Molecular Basis of Inheritance - Introduction to Biology - Lecture Slides, Slides for Biology. Allahabad University

Biology

Description: These are the lecture slides of Introduction to Biology. Key important points are: Molecular Basis of Inheritance, Hereditary Material, Griffith Experiment, Double Helix, Strand Complementarity, Antiparallel Strands, Meselson-Stahl Experiment, Semiconservative DNA Replication
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The Chromosomal Basis of Inheritance

Chapter 16: The Molecular

Basis of Inheritance

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Th e

H er

ed ita

ry M

at er

ia l  Chromosomes consist of both DNA and Protein

 DNA was discovered before its role in heredity was understood

 People had a sense that chromosomes embodied inheritance before they understood that DNA was the hereditary material

 People did not want to believe that DNA was the hereditary material since it is not complex enough

 Instead, people believed that proteins must be the hereditary material—they were wrong

 Transformation (I.e., Griffith’s experiment, which is mediated by DNA) was discovered before it was understood that it was mediated by DNA

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The Double Helix Strand

complementarity

Antiparallel strands

Strand polarity

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Meselson-Stahl Experiment (1957)

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Semiconservative DNA Replication

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Nucleotide Incorporation

3’ OH

Pyrophosphate hydrolysis

powers nucleotide addition

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La gg

in g

& L

ea di

ng S

tra nd

s

Both daughter

strands are laid down in the 5’ to 3’ direction

~100-2000 bases long, depending on species

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La gg

in g-

S tra

nd S

yn . (

1/ 2)

Solves DNA polymerase

requirement for 3’ OH

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Replication Fork Components

Yes, difficult to read, but it is in your text!

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DNA Replication Enzymes

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Proofreading “During DNA replication, DNA polymerases proofread each nucleotide against its template as soon as it is added to the

growing strand. Upon finding an incorrectly paired nucleotide, the polyerase removes the nucleotide and then resumes

synthesis. (This action is similar to fixing a typing error by using the ‘delete’ key and then entering the correct letter.)” p. 305,

Campbell & Reece (2005)

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A Solution: Telomeres

Telomere are sequences found

on the ends of Eukaryotic DNA that are added on by an

enzyme called telomerase

Telomeres erode so that genes don’t have to!

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