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Edexcel Biology B > 1.4 DNA and protein synthesis > Flashcards

1.4 DNA and protein synthesis Flashcards

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1
Q

What is a gene?

A

A sequence of bases on a DNA molecule that code for a sequence of amino acids in a polypeptide chain

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2
Q

What is a gene mutation?

A

A change to at least one nucleotide base or the arrangement of the bases in DNA

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3
Q

Coding DNA

A

The sections of DNA which code for proteins

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4
Q

Non-coding DNA

A

The sections of DNA which do not code for proteins

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5
Q

What are the purines?

A

A class of nitrogenous bases that are made up of two rings

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6
Q

What are the pyrimidines?

A

A class of nitrogenous bases that are made up of a single ring

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7
Q

What 2 bases are purine?

A

Adenine and guanine

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8
Q

What 3 bases are pyrimidines?

A

Cytosine, thymine and uracil

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9
Q

What does the term triplet describe in reference to genetic code?

A

The way that DNA is grouped into three base long codons that are read together and code for an amino acid

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10
Q

What does the term non-overlapping describe in reference to genetic code?

A

The way that each base is only part of one codon and how each codon is read one at a time in order

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11
Q

What does the term degenerate mean in reference to genetic code?

A

The way that some amino acids can be coded for by multiple different codons

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12
Q

What is a deletion mutation?

A

A type of mutation where a nucleotide or multiple nucleotides are not incorporated into the DNA chain and are lost, resulting in a frameshift mutation

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13
Q

What is an insertion mutation?

A

A type of mutation where an extra nucleotide or multiple extra nucleotides are incorporated into the growing DNA chain, resulting in a frameshift mutation

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14
Q

What is a frameshift mutation?

A

A type of mutation where a nucleotide or multiple nucleotides are lost or added to a DNA chain, displacing all other nuceleotides downstream from the mutation and leading to an incorrect reading of them

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15
Q

What is a substitution mutation?

A

A type of mutation where the incorrect nucleotide is incorporated into the growing DNA chain

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16
Q

What is transcription and where does it occur?

A

It is the process of synthesising a new mRNA strand from a molecule of DNA and it occurs in the nucleus

17
Q

What is translation?

A

The process of protein synthesis where complementary tRNA strands carrying amino acids are brought to each codon in an mRNA molecule as it moves through a ribosome

18
Q

What is DNA?

A

A helical double stranded polymer made of deoxyribose monomers joined by phosphodiester bonds which contains genes that code for proteins

19
Q

What is an anti-sense strand?

A

The strand of DNA which is used as a complementary template and is used for complementary mRNA synthesis

20
Q

What is DNA helicase?

A

The enzyme that unzips the DNA helix by breaking the hydrogen bonds between the chains during DNA replication and transcription

21
Q

What is DNA polymerase?

A

The enzyme that catalyses the formation of phosphodiester bonds between nucleotides during the sysnthesis of a new DNA strand

22
Q

What is ligase?

A

The enzyme that joins Okazaki fragments on the lagging strang together by forming phosphodiester bonds between them

23
Q

What is messenger RNA (mRNA)

A

A type of single-stranded RNA molecule that carries genetic information from the DNA in the nucleus to the ribosomes for translation

24
Q

What are nucleotides?

A

The individual monomers that make up polynucleotides which are composed of a phosphate group, a pentose sugar and a nitrogenous base

25
Q

What are ribosomes and where are they found?

A

They are organelles that catalyse protein synthesis, and are found either free in the cytoplasm or as a part of the rough endoplasmic reticulum

26
Q

What is RNA polymerase?

A

An enzyme that catalyses the formation of phosphodiester bonds between nucleotides during the synthesis of a new RNA strand

27
Q

What is semi-conservative replication?

A

A type of DNA replication where each new molecule of DNA produced contains one original strand and one newly synthesised strand

28
Q

What is a sense strand?

A

The strand of DNA which is complementary to the anti-sense strand and is identical to the transcribed mRNA (with the exception of the sense strand containing thymine in the place of uracil)

29
Q

What is sickle cell anaemia?

A

A type of genetic disease which produces a faulty ‘sickle shaped’ haemoglobin due to a point mutation, causing a change in a single amino acid in the polypeptide sequence

30
Q

What is transfer RNA (tRNA)?

A

A type of RNA that has three hairpin loops, an anticodon for attachment to the mRNA codon and an amino acid binding site that is used to carry amino acids to the ribosome for translation

31
Q

What are the stop and start codons in a DNA strand?

A

The codons which either stop or start protein synthesis

32
Q

What does the term universal mean in reference to genetic code?

A

The way that the genetic code is the same in all organisms and species

33
Q

What are the 4 stages of DNA replication?

A
  • DNA helicase catalyses the hydrogen bonds between the complimentary bases to be broken, unravelling the DNA helix
  • One of the strands is used as a template, where complimentary base pairing occurs between the template strand and free nucleotides
  • DNA polymerase catalyses adjacent nucleotides to be joined by phosphodiester bonds in condensation reactions
  • The new DNA molecules then automatically fold into double helices as hydrogen bonds are formed between the strands
34
Q

What are the 4 stages involved in transcription during protein synthesis?

A
  • DNA helicase catalyses the hydrogen bonds between complimentary bases to be broken, unrevalling the DNA helix
  • One of the strands is used as a template (known as the anti-sense strand), where complimentary base pairing occurs between the template strand and free nucleotides
  • RNA polymerase catalyses adjacent nucleotides to be joined by phosphodiester bonds in condensation reactions, forming a molecule of mRNA
  • The newly made mRNA molecule then moves out of the cytoplasm through a nuclear pore and attaches to a ribosome in the cytoplasm ready for the translation stage of protein synthesis
35
Q

What are the stages involved in translation during protein synthesis?

A
  • A tRNA molecule with a specific amino acid attached to its amino acid binding site binds to the mRNA via its anticodon
  • Hydrogen bonds form between the anticodon of the tRNA and the codon of the mRNA
  • A second tRNA molecule binds to the next codon of the mRNA and the two amino acids form a peptide bond
  • A third tRNA molecule joins the ribosome as the first one leaves
  • This process is repeated until the stop codon on the mRNA is reached, forming a completed polypeptide chain

Edexcel Biology B (8 decks)

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