DNA Flashcards

1
Q

Name the purines

A

Adenine & guanine

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2
Q

Name the pyrimidines

A

Thymine, cytosine & uracil

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3
Q

Name the bases

A

Adenine, Thymine, Uracil, Guanine & Cytosine

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4
Q

Name the nucleotides in DNA

A
deoxy ..... Monophosphate (d..MP)
adenosine dAMP
thymidine dTMP
guanosine dGMP
cytidine dCMP
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5
Q

Name the nucleotides in RNA

A
... Monophosphate (..MP)
adenosine AMP
cytidine CMP
guanosine GMP
uridine UMP
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6
Q

How do nucleotides linked together?

A

Phosphodiester bonds between C3 & C5

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7
Q

How are strands held together in DNA?

A

Hydrogen bonds between bases

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8
Q

How many hydrogen bonds form between the base pair C & G?

A

3 (higher melting point)

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9
Q

How many hydrogen bonds form between the base pair A & T/U?

A

2 (melt at lower temp)

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10
Q

What’s a nucleosome?

A

Histone protein with DNA wrapped around it twice

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11
Q

Where does the primer attach?

A

3’ (complementary base pairs, if polymerisation occurs from 5’to 3’ then the 5’ end of the new strand is complementary to the 3’ end of the template)

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12
Q

Which enzyme, that is part of DNA replication, assembles nucleotides?

A

DNA polymerase III

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13
Q

What joins okazaki fragments together?

A

DNA ligase

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14
Q

What does DNA polymerase I do?

A

Removes the RNA primer & replaces it using deoxynucleoside triphosphate

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15
Q

What does RNA primase I do?

A

Adds nucleoside triphosphates on the lagging strand to form an RNA primer

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16
Q

Which new strand of DNA is synthesised in the same

direction as the unzipping?

A

Leading strand - synthesised continually

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17
Q

What is a lagging strand?

A

A new strand of DNA that is synthesised in the opposite direction as the unzipping. It is made by joining the Okazaki fragments together.

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18
Q

What unwinds DNA at replication fork & how?

A

DNA helicase by breaking the H bonds between complementary base pairs

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19
Q

What is a primer?

A

3’ OH group

20
Q

What’s the length of an Okazaki fragment?

A

Short - 1000 base pairs long

21
Q

Why do chromosomes shorten as they replicate?

A

On lagging strand, upstream to the final 5’ there is no Okazaki fragment to act as a primer

22
Q

How do germ line cells, stem cells & cancer cells circumvent (find a way around) chromosome shortening during DNA replication?

A

They contain the enzyme telomerase that extends the ends of chromosomes

23
Q

Entire piece of DNA necessary for the production of a particular product e.g. protein/ RNA

A

Gene

24
Q

DNA strand with the same base sequence as RNA being synthesised - except T for U

A

Coding strand

25
Q

Enzyme that carries out transcription

A

RNA polymerase

26
Q

DNA sequence that signals the start of a gene/ binding site for RNA polymerase

A

Promotor

27
Q

DNA sequence that signals the end of a gene/ site where RNA polymerase dissociates from DNA

A

Terminator

28
Q

DNA sequence in eukaryotes that varies in position but boosts transcription of a nearby gene

A

Enhancer

29
Q

Intron

A

DNA sequence present in the gene but not in corresponding mRNA, removed from transcript by RNA splicing

30
Q

Exon

A

(E in exon for Express proteins)

DNA sequence present on gene & corresponding mRNA

31
Q

Codon

A

Triplet of nucleotides

32
Q

Degenerate

A

Some amino acids are coded for by multiple codons

e.g. GGC/ GGU/ GGA/ GGG = glycine

33
Q

Initiation codon

A

AUG (methionine)

34
Q

Termination codons

A

UGA
UAG
UAA

35
Q

Role of tRNA

A

Deliver a.a. to codons

36
Q

What is an aminoacyl tRNA/ charged tRNA?

A

tRNA attached to its a.a.

37
Q

How it an a.a. activated?

A

By attaching to a tRNA

38
Q

Function of Aminoacyl-tRNA synthetase

A

Links tRNA to a.a.

20 of these enzymes as 20 different a.a.

39
Q

organelle involved in translation

A

Ribosome

40
Q

What are ribosomes composed of?

A

50 % protein & 50% rRNA (ribosomal RNA catalyses peptide bond formation)

41
Q

3 ribosomal tRNA binding sites

A

A - aminoacyl
P - peptidyl
E - exit

Ribosome is made of large & small subunits, mRNA binds to the small

42
Q

Transcription

A

DNA -> RNA

43
Q

Reverse transcription

A

RNA -> DNA

44
Q

Translation

A

RNA -> Protein

45
Q

Difference between RNA & DNA polymerase

A

DNA polymerase cannot unwinds strands of duplex & used in DNA replication DNA
RNA polymerase can & used in transcription

46
Q

DNA replication is semi-conservative, what does this mean?

A

Parental template strand remains base paired to new daughter strand