Protein Synthesis (Cambridge (CIE) AS Biology): Flashcards
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Define gene.
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Define gene.
A gene is a sequence of nucleotides that forms part of a DNA molecule and codes for a polypeptide.
What does a gene code for?
A polypeptide.
A gene is a sequence of that forms part of a DNA molecule.
A gene is a sequence of nucleotides that forms part of a DNA molecule.
True or False?
A polypeptide is coded for by a gene.
True.
A gene is the sequence of DNA nucleotides that codes for a polypeptide.
What is the genetic code?
The set of DNA base triplets that code for specific amino acids, or for start and stop signals.
Why is the genetic code described as universal?
The same triplet codes for the same amino acid in almost all living organisms.
What can a triplet of DNA bases code for?
A specific amino acid.
Or a start or stop codon.
A sequence of three DNA bases that codes for one amino acid is called a .
A sequence of three DNA bases that codes for one amino acid is called a triplet.
True or False?
Some base triplets act as start and stop codons rather than coding for an amino acid.
True.
Start and stop codons signal where translation begins and ends.
Define transcription.
The process in which a complementary mRNA copy is made from a DNA template strand.
Define translation.
The process in which the sequence of codons on mRNA is used to assemble amino acids into a polypeptide at a ribosome.
What is the role of RNA polymerase?
It joins RNA nucleotides together to form mRNA during transcription.
What is the role of tRNA (transfer RNA)?
It carries a specific amino acid to the ribosome.
Its anticodon pairs with the complementary codon on mRNA.
What is the role of the ribosome in translation?
It holds the mRNA and tRNA in place so that peptide bonds form between adjacent amino acids.
What is the difference between a codon and an anticodon?
A codon is a triplet of bases on mRNA.
An anticodon is the complementary triplet of bases on tRNA.
During translation, mRNA carries codons to a where the polypeptide is assembled.
During translation, mRNA carries codons to a ribosome where the polypeptide is assembled.
What is the template strand?
The DNA strand that is used during transcription to make mRNA.
It is also called the transcribed strand.
What is the DNA strand that is not used in transcription called?
The non-transcribed strand.
The DNA strand used during transcription is called the template or strand.
The DNA strand used during transcription is called the template or transcribed strand.
What is an intron?
A non-coding sequence that is removed from the primary transcript during modification.
What is an exon?
A coding sequence that is joined to other exons to form the final mRNA.
In eukaryotes, how is the primary transcript modified to form mRNA?
The introns (non-coding sequences) are removed.
The exons (coding sequences) are joined together.
In eukaryotes, non-coding sequences called are removed to form mRNA.
In eukaryotes, non-coding sequences called introns are removed to form mRNA.
What is a gene mutation?
A change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide.
What are the three types of gene mutation?
Substitution
Deletion
Insertion
How can a substitution mutation affect the polypeptide?
One base is replaced by another, changing only one triplet.
So at most one amino acid is altered — and sometimes none, because the code is degenerate.
Why do deletion and insertion mutations often have a large effect?
They cause a frameshift.
Every triplet after the mutation is changed, so many amino acids in the polypeptide may be altered.
A change in the sequence of base pairs in DNA is called a gene .
A change in the sequence of base pairs in DNA is called a gene mutation.
True or False?
A substitution mutation always changes the polypeptide produced.
False.
The genetic code is degenerate, so the new triplet may still code for the same amino acid.
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