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Biology > RNA and polypeptide synthesis 8.3 - 8.5 > Flashcards

RNA and polypeptide synthesis 8.3 - 8.5 Flashcards

1
Q

Which 4 nucleotide bases are found in RNA?

A

Uracil
Adenine
Cytosine
Guanine

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2
Q

What are the 2 types of RNA?

A

1) Messenger RNA (mRNA)

2) Transfer RNA (tRNA)

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3
Q

How does DNA reach ribosomes for protein synthesis?

A
  • The protein to be synthesised is coded for by a particular gene
  • In the process of transcription, this gene is copied into mRNA
  • In translation, the mRNA leaves the nucleus and enters the ribosomes, where the genetic code is read
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4
Q

What is a genome?

A

Complete set of genes in a cell, including those in the mitochondria and/or chloroplasts

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5
Q

What is a proteome?

A

Full range of proteins produce by the genome

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6
Q

What is messenger RNA?

A

Single stranded molecule that transfers the DNA code from the nucleus to the ribosomes

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7
Q

Outline the process of transcription

A
  1. DNA helicase separates the 2 strands - exposing nucleotide bases
  2. Nucleotide bases on ONE of the strands pairs with free complementary bases from nucleus
  3. RNA polymerase moves along this strand joining nucelotides together
  4. As RNA polymerase moves down, DNA helix rewinds behind itself
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8
Q

What molecule does transcription produce?

A

pre-mRNA

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9
Q

In transcription, how many nucleotide bases are exposed at any one time?

A

12(ish)

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10
Q

In transcription, which base on the template strand is complementary to adenine?

A

Uracil

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11
Q

How does the transcription process finish?

A

RNA polymerase reaches STOP codon in DNA sequence and detaches - leaving a pre-mRNA molecule

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12
Q

What happens to mRNA once formed?

A

Leaves the nucleus via pores in the nuclear envelope (too big to diffuse) and enters the cytoplasm, where it associates with ribosomes.

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13
Q

What is the function of mRNA?

A

The sequence of codons it contains (genetic code) determines the order of amino acids for a specific polypeptide to be synthesised in the ribosomes.

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14
Q

What shape is transfer RNA?

A

Clover

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15
Q

Which part of the tRNA molecule does the amino acid attach to?

A

The end of the longest chain originating at the centre (opposite to the anticodon)

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16
Q

How many nucleotide bases are found in the anticodon of 1 tRNA molecule?

A

3

17
Q

Why is it necessary to have as many tRNA molecules as coding triplets??

A

Genetic code is degenerative

18
Q

How stable is tRNA in relation to mRNA?

A

More stable

19
Q

How stable is tRNA in relation to DNA?

A

Less stable

20
Q

Do all cells have the same amount of RNA?

A

No, it differs depending on level of metabolic activity

21
Q

Outline the main stages of polypeptide synthesis

A
  1. DNA provides the instrutions to form a long sequence of bases
  2. A complementary section of part of this sequence is made in the form of pre-mRNA (transcription)
  3. pre-mRNA is spliced to form mRNA
  4. mRNA is used as a template for tRNA molecules to attach to and amino acids they carry are linked to form a polypeptide (translation)
22
Q

In which types of cells does splicing not occur?

A

prokaryotic

23
Q

What is splicing?

A

The removal of non-functional introns and joining of functional exons

24
Q

Describe the process of translation

A
  1. Ribosome attaches to starting codon at end of mRNA
  2. Ribosome moves along mRNA bringing together 2 tRNA molecules at a time, each with an anticodon complementary to the mRNA codon.
  3. tRNA carries amino acid which isjoined to other amino acids in sequence by peptide bond
  4. Ribosome moves down mRNA to continue this process
25
Q

In translation how are amino acids joined together?

A

Peptide bond formed using an enzyme and ATP (which is hydrolysed to provide the energy required)

26
Q

Explain how a change in a sequence of DNA bases could result in a non-functional enzyme

A
  • Change in amino acid sequence/primary structure
  • Change in hydrogen/ionic/disulfide bonds
  • Alters tertiary structure/shape of active site
  • E-S complex cannot form
27
Q

Why does the proportion of each base change at different sections on a chromosome?

A

Different genes have different base sequences

28
Q

How is the structure of an mRNA molecule different from the structure of a tRNA molecule?

A
  • mRNA does not contain hydrogen bonds
  • mRNA contains codons but not anticodons
  • No amino acid binding site
  • mRNA is longer than tRNA
  • straight molecule/not folded
29
Q

Why is base pairing important in DNA replication?

A

Free nucleotides bind to exposed strands so complementary base pairs can join (A to T and C to G) to produce identical copies of DNA

Biology (6 decks)

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