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biology > nucleic acids > Flashcards

nucleic acids Flashcards

1
Q

what is DNA

A

-polymer made up of monomers called nucleotides

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2
Q

what does nucleotide consist of

A

-in the centre there’s a 5 carbon deoxyribose sugar
-attached to the sugar there’s is a nitrogenous base at C1
-on the other side of the sugar is attached to a negatively charged phosphate group at C4

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3
Q

which elements do nucleotides consist of

A

carbon
hydrogen
oxygen
nitrogen
phosphorus

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4
Q

what does a sugar and phosphate group make up

A

sugar phosphate backbone

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5
Q

compare DNA and RNA

A

DNA
-pentose sugar is called deoxyribose
-this has 1 less oxygen atom (bc of 1 less hydroxide group)

RNA
-pentose sugar is called ribose sugar

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6
Q

what are the bases found in DNA

A

Adenine
Thymine
Guanine
Cytosine

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7
Q

what are DNA and RNA

A

important information carrying molecules

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8
Q

what are the bases found in DNA

A

Adenine -Thymine
Guanine-Cytosine

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9
Q

what are purines

A

bases that have a double ring structure
Adenine and Guanine

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10
Q

what are pyrimidines

A

single ring structures like thymine and Cytosine

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11
Q

how does DNA codes affect the function of a protein

A

DNA codes for the sequence of amino acids on the primary structure of protein which determines the final 3D structure and function of protein

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12
Q

what are the bases found in RNA

A

Adenine-Uracil
Guanine-Cytosine

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13
Q

where is the phosphodiester bond formed

A

between the phosphate group of one nucleotide and the hydroxyl group of the pentose sugar of other nucleotide

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14
Q

what happens when a phosphodiester bond forms

A

water is released

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15
Q

how is dna formed

A

by forming a polymer of nucleotides called a polynucleotide

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16
Q

describe the structure of DNA

A

-it consists of 2 polynucleotide strands

-bases on one strand are complimentary to the other

-purines on one strand always pairs with pyrimidine on opposite strand

-2 strands are anti paralel

-3 bases code for one amino acid (triplet code)

17
Q

describe an mRNA molecule

A

-short polynucleotide chain
-usually single stranded
-mRNA used to transfer genetic information from DNA to ribosomes

18
Q

what ensures that the 2 strands remain same distance apart

A

-adenine pairs with thymine
-guanine pairs with cytosine

19
Q

why are the 2 strands in DNA antiparallel

A

because they run in opposite directions

20
Q

What is the function of a sugar phosphate backbone and double helix structure

A
  • provides strength and stability
    -protects information coded in bases
    -protects hydrogen bonding between bases
21
Q

what is the function of DNA being a large molecule

A
  • stores a lot of information
22
Q

what is the function of the base sequence in DNA

A

allows information to be stored and codes for amino acids therefore codes for proteins

23
Q

what is the function of dna being double stranded

A

so that replication can occur semi conservatively because each strand acts as a template

24
Q

what is the function of complementary base pairing

A

allows accurate replication, so identical copies are made (prevents mutations)

25
Q

what is the function of hydrogen bonding between bases being weak

A

allows for easy strand separation for semi-conservative replication

26
Q

what is the function of there being many weak hydrogen bonds in DNA

A

SO DNA is a Strong / stable molecule

27
Q

what does semi conservative replication ensure

A

Semi-conservative replication ensures that each new DNA molecule contains an original and a new strand and is identical to the original DNA.

28
Q

Function of DNA polymerase

A

catalyses the condensation reactions between DNA nucleotides to form the
sugar-phosphate backbone of the new strand.

29
Q

Function of DNA helicase

A

breaks the hydrogen bonds between complimentary base pairs so each strand can act
as a template.

30
Q

how does semi conservative replication occur

A

The enzyme DNA Helicase attaches and unwinds the DNA and breaking hydrogen bonds

The two strands separate.

Each strand acts as a template.

New DNA nucleotides attracted to bases that are complementary

U-A G-C

The enzyme DNA polymerase joins the adjacent nucleotides together in a 5’ to 3’ direction.

31
Q

why does DNA polymerase only act in a 5’ to 3’ direction.

A

DNA polymerase has a specific active site, only complementary to the 5’ end of the incoming free DNA nucleotide and the 3’ end of the developing strand.

32
Q

what where the other 2 theories for the replication of DNA

A

Dispersive Model – New molecules are made of segments of new and old DNA.

Conservative Model – An entirely new molecule is synthesized from a DNA template (which remains unaltered).

33
Q

who designed an experiment to determine the correct theories for DNA replication

A

Meselson and Stahl

34
Q

describe the Meselson and Stahl experiment

A

They began by growing E. coli in medium, containing a “heavy” isotope of nitrogen.
Then the DNA strands will be spun in a centrifuge to confirm density, N15 will form a band near the bottom. This generation will be 100% N15 containing
Bacteria is grown in medium with N14 and 100% DNA is N14 and N15

biology (17 decks)

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