RNA Flashcards
Is DNA or RNA expressed?
DNA has the template for the genes that code for the synthesis of RNA which is then expressed as proteins through translation of the mRNA. Alteration of the process may affect the protein formation and therefore phenotype expression. Some mutations will not affect expression of the protein but may affect regulatory RNA
What are the differences and similarities between DNA and RNA?
- DNA is double stranded and RNA is single stranded
- DNA is made up of deoxyribose where as RNA is made up of ribose
- DNA contains ATGC and RNA contains AUGC
- DNA codes for RNA which is then expressed
- Coded in a 5’ to 3’ direction
- RNA sequence is transcribed from DNA
- RNA carries the genetic information and is what expresses the gene that DNA codes for
- Single stranded RNA can form hairpin structures which add stability and protection
- RNA is shorter than DNA
- RNA is less stable than DNA (exposed bases)
What are the differences between the DNA and RNA nucleic acids and what does it allow?
- DNA has 2-deoxyribonucleic acids and RNA has ribonucleic acids
- On the second carbon of 2-deoxyribose there is a H group whereas there is an OH group in the ribose
- The differences allow the 2 molecules to be identified by enzymes and other protein factors
Differences and similarities between thymine and uracil
- Thymine is present in DNA
- Uracil is present in RNA
- Similar structures (only difference being the group attached to the second carbon - methane in thymine and H in uracil)
- Take up the same amount of space in the nucleus
What are hairpin loops and why do they occur?
Hair pin loops exist to protect the RNA, single stranded RNA is exposed and unstable. Base pairing along the stem of the hairpin loop offers protection and stability to the RNA
What is the structure of tRNA?
- 3 Hairpin loops
- 1 hairpin loop contains the anticodon for the amino acid that will be attached at the 3’ end of the acceptor stem
- Stabilised from base pairing within the stems of the hairpin loops
- Each tRNA has a variable loop
- transfer RNA, brings amino acids to ribosome during translation (coded for by a tRNA gene on DNA)
What is mRNA, how does its structure vary and how does this affect its function?
- mRNA is a protein coding RNA
- complexity is dependent on the gene from which the mRNA was made
- mRNA has 4 domains which are dependent on the length of the RNA transcript which has been made from a specific gene
- Stability is created through base pairing on the stem of hairpin loops which allows the mRNA to be exported out of the nucleus and into the cytoplasm for translation at the ribosomes on the rough endoplasmic reticulum
- messenger RNA, encodes amino acid sequence of a polypeptide (coded for by a protein coding gene on DNA)
What is the process of transcription?
- A protein coding gene in DNA which is identified by protein factors is subsiquently unwound and opened up by helicase (stabilised by topoisomerase (prevents supercoils))
- The DNA template strand is read 3’ to 5’ so the Pre-mRNA is coded in the 5’ to 3’ direction (Coding strand is not used but is identical to the subsequent Pre-mRNA formed but with uracil present in the place of thymine in the Pre-mRNA)
- RNA polymerase identifies the protein coding gene (by identifying the promoter region) and binds to the specific DNA region and travels along the DNA in a 3’ to 5’ direction, synthesising Pre-mRNA in a 5’ to 3’ direction (same length as gene being transcribed)
- RNA polymerase transverses the the RNA coding sequence laying down complimentary RNA nucleotides in a 5’ to 3’ direction which are bound together by ligase
- Once the RNA polymerase has transversed the RNA coding sequence and the terminator region is identified the Pre-mRNA formed is released
- As the Pre-mRNA is released the double helical DNA can reform
- Pre-mRNA is then processed to produced mRNA which can then be exported out of the nucleus and into the cytoplasm where translation can occur
What is rRNA?
ribosomal RNA, with ribosomal proteins, makes up the ribosomes (organelles that translate the mRNA)(coded for by rRNA gene)
What is snRNA?
mall nuclear RNA. With proteins, forms complexes that are used in RNA processing (spliceosome) in eukaryotes (coded for by snRNA gene)
What is a protein coding gene?
- DNA that codes for mRNA
- Consists of a promoter region, RNA coding sequence and a terminator region
What is an RNA coding sequence?
- In DNA
- Follows a promoter region
- Base pair sequence that includes coding info for the polypeptide
- Followed by a terminator region
What is a terminator region?
- Sequence that specifies the end of the mRNA transcript
- Signals the release of formed Pre-mRNA by RNA polymerase
What is a promoter region?
- identifiable by protein factors which bind to specific motifs in the promoter region to signal the RNA polymerase to bind and identifies the genes that need to be transcribed
- Sequence that specifies the start of the mRNA transcript
Why does the protein coding gene contain a promoter and terminator region?
- Protects the DNA
- Ensures the RNA coding sequence is identifies by RNA polymerase
