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Biology > 3.1.5 - Nucleic acids are important information-carrying molecules > Flashcards

3.1.5 - Nucleic acids are important information-carrying molecules Flashcards

1
Q

what are DNA and RNA both types of?

A

nucleic acid

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2
Q

what does DNA stand for?

A

deoxyribonucleic acid

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3
Q

what is DNA used for?

A

to store your genetic information

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4
Q

what does RNA stand for?

A

ribonucleic acid

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5
Q

what is the RNA structure similar to?

A

similar in structure to DNA

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6
Q

RNA function

A

transfer genetic information from the DNA to the ribosomes.

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7
Q

RNA and ribosomes

A

ribosomes read the RNA to make polypeptides during translation

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8
Q

what are molecules of DNA and RNA polymers of?

A

molecules of DNA and RNA are polymers of nucleotides

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9
Q

what components make up a nucleotide?

A
  • pentose sugar (5 C atoms)
  • a nitrogen containing organic base
  • phosphate group
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10
Q

what forms when many nucleotides join together

A

many nucleotides join together to form polynucleotide strands (or chains)

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11
Q

how do the nucleotides join up to form a polynucleotide?

A

the nucleotides join up via a condensation reaction

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12
Q

condensation reaction forming polynucleotides

A

condensation reaction between the phosphate group of one nucleotide and the sugar of another

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13
Q

bond formed in condensation reactions to form polynucleotides

A

this forms a phosphodiester bond (phosphate group and 2 ester bonds). chain of phosphates and sugars is known as the sugar-phosphate backbone

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14
Q

DNA structure

A

double helix structure

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15
Q

what are the strands in the DNA double helix

A

polynucleotides

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16
Q

DNA’s structure and use

A

DNA molecules are very long/coiled up very tightly so lots of genetic information can fit into a small space in the cell nucleus

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17
Q

DNA nucleotide structure

A

a DNA nucleotide is made from a phosphate group, the pentose sugar deoxyribose and a nitrogen containing organic base

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18
Q

DNA nucleotide structure :
sugar/phosphate

A

each DNA nucleotide has the same sugar and phosphate

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19
Q

DNA nucleotide structure :
nitrogen containing organic base

A

the organic base can either be adenine (A), thymine (T), guanine (G) or cytosine (C)

20
Q

what do 2 DNA polynucleotide strands join together by

A

2 DNA polynucleotide strands join together by hydrogen bonds between the bases

21
Q

what is complementary base pairing

A

each base can only join with one particular other base = complementary base pairing

22
Q

what are the complementary base pairs in DNA?

A

adenine pairs with thymine
cytosine pairs with guanine

23
Q

what does complementary base pairs result in, in terms of amount of bases in DNA

A

there will always be equal amounts of adenine and thymine and equal amounts of cytosine and guanine

24
Q

how many hydrogen bonds form between the complementary bases pairs in DNA?

A
  • two hydrogen bonds form between adenine and thymine
  • three hydrogen bonds form between cytosine and guanine
25
Q

RNA structure

A

RNA is made of nucleotides that contain a sugar, a phosphate group and one of four different bases

26
Q

RNA structure
what do the nucleotides form

A

the nucleotides form a polynucleotide strand with a sugar-phosphate backbone

27
Q

RNA structure
what is the sugar in RNA nucleotides

A

the sugar in RNA nucleotides is a ribose sugar which is a pentose sugar

28
Q

RNA structure
bases

A

Uracil (U, a pyrimidine) replaces thymine as a base. Uracil always pairs with adenine in RNA

29
Q

RNA structure
polynucleotide strands

A

nucleotides form a single polynucleotide strand, not a double one

30
Q

RNA structure
RNA strand length

A

RNA strands are much shorter than most DNA polynucleotides

31
Q

why did scientists initially have doubts about DNA carrying the genetic code

A

DNA was 1st observed in the 1800s, lots of scientists then doubted it could carry the genetic code as it had a relatively simple chemical composition

32
Q

what did some scientists initially think carried genetic code

A

some scientists thought genetic information must be carried by proteins which are much more chemically varied

33
Q

when was it discovered that DNA was the carrier of the genetic code

A

by 1953, experiments had shown that DNA was the carrier of the genetic code

34
Q

when was DNA’s double helix structure discovered

A

in 1953, Watson and Crick discovered DNA’s double helix structure

35
Q

why does DNA replicate

A

DNA copies itself before cell division so that each new cell has the full amount of DNA

36
Q

what is the name for the DNA copying itself before cell division

A

it is called semi-conservative replication

37
Q

why is it called semi-conservative replication

A

as half of the strands in each new DNA molecule are from the original DNA molecule

38
Q

what does the semi-conservative replication of DNA ensure

A

means there’s genetic continuity between generations of cells

39
Q

what happens in the 1st stage of DNA replication?

A

enzyme DNA helicase breaks the hydrogen bonds between bases on the 2 polynucleotide DNA strands. this makes the helix unwind to form 2 single strands

40
Q

what happens in the 2nd stage of DNA replication?

A

each original strand acts as a template for a new strand. complementary base pairing means that free floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand - A with T, C with G

41
Q

what happens in the 3rd stage of DNA replication?

A

condensation reactions join the nucleotides of the new strand together, catalysed by the enzyme DNA polymerase. hydrogen bonds form between the bases on the original and new strands. each new DNA molecule contains 1 strand from the original DNA molecule and 1 new strand

42
Q

3’ (3 prime) and 5’ (5 prime) ends of DNA

A

each end of a DNA strand is slightly different in its structure, one end is called the 3’ end and the other is called the 5’ end

43
Q

the action of DNA polymerase

A

in DNA replication, DNA polymerase’s active site is only complementary to the 3’ end of the newly forming DNA strand, so the enzyme can only add nucleotides to the new strand at the 3’ end so the new strand is made in a 5’ to 3’ direction and the DNA polymerase moves down the template strand in a 3’ to 5’ direction

44
Q

DNA polymerase working on a double stranded DNA molecule

A

as the strands in the double helix are antiparallel, the DNA polymerase working on 1 of the template strands moves in the opposite direction to the DNA polymerase working on the other template strand

45
Q

who came up with the theory of semi-conservative DNA replication?

A

watson and crick

46
Q

what validated watson and crick’s theory of semi-conservative DNA replication?

A

Meselson and Stahl’s experiment a few years later validated their theory

Biology (12 decks)

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