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What is transcription?
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What is transcription?
Transcription is the process where the nucleotide base sequence of a section of DNA is used to synthesize an mRNA molecule using complementary base pairing.
Define mRNA.
mRNA (messenger RNA) is a single-stranded RNA molecule that transfers genetic information from the DNA in the nucleus to the cytoplasm.
True or False?
RNA polymerase is involved in DNA replication.
False.
RNA polymerase is involved in transcription, not DNA replication.
What happens during the elongation phase of transcription?
During elongation, RNA polymerase builds the mRNA molecule by bonding RNA nucleotides together.
Define gene expression.
Gene expression is the process by which a gene is 'switched on' and undergoes transcription and translation.
True or False?
The template strand of DNA is transcribed to form mRNA.
True.
The template strand of DNA is transcribed to form mRNA.
What is the role of hydrogen bonds in transcription?
Hydrogen bonds form between RNA nucleotides and their complementary DNA bases during transcription.
What is the function of RNA polymerase?
RNA polymerase is the enzyme responsible for synthesizing mRNA during transcription.
Define complementary base pairing in transcription.
Complementary base pairing in transcription is the process where RNA nucleotides pair with their complementary DNA bases.
True or False?
The coding strand of DNA is the one that is transcribed during transcription.
False.
The template strand of DNA is the one that is transcribed during transcription.
Identify the four RNA bases.
The four bases in RNA are:
Adenine
Uracil
Cytosine
Guanine
What is a polypeptide?
A polypeptide is a chain of amino acids covalently bonded together with peptide bonds.
Define the term codon.
A codon is a sequence of three mRNA bases that codes for a specific amino acid.
True or False?
Translation occurs in the nucleus.
False.
Translation occurs in the cytoplasm, transcription occurs in the nucleus.
What role does tRNA play in translation?
tRNA binds with specific amino acids and brings them to the mRNA on the ribosome.
What is the function of ribosomal RNA (rRNA)?
Ribosomal RNA (rRNA) is part of the ribosome structure and helps catalyse the formation of peptide bonds in proteins.
Define the term anticodon.
An anticodon is a sequence of three bases on the tRNA molecule that are complementary to a codon on mRNA.
True or False?
The codon GAC on mRNA would pair with the anticodon CTG on tRNA.
False.
The codon GAC on mRNA would pair with the anticodon CUG on tRNA.
What is the stop codon?
A stop codon is a specific sequence of mRNA bases that signals the end of translation.
What happens after the mRNA leaves the nucleus?
After leaving the nucleus, the mRNA attaches to a ribosome in the cytoplasm for translation.
State the role of the ribosome during translation.
The ribosome facilitates the binding of tRNA to mRNA and catalyses the formation of peptide bonds to synthesize a polypeptide.
Define what is meant by the term "triplet code"
A triplet code is a sequence of three DNA nucleotide bases that codes for one amino acid.
True or False?
Each amino acid is coded by only one triplet.
False.
Each amino acid can be coded by multiple triplets, making the genetic code degenerate.
Define the term codon.
A codon is a sequence of three mRNA bases that codes for a specific amino acid.
What does the term "degenerate code" mean?
A degenerate code means that multiple codons can code for the same amino acid.
What is the significance of the start codon (TAC)?
The start codon TAC codes for methionine and signals the beginning of a gene in protein synthesis.
True or False?
The genetic code is universal across all organisms.
True.
The genetic code is universal, meaning the same triplets code for the same amino acids in all living organisms.
What is the purpose of a stop codon?
A stop codon signals the end of translation, indicating where the polypeptide chain should stop being synthesized.
The genetic code is non-overlapping, how does this affect protein synthesis?
The genetic code being non-overlapping means each base is read only once in a single codon, preventing overlap in the sequence interpretation.
What is the role of ATP during translation?
ATP provides the energy required for forming peptide bonds between amino acids during translation.
Why is it important that the ribosome can bind with more than one tRNA molecule at a time?
Binding with two tRNA molecules at a time allows the formation of a peptide bond between adjacent amino acids to accurately build up the amino acid sequence in the polypeptide chain.
What is a gene mutation?
A gene mutation is a change in the sequence of bases in a DNA molecule that may result in a new allele.
True or False?
Most mutations are beneficial.
False.
Most mutations are harmful or neutral (have no effect).
Define the term point mutation.
A point mutation is a mutation where one base in the DNA sequence is altered, potentially changing the amino acid at that location.
True or False?
Mutations in body cells are inherited by offspring.
False.
Mutations in body cells are not inherited; only mutations in gametes are passed on to offspring.
Define the term allele.
An allele is a variant form of a gene that may result from a mutation and can lead to different traits or conditions.
Why do some mutations have no impact on the amino acid sequence or the final polypeptide structure?
As the genetic code is degenerate, a change in nucleotide base sequence may still code for the same amino acid despite being a different codon. This means that some mutations will have no impact on the amino acid sequence or the structure of the polypeptide that is produced.