas

Hugo de Vries

different plant species Erich von Tschermark peas

They set awareness about the laws of

inheritance and set forth research on gene

structure and function Zoologists

William Bateson fowl 1902


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Simple dominant trait


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Proband

affected individual throughwhom the pedigree is

discovered


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Result from loss-of-

function mutations

or modified function

of a gene product


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Most affected individuals have two normal

parents (heterozygotes)

Mating of two normal heterozygotes should

produce a 3:1 ratio (normal:recessive) The trait usually skips generations

Matings of two affected individuals bears

children with a 100% chance of expressing

the trait


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Result from gain-of-function mutations that result in

gene products with new functions

Gene FGFR3 fibroblast growth factor receptor

Individuals suffering the condition are heterozygotes


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Every affected person in the pedigree must

have at least one affected parent

The trait usually does not skip generations

On average a heterozygote will transmit themutant gene to half of his or her progeny

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Chapter 11 Mendelian Genetics I Genetics book