KA3: gene expression Flashcards
every cell in the body contains a …….. therefore all of the ____ required to make __ of the proteins required for the organism.
complete set of chromosomes
genes
all
what does gene expression involve?
the transcription and translation of dna sequences
what do we know about the amount of genes expressed in a cell?
only a fraction of them are expressed since each cell is specialised to suit a particular function
what are the differences between DNA and RNA?
DNA: double stranded
deoxyribose sugar
thymine - adenine
RNA: single stranded
ribose sugar
uracil replaces thymine
what is messenger RNA?
it carries a copy of the DNA code from the nucleus to the ribosome.
why does tRNA fold and role of tRNA?
transfer RNA which folds due to complementary base pairing.
each of these molecules carry their specific amino acid to the ribosome
what is rRNA?
ribosomal RNA which combines with proteins to form the ribsome.
what is a simple definition of transcription?
the synthesis of mRNA from a section of dna(gene)
mRNA is _________ from DNA in the _________ and translated into ______ by ribosomes in the ________.
transcribed
nucleus
proteins
cytoplasm
explain what a codon is and its purpose in gene expression.
a triplet of bases on the mRNA strand is a codon
it codes for specific amino acids
describe the structure of a tRNA molecule and its purpose?
it has an anticodon (exposed triplet of bases) at one end, then the other end has an attachment site for a specific amino acid at the other end.
it carries its specific amino acids to the ribosome
where does transcription begin?
region called the promoter
what is the first thing that RNA polymerase does during transcription?
it moves along the DNA unwinding the double helix, breaking the hydrogen bonds between the bases.
how are the free RNA nucleotides added?
by the complementary base pairing rules
what does RNA polymerase synthesis during transcription?
the primary transcript of RNA
in RNA what is adenine complementary to?
uracil
the mRNA produced is complementary to the _____ _____ containing the info to make a protein
coding strand
what is the end result of mRNA splicing(what does it form)?
mature mRNA transcript
how do we know that not all regions in the gene are required?
since introns are the non coding regions of the primary transcript and are removed
exons are coding regions and are joined
together to form the mature transcript.
during splicing the order of exons changes. (True or False)
false- the orders remains unchanged.
how would we know that alternative RNA splicing had occurred? (vague)
because different proteins would have been expressed.
______ mature mRNA transcripts are produced from the ____ primary transcript depending on which ____ are _______.
different
same
exons
retained
describe briefly what happens during translation.
tRNA is involved in the translation of
mRNA into a polypeptide at a ribosome.
where does translation start and finish?
Translation begins at a start codon and
ends at a stop codon.
