DNA Replication, Transcription, and Translation Flashcards
What are the three tenants of cell theory?
- All living things are composed of cells
- Cells are the basic units of structure and function in living things
- New cells are produced from existing cells
What are 5 differences between eukaryotes and prokaryotes?
Prokaryotes
-Cell wall usually present and it is chemically complex
-Single circular chromosome (lacks histones)
-Lacks membrane enclosed organelles
-No nuclear membrane
-No cytoskeleton
Eukaryotes
-When cell wall is present it is usually chemically simple
-Multiple linear chromosomes packaged around histones
-Has membrane enclosed organelles
-True nucleus
-Cytoskeleton
Explain the structure and function of DNA
-DNA is the carrier of genetic material. It contains the information that determines how, when, and where to produce each kind of protein in a cell
- DNA is comprised of monomers called nucleotides that make specific pairs
How is DNA packaged in chromatin
DNA - double helix - wraps around histones - packed tightly into chromatin - chromosomes
What are the 5 enzymes associated with DNA replication and their roles
1.DNA Helicase: unwinds the DNA to allow access to the template strand
2. Tipoisomerase: relieves supercoiling stress caused by the unwinding of DNA
3. DNA primase: A specialized RNA polymerase that forms short RNA primers on unwound template. Needed by DNA poly to attach and initiate elongation
4. DNA polymerase : uses template strand to add dNTPs in a 5’ to 3’ direction
5. DNA ligase: joins the Okazaki fragments on the lagging strand
Name the two types of DNA damage and give example
Endogenous:
- Replication errors
-attack by reactive oxygen species
Exogenous:
-radiation
-toxins
-hydrolysis
-virus
Name the 4 DNA repair systems
- Direct chemical reversal
- Base excision repair
- Nucleotide excision repair
- Mismatch repair (proofreading)
What is the role of RNA polymerase in DNA transcription
RNA polymerase is the primary enzyme responsible for transcription (5’-3’)
How many main types of RNA polymerases exist in eukaryotes? Name them and their roles
Three
1.Pol 1: large ribosomal DNA
2.Pol II: mRNA
3.Poll III: small tRNA and rRNA
Basal expression and regulated expression in eukaryotes are controlled by what?
proximal promoter elements and distal regulatory elements respectively
What are the three steps of transcription?
1.Initiation
2.Elongation
3.Termination
Describe the Initiation step of transcription
RNA poly recognized and binds to specific promotor site, separates the strands to expose the template strand, begins synthesis of RNA
Describe the elongation step of transcription
Occurs along the DNA molecule and therefore DNA unwinding must occur. RNA poly has “unwindase” activity that opens the DNA helix. Topoisomerase precedes the RNA poly and relieves supercoiling. RNA is elongated in the 5’ - 3’ direction
Describe the termination step of transcription
There are two types of termination:
Rho Dependent- where the rho protein knocks off the RNA poly when it is instructed to pause by the DNA
Rho Independent- there is a downstream terminator sequence on the DNA
Name the three post transcriptional RNA modifications
1.Methylated guanine cap: added to the 5’ end of the mRNA
- ribosomal subunits recognize the 5’ cap and use it to initiate translation
2.Poly A tail: added to the 3’ end of the mRNA
3. The RNA is spliced to remove introns
-alternative splicing can yield different protein products as well as mechanism for differential regulation of the same protein
