Eukaryotes And Prokaryotes Flashcards
How many genes do prokaryotes have
500 to 4000
How many genes do eukaryotes have
6000 to 30,000
True or false: Prokaryotes have Introns (non-codon regions)
False, eukaryotes do
What are the components of a chromatid (chromosome)
Chromatin (DNA strands) wrapped around histomes, (8) clustered into a nucleosome, nucleosides fold into coils, coil further and further to make the chromatid of a chromosome
What is chromatin
Combination of DNA, RNA and proteins that make up eukaryotic chromosomes
What is euchromatin
Lightly asked form of chromatin rich in gene conc. usually actively being expressed, loosely packed to allow RNA in to transcribe
What is heterochromatin
Tightly packed form of DNA, little or no expression. RNA can’t access it because it’s too tight
Why do the number of proteins coded for far exceed the number of genes we have
Because introns can be cut out and different exons can be spliced together, alternative splicing
What is epigenetics
Wheh environmental factors change genotype or expression, can be inherited
What is DNA transcription
DNA-directed synthesis of RNA
What aids mRNA I’m getting from nucleus to ribosome
The addition of a 5’ cap (prevents premature breakdown) and a Poly-A tail (helps with transport out of nucleus)
Describe the initiation of RNA polymerase
Polymerase binds to Promoter, DNA strand unwinds and enzyme initiates RNA synthesis at start point on template strand
Describe the elongation step of RNA polymerisation
Polymerase runs DOWNstream, unwinding and elongating RNA transcript 5’ to 3’.
Describe termination of RNA Polymerase
Eventually polymerase transcribes terminator sequence which signals end of transcription unit. RNA transcription released and polymerase detaches from DNA
What processes do eukaryotic genes have to go through that prokaryotic genes don’t
RNA Splicing RNA capping (5’ capping) Poly-A tail (3’ Polyadenylation) exporting miRNA Gene silencing
What are snRNAs and Spliceosomes
snRNAs and proteins come together into a spliceosome. SnRNAs then base pair with nucleotides at the end of the introns. RNA transcriptase then cuts to release introns and the Exon’s are spliced back together and released from spliceosome.
What is an operon
Clustered genes in a prokaryote (functionally related)
What is a repressive protein
Protein activated by specific molecule, then binds to operator and blocks transcription (prokaryote)
What is the de-repression of transcription
Molecules bind to depressor and lower DNA binding cap
What is “Activation possible” gene control in prokaryotes
When proteins bind to promoter and stimulate RNA polymerase binding
How long is a poly-A tail
50-250 base pairs long
What is the TATA box
T & A bases ~25bp long in promoter region, transcription factor bonds to it and helps RNA polymerase II find and attach to the DNA strand
True or false: RNA synthesis is done by a transcription factor complex rather than just RNA Polymerase
True, RNA polymerase (II), transcription factor, enhancer, activated DNA binding proteins
Describe what a phosphorylated protein does in the nucleus
Addition of phosphate to protein, activated enzyme enters through nuclear pore and interacts with TFs. TFs modified (activated) and binds to enhancer region and moves to interact with the rest of the transcription protein. When complex is complete, transcription starts
