topic 4: gene expression Flashcards
what is genotype and phenotype?
genotype: the DNA sequence of an organism
phenotype: the observable physical characteristics
what is the central dogma of genetic information flow?
DNA (transcription) —> RNA (translation) —> protein
what is phenotype the result of?
protein production or gene expression
what is gene expression? how many stages does it include?
- it is DNA-directed protein synthesis
- includes 2 stages:
(1) transcription
(2) translation
what molecule acts as an intermediate between genes (genotype) and the proteins which they code for (phenotype)?
RNA
what is transcription?
- the DNA-directed synthesis of RNA
- transcription produces messenger RNA (mRNA)
what is translation?
- the synthesis of a polypeptide which occurs under the direction of mRNA
- translation occurs on ribosomes
what are the differences in gene expression between prokaryotes and eukaryotes?
prokaryotes:
- no nuclear envelope to separate transcription and translation: both take place in the cytoplasm
- mRNA produced by transcription is immediately translated without further processing (no RNA processing)
- translation can start before the end of transcription
eukaryotes:
- the nuclear envelope separates transcription from translation
- transcription: takes place in the nucleus
- RNA processing: (takes place in the nucleus) eukaryotic DNA transcripts are modified to yield the mRNA (final product of transcription)
- translation: takes place in the nucleus
what is pre-mRNA?
also known as primary transcript, is the initial RNA transcript
[only present in eukaryotes]
information flow from gene to protein is based on?
- a triplet code consisting of 3 consecutive nucleotides known as codon
- each gene is transcribed in a complementary mRNA containing the nucleotide triplets (codons)
- each codon specifies the addition of a specific amino acid
- the gene is translated into an amino acid chain forming a polypeptide chain
which DNA strand of the 2 is used as a template for the synthesis of the complementary RNA strand?
the 3’ to 5’ DNA strand (known as the template strand)
in what direction is RNA synthesized?
RNA polymerase synthesizes RNA in a 5’ - 3’ direction using the template DNA strand
in what direction are codons on the mRNA read during translation?
they are read in the 5’ - 3’ direction by the ribosomes
if you’re given the double stranded DNA figure unlabeled, which strand is used as a template for the mRNA strand synthesis?
the 3’ - 5’ strand
why is the DNA coding strand named so?
it is called the coding strand because it has the exact same sequence as the mRNA strand produced (with T replaced with U)
mRNA IS ALWAYS PRODUCED IN THE _______ DIRECTION
5’ - 3’