1.3 Gene Expression Flashcards
What 3 types of RNA does transcription and translation inolve?
- mRNA (messenger RNA)
- tRNA (Transfer RNA)
- rRNA (Ribosomal RNA)
What is gene expression?
the process by which specific genes are activated to produce a required protein
What are the differences between DNA and RNA?
- DNA is double stranded RNA is single stranded
- DNA nucleotides have a deoxyribose sugar whereas RNA nucleotides have a ribose sugar
- Bases in DNA are A,C,T and G whereas bases in RNA are A, U, C and G (uracil replaces thymine)
What is the role of RNA?
transcription and translation of DNA sequences
What is mRNA and what is its role?
- transcribed from DNA in the nucleus and translated into proteins by ribosomes in the cytoplasm
- mRNA carries a copy of the DNA code from the nucleus to the ribosome.
What is the role of tRNA?
carry its specific amino acid to the ribosome
What is the structure of tRNA?
- folds due to complementary base paining
- anti codon (an exposed triplet of bases) at one end
- specific amino acid attachment site at the other
What is the role of rRNA?
combine with proteins to from the ribosome
What is transcription?
transcription is the synthesis of mRNA from a section of DNA.
What is the role of RNA polymerase? and therefore what is the process of transcription
- the enzyme responsible for transcription
- moves along the DNA molecule unwinding the double helix and breaking the hydrogen bonds between bases
- synthesises a primary mRNA transcript from RNA nucleotides by complementary bas paring
What is the primary transcript?
The molecule produced when RNA polymerase transcribes a gene
What is an intron?
a non-coding region of a gene
What is an exon?
a coding region of a gene
What is RNA splicing?
- The removal of the introns from the primary transcript.
- The remaining exons are spliced together to form the mature transcript.
where does RNA splicing happen?
the nucleus
What is translation?
the synthesis of a polypeptide following the code within the mature mRNA transcript.
What is a codon and where is it found?
- The code for one amino acid.
- It is a sequence of 3 nucleotides (triplet of bases)
- it is a triplet of bases on the mature mRNA transcript
What is the structure of ribosomes and what is its function?
- small, roughly spherical structures found in all cells
- they contain the enzymes essential for protein synthesis
- they bring tRNA molecules bearing amino acids into contact with the mRNA
What is the translation process?
- begins at a start codon and ends at a stop codon
- anticodons bond to codons by complementary base pairing
- translating the genetic code into a sequence of amino acids
- peptide bonds join the amino acids together
- tRNA leaves the ribosome and a polypeptide is formed
what is alternative RNA splicing?
- the same gene can make several different proteins depending on which exons are used
- exons must stay in the same order
- some exons are treated as introns
- different mature mRNA transcripts are produced from the same primary transcript
What are the two stages of gene expression and where do they happen in a cell?
- transcription - nucleus
2. translation - ribosome
What is an anticodon and where is it found?
- an anticodon is an exposed triplet of bases on tRNA that is complementary to codons on the mRNA strand
- it is found at the opposite end of the tRNA from the amino acid attachment site
How are amino acids joined to make a protein?
peptide bonds
What are the chemical bonds that form to make proteins different shapes?
- hydrogen bonds
- other interactions between individual amino acids
Describe the structure of a protein
- amino acids are linked by peptide bonds to form polypeptides
- fold to form 3D protein
- held together by hydrogen bonds and other interactions between individual amino acids
- shape determines their function
What is phenotype determined by?
the proteins produced as a result of gene expression
-and environmental factors also influence
