Module 2 - Nucleotides and nucleic acids Flashcards

1
Q

Give two examples of nucleic acids

A

RNA and DNA

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2
Q

What three components make up a nucleotide?

A
  • a phosphate group
  • a pentose sugar
  • an organic base
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3
Q

What purines are found in DNA and RNA?

A

adenine and guanine

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4
Q

What pyrimidines are found in DNA?

A

cytosine and thymine

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5
Q

What pyrimidines are found in RNA?

A

cytosine and uracil

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6
Q

What is the difference between purines and pyrimidines?

A

purines are two carbon rings whilst pyrimidines are one carbon ring

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7
Q

What type of nucleotides are RNA and DNA?

A

polynucleotide

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8
Q

What is the structure of RNA?

A
  • single-stranded and short
  • sugar involved is ribose
  • base is ACGU
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9
Q

What are the three types of RNA?

A
  • messenger RNA - mRNA
  • tranfser RNA - tRNA
  • ribosomal RNA - rRNA
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10
Q

What is mRNA?

A
  • carries the code held in the genes to the ribosomes where the code is used to make proteins
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11
Q

What is tRNA?

A
  • transports amino acids to the ribosomes
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12
Q

What is rRNA?

A
  • makes up the ribosome
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13
Q

What does C bond to in DNA, what type of bond, and how many bonds?

A

Guanine, 3 hydrogen bonds

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14
Q

What does A bond to in DNA, what type of bond, and how many?

A

Thymine, 2 hydrogen bonds

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15
Q

Describe the structure of the DNA strands

A
  • antiparallel meaning they lie in opposite directions
  • the two strands combine and twist to make a double helix
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16
Q

Explain how the nucleotides in a DNA molecule are arranged as two polynucleotide strands.

A
  • adjacent nucleotides binding together via a condensation reaction to form phosphodiester bonds
  • this creates a sugar-phosphate backbone between the sugar of one molecule and the phosphate group of another
  • hydrogen bonds are between complementary base pairings.
  • polynucleotides are antiparallel
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17
Q

What are ATP and ADP?

A
  • phosphorylated nucleotides
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18
Q

What do ATP and ADP contain?

A
  • pentose sugar
  • nitrogenous base
  • two or three inorganic phosphates
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19
Q

How is ATP produced?

A
  • ADP is phosphorylated to form ATP
  • it is made during respiration from ADP through the addition of a phosphate inorganic ion and ADP synthase
20
Q

What are the properties of ATP?

A
  • small - moves easily in and out of the cells
  • soluble - most processes happen in aqueous environments
  • intermediate amounts of energy released - enough but not too much to be wasted as thermal energy
  • easily regenerated - renewable energy source
21
Q

What is complimentary base pairing?

A
  • base A pairs with T through 2 hydrogen bonds
  • base C pairs with G through 3 hydrogen bonds
22
Q

What does semi-conservative replication mean?

A
  • half of the original molecule is conserved in each of the new molecules
23
Q

Explain semi-conservative replication.

A
  • DNA unwinds its double helix through the enzyme DNA gyrase
  • DNA helicase breaks the hydrogen bonds between the CBP
  • both original strands of DNA act as a template for free-floating DNA nucleotides (within nucleus) to CBP with the bases on the template strands
  • DNA polymerase catalyses the formation of the sugar-phosphate backbone by catalysing the formation of phosphodiester bonds formed in condensation reactions between adjacent nucleotides.
24
Q

Why is the precise replication of DNA essential?

A
  • to ensure that identical copies of the gene are included in every cell of the body
25
Q

How does DNA fit inside the nucleus?

A
  • it wraps around histone proteins as DNA is negatively charged due to phosphate groups and histone is positively charged
  • these form a structure called nucleosomes
  • these form long chains of chromatins which are wound up to produce a single chromosome
26
Q

What is the genetic code?

A
  • the order of bases on DNA
27
Q

What is an allele?

A
  • a version of a gene
28
Q

What is every three bases on a gene known as?

A
  • a codon
29
Q

What is a gene?

A
  • a sequence of codons that code for a specific protein
30
Q

What are the three features of codons?

A
  • non-overlapping
  • degenerate
  • universal
31
Q

What does non-overlapping mean?

A
  • each codon only codes for its specific amino acid
32
Q

What does degenerate mean?

A
  • more than one triplet can code for a particular amino acid
33
Q

What does universal mean?

A
  • there are the same 64 codons in every organism
34
Q

What are the coding sequences in DNA?

A
  • regions of the DNA that code for a particular protein
35
Q

What are the non-coding sequences in DNA?

A

-regions of the DNA that do not code for anything

36
Q

What is discontinuous replication?

A
  • DNA polymerase can only synthesize the sugar-phosphate backbone in the 5’ - 3’ direction
  • due to the strands being antiparallel, only one strand will be synthesized as it is in this orientation
  • this is called the leading template and is synthesized continuously
  • the lagging template will have to be synthesized discontinuously
  • DNA polymerase synthesised short fragments of the strand called Okazaki fragments
  • these are then joined together by DNA ligase
37
Q

Why is DNA replication important?

A
  • cell division for growth and repair
  • produces replicated DNA for cell division
38
Q

How does the DNA molecule unwind?

A
  • DNA Helicase travels along the DNA backbone, catalysing reactions that break the hydrogen bonds between complementary base pairs as it reaches them
39
Q

What is transcription of a gene?

A
  • the DNA sequence in a gene is transcribed onto mRNA
40
Q

Where does transcription occur?

A
  • in the nucleus
41
Q

Why is gene transcription used in eukaryotes?

A
  • because the full chromosomal DNA molecules is too large to leave the nucleus via a nuclear pore.
42
Q

Explain the process of gene transcription

A
  • RNA polymerase attaches to DNA
  • DNA uncoils, breaking hydrogen bonds between CBP
  • one of these strands is used as a template to make mRNA
  • RNA polymerase then lines up free RNA nucleotides along the template strand and they undergo CBP
  • this means the mRNA strand is a copy of the DNA template strand
  • once they have paired up, adjacent nucleotides are joined together by RNA polymerase, catalyzing the formation of phosphodiester bonds and forming a mRNA strand
  • RNA polymerase then moves down the DNA strand
  • hydrogen bonds between uncoiled strands of DNA reform once RNA polymerase passes and the strands coil back to a double helix
  • once RNA polymerase reaches a stop codon, it detaches from the DNA
    -mRNA moves out through a nuclear pore then attaches to a ribosome
43
Q

Explain the process of protein translation

A
  • mRNA attaches to a ribosome and tRNA carries amino acids to the ribosome
  • tRNA attaches to a mRNA strand through CBP as it contains anticodons complimentary to mRNA codons
  • a second tRNA molecule attaches itself to mRNA in the same way
  • rRNA catalyses the formation of a peptide bond between the two amino acids attached to the tRNA molecules
  • this joins the amino acids together
  • 1st tRNA molecule moves away, leaving its amino acid behind.
  • 3rd molecule binds to the next codon, binding its amino acid to the 2nd tRNA
  • this cycle repeats until a stop codon is reached on the mRNA molecule
  • a polypeptide chain is produced and it moves away from the ribosome
44
Q

What is the first stage of protein synthesis and what does it include?

A
  • transcription and it involves the production of a mRNA strand
45
Q

What is included in protein synthesis?

A
  • transcription and translation of genes
46
Q

What is the second stage of protein synthesis and what does it include?

A
  • translation and it involves the production of a polypeptide chain by joining amino acids by ribosomes based on the order of codons in mRNA
47
Q

What direction does DNA polymerase only synthesize?

A
  • from the 3’ end to the 5’ end of the DNA strand