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nucleic acids Flashcards

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Biology 101 flashcards
1
Q

what is the structure of DNA?

A

two polynucleotide strands in a double helix
made of nucleotide monomers

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2
Q

what is in a nucleotide from DNA?

A

phosphate group
organic nitrogenous base
deoxyribose sugar

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3
Q

what are the bases in DNA?

A

adenine
thymine
cytosine
guanine

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4
Q

what are the two base groups?

A

pyramidines
purines

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5
Q

what bases are in the pyramidines groups?

A

thymine
cytosine
uracil

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6
Q

what bases are in the purines group?

A

adenine
guanine

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7
Q

how many rings do bases in the pyramidines group have?

A

1 ring

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8
Q

how many rings do bases in the purines group have?

A

2 rings

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9
Q

how many bonds are between adenine and thymine?

A

2 bonds

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10
Q

how many bonds are between cytosine and guanine?

A

3 bonds

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11
Q

what is in a nucleotide from RNA?

A

phosphate group
ribose sugar
organic nitrogenous bases

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12
Q

what are the bases in RNA?

A

adenine
cytosine
guanine
uracil

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13
Q

what are the three types of RNA?

A

mRNA
rRNA
tRNA

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14
Q

what is mRNA (structure)?

A

copy of one strand of DNA
helix shape

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15
Q

what does mRNA do?

A

carries genetic code from DNA in nucleus to ribosomes during protein synthesis

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16
Q

what does rRNA do?

A

component of ribosomes

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17
Q

what is rRNA (structure)?

A

large complex molecule made from both single and double helices

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18
Q

what is tRNA (structure)?

A

single stranded molecule
forms a clover leaf shape

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19
Q

what does tRNA do?

A

brings amino acids to the ribosome so that proteins can be synthesised

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20
Q

what is the first stage of DNA replication?

A

enzyme DNA helicase unwinds double strand of DNA
breaks hydrogen bonds between bases
creates two template strands for new strands

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21
Q

what is the second stage of DNA replication?

A

free DNA nucleotides bind to template strands and form hydrogen bonds with their complementary bases by the enzyme DNA polymerase

22
Q

what is the third stage of DNA replication?

A

new DNA strands rewind to form a double helix
DNA ligase joins the two fragments of DNA together

23
Q

what type of replication is DNA replication?

A

semi-conservative

24
Q

what happens in the practical that shows evidence for DNA replication?

A

bacterium E.coli in cultured medium
15N incorporated into E.coli nucleotides
bacteria washed and transferred to medium containing 14N
bacteria divided once then twice

25
Q

what are the 3 control variables in the DNA replication pratical?

A

temp
volume of DNA
time

26
Q

what part of the DNA molecule contains 15N?

A

nitrogenous bases

27
Q

how do tubes 1 and 2 support semiconservative replication?

A

tube 1 is all heavy 15N isotope
tube 2 is a mixture of heavy 15N and light 14N isotope
DNA in tube 2 must be made from one strand of heavy and one strand of light DNA

28
Q

explain how the results in generation 0 and 1 support the theory of semi-conservation.

A

generation 0 band/peak is all heavy isotope
generation 1 band/peak is a mix of heavy and light isotope because each molecule retains one strand of heavy and one strand of newly formed light isotope

29
Q

explain the height of the peaks in the scans for generation 2 and 3.

A

only 14N isotopes are available for replication
generation 2 has equal peaks because one strand of heavy and one strand of light isotope have been used as templates for the formation of new DNA molecules
generation 3 has a higher peak of 14N because more light strands are used as templates

30
Q

what is conservative replication?

A

replication produces one helix made entirely of old DNA and one helix made of entirely new DNA

31
Q

what is dispersive replication?

A

results in two helices that are mixtures of parental (old) and daughter (new) DNA

32
Q

what is a gene?

A

sequence of nucleotide bases found in DNA that code for one or more polypeptide

33
Q

what are the 4 different nucleotide bases found in DNA?

A

adenine
thymine
cytosine
guanine

34
Q

what are the characteristics of the genetic code?

A

triplet code
degenerate/redundant code
3 triplet codes code for STOP
universal codons
non-overlapping

35
Q

what can a triplet code also be called?

A

a codon

36
Q

how is the genetic code a triplet code?

A

3 bases code for 1 amino acid
(4 cubed = 64)

37
Q

how is the genetic code a degenerate/redundant code?

A

all amino acids have more than 1 triplet code that can code for them
(except methionine)

38
Q

how does the genetic code code for STOP?

A

3 codons indicate stop

39
Q

how is the genetic code universal?

A

codons are the exact same for all living organisms

40
Q

how is the genetic code non-overlapping?

A

each triplet is read separately
each base occurs only once in one triplet

41
Q

what are the 3 stages of protein synthesis?

A

transcription
activation
translation

42
Q

what happens in the first stage of transcription?

A

DNA helicase breaks hydrogen bonds between complementary bases
a gene to be transcribed unwinds

43
Q

what happens in the second stage of transcription?

A

RNA polymerase binds to the template strand
RNA polymerase reads nucleotides and allows free RNA nucleotides to bind to their complementary bases
stops transcribing mRNA when it reaches stop codon

44
Q

what happens in the last stage of transcription?

A

mRNA has been synthesised
RNA polymerase detaches

45
Q

what happens to the mRNA after transcription in eukaryotes?

A

has to be processed before made into polypeptide

46
Q

what happens to pre-mRNA to make it into mRNA in eukaryotes?

A

has introns and exons
SPLICING occurs to removes introns so exons can join together
(by ligase)

47
Q

what is the first stage of translation?

A

mRNA transfers nucleotides through nuclear pores to cytoplasm
mRNA attaches to ribosome

48
Q

what is the second stage of translation (tRNA)?

A

amino acid is activated by ATP and attaches to specific tRNA molecule

49
Q

what is the third stage of translation (start codon)?

A

ribosome binds to start codon on mRNA
tRNA with complementary anticodon to first codon binds the the first attachment site on mRNA and releases amino acid
occurs a second time

50
Q

what is the fourth stage of translation (two amino acids now)?

A

peptide bond forms between two amino acids
continues until stop codon is reached

51
Q

what is post-transcriptional modification?

A

where protein can be further modified in order to become functional
e.g. to become a glycoprotein or lipoprotein

bio core concepts (10 decks)

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