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