CHAP 2 Flashcards
What is the function of DNA polymerase?
travels along the single DNA strand and adds free nucleotides to 3’ end of the strand (replication always occurs 5’ to 3’
What is upstream and what is downstream?
5’ direction is upstream, 3’ direction is downstream
What are pyrimidines?
single carbon-nitrogen rings (Cytosine and thymine)
What are purines?
double carbon-nitrogen rings (adenine and guanine)
What makes up the sides of the double helix? and the middle?
sides- sugar and phosphate held together by phosphodiester bonds, chemical bonds held together by hydrogen bonding create the steps
What allows the replication process to occur more quickly?
replication origins and bubbles
What mediates transcription and translation?
RNA
How does RNA differ from DNA?
RNA contains ribose instead of deoxyribose, and uracil rather than thymine, It is also a single strand.
What is transcription
RNA is formed form a DNA template (mRNA)
Describe sense and antisense strands
When transcription begins, RNA polymerase binds to a promoter site on the DNA which seperates the DNA strands. The DNA strand that serves as a template is the antisense strand and the remaining strand is the sense strand (should be identical to the mRNA being transcribed)
What helps the RNA molecule from being degrade during synthesis?
5’ Cap- a chemically modified guanine nucleotide
After a termination sequence is reached what happens to the RNA strand?
100 - 200 adenine bases are added to the 3’ side –> poly-A tail PRIMARY TRANSCRIPT IS FORMED
What is the chain of interactions that increase transcription?
enchancer –> activator –> coativator –> general transcription complex –> gene
Describe the helix-turn-helix motif.
Two alpha-helices connected by a short chain of AA– HOX genes can cause synpolydactyly (BIND TO DNA GROOVE)
Describe a helix-loop-helix motif.
One short and one long helix connected by a flexible loop –Mutation in TWIST gene (Saethre-Chotzen syndrome)
Describe a zinc finger motif.
Zinc molecules that stabilize AA structures (BIND TO DNA GROOVE)– Breast cancer gene, Wilms tumor gene (WT1), Vit D receptors (rickets)
Describe a leucine zipper motif.
2 leucine-rich alpha-helices held together by AA side chains (BIND TO DNA GROOVE) –RB1 (retinoblastoma genes)
Describe a beta-sheet motif.
Side chains extend from 2 beta sheets to form contacts with DNA helix –TBX5 (Holt-Oram syndrom) TBX3 (ulnar mammary syndrome)
What are euchromatins?
TRANSCRIPTIONALLY ACTIVE opened/decondensed chromatin regions, characterized by histone acetylation (attachment of acetyle groups to lysine residue in histones)
What are heterochromatins?
Less acetylated more condensed and transcriptionally inactive chromatin regions
Describe the change from a primary mRNA transcript to a mature mRNA transcript.
Introns are spliced OUT and exons are left to code for proteins. mRNA then moves into the cytoplasm
What are the three STOP codons?
UAG UUA UGA
What is translation?
mRNA interacts with tRNA to synthesize polypeptides
Where does rRNA bind to and what is its function?
rRNA binds to the initiation site on the mRNA– methionnine (AUG). It binds tRNA and mRNA
