Transcription and Translation

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  • Created by: Lotto65
  • Created on: 04-02-17 14:22
The base sequence in genes codes for...
The polypeptide
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What is the first stage of protein synthesis?
Make a copy of the DNA in RNA form
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Where does the mRNA go once it has been made?
In the cytoplasm to the ribosomes
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Why is it called mRNA?
It gives the ribosomes information on how to synthesise a polypeptide like a messenger
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What is transcription?
The copying of the base sequence of a gene by making an RNA molecule
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What is stage 1 of transcription?
Helicase moves along the DNA molecule and unwinds it and separates it into two separate strands
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What is the name of the enzyme that assembles nucleotides along a strand?
RNA polymerase
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Do the same rules of complementary base pairing apply with RNA polymerase?
Yes
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What is the single difference in assembly between DNA and RNA polymerase?
Instead of thymine, RNA polymerase adds uracil
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Why does RNA polymerase add uracil instead of thymine?
RNA polymerase does not contain thymine
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Where are nucleotides covalently bonded together?
Between the pentose sugar of one nucleotide and the phosphate of the next
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What happens to the RNA strand when it has been formed?
It separates from the DNA strand and is released completely when the end of the gene is reached
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What is the last stage of transcription?
The two DNA strands twist back up and pair up into a double helix
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What is the DNA base sequence of an mRNA molecule with the sequence AGUCUUAC?
TCAGAATG
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What is the sense strand?
The DNA strand that is not being transcribed but has the same sequence as the mRNA albeit with thymine instead of uracil
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What is the antisense strand?
The DNA strand that is transcribed
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What is translation?
The synthesis of polypeptides on ribosomes
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What types of RNA are used in translation?
tRNA and mRNA
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What determines the amino acid sequence in a polypeptide?
The base sequence in mRNA
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How many bases code for one amino acid?
3
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What is a group of three bases called?
Codon
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What are the names of the groups of three bases on tRNA?
Anticodons
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Is there complementary base pairing between codons and anticodons?
Yes
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Where on the ribosome does mRNA bind to?
A site on the small sub unit
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What does tRNA stand for?
Transfer RNA
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Are there large or small amounts of tRNA around the ribosome?
Large
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An amino acid is specific to...
The anticodon and sequence of bases that make up the anticodon
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Where in the ribosome are the three binding sites for tRNA?
On the large sub-unit
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How many tRNA molecules can bind at once in the ribosome?
2
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When can tRNA bind to the ribosome?
If it contains the anticodon that is complementary to the codon on mRNA
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How do the bases on the codon and anticodon link together?
With hydrogen bonds
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How are the amino acids linked together to form a polypeptide?
With peptide bonds
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Do the base sequences in a gene give any observable characteristics?
No
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Do proteins give any observable characteristics?
Yes
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Why does transcription only use one strand of the DNA molecule?
Because mRNA is single stranded
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Which enzyme forms the covalent bonds between nucleotides?
RNA polymerase
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Which part of a ribosome is the part that makes peptide bonds between amino acids to form a polypeptide?
Large sub unit
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The antisense strand is in the ... to ... direction
5' to 3' direction
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The sense strand is in the ... to ... direction
3' to 5' direction
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What is the average length of mRNA?
2000 nucleotides
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Does the mRNA length vary? Why?
Yes because it depends on the number of amino acids in a polypeptide
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Do cells constantly make the same polypeptides?
No only when required so only certain genes are transcribed and certain mRNA molecules available for transcription
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How do cells that need to make large amounts of a polypeptide get around the demand issue?
They make multiple copies of the same mRNA strand
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Give an example of a type of cell that needs to make lots of a polypeptide
Insulin secreting cells
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What is the genetic code?
The 'translator' that enables the base sequence on mRNA to be converted into an amino acid sequence
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What are the dense regions in the nucleus called?
Heterochromatin
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What do heterochromatins contain?
Chromosome material not being used
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What are the less dense regions in the nucleus called?
Euchromatin
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What is the function of euchromatins?
Where chromosome material is being used
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Are ribosomes spacious inside? How does that help?
Yes - allows other substances to fit inside
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What code starts an mRNA sequence?
AUG
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Why can tRNA be described as recycling?
Free tRNA goes back to the cytoplasm to pick up more amino acids
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What makes translation stop?
When one codon does not attract a tRNA molecule
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What is a polysome?
A sequence of ribosomes
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Unless you have a faulty gene, how many copies of the same allele should you have?
2
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When enough of a protein has been made, what can happen?
Enzymes can digest ribosomes
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Translation is the synthesis of...
Polypeptides
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Other cards in this set

Card 2

Front

What is the first stage of protein synthesis?

Back

Make a copy of the DNA in RNA form

Card 3

Front

Where does the mRNA go once it has been made?

Back

Preview of the front of card 3

Card 4

Front

Why is it called mRNA?

Back

Preview of the front of card 4

Card 5

Front

What is transcription?

Back

Preview of the front of card 5
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