Chapter 13 Flashcards
What is all DNA present in a cell or virus?
Genome
Set of specific genes an organisms possesses
Genotype
Collection of observable characteristics
Phenotype
Who proposed the transformation principle?
Griffith
Who showed that the transformation principle was DNA
MacLeod and McCarty
Who showed that DNA is genetic material?
Hershey and Chase
What links polymers of nucleotides together?
phophodiester bonds
How do DNA and RNA differ?
nitrogenous bases
sugars
single or double stranded
What is the structure of DNA
polymer of nucleotides
sugar phosphate backbone
What are the bases for DNA?
Adenine, Guanine, Cytosine, and Thymine
What is the sugar for DNA?
deoxyribose
What is the structure of the phosphate backbone?
3’ to 5’ with covalent bonds between them
What pairs with Adenine?
Thymine; 2 hydrogen bonds
What pairs with Guanine?
Cytosine; 3 hydrogen bonds
What are the nucleotides for RNA?
Adenine, Guanine, Cytosine, Uracil
Are RNA single or double stranded?
Single
What are the three different functions of RNA?
mRNA
tRNA
rRNA
What is the protein structure?
polymer of amino acids linked by peptide bonds
What is C-terminal?
Carboxy group
What is N-Terminal?
amino group
How can amino acids be organized?
polar, non polar, or charged
2 strands separate, serving as a template for a complementary strand.
DNA Replication
What does it mean that DNA Replication is semi-conservative?
each daughter cell obtains one old and one new strand
Where is DNA unwound?
at the replication fork
Origin and is replicated as a unit?
Replicon
What protein synthesizes RNA primer?
DNA primase
What protein relieves supercoiling of DNA?
DNA gyrase
What protein removes RNA primers?
DNA polymerase 1
Which way is DNA synthesized?
5’ to 3’
What do polymerases require?
template
primer
dNTPs
What does the template do for polymerases?
directs synthesis of complementary strand
What is the primer for polymerase?
DNA or RNA strand
How many polymerases does E.coli have?
5
What is a complex of 10 proteins and 3 proteins for a core enzyme?
DNA polymerase holoenzyme
How many enzymes are in each polymerase and what do they do?
2; catalyze DNA synthesis and proofread
What protein keeps strands apart for replication to occur?
Single stranded binding proteins
What protein breaks one strand of DNA?
Topoisomerase
What happens at the replication fork?
- DNA is synthesized in the 5’-3’
- Okazaki fragments are formed
- A new primer is needed for each okazaki fragment
What protein bends strands in E.coli DNA?
DnaA
What protein separates strands in E.coli DNA?
DnaB
In E.coli, what removes RNA primers and fills it with DNA?
DNA polymerase I
What links a growing 3’ strand and a Okazaki 5’ fragment?
DNA ligase
What polymerase proofreads?
III
What removes the mismated base during proofreading?
exonuclease
When does replication stop in E.coli?
when the replisome reaches the termination site
What protein forms when two circular chromosomes do not separate?
Catenanes
What separates the catenanes?
topoisomerases
What is a problem with “end” replication?
it can be too short
How is short chromosomes solved in eukaryotes?
telomerase
How is short chromosomes solved in bacteria?
it disguises them
What is the basic unit of genetic information?
gene
What is a gene also defined as?
nucleic acid sequence
What is the structure of a gene?
linear sequence of nucleotides
Where are codons found?
mRNA
How is DNA read?
3’ - 5’
What is the coding strand?
complementary strand
What starts protein coding?
Promoter
What ends a coding region?
stop codon
DNA that codes for tRNA and rRNA are considered what?
genes
What is transcription?
RNA synthesis under the direction of DNA
What RNA carries the message for protein synthesis?
mRNA
What RNA carries amino acids during protein synthesis?
tRNA
What RNA carries components from the ribosome during protein synthesis?
rRNA
What type of mRNA is found in bacteria and archaea?
polycistronic mRNA
What initiates transcription?
a promoter
After the promoter binds in transcription, what happens?
RNA polymerase unwinds the DNA
What happens in transcription elongation?
a bubble is produced that holds a temporary RNA:DNA hybrid
When does transcription terminate?
when the core RNA polymerase dissociates from the template DNA
How long is a codon?
three base pairs
What does a codon do?
specifies amino acids
What is the start codon?
AUG
How many sense codons are there?
61
Termination signals for codons?
Stop codons
How many different codons can code for a single amino acid?
Up to six
What does a wobble do?
eliminate the needs for unique tRNA for each codon
Where is the site of translation?
ribosome
What is a complex of mRNA with several ribosomes?
polyribosome
What is the shape of tRNA?
tertiary
What end of tRNA binds to amino acids?
3’
What activates a amino acid?
attachment to a tRNA
how many amino acids are there?
20
What is the role of rRNA in translation?
contributes to the structure of the ribosome
What does the 16S RNA bind to?
mRNA for protein synthesis
What does the 23S RNA bind to?
ribozyme catalyzes peptide formation
What initiates protein synthesis?
ribosome subunit and numerous molecules
What is the elongation cycle?
addition of amino acids to growing polypeptide
What are the three phases of the elongation cycle?
amioacyl-tRNA
transpeptidation
translocation
What bind the tRNA to growing polypeptide?
peptidyl site
What binds incoming aminoacyl-tRNA
aminoacyl site
What binds empty tRNA before it leaves the ribosome?
Exit site
What catalyzes transpeptidation reactions?
peptidyl tranferase
What happen in translocation?
peptidyl tRNA moves from A to P site, ribosome moves down, tRNA leaves P site
What codons can stop protein synthesis?
UAA
UAG
UGA
During protein splicing what is the removed portion?
inteins
During protein splicing what is the portion that remains in the protein?
exteins
How does protein mature?
folding and association with other proteins
Where are proteins secreted?
subcellular or extracellular site
What do molecular chaperones do?
aid in folding
protect from thermal damage
aid in transport
What is protein translocation ?
movement of proteins from cytoplasm to p.m or periplasmic space?