Gene Expression Flashcards
What is gene expression?
The process of using information from a gene to synthesise a protein.
What is gene expression?
The process of using information from a gene to synthesise a protein.
What is a cell’s genotype?
It describes the alleles for that particular characteristic.
How is a cell’s genotype determined?
By the sequence of bases in its genes.
What is a cell’s phenotype?
The physical appearance for that particular characteristic.
What is a cell’s phenotype determined by?
The proteins that are synthesised when genes are expressed.
What are the two stages of protein synthesis?
Transcription and translation.
What happens during the transcription stage of protein synthesis?
The synthesis of mRNA from a section of DNA.
What happens during the translation stage of protein synthesis?
The synthesis of a protein using the instructions from mRNA.
How many strands does DNA have?
Two - it is double-stranded.
How many strands does RNA have?
One - it is single-stranded.
What are the base pairs in RNA?
Cytosine - Guanine
Adenine - URACIL
What is the sugar in DNA?
Deoxyribose
What is the sugar in RNA?
Ribose
What are the base pairs in DNA?
Cytosine - Guanine
Adenine - Thymine
How is mRNA used in protein synthesis?
It carries a copy of the genetic code from the nucleus to the ribosome.
What is a cell’s genotype?
It describes the alleles for that particular characteristic.
How is a cell’s genotype determined?
By the sequence of bases in its genes.
What is a cell’s phenotype?
The physical appearance for that particular characteristic.
What is a cell’s phenotype determined by?
The proteins that are synthesised when genes are expressed.
What are the two stages of protein synthesis?
Transcription and translation.
What happens during the transcription stage of protein synthesis?
The synthesis of mRNA from a section of DNA.
What happens during the translation stage of protein synthesis?
The synthesis of a protein using the instructions from mRNA.
How many strands does DNA have?
Two - it is double-stranded.
How many strands does RNA have?
One - it is single-stranded.
What are the base pairs in RNA?
Cytosine - Guanine
Adenine - URACIL
What is the sugar in DNA?
Deoxyribose
What is the sugar in RNA?
Ribose
What are the base pairs in DNA?
Cytosine - Guanine
Adenine - Thymine
What are the three types of RNA?
- mRNA - messenger
- tRNA - transfer
- rRNA - ribosome
How is tRNA used in protein synthesis?
Each tRNA molecule carries its specific amino acid to the ribosome.
How is rRNA used in protein synthesis?
It forms the ribosome with proteins.
How is mRNA used in protein synthesis?
It carries a copy of the genetic code from the nucleus to the ribosome.
What is the actual process of protein synthesis?
mRNA is transcribed from DNA in the nucleus and then translated into proteins by ribosomes in the cytoplasm.
What is a codon?
Triplet of bases on the mRNA molecule - they code for a specific amino acid.
How many amino acids are there?
21
What are introns?
Non-coding regions of the Primary mRNA transcript that are removed.
What are exons?
Coding regions which are spliced to form mature mRNA transcript.
What happens to the order of exons during splicing?
It is unchanged.
What does RNA splicing do?
Forms a Mature mRNA transcript from the Primary mRNA transcript.
‘Exons are Expressed’
How can you form several different proteins from the same gene through RNA splicing?
Treating different regions as exons and introns means the same Primary mRNA transcript can produce several Mature mRNA transcripts.
What is the first part of protein synthesis?
Transcription
What is the second part of protein synthesis?
Translation
Describe protein transcription.
- The enzyme RNA polymerase moves along the gene unwinding the double helix and breaking the hydrogen bonds between the bases.
- RNA polymerase synthesises a primary transcript of mRNA from free RNA nucleotides by complementary base pairings.
- RNA polymerase keeps adding nucleotides from the 5’ end to the 3’ end of the growing mRNA molecules until a specific sequence of nucleotides called a stop codon is reached - this resulting mRNA strand separates and is now called a Primary transcript of mRNA.
Why does tRNA fold?
Due to complementary base pairings.
During translation, what determines which amino acid will be joined together to make the protein?
The mRNA codons
What is a start codon?
On the mRNA transcript, it signals for translation to begin.
When does protein synthesis stop?
When a stop codon is reached on the mRNA transcript.
Where is the tRNA found?
Cytoplasm
What does every tRNA molecule have?
One triplet of bases exposed called an anticodon.
What is an anticodon complementary to?
An mRNA codon.
What is an anticodon specific to?
An amino acid that is carried to the ribosome by tRNA for protein synthesis.
Describe protein translation.
- Mature mRNA transcript attaches to a ribosome in the cytoplasm.
- Start codon begins the process of protein synthesis.
- Complementary tRNA anticodons attach to the mRNA strand, bringing a specific amino acid to form the protein molecule.
- Peptide bonds join the amino acid molecules. Each tRNA molecule leaves the ribosome once the amino acids are attached.
- A stop codon ends protein synthesis.
What are amino acids linked by?
Peptide bonds
When amino acids are linked by peptide bonds, what forms?
Polypeptides (proteins)
Why do polypeptide chains fold to form the 3D shape of a protein?
Because of the hydrogen bonds and other interactions between individual amino acids.
Why is the large variety of shapes of proteins important?
It determines their function.
Give a summary of transcription.
- Gene copied into mRNA strand using RNA polymerase.
- Primary mRNA transcript is spliced into Mature mRNA transcript.
- It takes place in the nucleus.
Give a summary of translation.
- mRNA attaches to the ribosome.
- tRNA anticodons bind with mRNA codons bringing amino acids together.
- Peptide bonds form between amino acids to create a protein.
- Takes place in the ribosome.
