Translation/transcription
Genotype
An organism's genetic makeup. It is heritable information contained in its DNA.
Phenotype
An organism's physical appearance, or specific visible traits.
Mutation
Any change in the nucleotide sequence of DNA
Triplet AUG
Codes for amino acid methionine (met) and also can provide a signal for the start of a polypeptide chain
RNA splicing
Cutting and pasting process is called this. It is done by a spliceosome (which acts/moves similarly to RNA polymerase). Usually catalyzed by a complex of proteins.
Triplet code
The flow of information from gene to protein is based on this (the genetic instructions for the aa sequence are written in DNA/RNA as a series of 3 base words) Ex: ATC on a DNA strand
A particular protein is 100 amino acids long. In the gene for this protein, how many nucleotides are necessary to code for this protein?
300
Poly-A tail
A chain of 50 to 150 A's: facilitates the export of the mRNA from the nucleus, protects the tail of the mRNA in case enzymes attempt to break it down, helps ribosomes bind
Messenger RNA (mRNA)
A kind of RNA that encodes amino acid sequences. It conveys genetic info from DNA to the translation machinery of the cell. Message transcribed from DNA is translated into polypeptides. - Prokaryotes: transcription and translation take place in the cytoplasm - Eukaryotes: mRNA molecules must exit the nucleus via a nuclear pore to enter the cytoplasm
Ribosomal RNA (rRNA)
A kind of RNA that makes up one subunit of a ribosome
Transfer RNA (tRNA)
A molecular interpreter/type of RNA that functions as an interpreter in translation. Each tRNA molecule has a specific anticodon, picks up a specific amino acid, and conveys the amino acid to the appropriate codon on mRNA. Made up of a single RNA strand with 80ish nucleotides. There is a site where an amino acid can attach, and anticodons below.
Mutagen
A physical or chemical agent: source of mutation
What is a promoter?
A promoter is a specific nucleotide sequence at the start of a gene where RNA polymerase attaches and begins transcription.
How does a ribosome function in the protein synthesis?
A ribosome holds mRNA and tRNAs together and connects amino acids from the tRNAs to the growing polypeptide chain.
Codon
A series of three base words, Ex: UAG on an mRNA strand
5' cap
A single G nucleotide: facilitates the export of the mRNA from the nucleus, protects the front end of the mRNA from attack by enzymes, helps ribosomes bind to mRNA
What is the molecular basis of sickle-cell disease?
A single base difference in a hemoglobin gene results in amino acid substitution in the protein, altering the structure and behavior of the hemoglobin.
Start codon
A specific codon that the initiator tRNA binds to: where translation is meant to begin on the mRNA molecule.
What would happen if a genetic mutation changed a start codon to some other codon?
Any messenger RNA transcribed from the mutated gene would be nonfunctional because ribosomes could not initiate translation correctly.
Initiation of polypeptide synthesis (translation)
Brings together the mRNA, a tRNA with the first amino acid, and two subunits of a ribosome. Meant to establish where translation will begin. Occurs in two steps: 1) mRNA binds to ribosomal subunit. Initiator tRNA binds to start codon. 2) Large ribosomal subunit binds to small one.
Which of the following molecules or structures does not participate directly in translation: ribosomes, transfer RNA, messenger RNA, DNA, ATP, enzymes?
DNA
Stop codon
Elongation continues until this codon reaches the A site. UAA, UAG and UGA act as signals to stop translation.
Hairpin loop structure
Forms in the mRNA causing the polymerase and mRNA to disconnect/associate from the DNA
What happens as a tRNA passes through the A and P binding sites on the ribosome?
In the A site, its amino acid receives the growing polypeptide from the tRNA that precedes it. In the P site, it gives up the polypeptide to the tRNA that follows it.
Intron
Internal noncoding regions ("intervening sequences"). These are intermediaries that sit between exons and are essentially in the way.
What is an anticodon, and what is its function?
It is the base triplet of a tRNA molecule that couples the tRNA to a complementary codon in the mRNA. This is a key step in translating mRNA to the polypeptide.
Translate the mRNA sequence CCAUUUACG into the corresponding amino acid sequence.
Pro-Phe-Thr.
Anticodon
Single stranded loop at 1 end of the folded molecule has a triplet of bases called this. It is complementary to a codon triplet on mRNA. It recognizes a particular codon by using base pairing rules. Ex: AUC
RNA polymerase
RNA nucleotides are linked by this
Translocation
Ribosome moves the tRNA in the A site to the P site. Codon/anticodon remain bonded (mRNA and tRNA move as 1 unit). Process starts again with step 1- codon recognition.
Terminator
Sequence of bases in the DNA template that signals the end of the gene, causing the polymerase molecule to detach from the RNA molecule and the gene.
Codon recognition
The anticodon of an incoming tRNA molecule pairs with the mRNA codon in the A site
Initiation (transcription)
The first phase of transcription: the attachment of RNA polymerase to the promoter and the start of RNA synthesis
Exon
The parts of a gene that are expressed as amino acids (the coding regions). Part of the mRNA that is going to be expressed.
Peptide bond formation
The polypeptide separates from the tRNA and attaches to the amino acid. 1 more amino acid is added to the chain.
Mutagenesis
The production of mutations
Elongation (transcription)
The second phase of transcription: the RNA elongates, and teh strand peels away from its DNA template
Genetic code
The set of rules giving the correspondence between codons in RNA and amino acids in proteins
Promoter
The signal to start transcribing is a nucleotide sequence called the promoter. It is a specific binding site for RNA polymerase and determines which of the two strands of the DNA helix will be used for the transcription template.
P site
The site where the protein grows (holds the growing polypeptide)
A site
The site where the tRNA arrives
E site
The site where the tRNA exits
Transcription
The transfer of genetic information from DNA into an RNA molecule. Called this because of the nucleic acid language of DNA has been rewritten (transcribed) as a sequence of bases on RNA (language is still that of nucleic acids though).
Translation
The transfer of the information in the RNA into a protein.
Explain why many eukaryotic genes are longer than the mRNA that leaves the nucleus.
These genes have introns, noncoding sequences of nucleotides that are spliced out of the RNA transcripts.
Termination (transcription)
Third phase of transcription: RNA polymerase reaches terminator
In the information flow from DNA to protein, what are the functions of transcription and translation?
Transcription is the transfer of information from DNA to RNA. Translation is the use of the RNA as information for making a protein.
Reading frame
Triplet grouping: Adding/subtracting nucleotides alters this part of the message, resulting in a nonfunctional nucleotide