6. Transcription: RNA structure and function

Question 1

Reverse transcription

Answer 1

Viruses using RNA as a template to synthesize DNA

Question 2

Central Dogma in Prokaryotes

Answer 2

mRNA is not modified, codons translate into an amino acid without modification

Question 3

Central Dogma in Eukaryotes

Answer 3

1. Transcription produces pre-mRNA, both ends are modified and introns spliced out
2. Modified mature mRNA leaves nucleus, goes into cytoplasm toribosomes, and protein synthesis occurs

Modification: addition of 5’ cap at 5’ end, and Poly-A Tail (3’ polyadenylation)

Question 4

Types of RNAs

Answer 4

mRNA: intermediates, carries gene info from DNA to ribosomes

rRNA: ribosomal RNA, structural and catalytic component

tRNA: brings amino acids into the ribosome

snRNA: small nuclear RNA–components of spliceosomes, regulates transcription factors and RNA polymerases

miRNA: microRNA–short single-stranded RNA that block the expression of mRNA

Question 5

Promoter for transcription

Answer 5

-an “upstream” nucleotide sequence that regulates binding
mRNA transcribed from one strand of DNA via RNA polymerase

Question 6

Steps of transcription

Answer 6

1. Initiation
2. Elongation
   3.Termination

Question 7

mRNA strand and dsDNA

Answer 7

-same as coding strand, but Treplaced by U
-complimentary to template strand

Question 8

Differenciation of cells + tissues

Answer 8

-all cells in an organism have the same genes
- control of cellular activity for different cells = control of gene expression

Question 9

Eukaryotic gene expression regulation

Answer 9

Transcriptional control:
-early + efficient but slow

Enzyme activiation:
-fast but wastes energy

More intermediatr oppoirtunities in eukaryotes