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Lecture 25: Genes & Genomes (Steps in production of functional gene…
Lecture 25: Genes & Genomes
Genomes vary widely in size
Gene number varies less than DNA content
Gene Duplication is important to evolution
Elements of Genome:
Dispersed Repeat
Present all over genome, not necessarily on one chromosome
Tandem Repeat
Many of the same gene in a row
Single-Copy Gene
Simple-Sequence Repeat
AAAAA, TATATA, etc.
Noncoding RNA
Genes go from:
DNA>
#
RNA>
#
Protein
3 nucleotides= 1 codon
RNA
RNA structure is determined by intramolecular base pairing
Types:
Transfer RNA (tRNA)
Brings amino acids to mRNA/ribosome
microRNA (miRNA)
RNA regulation/ transcription inhibition
Ribosomal RNA (rRNA)
Is part of ribosome
Steps in production of functional gene product
Transcription
RNA processing (Primary transcript turned to mRNA as introns removed)
DNA unpacked thru histone acetylation & DNA demethylation
Transport to cytoplasm
Translation (mRNA degraded, polypeptides formed)
Cleavage, chemical modification, transport to cellular destination
Degradation of protein
Three general Categories of Genes:
Transcribed, non-coding sequence
Introns
UTRs
Regulatory Sequences
Enhancer, Promoter
Coding Sequence
Exons, Poly-A signal sequence
3' UTR, 5' Cap (phosphorous), Poly-A tail
Viruses
Use Reverse Transcriptase to turn their RNA into cell's DNA
Retrotransposons make up the majority of human genome
Reverse transcriptase puts duplication of viral DNA into genome again; this is then itself transcribed
Transcription
Translation