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A LEVEL BIOLOGY AQA > 3.4.2 DNA and protein synthesis > Flashcards

3.4.2 DNA and protein synthesis Flashcards

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1
Q

What is the genome?

A

the complete set of genes in a cell

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2
Q

What is a proteome?

A

the full range of proteins that a cell is able to produce

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3
Q

DNA - RNA - PROTEIN what processes occur in the central dogma

A
  1. transcription

2. translation Trna

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4
Q

What is mRNA involved in? Where does it occur and why ?

A

transcription in the nucleus as DNA cannot leave

proteins synthesized in cytoplasm on ribosomes

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5
Q

Why must an RNA copy of DNA be made?

A

so the genetic code can leave the nucleus

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6
Q

What is mRNA?

A

a single strand copy of genes DNA sequence
acts as messenger between nucleus and cytoplasm
transcript

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7
Q

How is mRNA synthesised?

A
  • from template strand of DNA

template strand determines the sequence of bases on the mRNA

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8
Q

What is a sequence of 3 bases called and what do they do?

A
  • triplets/codon

- an amino acid

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9
Q

What is tRNA involved in?

Where is it found

A
  • translation which takes place on ribosomes

- cytoplasm and ribosomes (throughout cell)

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10
Q

What does tRNA do?

A

transfers free amino acid in the cytoplasm to the ribosome

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11
Q

Label tRNA parts?

A
  • 3’ 5’ end amino acid attachment site (ATP needed)
  • anticodon which is complementary to mRNA
  • Nucleotides
  • Hydrogen bonds due to complementary base pairs
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12
Q

What is the structure of tRNA?

A

single folded polypeptide chain with a clover shape

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13
Q

Where do amino acids attach to on the tRNA?

A

they attach to the amino acid attachment site on the 3’ 5’ end

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14
Q

What is the anticodon?

A
  • sequence of 3 bases which is complementary to codon on mRNA molecule
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15
Q

if mRNA codon is AUG what is tRNA’s?

A

UAC

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16
Q

if mRNA codon is GAC what is tRNA’s?

A

CUG

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17
Q

Do tRNA molecules work for all amino acids?

A

No there are many different tRNA molecules with specific anticodons therefore each tRNA molecule is specific for only one amino acid

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18
Q

Compare DNA, mRNA and tRNA structure.

A

Polynucleotide strands 2, 1, 1

Shape double helix, straight single strand, clover shape

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19
Q

Compare DNA, mRNA and tRNA sugar and bases.

A

deoxyribose, ribose, ribose

ATGC, AUGC, AUGC

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20
Q

What is the most stable out of mRNA, tRNA and DNA and why?

A

1st DNA as H bonding holds 2 antiparallel strands
2nd TRNA has some H bonding
3rd MRNA no H bonding

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21
Q

What is the location of DNA, tRNA and mRNA?

A
  • nucleus
  • nucleus, cytoplasm and ribosome
  • cytoplasm and ribosome
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22
Q

The genetic code is? (5)

A

NURDS

  • Nonoverlapping
  • Universal
  • Read in triplets
  • Degenerate
  • Stop codons
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23
Q

Why is the genetic code non-overlapping?

A

each base is only read once during transcription this means each base is only part of 1 codon only

24
Q

Would the same bases code for the same amino acids in all species?

A

yes as genetic code is universal

25
Q

What is it meant by the genetic code is read in triplets?

A

each amino acid is coded for by an mRNA codon which is coded by a sequence of 3 bases

26
Q

Why is the genetic code degenerate?

A

a specific amino acid can be coded for by more than one codon

27
Q

What is a stopcodon?

A

they don’t code for amino acids but mark then end of the code of a polypeptide chain

28
Q

Importance of a startcodon?

A

synthesis of a polypeptide chain will not begin until the ribosomes has read a start codon which is always AUG

29
Q

What is noncoding parts of gene’s DNA called?

A

introns these are spliced out

leaving only coding

30
Q

What is coding part of gene’s DNA called?

A

exons

31
Q

What determines amino acid?

A

mRNA codons not tRNA

32
Q

What is the purpose of eukaryotic transcription?

A

production of mRNA from DNA
Production of mRNA transcript from DNA template in nucleus
Once mRNA transcript made this can travel out of nucleus to be translated into a protein at the ribosome

33
Q

Stages of eukaryotic transcription?

A

IETS

  1. Initation
  2. Elongation
  3. Termination
  4. Splicing
34
Q

Stage 1 of eukaryotic transcription?

A

Initiation- transcription factors move from cyto to DNA in nuc

  • they bind to specific sequence of bases called promoter region
  • this allows enzymes RNA polymerase and DNA helicase to bind to the promoter region
35
Q

Stage 2 of eukaryotic transcription?

A

Elongation- DNA helicase unwinds double stranded DNA exposing template strand

  • Free rna nucleotides in nucleus complementary base pair with DNA template strand
  • RNA polymerase joins adjacent rna nucleotides together in 5’-3’ direction by forming phosphodiester bonds ( CR uses ATP)
  • PRE-MRA strand made
  • DNA strands reform and rewind back into a double helix, h bond reform
36
Q

Stage 3 of eukaryotic transcription?

A

Termination- when RNA polymerase reaches termination sequence the enzymes detach and the pre-mRNA molecules are released
this contains introns and exons

37
Q

Stage 4 of eukaryotic transcription?

A

Splicing- a protein called spliceosomes splices introns out of the pre- mRNA
- exons joined by enzymes to form mature MRNA taht can leave the nucleus via nuclear pores and travel out of the cytoplasm

38
Q

Similarities in prokaryotic and eukaryotic transcription?

A
  • both mRNA strands are synthesised in 5’ to 3’

- both use DNA helicase and RNA polymerase

39
Q

Differences in prokaryotic and eukaryotic transcription?

A
  • P occurs in cytoplasm E in nucleus
  • P no processing, no introns, no splicing
    E processing, introns and splicing
  • P translation can occur whilst mRNA transcript is being made (simultaneous)
    E these 2 processes are distinct one has to be complete before other one starts
40
Q

Purpose of translation?

A
  • production of a polypeptide chain from a sequence of codons on an mRNA strand (at ribosomes)
41
Q

What are the first 3 steps of translation?

A
  1. mRNA associates with the ribosomes and ribosome moves to find the start codon
  2. tRNA molecules bring the specific amino acids needed to the ribosome
  3. the anticodons on tRNA molecules are complementary to mRNA codons. ribosome moves along mRNA bringing in 2 tRNA molecules at a time
42
Q

What are the last 3 steps of translation?

A
  1. peptide bond is formed between AA via CR. bonds between tRNA and amino acid hydrolysed and tRNA leaves to pick up another specific amino acid
  2. ribosomes move along mRNA by 1 codon and new tRNA molecules arrive with complementary anticodons
  3. this is repeated until the ribsome reads a noncoding stop codon and ribosome detaches from the polypeptide chain
43
Q

Where does translation occur in both eukaryotes and prokaryotes?

A

At ribosomes in cytoplasm

44
Q

What determines how the folded protein structure of protein will be?

A

Position of R groups in polypeptide chain

45
Q

Transcription Makes _______ Products in Eukaryotes and Prokaryotes

A

Different

46
Q

Why does pre-mRNA contain introns and exons?

A

Introns and exons are both copied into mRNA during transcription

47
Q

Where does splicing occur?

A

Nucleus

48
Q

Explain why the percentage of bases from the middle part of the chromosome and end part are different (2)

A

Different genes
Have different base sequences
Codes for different proteins

49
Q

Different sequences of bases code for different proteins. Explain how. (2)

A

Protein made up of (chain of) amino acids

Each amino acid has its own base code

50
Q

Explain how copying bases more than once may give rise to differences in the protein (2)

A

Changes base sequence of later triplets/amino acid codes

51
Q

How many tRNA molecules does the ribosome bring together at once?

A

2

52
Q

What happens as the third amino acid is attached to the sequence?

A

The first tRNA is released and it is free to collect another amino acid

53
Q

How is a protein produced from a polypeptide chain?

A

Polypeptide is folded to form the secondary structure
Secondary structure is folded to to produce the tertiary structure
Polypeptide chains are joined together to form a quaternary structure

54
Q

What is the role of ATP during translation?

A

Required to provide energy to attach amino acids to tRNA

To form peptide bonds between amino acids

55
Q

What is the role of the ribosomes?

A

the ribosomes move along the mRNA by 1 codon and bring in 2 tRNA molecules at a time

A LEVEL BIOLOGY AQA (5 decks)

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