Week 6_Alternative splicing and translation Flashcards
what is alternative splicing?
when some exons are also spliced out
alternative splicing allows:
multiple versions of a gene’s mRNA to be produced
multiple versions of the protein to be produced
what is an example of alternative splicing?
dystrophin gene (79 exons), 19 different splice variants
alternative splicing allows ~___ protein coding genes to produce ~___ different proteins
20,000 protein coding genes to produce 100,000 different proteins
alternative splicing is regulated (in part) by…
each influences how…
splice site activator proteins
splice site repressor proteins
each influences how mRNAs will be spliced
proper regulation of ___ is important to biological functions
alternative spliicng
altered regulation of alternative splicing may be a factor in ___ and in ___
autism
cancer cell biology
what is translation?
when information in an mRNA is translated into a protein
what are the necessary components of protein synthesis/translation?
a mature mRNA that contains a genetic code
transfer RNAs (tRNAs)
ribosomes
the genetic code is a series of ___
codons
what is a codon?
a sequence of 3 nucleotide bases
what are the functions of a codon?
specify a particular amino acid
signal where translation should ‘start’ or ‘stop’ on the mRNA
who deciphered the code?
Marshall Nirenberg
what experiments did Marshall Nirenberg do to decipher the code?
(1) generated and translated mRNAs
(2) examined the amino acid content of the proteins
how do you identify code?
(1) make synthetic mRNAs containing 1 repeated base
- translate the mRNAs using cytoplasmic extract
- determine the amino acid content of the resulting proteins
(2) make mRNAs with different combinations of RNA nucleotides
- test all possible codon sequences
what is the universal nature of genetic code?
the code is the same in virtually all organisms (rare exceptions exist)
the genetic code is ___
redundant
how is the genetic code redundant?
61 codons encode 20 amino acids
more than 1 codon for some amino acids
code has ___ translation START codon, which is…
1
AUG, Met
there are ___ translation STOP codons
3
what are ribosomes?
enzymes that translate information in mRNAs into proteins
ribosomes are made of ___ subunits
they are…
2
large ribosomal subunit
small ribosomal subunit
each ribosomal subunit is made up of multiple ___ and ___
ribosomal proteins
ribosomal RNAs
function of small subunit of ribosome
positioning of the mRNA
function of both subunits of ribosome
binding tRNAs
function of large subunit and rRNA in ribosome
peptide bond formation
function of large subunit, rRNA, release factor in ribosome
recognition of ‘Stop’ codon and protein release
which ribosome subunit is in charge of positioning of the mRNA?
small subunit
which ribosome subunit is in charge of binding tRNAs?
both subunits
which ribosome subunit is in charge of peptide bond formation?
large subunit, rRNA
which ribosome subunit is in charge of recognition of the ‘Stop’ codon and protein release?
large subunit
rRNA
release factor
rRNAs have ___ function
enzymatic
what are ribozymes?
RNA molecules that catalyze reactions, like protein enzymes
what do tRNAs molecules do?
carry amino acids to the ribosome for incorporation into a protein
what are the parts of a tRNA molecule?
amino acid
acceptor stem
anticodon loop
anticodon
the anticodon associated with the codon thru…
complementary base pairing
what is a charged tRNA?
a tRNA with an amino acid attached
how does a tRNA become charged?
aminoacyl-tRNA synthetase (aaRS) enzymes bind to:
- an amino acid
- an ATP
- an ‘uncharged’ tRNA (not bound to an amino acid)
using the energy from ATP hydrolysis, the amino acid is covalently bound to the tRNA
there are ___ aaRS enzymes (___ for each amino acid)
20
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