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biology > Nucleic Acids > Flashcards

Nucleic Acids Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

2 examples of nucleic acids

A

DNA

RNA

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2
Q

Monomer and polymer

A 
Monomer = nucleotide 
Polymer = nucleic acids / polynucleotides
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3
Q

Components of nucleotides

A

Phosphate group
Nitrogenous bases (organic)
Pentose sugar

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4
Q

DNA and RNA structure

A 
DNA
Deoxyribose (pentose sugar)
Bases = G , C , A , T
Phosphate group
2 polynucleotide strands (double helix)
RNA
Ribose (pentose sugar)
Bases = G , C , A , U
Phosphate group
1 polynucleotide strand (single stranded)
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5
Q

Purines and Pyrimidines

A

Purine
-2 carbon-nitrogen ring and larger in size

Pyrimidine
-1 carbon-nitrogen ring and smaller in size.

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6
Q

Phosphodiester bond

A
  • nucleotides join together to form nucleic acids.
  • nucleotides join between phosphate group of one nucleotide and the pentose sugar of another.
  • this forms a Phosphodiester bond.
  • chain of sugar and phosphate molecules makes a sugar-phosphate backbone.
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7
Q

Hydrogen bonds between bases

A

2 H bonds = Adenine and Thymine
3 H bonds = Cytosine and Guanine

Bases join together by hydrogen bonds forming between complementary bases.

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8
Q

Anti parallel strands in DNA

A

Anti parallel strands are strands which run in opposite directions.
2 anti parallel polynucleotide strands twist to form a DNA double helix which gives DNA stability.

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9
Q

Semi-conservative replication of DNA

A
  • DNA helicase catalyses breakdown of hydrogen bonds between the complementary base pairs of the 2 polynucleotide DNA strands.
  • the double helix unzips to for, 2 single strands of DNA with exposed nucleotide bases.
  • Each original DNA strand acts as a template for a new strand. Free floating DNA nucleotides join to the exposed bases on each original template strand by complementary base pairing.
  • DNA polymerase joins the nucleotides of the new strand together in 5’ to 3’ direction to the single strand of DNA.
  • Sugar-phosphate backbone formed.
  • leading strand is synthesised continuously in 5’ to 3’ direction.
  • lagging stand is synthesised discontinuously in short sections called Okazaki fragments.
  • Hydrogen bonds form between the bases on the original strand and the new strand.
  • strands twist to form a double-helix.
  • 2 DNA molecules are formed.
  • Each DNA molecule contains 1 strand from the original DNA molecule and 1 new strand so termed as semi-conservative replication.
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10
Q

Mutations in DNA

A
  • Sometimes random, spontaneous mutation occur.
  • Mutation is changes to the DNA base sequence.
  • Mutations can change the sequence of amino acids in a protein.
  • Results in the formation of abnormal proteins.
  • these can work better than normal proteins or may not work at all.
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11
Q

Protein synthesis: transcription

A
  • enzyme helicase unzips the part of double helix which codes for a specific protein only by breaking hydrogen bonds so bases are exposed.
  • RNA polymerase catalyses the formation of temporary hydrogen bonds between free RNA nucleotides and the complementary DNA bases on the template strand (one of the strands from the unzipped double helix)
  • as RNA nucleotides bond to the DNA bases on the template strand by complementary base pairing, RNA nucleotides are joint together forming an mRNA molecule.
  • hydrogen bonds between the uncoiled DNA strands re-form after RNA polymerase has passed by so the strands coil back into the double helix.
  • RNA polymerase reaches a stop codon. It stops making mRNA and detaches from the DNA.
  • mRNA moves out of the nucleus via the pores and attaches to the cytoplasm for translation.
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12
Q

Protein synthesis: translation

A
  • occurs at ribosomes
  • mRNA attaches to ribosome. tRNA carries a mink acids to ribosomes.
  • tRNA molecule with a complementary anticodon to the start codon on the mRNA attaches to the mRNA by complementary base pairing.
  • second tRNA molecule attaches to the next codon in the same way.
  • rRNA catalyses formation of peptide bonds between 2 amino acids attached to the tRNA molecule to join the amino acids together.
  • then first tRNA molecule moves away leaving the amino acid behind.
  • third tRNA molecule binds to next condon on mRNA. It’s amino acids binds to the first two and the second tRNA moves away.
  • process continues until there is a polypeptide chain is formed until there is a stop codon on the mRNA.
  • polypeptide chain moves away from the ribosome and translation is complete.
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13
Q

Base triplet

A

Triplet of bases on DNA molecule.

  • each amino acid is coded for by a sequence of three bases (triplet) in a gene.
  • sequence of bases in a section of DNA is a template used to make proteins in protein synthesis.
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14
Q

Codon

A

A triplet of bases on a length of mRNA.

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15
Q

Anticodon

A

Triplet of bases on a tRNA molecule, complementary to mRNA codon, is an anticodon.

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16
Q

Genetic code

A

Sequence of base triplets/codons in DNA or mRNA, which codes for specific amino acids.

17
Q

Non-overlapping code

A
  • In genetic code, each base triplet is read in order, separately to the triplet before and after.
  • Base triplets don’t share bases so their code is non-overlapping.
18
Q

Degenerate code

A
  • genetic code is degenerate.
  • degenerate means that there are many possible combinations of triplets compared to amino acids.
  • so some amino acids are coded by more than one base triplet.
19
Q

Start codon and stop codon

A
  • at the beginning of a gene, there is a triplet to tell the cell to start protein synthesis.
  • at the end of a gene, there is a base rip let to tell the bell to stop protein synthesis.
20
Q

Universal code

A
  • genetic code is universal.

- universal means that the same specific base triplets code for the same amino acids in ALL living organisms.

21
Q

Gene

A

-a gene is a sequence of DNA nucleotides that codes for a polypeptide. (Sequence of amino acids in a polypeptide for,s the primary structure for a protein)
-the order of nucleotides bases in a gene that determines the order of amino acids in a specific protein.
-

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