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Biology > 12.3 Nucleic acids > Flashcards

12.3 Nucleic acids Flashcards

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1
Q

what does DNA stand for

A

deoxyribonucleic acid

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2
Q

what does RNA stand for

A

ribonucleic acid

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3
Q

DNA and RNA are…

A

important information carrying molecules

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4
Q

what does DNA do

A

holds genetic information

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5
Q

what does RNA do

A

transfers genetic info from DNA to the ribosomes

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6
Q

monomer in DNA

A

DNA nucleotide: a deoxyribose sugar, a phosphate group and a nitrogen containing base (adenine, cytosine, guanine or thymine)

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7
Q

monomer in RNA

A

RNA nucleotide: a ribose sugar, a phosphate group and a nitrogen containing base (adenine, cytosine, guanine or uracil)

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8
Q

polynucleotide formation

A

condensation reaction between 2 or more nucleotide monomers forming a phosphodiester bond

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9
Q

polynucleotide strands are formed when…

A

many nucleotides link to form a long chain

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10
Q

a phosphodiester bond forms between…

A

the phosphate group of 1 nucleotide to the 3rd C of the (D/R) sugar in the next nucleotide

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11
Q

what makes a nucleic acid very strong and stable

A

the sugar-phosphate backbone of the nucleic acid

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12
Q

structure of a DNA molecule

A

double helix

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13
Q

DNA consists of…

A

2 polynucleotide chains held together by many weak H bonds between specific complementary base pairings

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14
Q

how many H bonds are formed between Adenine and Thymine

A

2

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15
Q

how many H bonds are formed between Cytosine and Guanine

A

3

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16
Q

top of the chain

A

5’ to 3’

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17
Q

bottom of the chain

A

3’ to 5’

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18
Q

bonds in the backbone

A

phosphodiester

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19
Q

bonds that bring both the strands together

A

H bonds

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20
Q

How do you answer percentage questions DNA

A

If we are given the % of 1 base, we can use that to work out the % of the other complementary base. And then the % of the 2 other bases.

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21
Q

The sequence of the bases along the nucleotide chain is…

A

Variable (basis of the genetic code and how info is stored in DNA)

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22
Q

The function of DNA is that it…

A

Codes for the sequence of amino acids (3 bases = triplet = 1 amino acid).

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23
Q

Long strands of DNA code for…

A

The primary structure of polypeptide chains and proteins.

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24
Q

What is an mRNA molecule?

A

A relatively short polypeptide chain, which is normally a single stranded helix.

25
Q

What is mRNA used to do?

A

To transfer genetic information from DNA to ribosomes.

26
Q

Structure of DNA

A
27
Q

Structure of RNA

A

sugar phosphate backbone with bases

28
Q

DNA consists of…

A

2 antiparallel nucleotide strands

29
Q

To make sure the 2 strands remain parallel (the same distance apart)…

A

Adenine pairs with Thymine and Cytosine pairs with Guanine.

30
Q

What does it mean when we say the DNA is parallel?

A

The 2 strands of DNA run in opposite directions.

31
Q

What does the 5’ and 3’ indicate?

A

Which carbon is involved in the phosphodiester bond.

32
Q

If you follow the left hand chain up to the end at the top you would have…

A

A phosphate group attached to C5 on the deoxyribose sugar.

33
Q

If you follow it to the other end you would have…

A

An hydroxyl (OH) group attached to C3 on the received sugar

34
Q

On the complementary strand…

A

The top has a 3’ end and the bottom has a 5’ end.

35
Q

Why is it important that on the complementary end the top has a 3’ end and the bottom has a 5’ end?

A
  • when making proteins (It ensures that only 1 strand is read to make the protein)
  • in DNA replication as DNA polymerase only has a complementary AS to the 5’ end (or phosphate group) of the molecule
36
Q

structure of DNA: sugar-phosphate backbone and double helix structure whats the function

A

1 provides strength + stability
2 protects (info coded in) the bases
3 protects H bonding between bases

37
Q

structure of DNA: long/ large molecule whats the function

A

so stores a lot of info

38
Q

structure of DNA: helical / coiled structure whats the function

A

so compact

39
Q

structure of DNA: base sequence whats the function

A

allows info to be stored / codes for amino acids and therefore proteins

40
Q

structure of DNA: double stranded whats the function

A

so replication can occur semi-conservatively because each strand can act as a template

41
Q

structure of DNA: complementray base pairing A-T and C-G whats the function

A

allows accurate replication / identical copies are made (prevents mutations)

42
Q

structure of DNA: H bonds between bases are weak whats the function

A

allows for easy strand separation for semi-conservative replication

43
Q

structure of DNA: many weak H bonds whats the function

A

so DNA is a strong / stable molecule

44
Q

why does DNA replication occur

A

so that when new cells are created in the body they all have the exact same copy of DNA

45
Q

what method of DNA replication occurs

A

semi-conservative

46
Q

what does semi-conservative replication produce

A

a new molecule of DNA half the molecule is old and half of it is new

47
Q

what does semi-conservative DNA ensure

A

that genetic info stays the same between generations of cells

48
Q

function of DNA helicase

A

breaks the H bonds between the complementary base pairs so each strand can act as a template

49
Q

function of DNA polymerase

A

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

50
Q

process of semi-conservative replication

A

1 enzyme DNA helicase attches and moves along the DNA molecule unwinding the DNA and breaking the H bonds between complementary bases
2 the 2 strands separate
3 each strand acts as a template
4 new DNA nucleotides are attracted to exposed complementary bases on template strands by base pairing a-t + c-g
5 enzyme DNA polymerase joins adjacent nucleotides together through a condensation reaction forming phosphodiester bonds between new nucleotides and water in a 5’ to 3’ direction
6 semi-conservative replication ensures that each new DNA molecule contains an original and a new strand and is identical to the original DNA

51
Q

why was bacteria used in Meselson and Stahl’s experiment

A

bacteria was used as it replicated quickly (every 20 minutes)

52
Q

what were the names of the 3 theories of DNA replication

A
  • conservative
  • semi-conservative
  • dispersive
53
Q

conservative model

A

an entirely new molecule is synthesised from a DNA template (which remains unaltered)

54
Q

semi-conservative model

A

each new molecule consists of 1 newly synthesised strand and 1 template strand

55
Q

dispersive model

A

new molecules are made of segments of new and old DNA

56
Q

centrifugation meaning

A

separates mixtures according to its density

57
Q

Meselson stahl experiment

A

1 bacteria grown in 15N medium for many generations (original)
2 bacteria transferred to 14N, allowed to replicate once here for / for 1st gen. DNA extraction and centrifugation
3 bacteria allowed to replicate a 2nd time / for 2nd gen in 14N medium. DNA extraction and centrifugation
4 bacteria allowed to replicate a 3rd time / for 3rd gen in 14N medium. DNA extraction and centrifugation

58
Q

Meselson stahl experiment summary

A
  • bacteria with 15N containing DNA molecules allowed to replicate their DNA and divide by binary fission multiple times in 14N medium, the formed DNA
  • molecules being extracted, centrifugated, and their different masses separated between each round of replication to analyse the distributions of different mass DNA as a result of a particular model of replication.

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