vocab

transcription - the 1st step in gene expression

  • is a process where genetic info encoded in the DNA is copied in order to produce mRNA

    • this mRNA is used to produce proteins

  • eukaryotic cells - transcription takes place in nucleus

  • prokaryotic cells - transcription takes place in cytoplasm

  • occurs in 5’ to 3’ direction

  • RNA polymerase is one enzyme involved in transcription

  • occurs in 3 stages

    • initiation

    • elongation

    • termination

template/antisense strand - DNA strand that’s being used as the template to synthesize complementary RNA molecule

coding/sense strand - DNA strand that has same sequences as RNA molecule (except thymine replaced with uracil)

gene expression - process where genetic info encoded in genes is used to synthesize proteins

translation - the 2nd step in gene expression?

  • process by which ribosomes use the genetic info carried by mRNA to synthesize proteins

    • so basically the base sequence of mRNA is translated into the amino acid sequence of a polypeptide

  • has same 3 stages as transcription

  • occurs at free ribosomes in cytoplasm or ribosomes attached to ER

tRNA - a type of RNA molecule that has amino acids attached to it, and will bring these amino acids to the ribosome during translation

  • tRNA’s will bind based on the mRNA sequence, so the order of the amino acids is dictated by the mRNA sequence

codon - a set of 3 adjacent nucleotides in DNA or mRNA that code for a particular amino acid

anticodon - located on the tRNA & is complementary to the matching codon

  • anticodons & codons are complementary = the correct tRNA with the correct amino acid binds to the correct codon, so the amino acid is placed correctly in the sequence

degeneracy - the redundancy of the genetic code, as multiple codons can code for the same amino acid

  • i think this is important cuz it reduces the potential for mutations

universal - genetic code is found in most organisms

mutation - a mistake made when synthesizing either RNA or RNA

  • play an important role in introducing genetic variation

    • so are essential for survival

point mutation - a type of mutation where a single nucleotide is changed (either deleted, added, or replaced with another)

  • ex - sickle cell anaemia

  • this results in frameshift mutation

frameshift mutation - all the codons following that mutation are altered, as there’s been a change in the base sequence

silent mutation - type of mutation where there is no difference in produced protein, even if there has been a mutation

  • degeneracy of genetic code means that the change in nucleotide could result in a codon that codes for the same amino acid

promoter - a non-coding region of DNA that’s located right before a gene?

transcription factors - a group of proteins that bind to promoter, initiating transcription (& gene expression)

  • if these are missing or are unable to bind, then transcription doesn’t occur & gene isn’t expressed

non-coding regions of DNA/non-coding DNA - DNA sequences with a genome, that dont consist of info needed to synthesize a protein

  • include: promoters, introns, telomeres, genes for tRNAs & rRNAs

introns - sections in eukaryotic DNA that’re transcribed into mRNA but are edited out before translation

telomeres - repeated nucleotide sequences that protect end of chromosomes

  • help ensure DNA correctly replicated

  • maintain chromosome stability during DNA replication

genes for tRNAs & rRNAs - genes that code for RNA molecules that form tRNA or rRNA (which forms part of structure of ribosome)

exons - coding sections within gene that contain instructions for synthesizing a protein & are kept in the mature RNA molecule

post-transcriptional modification - changes are made to mRNA after transcription, to change pre-mRNA into mature mRNA

  • 5’ cap & poly-A tail are added

  • introns are excised (using spliceosome)

  • exons are ligated

alternative splicing - is when a gene is spliced in different ways by combining different exons & omitting others

  • the result is different versions of proteins that function differently

  • important as it means that one gene can code for different polypeptides

post-translational modification - many polypeptides undergo modification in order to become functional

  • occurs in Golgi apparatus (in eukaryotes?)

  • ex: modification of pre-proinsulin into insulin

proteasomes - protein complexes that’re involved in breaking down/recycling unwanted proteins or damaged proteins, to amino acids

  • found in nucleus & cytoplasm in eukaryotes