Unit 1: Nucleic Acids Flashcards

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1
Q

what is a nucleic acid made up of?

A

nucleotides

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2
Q

what are the differences between DNA and RNA

A

DNA - double stranded, deoxyribose sugar, bases A,T,C,G

RNA - single stranded, ribose sugar, bases A,U,C,G

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3
Q

Why are hydrogen bonds important in base pairing?

A

A hydrogen bond is weak, this means that its relatively easy for these bonds to be formed and broken. This is very important if information is to be copied from a sequence of bases as in during DNA replication

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4
Q

what is a nucleotide made up of?

A

nitrogen containing ring (base)
five carbon sugar (pentose)
phosphate

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5
Q

what is attached to C1 in a nucleotide?

A

base

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6
Q

what is attached to C2 in a nucleotide?

A

Hydrogen or Hydroxyl group

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7
Q

what is attached to C3 in a nucleotide?

A

hydroxyl group

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8
Q

what is attached to C5 in a nucleotide?

A

phosphate

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9
Q

what are the two main types of bases called?

A

purines and pyrimidines

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10
Q

what is a purine?

A

base that has a double ring structure - adenine and guanine

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11
Q

what is a pyrimidine?

A

base that has a single ring structure - cytosine and thymine/uracil

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12
Q

what is the trick to remember Purine and Pyrimidine?

A

Pure Agony

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13
Q

what bond holds complementary base pairs together?

A

weak hydrogen bonds

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14
Q

For the hydrogen bond to be stable, what must each base be?

A

the base pair must consist of one purine and one pyrimidine

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15
Q

how are nucleotides joined together?

A

by condensation reaction between phosphate of one nucleotide and the hydroxyl group on the sugar of the next nucleotide. link by 5’ to 3’

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16
Q

what is the bond between nucleotides called?

A

phosphodiester bond

17
Q

are the double strands in DNA, parallel or antiparallel?

A

antiparallel

18
Q

what is polymerase?

A

an enzyme capable of adding nucleotides to a DNA strand during replication or an RNA strand during transcription

19
Q

what is ligase?

A

an enzyme that catalyses the formation of phosphodiester bonds to join nucleotides together.

20
Q

what is the purpose of copying DNA?

A

for DNA replication during the S phase of the cell cycle

for transcription of DNA and RNA during protein synthesis

21
Q

what is the difference between replication and transcription?

A

new strand of nucleic acid can only happen in 5’ to 3’ direction because of the polymerase enzyme, so can only add on 3’
RNA - one strand
DNA - double strand so 5’ to 3’ and 3’ to 5’ need to be replicated

22
Q

what are the requirements for DNA replication?

A

DNA template
enzymes
four types of nucleotide
ATP

23
Q

DNA polymerase and RNA polymerase can only build in a what direction?

A

5’ to 3’

24
Q

What are the steps in DNA replication?

A
  1. Enzymes open up a replication fork in the DNA double helix
  2. the leading strand is synthesised complete in the 5’ to 3’ direction
  3. replication starts with a short RNA primer, this is replaced with DNA later
  4. DNA polymerase adds a new nucleotide to the 3’ end of the primer and so starts to build the new DNA chain
  5. DNA polymerase matches free DNA nucleotides to their complementary bases on the template strand of DNA and then catalyses the formation of the phosphodiester bond between the end of the growing strand and the nucleotides
  6. The phosphodiester bond is formed when the OH of the 5’ phosphate and the OH of the 3’ deoxyribose are involved in a condensation reaction
  7. The other strand is called a lagging strand and is made in short 5’ to 3’ fragments (okazaki fragments)
  8. as on the leading strand, the RNA primers are made first and DNA polymerase adds nucleotides to the 3’ end.
  9. After the RNA primer has been replaced with DNA, DNA ligase links to 5’ to 3’ fragments of the lagging strand together and catalyses the formation of phosphodiester bonds between the nucleotides at the end of the fragments.
25
Q

what bond is between a phosphate and a sugar in a nucleotide?

A

phosphoester bond

26
Q

what is the difference between an Ribose and a Deoxyribose sugar?

A

RNA has an OH on carbon 2 whereas DNA has an H on carbon 2

27
Q

How many hydrogen bonds are there between cytosine and guanine?

A

3

28
Q

How many hydrogen bonds are there between adenine and thymine?

A

2