from gene to protein
Transcription
Transcription: is the synthesis of RNA using information in DNA. DNA provides the template upon which the RNA is transcribed and controls the sequence of RNA nucleotides
Describe termination in prokaryotes
in prokaryotes a terminator sequence indicates that a particular gene is complete. This sequence causes the RNA polymerases to be released from the DNA, no further modification is required before translation
A triplet code
is that the 20 amino acids found in proteins are coded four by groups of three nucleotides sequences.
Terminator
a sequence that signals the end of transcription
List the ways in which pre-mRNA is modified during RNA processing in eukaryotes
1. Bothe ends of the primary mRNA transcript are altered 2. in most cases certain interior sections of the RNA molecule are cut out and the remaining sections spliced together
Describe the steps of transcription in prokaryotes
1. Initiation, RNA polymerases binds to the promoter sequence on DNA unwinding the DNA strands and indicates RNA synthesis at the start point of the template strand 2. Elongation: RNA ol moves down the DNA molecule in the 5'-3' direction adding to the growing mRNA molecule as it moves, the DNA strands re-form behind the RNA polymerases 3. Termination: once complete the mRNA transcript is released, the RNA polymerases become detached from the DNA and the DNA re-forms.
Suppose an mRNA sequence is 1200 nucleotides long. How many amino acids would there be in the initial polypeptide translation from this mRNA sequence?
399-400
Suppose a triplet on the template strand of DNA is 3' - CAG- 5'. What is the mRNA codon transcribed from this template sequence? And what amino acid would this mRNA codon call for.
5'-GUC-3' It would code for the amino acid glutamine (Gln)
How fast can a single RNA polymerases add nucleotides
A single RNA polymerases can add nucleotides at a rate of about 40 per second in eukaryotes
Exons and introns
Exons are the coding regions of the mRNA (and DNA) and the introns are the non-coding regions of the mRNA (and DNA). The introns are removed from the mRNA molecule and the remaining exons are spliced together, an exception to this is the non-coding UTR's at the ends of the mRNA, which remain on the molecule when it exits the nucleus.
what is gene expression and what are the two stages of gene expression
Gene expression has two stages. It is the process by which DNA directs the synthesis of proteins and, in some cases, just RNA's. it occurs in two stages, transcription and translation.
Imagine that the non template sequence in the question above was transcribed instead of the template sequence, draw the mRNA sequence and translate it to show the polypeptide produced, predict how well the protein synthesized from the non template strand would function, if at all.
Nontemplate sequence:5'-AAGTCAGCA-3' mRNA Sequence :5'- UGCUGACUU-3' amino acid sequence : cystine- STOP(last codon not translated because of STOP codon) The mRNA is antiparallel to the DNA strand; a protein translated from the non template sequence would have a completely different amino acid sequence and would most likely be nonfunctional. It would also be shorter because of the STOP signal in the mRNA sequence above.
What would happen if the 5-cap was removed from mRNA
Once the mRNA has exited the nucleus, the cap prevents it from being degraded by hydrolytic enzymes and facilitates its attachment to ribosomes, if the cap were removed from all mRNA's the cell would no longer be able to synthesize any proteins and would probably die
how do organisms their rate of transcription
Organisms increase their rate of transcription by having many RNA polymerases molecules acting on a single gene simultaneously
Where is Pre-mRNA modified
Pre-mRNA is modified within the nucleus
what are the properties of introns that suggest evolutionary significance
Properties of introns that suggest evolutionary significance 1. Introns are known to contain sequences that regulated gene expression 2. The presence of introns allow organism to produce more than on polypeptide per gene 3. Introns may facilitate the evolution of new and potentially beneficial proteins through a process called exon shuffling, in which crossing over rates between exons increases because of the increased distance between them.
how is rna different that dna
RNA has the sugar, ribose, as opposed to deoxyribose in DNA and has the nitrogenous base, uracil, which replaces the thymine of DNA. Additionally, RNA is single stranded.
The template strand of a gene containing the sequence 3'- TTCAGTCGT- 5'. Draw the non template sequence and the mRNA sequence, indicating 5' and 3' ends of each, compare the two sequences, also draw the amino acid sequence of the polypeptide translated from this mRNA sequence.
Template Strand: 3'- TTCAGTCGT- 5' non Template Strand :5'- AAGTCAGCA-3' mRNA sequence : 5'- AAGUCAGCA-3' amino acid sequence : lysine-serine-alanine
Describe the template strand of dna
Template strand of DNA is the strand of DNA that transcribes the mRNA molecule. The other strand of DNA is not active in the process of transcription.
what is the modification at the 5' end of the pre-mRNA molecule
The modification at the 5' end of the pre-mRNA molecule is that 5' end receives a 5' cap, which is a modified form of guanine
what is the modification at the the 3' end of the pre-mRNA molecule
The modification at the the 3' end of the pre-mRNA molecule is an enzyme adds 50-250 more adenine nucleotides to the polyadeylation signal, forming a poly-A-tail
describe the process of translation
The process of translation is the synthesis of a polypeptide using the information in mRNA. The sites of translation are ribosomes, which facilitate the orderly linking of amino acids
what is mean by the statement " nucleic acids and proteins contain information written in two different chemical languages"
The statement " nucleic acids and proteins contain information written in two different chemical languages" means the information of DNA is found in the sequence its nitrogenous bases while the information of proteins is found in its sequence of amino acids
What does the statement" the sequence of DNA nucleotides that codes for eukaryotic polypeptides is usually not continuous" mean
The statement" the sequence of DNA nucleotides that codes for eukaryotic polypeptides is usually not continuous" means that in a gene of eukaryotic DNA ther are sections that cod for polypeptides with non-coding sequences of DNA nucleotides interspersed. The entire gene, including coding and not- coding regions is transcribed into the mRNA molecule, the non-coding regions, which lie between the coding regions, must be removed before translation commences
what are the three properties that allows RNA to act as an enzyme
The three properties that allows RNA to act as an enzyme 1. because RNA is single stranded it can base pair with itself to produce a specific three dimensional conformation 2. some of the bases or RNA contain functional groups that may participate in catalysis 3. the ability of RNA to hydrogen-bond with other nucleic acid molecules adds specificity to its catalytic activity
name the three stages of transcription
The three stages of transcription are initiation, elongation, and termination
Pre-mRNA splicing
a short nucleotide sequence at the ends of each introns indicates the splicing point and is recognized by snRNP (small nuclear ribonucleoprotein) molecules which attach at these sites and join with additional proteins to form a splicosome. The splicosome cuts out the introns, which is released and rapidly degrades, in addition, the splicosome joins the exons together.
Promoter:
a specific sequence of DNA nucleotides that indicates RNA polymerases where to begin transcription
Describe termination in eukaryotes
in eukaryotes RNA polymerases II transcribes the polyadeylation signal (AAUAAA) in the re-mRNA. About 10-35 nucleotides downstream from the polyadeylation sequence proteins associated with the ran transcript cut it free from the polymerases
what is meant by the statement "the genetic code is nearly universal"
it is significant in evolutionary terms because it means that nearly all organisms use the same genetic language to encode the primary sequence of their polypeptides, the veracity of this statement is strong evidence for the common ancestry of organisms.
codon
it is used to describe the triplet sequences of mRNA and also DNA nucleotide triplets in the non-template strand
Compare and contrast the actions of DNA and RNA polymerases
like DNA pol RNA pol must assemble a polynucleotide in the 3'-5' direction. Unlike DNA pol RNA pol does not require a primer.
what type of rna is produced in the transcription stage of protein synthesis
mRNA is produced in the transcription stage of protein synthesis
What are the shared functions of the 5'cap and poly-A-tail?
shared functions of the 5'cap and poly-A-tail 1. They facilitate the export of the mature mRNA from the nucleus into the cytoplasm 2. They help to protect the mRNA from hydrolytic enzymes in the cytoplasm 3. They help in the attachment of ribosome to the 5' end of the mRNA once in the cytoplasm
Central dogma
states that genetic information flows from DNA → RNA → protein. However, in some cases (viruses) genetic information can flow from RNA → protein.
Compare and contrast transcription and translation in prokaryotes and eukaryotes
the basic mechanisms of transcription and translation are similar. However, some important differences exist. In prokaryotes transcription and translation can proceed simultaneously, this is not possible in eukaryotes because the equipment that controls translation is in the cytoplasm and mRNA transcribed must leave the nucleus to be translated, additionally, the initial mRNA transcribed in eukaryotes (called the primary transcript) is modified before translation.
what is the role RNA polymerase in transcription
the role of RNA polymerases is the to separate the two strands of DNA and join together RNA nucleotides that are complimentary to the template strand of DNA
transcription unit
the stretch of DNA that is transcribed into a RNA molecule
Ribozymes
they are RNA molecules that function as enzymes The introns excision can proceed without proteins or additional RNA in some eukaryotic organisms. In these organisms the introns function as ribozymes to catalyze their own excision.
UTR's
they are un- translated regions of the mRNA found at the 5' and 3' ends of the mRNA. These regions will not be translated into proteins, They assist in the binding of ribosome to the mRNA molecule
Alternative RNA splicing
through alternative RNA splicing several proteins may be made from a single gene depending on which segments are treated as exons during mRNA processing.
