Final Study Guide Deck Flashcards
What are 2 strands of DNA held together by
Hydrogen bonds
How many hydrogen bonds are between G and C
3
How many hydrogen bonds between A and T
2 ( that’s why there is a TATA box at the beginning of Transcription- break apart the A-T double bond bc its weaker than G-C triple bond)
Nucleoside vs Nucleotide
Nucleoside: Sugar and base
Nucleotide: Sugar, Base, Phosphate group
What are the purines and what are the pyrimidines
Purines: A/G (double ringed)
Pyrimidines: C and T, U (single ringed)
What are 3 structural features of DNA
- Right handed double helix, antiparallel, complementary
Which enzyme seperates the 2 strands of DNA during replication
Helicase
Which enzyme makes the RNA primer
Primase
Difference between DNA polymerase 1 and DNA polymerase 3
1: Removes DNA primers
3: Adds DNA bases 5’–>3’
What are telomeres
At the end of the chromosomes, prevent gene loss ( In somatic cells, the telomeres shorten whith every dvision. In Stem/Cancer cells, telomerase ensures that telomeres do not shorten).
Where is the telomerase gene found
In stem cells and gametes
What is a clinical application with telomerase
Premature aging occurs when there is no telomerase.
Telomerase is expressed in 90% of cancers, stimulates cell division.
What is Mismatch repair, and which cancer is related to it?
Mismatch repair: One nucleotide is removed by an exonuclease and strand is repaired
Colorectal cancer (lynch syndrome) loss of function in DNA mismatch repair
What is nucleotide excision repair and its clinical application
- Remove bulkey DNA lesions (caused by UV light, i.e. skin cancer)
- Xeroderma Pigmentosum is a defect in nucleotide excision, skin cells can’t fix themselves, so early and frequent skin cancers
Base excision repair
One or a few bases damaged, corrected easily
Double strand break repair and clinical correlation
- Most dangerous- A number of bases are damaged and there is non-homologous end joining, not accurate, and DNA lost in process.
- BRCA 1 associated (Breast Cancer)
rRNA function
site of translation, structural and functional components of ribosome
tRNA function
transfers amino acid for protein synthesis
Common structure of tRNA
cloverleaf
mRNA function
template for protein synthesis, carries genetic information from DNA to ribosome
What do eukaryotes have in their mRNA that differs from prokaryotes?
Poly- A tai and Cap
Enhancer vs silencer at promotor
Enhancer: bound by enhancer-binding transcription factor
Increase the rate of txn
Silencer: Decrease the rate of txn
3 steps of transcription in Eukaryotes
Initiation, Elongation, Termination
Transcription difference between bacteria and Eukaryotes:
SImilar
Steps: initiation, elongation and termination
Differences:
Euk have 3 different polymerase and bacteria have one
Euk DNA is complexed with proteins
Where does splicing occur
in the nucleus ( Introns taken out, exons left in and EXPRESS)
Beta Thalassemia is a condition where there is an error in which protein?
Splisosome, there is inproper splicing of the genes.