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Biology > Nucleotides and nucleic acids > Flashcards

Nucleotides and nucleic acids Flashcards

1
Q

Describe the structure of a nucleotide?

A
  • phosphate group
  • pentose sugar
  • ribose base
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2
Q

Name the pentose sugars in DNA and RNA?

A

DNA = deoxyribose
RNA = ribose

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3
Q

What is the difference between ribose and deoxyribose?

A

Ribose has a hydroxyl (OH) group at position 2 whereas deoxyribose has a hydrogen atom (H) there

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4
Q

How are polynucleotide strands formed and broken down?

A
  • formed through condensation reactions between nucleotides form strong phosphodiester bonds (sugar-phosphate backbone)
  • broken down by hydrolysis reactions using a molecule of water
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5
Q

Describe the structure of DNA?

A
  • 2 deoxyribose polynucleic strands arranged in a double helix with 2 sugar-phosphate backbones
  • H bonds form between complementary base pairings on the strands (AT,GC)
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6
Q

Name the purine bases and describe there structure?

A
  • adenine and guanine
  • 2 ring structures
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7
Q

Name the pyrimidine bases and describe there structure?

A
  • thymine, cytosine and uracil
  • 1 ring structures
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8
Q

Name the complementary base pairs in DNA and RNA and describe there hydrogen bonding?

A

DNA - 2 H bonds between adenine and thymine
RNA - 2 hydrogen bonds between adenine and uracil
Both - 3 hydrogen bonds between guanine and cytosine

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9
Q

Why is DNA replication semi conservative?

A
  • strands from original DNA molecule act as a template
  • new DNA molecules contain 1 old strand and one new strand
  • specific base pairing enables genetic material to be conserved accurately
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10
Q

Explain the role of DNA helicase in semiconservative DNA replication?

A

Breaks H bonds between complementary base pairs to form 2 single strands which can act as templates

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11
Q

How is a new strand formed by semiconservative DNA replication?

A
  • free nucleotides attach to exposed bases by complementary base pairing
  • DNA polymerase joins adjacent nucleotides on new strands in a 5’ to 3’ direction via condensation reactions to form phosphodiester bonds
  • H bonds reform
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12
Q

Identify the features of the genetic code?

A
  • non-overlapping (each triplet is only read once)
  • degenerate (more than one triplet codes for the same amino acids)
  • universal (same bases and sequences used by all species)
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13
Q

How does a gene determine the sequence of amino acids in a protein?

A

consists of base triplets that code for a specific amino acid

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13
Q

What does transcription produce and where does it occur?

A
  • produces mRNA
  • occurs in the nucleus
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13
Q

Outline the process of DNA transcription?

A
  • RNA polymerase binds to promoter region on a gene
  • section of DNA uncoils into 2 strands with exposed bases, antisense strand acts as a template
  • free nucleotides are attracted to their complementary bases
  • RNA polymerase joins adjacent nucleotides to form phosphodiester bonds
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13
Q

What’s the difference between the sense and antisense strand?

A

Sense strand = provides the code to make a protein when read in the right direction

Antisense strand = non-coding strand that serves as a template for RNA synthesis

14
Q

What happens after a strand of mRNA is transcribed?

A
  • RNA polymerase detaches at a terminator region
  • H bonds reform and DNA rewinds
  • splicing removes introns from pre-mRNA in eukaryotic cells
  • mRNA moves out of the nucleus via nuclear pores and attaches to ribosomes
15
Q

What are introns and exons?

A

introns = intervening non-coding regions of a gene

exons = coding regions of a gene

16
Q

What does translation produce and where does it occur?

A
  • produces proteins
  • occurs in cytoplasm on ribosomes (made of protein and rRNA)
17
Q

Outline the process of translation?

A
  • ribosomes move along the mRNA until “start” codon
  • tRNA anticodons attach to complementary bases on mRNA
  • condensation reactions between amino acids on tRNA form peptide bonds (requiring energy from ATP hydrolysis)
  • process continues to form polypeptide chains until “stop” codon is reached
18
Q

What is mRNA?

A

mRNA = (messenger RNA) is a single strand of RNA made from a DNA template that carries a genetic sequence to the ribosomes that read by a ribosome in the process of synthesizing a protein

19
Q

What is tRNA?

A

tRNA = (transfer RNA) is a small RNA molecule that helps decode a mRNA sequence into a protein

20
Q

What is rRNA?

A

rRNA = (ribosomal RNA) is a part of the ribosome that reads the order of amino acids and builds proteins through protein synthesis

21
Q

Describe the structure of ATP and ADP?

A

Both = nucleotide derivatives of adenine
ATP = has three inorganic phosphate groups
ADP = has 2 inorganic phosphate groups

22
Q

What is a mutation?

A

An alteration to the DNA base sequence often arising spontaneously during DNA replication

Biology (22 decks)

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