UNIT 1: Key area 3 - gene expression Flashcards
where is genetic code used and found ?
used in transcription and translation
found in ALL forms of life
what is gene expression controlled by ?
regulation of transcription and translation
what do genes code for ?
proteins
what are proteins made of ?
long chains of amino acids
what are amino acids joined together by ?
peptide bonds
what shapes to proteins fold into ?
different shapes
what does the shape of a protein dictate ?
the role it will have in cell
where do hydrogen bonds form ?
between certain amino acids in a poly peptide chain
when does a polypeptide chain becoem coiled or in a 3d shape ?
when hydrogen bonds are formed
where does protein synthesis begin and end ?
begins in the nucleas of cell and end sun the cytoplasm
what plays a vital role in the production of protein from the code of DNA ?
RNA
compare DNA with RNA
3 points
- DNA is doubke stranded whereas RNA is single stranded
- RNA uses the base URACIL whereas DNA uses thymine
- RNA nucleotides are similar in structure to DNA but RIBOSE replaces deoxyribose sugar
Name the three types of RNA
- messenger RNA
- transfer RNA
- ribosomal RNA
explain messenger RNA (mRNA)
- formed in the nucleas
- carries a copy of the DNA from the nucleas to RIBOSOMES
explain transfer RNA (tRNA)
molecules carry specific amino acids and bring them to ribosomes to build proteins
explain ribosomal RNA (rRNA)
molecules combine with proteins to make a ribosome
ribosomal RNA is combined with proteins to form ribosomes
where does transcription take place ?
nucleas
what is transcription ?
the synthesis of mRNA from a section of DNA
what is required fro transcription?
- RNA polymerase
- DNA template strand
- primer
- free RNA nucleotides
- ATP
name the stages of transcription
- RNA polymerase unwinds the dna strand exposing bases
- primer attaches to complementary bases to start the mRNA chain
- RNA polymerase adds nucleotides onto the 3 end
this is called primary transcript/mRNA
what is RNA polymerase responsible for ?
this enzyme is responsible for transcription
what does RNA polymerase molecule produce ?
primary transcript
what are non coding regions called ?
where are they ?
IN trons they stay IN the nucleas
what are codon regions called and where are they ?
EXons EXit the nucleas
what is translation ?
synthesis of polypeptide protein
where does translation occur ?
ribosome
mRNA is made of sequencers of three nucleotides called ?
codons
what are codons ?
mRNA made of sequences of three nucleotides
what is each codon code for ?
one amino acid
remaining exons are spliced together to make a continuous sequence
what is this called ?
mature transcript
what does each gene start and end with ?
start codon and stop codon
tRNA is made of what ?
and found where ?
a single chain of nucleotides
found int he cytoplasm
what do lomg amino acid chains make ?
proteins
what are ribosomes composed from ?
proteins and rRNA
steps of translation
- ribosome bonds to mRNA at start codon
- complementary anticodon carrying an amino acid attaches
- next mRNA codon bonds with complementary anticodon
- a peptide bond forms between 2 amino acids
- ribosome moves one codon
- tRNA release amino acid this can be reused
- steps 3-6 relay until ribosome reaches stop codon
what is alternative RNA splicing ?
certain conditions allow alternative segments of RNA to be treated as exons and introns
summarise alteranative RNA splicing
a gene can make many differnt mature mENA transcripts
therefore many different proteins
why is tRNA folded ?
for atincodon site and attachment of specific amino acid
