Ch 17: Gene Expression from Gene to Protein Flashcards
What is gene expression?
the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce and products, proteins or non-coding RNA, and affect a phenotype
What are the two processes in gene expression?
transcription and translation
What does DNA dictate?
the synthesis of proteins
What do proteins link?
genotype and phenotype
What is the one-gene-one enzyme hypothesis?
the function of a gene is to dictate production of a specific enzyme
What is the newest name for the one-gene-one protein hypothesis?
it is now restated as the one-gene-one polypeptide hypothesis
What did Archibald Garrod first suggest?
he suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions
What is translation?
the synthesis of a polypeptide using information in the mRNA
What is RNA?
the bridge between genes and protein synthesis
What is transcription?
the synthesis of RNA using information in DNA
Where does transcription occur?
in the nucleus
What does transcription produce?
mRNA and primary transcripts
Where does translation take place?
in the cytoplasm (ribosomes)
How many total amino acids are there?
only 20 amino acids
What is the flow of information from gene to protein based on?
the reading of a codon, or a triplet code
What is a template strand?
template for ordering the sequence of complementary nucleotides in an RNA transcript
During translation, what direction are the codons read?
5’ —-> 3’
What is a coding strand?
nontemplate strand, nucleotides are identical to codons except that T is present in the DNA in place of U in the RNA
What are the two type of amino acids?
61 code for amino acids, while only 3 are “stop” signals that end transcription
What is the reading frame?
the correct order in which the codons must be read in for the specified polypeptide to be produced
What is the function of the RNA polymerase?
catalyzes RNA synthesis, pries the DNA strands apart, and joins together RNA nucleotides
What is the one difference between DNA polymerase and RNA polymerase?
RNA polymerase does not need a primer
What is a start point?
an area that is signaled by a promoter for transcription to start
What is a promoter?
a specific nucleotide sequence in the DNA of a gene that binds RNA polymerase, positioning it to start transcribing RNA at an appropriate place
What is a terminator?
specific sequences of DNA that end transcriptions
What is a transcription unit?
a region of DNA that is transcribed into an RNA molecule
What are the three stages of transcription?
initiation, elongation, termination
What is a TATA box?
a promoter that is crucial in forming the initiation complex in eukaryotes
What are the functions of transcription factors?
they guide the binding of RNA polymerase and the initiation of transcription
What is a transcription initiation complex?
the completed assembly of transcription factors and RNA polymerase II bound to a promoter
What end of an RNA strand are nucleotides added to?
the 3’ end
What is RNA processing in Eukaryotic cells?
enzymes in the eukaryotic nucleus modify pre-mRNA before the genetic messages move to the cytoplasm where certain interior sections of the molecule are cut out and the remaining parts spliced together
How are each end of a pre-mRNA molecule modified?
the 5’ end receives a modified nucleotide 5’ cap and the 3’ end gets a poly-A tail
What are the functions of a 5’cap and a poly-A tail?
they seem to facilitate the export of mRNA to the cytoplasm, they protect mRNA from hydrolytic enzymes, and they help ribosomes attach to 5’ end
What are introns?
non-coding stretches of nucleotides
What are exons?
non-coding stretches of nucleotides that are eventually expressed and translated into amino acid sequences
What are spliceosomes?
they remove introns, made of proteins and several small RNAs that recognize the splice sites
What are ribozymes?
catalytic RNA molecules that function as enzymes and can splice RNA
What are the three properties of RNA that enable it to function as an enzyme?
it can form a three-dimensional structure because of its ability to bas-pair, some bases in RNA contain functional groups that participate in catalysis, and RNA make hydrogen bonds with other nucleic acid molecules
What is alternative RNA splicing?
some genes encode more than one kind of polypeptide depending on which segment is treated as exon during splicing
What are domains?
modular structures in proteins that consist of regions
What is exon shuffling?
it may result in the evolution of new proteins by mixing and matching exons between different genes
