What is the central dogma? Flashcards
A description of information flow in the cell
The central dogma
basically the information in DNA is unraveled and decoded.
What is the first step in getting information from DNA to protein?
- Transcription
what is the process of transcription?
RNA is made using a DNA parental template
From one nucleic acid to another
what is the second step?
- Translation
what is the second step?
- Translation
what is the process of translation?
polypeptides get made using the information from a messenger RNA (remember polypeptides are a polymer of amino acids)
This process produces a specific sequence of amino acids
Nucleic Acid to Polypeptide
What is the difference between DNA replication and Transcription?
Unlike DNA replication, transcription occurs one gene at a time
A hereditary information consisting of a specific sequence of nucleotides in DNA
GENE
Can all genes be transcribed to make RNA?
YES
The process by which DNA directs the synthesis of proteins (what is the process where DNA directs the making of proteins?
Gene expression
What is the enzyme used in RNA transcription?
RNA polymerase
How does RNA polymerase know where to start and where to end?
Terminator- ENDS- RNA polymerase falls off template and transcription has stopped
Promoter- STARTS-RNAP binds and begins transcription
what is the function of the RNA polymerase?
similar to DNA polymerase, RNA polymerase adds new nucleotides onto a 3’ end of a growing RNA molecule
What bonds are being formed during this addition of nucleotides?
phosphodiester bonds
What is the template strand?
the template strand is where the RNA polymerase will attach and create RNA
What is the non template strand or otherwise known as coding strand?
the coding strand is not read by the RNA polymerase
Eukaryotes can modify their RNA before it goes through translation but prokaryotes cannot. What is this modification?
the changed made to the ends and interior sequences of RNA
pre-mRNA
before modifications have been made
Mature mRNA
modifications have been made
What are the alterations made to the mRNA ends?
In the 5’Cap: modified guanine nucleotide added to the 5’ end
protects mRNA from degradation
the 5 cap also helps in attaching the mRNA to ribosomes
3’ Poly Tail:
50 to 250 adenine (A) nucleotides are added to the 3’ end
protects from degradation
helps export mRNA from nucleus to cytoplasm
What is the goal of mRNA splicing?
mRNA splicing cuts out all the introns and keeps all extrons
why does the cell not want introns?
introns are intervening as well as non coding. Therefore they aren’t useful in the next step of information decoding
Encode proteins and useful for translation
exons
which enzyme helps cut out these introns?
splicesome enzyme cuts out introns from pre mRNA and joins exons together.
the process of polypeptide synthesis using mRNA sequence as a template
translation
which enzyme helps synthesize polypeptides during translation?
ribosome rna ( rRNA)
mRNA carries the
order of amino acids
tRNA delivers
amino acids
how are amino acids attached in order?
ribosome contains the ribosome rRNA enzyme and uses the information in mRNA to attack amino acids in order
what energy is used in translation?
GTP (guanine)
delivers amino acid to the ribosome during translation
tRNA
what are the two parts of a tRNA?
- Anticodon
2. Amino Acid attachment site
what is the amino acid attachment site?
amino acids are covalently bonded to the tRNA and each tRNA only carries one amino acid and that depends on the anticodon
Enzyme that catalyzes peptide bond formation between amino acids
Ribosome
What are the two complexes that come with ribosome enzyme?
- Ribosomal RNA rRNA
2. Ribosomal proteins
The ribosome contains 5 binding sites what are they?
one mRNA site (help make the active site)
two tRNA sites
A site ( new amino acid carrying tRNA binds)
P site (tRNA that is holding a growing polypeptide binds)
E site (empty tRNA leaves ribosome)
what are some jobs the ribosome does?
- holds mRNA and tRNA together
- positions new amino acid for adding to growing polypeptide chain
- catalyzes the formation of peptide bonds
what initiates translation?
a start codon
how are amino acids added to growing polypeptides?
tRNA has the job of delivering amino acids to the ribosome by base pairing to mRNA codon in the A site (because the A site is where new tRNA binds)
the rRNA enzyme has the job of creating the peptide bond between new amino acid and the already existing polypeptide chain
ribosome moves 5’-3’ down mRNA to read the next codon
finally empty tRNA (no more amino acids being carried) is released
What recognition terminates the process of translation?
recognition of the stop codon!
what are some similarities between prokaryotes and eukaryotes in transcription and translation?
Both eu’s and pro’s have synthesis of RNA using a DNA template for transcription
Both eu’s and pro’s synthesis polypeptides using mRNA sequence as a template
Ribosome is the enzyme used for both in translation
they both use the same genetic code
What are some differences in prokaryotes and eukaryotes ribosomes?
- different types of rRNA and proteins used for both eu’s and pro’s
- bacterial ribosomes are susceptible to antibiotics
- eukaryotic ribosomes are not
- translation startes before transcription is finished for prokaryotes
because translation starts before transcription can finish in prokaryotes what does this allow to form?
polyribosomes (a chain of ribosomes)
where does translation and transcription occur in prokaryotes?
in the cytoplasm
what about transcription and translation in eukaryotes?
in eukaryotes timing and location is different for transcription and translation.
where does transcription occur in eukaryotes?
in the nucleus (because that is where DNA is found)
where does translation take place in eukaryotes?
in the cytoplasm (where lots of ribosomes are found!)
why are transcription and translation seperated?
well transcripts are processed before translation can begin and mRNA must be exported from the nucleus
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