Unit 6? Flashcards
What are the purines
A and G
What are the pyrimidines
C and T
Are purines or pyrimidines wider
Purines
DNA strands run (direction)
Antiparallel
Where does the replication of chromosomal DNA begin
Origins of replication
What is at each end of a replication bubble
Replication fork
What untwists the double helix at the replication forks
Helicases
What keeps the DNA open in the replication bubble
Single-strand binding proteins
What breaks and rejoins dna strands during dna replication before the replication bubble
Topoisomerase
How does the Antiparallel arrangement of the double helix affect replication?
Because of their structure, DNA polymerases can add nucleotides only to the free 3’ end of a primer or growing DNA strand, never to the 5’ end
DNA strands can only elongate in the direction of
5’ -> 3’
What enzyme synthesizes new complementary strands
DNA polymerase III
What’s the DNA strand made by DNA polymerase called
The leading strand
What strand is synthesized discontinuously
Lagging strand
The lagging strand is made of little segments. What are the segments called?
Okazaki fragments
Three stages of translation?
Initiation, elongation, termination
Initiation begins when…
Small ribosomal subunit binds to mRNA and charged tRNA binds to start codon on mRNA
What is the start codon?
AUG
What’s the second step of initiation
Large ribosomal subunit binds to mRNA
What starts elongation?
Next tRNA comes to the A site, mRNA is moved through the ribosome and it’s codons are read
What does all organisms using the same genetic machinery imply?
THERE IS COMMON ANCESTRY ‼️‼️
First part of elongation?
The appropriate anticodon of the next tRNA goes to the A-site
Second part of elongation
Peptide bonds are formed that transfer the polypeptide to the A site tRNA
Third part of elongation
the tRNA in the A site moves to the P site, the tRNA in the P site goes to the E site. The A site is open for the next tRNA
What is the A site
Amino acid site
What is the P site
Polypeptide site
What is the e site
Exit site
Where are the three sites?
On the large ribosomal subunit
What happens in termination
A stop codon in the mRNA reaches the A site of the ribosome
How does transcription work in retro viruses
Information flows from RNA to DNA, enzyme used called reverse transcriptase, viral RNA is coupled to DNA, DNA becomes part of RNA
What is gene expression
The process by which DNA directs the synthesis of proteins
What is transcription
The synthesis of RNA using information from DNA
Where does transcription occur
Nucleus
What is translation
The synthesis of a polypeptide using information from RNA
Where does translation occur
At the ribosome
Functions of tRNA
They carry amino acids and can attach to mRNA via their anticodon. They allow information to be translated into a peptide sequence
What is the DNA strand that gets transcribed called
Template strand
Transcribed mRNA strands are
Antiparallel and complementary to the DNA nucleotides
What are the mRNA nucleotide triplets are called
Codons. Codons code for amino acids
For most amino acids, there are multiple codons that can code for them. What is this called?
Redundancy
Three steps of transcription
C Initiation
C Elongation
C Termination
What happens in C Initiation
RNA polymerase attach to a promoter region of DNA (no primer needed)
Where are promoter regions (transcription)
Upstream of the desired gene to transcribe
C Initiation in eukaryotes
Promoter region is called TATA box, transcription factors help RNA polymerase bind
if DNA can’t unwind, no initiation can happen
C initiation prokaryotes
RNA polymerase can bind directly to promoter
Why is there a lagging strand
The strand runs in the 3’ to 5’ direction, but it must be built in the 5’ to 3’ direction. The lagging strand has to wait for a long segment of DNA to become unwound and exposed before replication can start with the addition of a primer
What puts together the Okazaki fragments
Ligase
What’s mismatch repair
A protein complex binds to mispaired bases, the mispaired base it cut out with enzymes and replaced by DNA polymerase
What has to happen before dna replication can occur
Primase has to put RNA primers on the DNA template strand
What’s the role of microRNA (mrRNA) in gene expression
microRNA helps pick which genes are expressed
How does the process of horizontal/lateral gene transfer lead to genetic diversity
Organisms can acquire new genetic information from other organisms
What’s transformation?
when cells can take in DNA that is placed near them, transformation is often used in experiments
What are nucleotides made of
Nitrogen base, sugar, phosphate group
How many rings do purines have
2
DNA is made of
A sugar-phosphate backbone, nucleotides paired with hydrogen bonds
How many bonds between A and T
2 hydrogen bonds
How many bonds between C and G
3 hydrogen bonds
Are plasmids part of the prokaryotic cells DNA
they are distinct from the chromosomal DNA
Which strand is the leading strand
The one that runs 5 to 3 toward the replication fork
Operons are only in
Prokaryotes
Difference between DNA Polymerase I and DNA Polymerase III
DNA polymerase III does most of the replicating,Polymerase I removes RNA primers
What does telomerase do
Adds DNA to the ends of chromosomes to keep them from being damaged, it also adds RNA bases to the 3’ end of the DNA strand in replication
RNA primers function
It attaches to leading strand of DNA and allows DNA polymerase to add new nucleotides to the strand
What’s morphogenesis
The shaping of an organism by embryological processes of differentiation
What’s DNA sequencing
Determining the order of the bases that make up the DNA molecule
What’s the 5’ cap on mRNA for
It keeps the mRNA from degrading
Where do transcription factors bind
Enhancer on rna
