DNA & RNA Flashcards

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1
Q

Human genome contains approximately how many base pairs?

A

3 billion

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2
Q

How many amino acids are encoded by DNA?

A

20

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3
Q

Codon

A

A sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid or stop signal during protein synthesis

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4
Q

A nucleotide consists of:

A

A nitrogenous base + ribose/deoxyribose sugar + phosphate group

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5
Q

Main differences between DNA and RNA

A
  1. RNA is single stranded
  2. Uracil replaces thymine in RNA
  3. Ribose replaces deoxyribose as the sugar in RNA
  4. Various forms of RNA exist: tRNA, mRNA, rRNA
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6
Q

Where in the cell does transcription occur?

A

Within the nucleus in eukaryotic cells and in the cytoplasm of prokaryotic cells.

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7
Q

Where in the cell does translation take place?

A

In the cytoplasm in both prokaryotic and eukaryotic cells.

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8
Q

How many essential amino acids in humans?

A

9

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9
Q

How many proteinogenic amino acids exist in eukaryotes?

A

21 - 20 in the standard genetic code plus selenocysteine.

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10
Q

Of the 64 possible codon combinations, how many code for aa?

A

61, the other 3 codons are stop-signals.

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11
Q

What is the start codon?

A

The codon AUG codes for Methionine and signals start of sequencing.

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12
Q

In transcription, nucleotides are added to which end of the growing pre-mRNA molecule?

A

Nucleotides are added to the 3’ end. The growing pre-mRNA strand is being built in a 5’→ 3’ direction.

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13
Q

In transcription, the template DNA strand is being copied in which direction?

A

3’→5’

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14
Q

In transcription, what modifications is made to the 5’ end of the pre-mRNA molecule?

A

Addition of a 5’ cap composed of phosphates

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15
Q

In transcription, what modifications is made to the 3’ end of the pre-mRNA molecule?

A

Addition of a poly-A tail composed of recurring sequences of adenine residues

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16
Q

T or F: 5’ capping does not occur in mitochondrial and chloroplast DNA

A

True

17
Q

Eukaryotic 5’ cap structure

A

In eukaryotes, the 5’ cap consists of a guanine nucleotide connected to mRNA via 5’ to 5’ triphosphate linkage.

18
Q

The guanosine is methylated on a) ___ position directly after capping in vivo by b) ______.

A

a) 7’

b) methytransferase