DNA structure and replication Flashcards by Jonathan Biss

DNA structure and replication

Griffith’s experiment

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DNA structure and replication

What bacteria was Griffith working with?

Streptococcus pneumoniae

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DNA structure and replication

Who used purification methods to reveal that DNA is the genetic material?

Avery, Macleod and McCarty

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DNA structure and replication

Avery, MacLeod and McCarty’s experiment

Built on the work of Griffith

Added DNase, RNase and proteases to the collonies of type R bacteria with purified type S DNA

RNase and protease had no effect on transformation

When DNase applied no transformation occured

DNA was proven to be the genetic material

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DNA structure and replication

Why did Avery, MacLeod and McCarty need to carry out their test?

The purified DNA from type S could still contain peices of RNA and protein that could be causing the transformation rather than the DNA

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DNA structure and replication

Hershey and Chase

Studied T2 virus infecting Escherichia

Put them in a blender to seperate the virus coat from the bacteria

Used radioactive labels on proteins and DNA

Found that it was DNA that was injected into bacteria and not protein

Supported DNA as the genetic material

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DNA structure and replication

Radioactive labels Hershey and Chase used and what they labeled

³⁵S labelled proteins

³²P labelled DNA

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DNA structure and replication

What year was Hershey and Chase’s experiment?

1952

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DNA structure and replication

Bacteriophage

Virus that infects bacterial cells

Made of protein and DNA

Injects it’s DNA into the bacteria

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DNA structure and replication

Genome

The complete complement of an organisms genetic material

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DNA structure and replication

3 components of nucleotides?

Phosphate group

Pentose sugar

Nitrogenous base

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DNA structure and replication

What pentose sugar is used in DNA?

Deoxyribose

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DNA structure and replication

What bases are found in DNA?

Adenine

Guanine

Thymine

Cytosine

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DNA structure and replication

2 types of nitrogenous base

Purines

Pyrimidines

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DNA structure and replication

Which nitrogenous bases are Purines?

Adenine

Guanine

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DNA structure and replication

Which nitrogenous bases are Pyrimidines?

Cytosine

Thymine (DNA)

Uracil (RNA)

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DNA structure and replication

Way of remembering which base is a purine and which is a pyrimidine in DNA

Pyrimidines have y’s in their name

Thymine

Cytosine

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DNA structure and replication

What is the difference between deoxyribose and ribose?

Ribose has a OH instead of a H on 2’ carbon

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DNA structure and replication

Differences in bases between DNA and RNA

Uracil replaces Thymine

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DNA structure and replication

Which part of the deoxyribose does the base attach to?

Which part of the deoxyribose does the phosphate attache to?

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DNA structure and replication

Which part of the nucleotides form the backbone of DNA?

Phosphates

Pentose sugars

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DNA structure and replication

What projects from the DNA backbone

The bases

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DNA structure and replication

Which direction does DNA go?

5’ to 3’

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DNA structure and replication

Who proposed the double helix structure of DNA?

Watson and Crick with Wilkins

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# DNA structure and replication Erwin Chargoff

Analysed the base composition of DNA Discovered the specific pairing of base pairs

# DNA structure and replication Rosalind Franklin

Used X-ray diffraction Findings were crucial to Watson and Crick

# DNA structure and replication What keeps the two strands of DNA held together?

Hydrogen bonds between the base pairs

# DNA structure and replication Even though hydrogen bonds are quite weak, how does it keep the DNA strands together?

Lots of them so creates a lot of strength together

# DNA structure and replication Which base pairs pair with which other base pair in DNA?

A - T C - G

# DNA structure and replication How many base pairs are there per turn of the helix?

# DNA structure and replication DNA is antiparralel, what does this mean?

One strand runs 5' to 3' The other runs 3' to 5'

# DNA structure and replication Is DNA uniform in it's helix shape?

# DNA structure and replication What were the proposed models of DNA replication in the 1950's?

Semi-conservative Conservative Dispersive

# DNA structure and replication Semi-conservative model of replication

# DNA structure and replication Conservative model of DNA replication

# DNA structure and replication Dispersive model of DNA replication

# DNA structure and replication Meselson and Stahl experiment

Grew *E.coli* in medium with only ¹⁵N Then switched to a medium with only ¹⁴N Collected smaple after each generation

# DNA structure and replication Meselson and Stahl Results

Parental generation formed a heavy band Strands of generation after parental formed a band that was half-heavy Generation after that formed a hald-heavy band and a light band

# DNA structure and replication Meselson and Stahl interpretation of results

As there were still a half-heavy band after a few generations DNA replication must produce a parental strand and a new strand Supports semi-conservative model

# DNA structure and replication Why did Meleson and Stahl's research not support the conservative theory?

If the theory was correct then there would be a heavy band and a light band after the first round of DNA replication

# DNA structure and replication Why does Meleson and Stahl's research not support the dispersive theory of DNA replication

There wouldn't be too bands There would be a increasingly lighter band as the daughter cells would each recieve half the ¹⁵N DNA the parental cell had

# DNA structure and replication How many origins of replication do eukaryots have?

Multiple

# DNA structure and replication Which way does DNA replicate?

From the 5' end to the 3' end (from the point of view of the new strand)

# DNA structure and replication What are the building blocks of DNA?

Nucleotides

# DNA structure and replication What is the opening the origin of replication creates called?

Replication bubble

# DNA structure and replication Which is the leading strand in DNA replication?

The strand that runs 5' to 3' in the direction the direction the replication fork is moving

# DNA structure and replication Which is the lagging strand in DNA replication?

The strand that runs 3' to 5' in the direction the replication fork is moving As if it's going the wrong way

# DNA structure and replication How is the lagging strand produced in DNA replication?

Okazaki fragments are created and then later connected to each other

# DNA structure and replication DNA helicase

Binds to DNA and travels 5' to 3' Uses ATP to seperate the strands and move the replication fork forward

# DNA structure and replication DNA topoisomerase

Relives additional coiling ahead of the repliaction fork

# DNA structure and replication What keeps the parental strands open to act as templates?

Single-strand binding proteins

# DNA structure and replication DNA polymerase III

Covalently links nucleotides together

# DNA structure and replication What seperates the strands of DNA during DNA replication?

DNA helicase

# DNA structure and replication Deoxynucleoside triphsophates

Free nucleotides with 3 phosphate groups

# DNA structure and replication What provides the energy to connect adjacent nucleotides?

Breaking the covelant bond to release pyrophosphate (2 phosphate groups) from the deoxynucleoside triphosphates

# DNA structure and replication Why can DNA only be synthesised in the 5' to 3' direction?

DNA polymerase III can only work in the 5' to 3' direction of the new strand

# DNA structure and replication Why is DNA replication very accurate?

1. Hydrogen bonding between complementary base pairs is more stable than mismatched base pairs 2. The active site of DNA polymerase if unlikely to form bonds if nucleotides pairs are mismatched 3. DNA ploymerase removes mismatched pairs

# DNA structure and replication DNA ligase

Links together gaps between nucleotides

# DNA structure and replication Where are telomeres found?

At the end of DNA strands

# DNA structure and replication Role of telomerase

Attaches many copies of repeated DNA sequences to the ends of the chromosomes This provides and upstream site for the DNA primer

# DNA structure and replication If it wasn't for telomerase what would happen?

Our chromosomes would shorten every time our DNA replicated

# DNA structure and replication What is required for DNA sysnthesis to begin on a template strand

A RNA primers needs to be placed

# DNA structure and replication What makes the RNA primer?

DNA primase

# DNA structure and replication 3' overhang

Telomere at 3' end does't have a complimentary strand

# DNA structure and replication Senescent cells

Cells that have lost the ability to divide Stuck in G1

# DNA structure and replication How many times will an infant's cell double?

About 80 times

# DNA structure and replication How many times can an older person's cells double?

10-20 times

# DNA structure and replication Why do older people's cells multiply less than infants?

Their telomeres are shorter This is because the function of telomerase decreases with age

# DNA structure and replication If the decreasing function of telomerase is at fault for cells aging and being able to multiple less and less, why not insert more into our bodies?

Leads to uncontrollable cell division - cancer 90% of cancers involve high levels of telomerase

DNA structure and replication Flashcards

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