AP Bio Chapter 17 Part 3 Flashcards
Each round of replication does what to the lagging strand
Shortens the 5’ end by 100-200 bp
What poses a unique challenge during DNA replication
The ends of linear chromosomes
What would happen if the shortening of the lagging strand continued indefinitely
Chromosomes would get shorter and shorter after each replication, and information would begin to get lost
Telomeres
The ends of eukaryotic chromosomes. Consists of short, repeating DNA sequence
What is the vertebrate telomere
TTAGG
Telomerase
The enzyme responsible for replicating the ends of eukaryotic chromosomes
What does telomerase use
An RNA template to add more telomere sequence during replication.
Where is telomerase not active
Senescent cells
After DNA is replicated what does a proof reader enzyme do
Checks to be sure there’s no mutations, and fixes them (most mutations corrected before they have an effect)
What’s transcription
DNA-RNA
What happens in initiation of transcription
RNA Polymerase attaches to a “promoter” region in front (upstream) (where it will bind to) of a gene
Where does RNA polymerase bind in prokaryotes
Directly to the promoter
How does RNA polymerase bind in eukaryotes
Requires an assemblage of “transcription factor” proteins to be able to bind to the promoter
What characteristic things do promoters have
Characteristic DNA sequences (ex. TATA box in eukaryotes)
What happens during elongation in transcription
Similar to DNA replication, RNA production occurs in a 5’ to 3’ direction
The template strand of DNA
The strand that the RNA transcript is being produced off of (its sequence is opposite to the transcript)
The nontemplate strand of DNA
Coding strand
Same sequence as RNA transcript (with uracil instead of thymine in the transcript)
What happens in termination of DNA replication
Transcript production continues until the end of the transcription unit is reached
What happens after termination
Many types of protein play a role.
Approx. 10 types
3 major types
What are the 3 major types of RNA
mRNA
tRNA
rRNA
Messenger RNA
Carries DNA sequence information to the ribosome
Transfer RNA
Carries specific amino acids to the ribosome
Ribosomal RNA
Major structural building block of ribosomes
What happens to the mRNA transcript in prokaryotes
Immediately translated
What happens to the mRNA transcript in eukaryotes
The mRNA transcript is extensively processed in the nucleus before it leaves to be translated. While processed in the nucleus, 5’ cap and poly-A tail put on post transcription and RNA processing
What is added to the 5’ end of the transcript
A modified nucleotide
What is added to the 3’ end of the transcript and what does it function as
A tail of several hundred adenine residues, these modifications function in the nuclear export and maintenance of the mRNA
What do eukaryotic genes contain regarding “exon splicing”
Eukaryotic genes contain large stretches of non coding DNA (introns) interspersed between coding DNA (exons)
How is a functional protein produced in exon splicing, and what completes the process
Introns are removed and the exon she must be spliced together prior to the movement of the mRNA transcript to the nucleus
Accomplished by a splicesome (type of enzymatic DNA molecule)
Why are introns spliced?
Not answered
Evolutionary baggage? Selfish genes?
What do we know about having multiple exons in a gene
Allows eukaryotes to have multiple functional proteins from one gene (alternative splicing)
What can be interchangeable
Introns and exons
SORT OF IDRK MAN
