From genes to phenotype Flashcards
(26 cards)
What must happen for genes to affect phenotype?
Genes must be expressed
What is the central dogma of molecular biology?
The flow of information from DNA to RNA to protein
Are there exceptions to the central dogma?
Yes, a small number, e.g., RNA genomes of some viruses
What is transcription?
DNA is used as a template to make a complementary RNA transcript using the enzyme RNA polymerase
Which DNA strand is transcribed?
Only the template strand
Where are ribonucleotides added during transcription?
To the 3’ end of the RNA transcript
What forms the transcription bubble?
Two DNA strands separate within RNA polymerase to allow transcription
What protein helps RNA polymerase bind to promoters in bacteria?
Sigma factor
How is transcription initiation regulated in eukaryotes?
Through general transcription factors and mediator complexes interacting with RNA polymerase II and enhancer-bound proteins
Why can’t translation occur immediately in eukaryotes?
Primary transcripts are in the nucleus; ribosomes are in the cytoplasm
What modifications happen to primary transcripts?
- 5’ cap added
- Poly(A) tail added to 3’ end
- RNA splicing removes introns
What are exons and introns?
Exons code for protein; introns do not and are removed
What is alternative splicing?
The process where primary transcripts from the same gene are spliced differently to produce various mRNAs and proteins
What is the function of rRNA?
Forms the bulk of ribosomes, essential for translation
What does tRNA do?
Carries amino acids to the ribosome during translation
What is snRNA?
Small nuclear RNA, essential for the spliceosome function
What are the three main stages of translation?
Initiation, elongation, termination
What happens during initiation?
nitiation factors recruit the small ribosomal subunit and tRNA, scan for AUG start codon; large subunit joins; tRNA binds A site
What happens during elongation?
Ribosome moves codon by codon; polypeptide chain grows as amino acids are added
What happens during termination?
Stop codon is reached; release factor binds; polypeptide is released
At which stages can gene expression be regulated?
At any stage—epigenetics, chromosomal regulation, transcriptional regulation, post-translational regulation
How does chromatin remodeling regulate gene expression?
Histone modifications expose or hide DNA, affecting transcription
What does DNA methylation do?
Adds CH3 groups to DNA bases, restricting transcription factor access and repressing transcription
What do regulatory transcription factors do?
They bind enhancers to promote transcription or silencers to repress transcription
