Study Unit 4: RNA molecules and RNA processing:
1) Gene Organization:
1) Collinearity: number of nucleotides in a gene should be proportional the
number of amino acids in a protein
2) Problems with collinearity
mRNA contains sequences at their ends that do not lead to the
incorporation of amino acids
eukaryotic cells have far more DNA than is required to encode
proteins
large RNA in nucleus is not observed in the cytoplasm (this
indicates that RNA is changed before being transported to
cytoplasm)
3) Introns vs Exons
Introns are non-coding regions of the gene and exons are coding
regions of the gene
Introns are removed from RNA during RNA splicing
Major groups of introns
Type of intron Location Splicing Mechanism
Group I Genes of bacteria Self-splicing:
and eukaryotes catalyzes its own
splicing
Group II Organelles of Self-splicing:
bacteria and catalyzes its own
eukaryotes splicing
Group III Protein encoding Spliceosome;
genes in the nucleus requires RNA for
splicing
tRNA tRNA: bacteria and Enzymatic: requires
eukaryotes enzymes for splicing
4) Concept of a gene:
Sequence of DNA that encodes introns and exons
Includes regions that do not encode proteins such as promoters
and the terminator sequence
2) Structures of mRNA:
, 1) Made of 3 parts: 5’ UTR (untranslated region), protein coding region and
3’ UTR (untranslated region)
2) The 5’ UTR site
Consensus sequence at the 5’ end of mRNA that does not encode
proteins (not translated)
Shine Dalgarno sequence in RNA serves as ribosome binding site
3) Protein coding region:
Start codon: where translation starts
Codons: 3 nucleotides that encode for a specific amino acid
Stop codon: where translation ends
4) The 3’ UTR
Does not get translated
Important for the stability of mRNA
3 Pre-mRNA processing:
Bacteria Eukaryotic cells
mRNA does not undergo pre-mRNA Does undergo pre-mRNA processing
processing
Transcription and translation both mRNA has to be transported to
occurs in the cytoplasm cytoplasm
5’ end binds to ribosome (translation) Translation and transcription are
while 3’ end is still being synthesized separated in time and space, allowing
(translation) time for pre-mRNA processing
3.1) Addition of 5’ cap
1) Gene Organization:
1) Collinearity: number of nucleotides in a gene should be proportional the
number of amino acids in a protein
2) Problems with collinearity
mRNA contains sequences at their ends that do not lead to the
incorporation of amino acids
eukaryotic cells have far more DNA than is required to encode
proteins
large RNA in nucleus is not observed in the cytoplasm (this
indicates that RNA is changed before being transported to
cytoplasm)
3) Introns vs Exons
Introns are non-coding regions of the gene and exons are coding
regions of the gene
Introns are removed from RNA during RNA splicing
Major groups of introns
Type of intron Location Splicing Mechanism
Group I Genes of bacteria Self-splicing:
and eukaryotes catalyzes its own
splicing
Group II Organelles of Self-splicing:
bacteria and catalyzes its own
eukaryotes splicing
Group III Protein encoding Spliceosome;
genes in the nucleus requires RNA for
splicing
tRNA tRNA: bacteria and Enzymatic: requires
eukaryotes enzymes for splicing
4) Concept of a gene:
Sequence of DNA that encodes introns and exons
Includes regions that do not encode proteins such as promoters
and the terminator sequence
2) Structures of mRNA:
, 1) Made of 3 parts: 5’ UTR (untranslated region), protein coding region and
3’ UTR (untranslated region)
2) The 5’ UTR site
Consensus sequence at the 5’ end of mRNA that does not encode
proteins (not translated)
Shine Dalgarno sequence in RNA serves as ribosome binding site
3) Protein coding region:
Start codon: where translation starts
Codons: 3 nucleotides that encode for a specific amino acid
Stop codon: where translation ends
4) The 3’ UTR
Does not get translated
Important for the stability of mRNA
3 Pre-mRNA processing:
Bacteria Eukaryotic cells
mRNA does not undergo pre-mRNA Does undergo pre-mRNA processing
processing
Transcription and translation both mRNA has to be transported to
occurs in the cytoplasm cytoplasm
5’ end binds to ribosome (translation) Translation and transcription are
while 3’ end is still being synthesized separated in time and space, allowing
(translation) time for pre-mRNA processing
3.1) Addition of 5’ cap
