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nucleic acids Flashcards

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Biology 101 flashcards
1
Q

what are nucleic acids

A

organic compounds that include important macromolecules such as DNA

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2
Q

what does DNA contain

A

genetic material ( structural and functional role)

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3
Q

what is the thing that DNA is made of and thus this means it is…

A

its a polymer made up of NUCLEOTIDE MONOMERS thus its a POLYNUCLEOTIDE

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4
Q

what is a single nucleotide called

A

a mononucleotide

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5
Q

what are the 3 components that a nucleotide is made up of

A

-a phosphate group
-a pentose sugar (5 carbon sugar)
-a nitrogen containing organic base

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6
Q

DEFINITION: what is a nucleotide

A

A nucleotide is a molecule that is composed of a pentose sugar, a phosphate group and a nitrogen containing base. It is the monomer unit of nucleic acids.

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7
Q

In DNA what is the pentose sugar?

A

deoxyribose

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8
Q

In RNA what is the pentose sugar?

A

ribose

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9
Q

in DNA, what are the 4 organic bases?

A

Guanine
Adenine
Cytosine
Thymine

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10
Q

what are the two sectors organic bases can be classified as

A

Purine bases
Pyrimidine bases

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11
Q

what are Purine bases and examples

A

bases with two carbon rings (bigger)
G and A

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12
Q

what are Pyrimidine bases and examples

A

bases with one carbon base (smaller)
C and T

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13
Q

what forms when two mononucleotides join and what reaction allows this to occur

A

dinucleotide
-condensation reaction

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14
Q

where does the condensation reaction occur between mononucleotides, what bond does this create

A

between the hydroxyl group (-OH) on the phosphate group and pentose sugar, this creates a phosphodiester bond and forms a molecule of H2O

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15
Q

what does a series of condensation reactions form between multiple mononucleotides

A

a polynucleotide

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16
Q

DEFINITION: what is a polynucleotide

A

a polymer made up of many nucleotide monomers joined together by a series of condensation reactions

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17
Q

what breaks phosphodiester bonds

A

hydrolysis reaction ( addition of water needed)

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18
Q

describe the structure of DNA

A

double helix composed of 2 long polynucleotide chains.
The sides of the DNA double helicase are made from pentose sugar and phosphate groups forming a SUGAR-PHOSPHATE BACKBONE.(alternation of these units)
Two strands of DNA are held by hydrogen bonds between the bases.
The double helix of DNA= antiparallel- the strands of DNA run in opposite directions to each other

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19
Q

how many hydrogen bonds form between A and T

A

2

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20
Q

how many hydrogen bonds form between G and C

A

3

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21
Q

what will a larger purine always pair with?

A

a smaller pyrimidine

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22
Q

what dos it mean when DNA is stated as antiparallel

A

the two polynucleotide strands run in opposite directions
one of the strands run 5’ to 3’ while the other runs 3’ to 5’

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23
Q

how many polynucleotide strands does RNA consist of

A

1

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24
Q

what is the role of RNA

A

RNA acts as a messenger molecule- it helps transfer information from DNA to proteins
RNA also has roles in the regulation and synthesis of proteins

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25
Q

what are the nitrogen containing bases in RNA

A

adenine, guanine, cytosine and uracil

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26
Q

what type of base is uracil

A

pyrimidine base

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27
Q

outline the similarities and differences in RNA and DNA

A

RNA:
one strand
relatively short
ribose pentose sugar
G, A ,U, C
DNA:
two strands
very long
deoxyribose pentose sugar
G, A, T, C

28
Q

during what phase does DNA replication occur

A

interphase ( S phase)

29
Q

in eukaryotes, what is DNA stored in

A

long linear molecules called chromosomes

30
Q

in prokaryotes, what is DNA found as

A

in long circular loop of DNA and smaller circles (plasmids)

31
Q

what is DNA helicase

A

the enzyme that catalyses the breaking of hydrogen bonds between the complimentary organic bases in DNA

32
Q

What is DNA polymerase

A

the enzyme that catalyses the synthesis of DNA by joining adjacent nucleotides , using the single stranded DNA as a template

33
Q

DNA replication, describe the two strands in the replicated DNA

A

composed of one old strand and 1 new strand (semiconservative)

34
Q

what is semiconservative replication

A

the method in which DNA replicates, creating two molecules of DNA that consist of one og DNA strand and one newly synthesised strand

35
Q

what direction does DNA polymerase only move on new strands

A

5’ to 3’
-it works in both directions

36
Q

DNA replication: what is the leading strand

A

the strand that is synthesised continuously following the movement of the replication fork

37
Q

DNA replication: what is the lagging strand

A

the strand where the synthesis is discontinuous as DNA polymerase moves away from the fork, this is the lagging strand- areas are synthesised in short sections called okazaki fragments (fragments joined by the enzyme ligase)

38
Q

what could be an error with DNA replication, what does this lead to

A

sometimes the wrong base pairs up during DNA replication -this happens randomly and spontaneously
this results in a change in base sequence in the newly copied DNA which is known as a mutation

39
Q

functions of :
1-DNA polymerase
2-Ligase
3-Helicase

A

1-joins DNA back up hydrolysis and condensation) and catalysis of H-bonding
2-hydrolysis and condensation
3- unwinding DNA

40
Q

what are genes

A

genes are sections of DNA that code for polypeptides and functional RNA

41
Q

what is transcription? (simple)

A

transcription is the process of making messenger RNA from a DNA template

42
Q

what is translation? (simple)

A

RNA molecules translated into a specific amino acid sequence

43
Q

what is the genetic code?

A

The genetic code is the specific sequence of bases in DNA or RNA that codes for a sequence of amino acids during protein synthesis

44
Q

4 features of genetic code

A
  1. its read in triplet code
  2. it is a degenerate code
  3. its a non overlapping code
  4. its universal
45
Q

features of genetic code: degenerate def

A

an amino acid can be coded for by more than 1 group of bases

46
Q

codon definition

A

a sequence of 3 bases of RNA that codes for a specific amino acid

47
Q

how many codons are special and do not code for an amino acid

A

4 codons (1 start codon and 3 stop codons)

48
Q

whqat dos the start codon code for?

A

the amino acid methionine

49
Q

start codon sequence?

A

ATG

50
Q

stop codon sequences?

A

TAG TAA TGA

51
Q

How many combos does triplet code produce

A

64 combos

52
Q

degeneracy means that amino acids can be made by multiple codons, why is this an advantage to organisms

A

degeneracy means that different codons can code for the same amino acid. This could be protective against mutations as there is a chance a codon could undergo a mutation (base substitution) to become another coding for the same amino acid (silent mutation)

53
Q

describe the structure of mRNA

A

single stranded polynucleotide that coils into a single helix
mRNA length varies depending on the length of the gene transcribed

54
Q

which strand of DNA contains the codons that are used to code for amino acids

A

the sense strand ( runs 5’ to 3’)

55
Q

what strand of DNA acts as the template for transcription and what does this mean

A

the antisense strand so that the mRNA synthesised has the same sequence as the sense strand

56
Q

describe transcription (6)

A

-in order for transcription to occur, the DNA double
helix must first be unzipped and H bonds broken.
- a gene unwinds and unzips
-the enzyme that catalyses this is called DNA helicase which moves along the sugar-phosphate backbone, beginning at the start codon
-this exposes a section of both coding sense strand and the template antisense strand
-the DNA antisense strand then acts as a template for the mRNA as free RNA nucleotides pair with the exposed complimentary bases.
-the RNA nucleotides are then joined to adjacent nucleotides by phosphodiester bonds to form the mRNA strand ( this reaction is catalysed by the enzyme RNA polymerase which travels along the sugar phosphate backbone in the 3’ to 5’ direction.
-when the transcription ends, the mRNA strand detaches from the DNA, allowing the double helix to reform. The mRNA contains codons ( groups of 3)

57
Q

what does tRNA specify for

A

which amino acid is coded for by which specific triplet codon

58
Q

talk abt the structure of tRNA

A

-a very short RNA molecule
-single stranded: can form complimentary base pairs with itself, folds into clover leaf shape
-one end of tRNA molecule extends out providing site for attachment for amino acids
-the opposite side of the tRNA contains the anticodon that is complimentary to a specific codon.

59
Q

why can tRNAs with different anticodons bind to the same amino acid?

A

because code is degenerate

60
Q

what are ribosomes the site of

A

site of translation

61
Q

talk about structure of ribosomes

A

1 large subunit
1 small subunit
composed of 40% proteins and 60% RNA
-contains ribosomalRNA->(rRNA) (important for process of translation)

62
Q

what does the rRNA in the large subunit act as and what does it do

A

it acts as a catalyst ( its an enzyme=(ribozyme)) and it catalyses the formation of peptide bonds as polypeptides are formed

63
Q

describe the process of translation (6)

A

-the mRNA associates with a ribosome by binding to the small subunit at the start codon.
-the first tRNA molecule (carrying amino acid methionine) the binds to the start codon by H bonding, the tRNAs anticodon is complimentary to the mRNAS start codon.
-once the first tRNA has bound to the start codon, the large ribosomal subunit binds. The second tRNA binds which carries the specific amino acid coded for by the mRNA codon.
-the ribosome moves along the mRNA, it reads code
- a condensation reaction takes place, forming a peptide bond between the two amino acids, this then rereleases methionine from the first tRNA.
-The ribosome then moves forward 3 bases ( a codon) and the first tRNA is released.
-this process continues, extending the peptide by one amino acid each time, eventually a polypeptide is formed.
- Translations stop when the stop codon is reached, thsi codon has no complimentary tRNA. the subunits of the ribosome separate releasing the polypeptide.

64
Q

What are base triplets in mRNA called!!!

A

codons

65
Q

what is the sense strand

A

the sense strand is the coding strand which runs in a 5’ to 3’ direction

66
Q

what is the antisense strand

A

the antisense strand is the non-coding strand running in a 3’ to 5’ direction

67
Q

what are base triplets on DNA called!!!!

A

a triplet of bases

bio (29 decks)

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