DNA and proteinsynthesis. Flashcards
what does DNA stand for?
deoxyribonucleic acid
what is DNA made from?
chain of sugar-phosphates and one of four bases
what does DNA do?
codes for individual proteins
contain instructions on how to build proteins used in the body
where is DNA found?
the cell nucleus
what are the complementary base pairs of DNA and how are they held together?
A + T (straight A, straight T)
C + G (curly C, curly G)
held together by hydrogen bonds (2 between A/T, 3 between C/G)
what is the ‘back bone’ of DNA made of?
sugar (deoxyribose) and phosphate
what is a genome?
an organisms complete set of DNA
what structure does DNA have?
double helix
what is a protein?
a polymer of units linked by peptide bonds
what are proteins made from?
built of 20 amino acids
where are proteins made?
ribosomes
what to proteins do?
they perform nearly all biological functions: enzymes, antibodies, structural bodies, hormones
what is messenger RNA (mRNA)?
intermediary messenger, takes DNA from nucleus to ribosomes in cytoplasm to create proteins
what does RNA stand for?
ribosenucleic acid
what sugar group makes up RNA?
ribose
what does RNA do?
codes for proteins that cell needs
what’s the difference between DNA and RNA bases?
in RNA, adenine (A) pairs with uracil (U) instead of thymine (T)
what are the two stages of protein synthesis?
transcription
translation
why is mRNA created during transcription?
proteins are made in the cell cytoplasm but the code for these is found in DNA
but DNA is too big to move out of the nucleus so a molecule of messenger RNA (mRNA) is created
steps of transcription:
- an enzyme called RNA polymerase attaches to the DNA in front of a gene in a non-coding region
- the enzyme separates the DNA strands, and moves along one strand (the template strand) adding complementary RNA nucleotides- these are the same bases as DNA except that uracil replaces thymine
- the nucleotides are linked to form a strand of messenger RNA (mRNA) which leaves the nucleus through nuclear pores where it is met by a ribosome and is ready to undergo TRANSLATION
- the DNA strands then join back together
what is transfer RNA (tRNA)?
a unit which carries specific, individual, amino acids
steps of translation:
- the mRNA strand attaches to a ribosome in the cytoplasm and is read’ 3 bases at a time (a codon)
- a tRNA molecule with a complementary anticodon lines up and carries a specific amino acid
- as the ribosome moves along, it joins the amino acids from the tRNA together, forming a polypeptide
- the polypeptide chain made up
of amino acids then folds up to form a protein (i.e. an enzyme) with a specific shape. some proteins contain more than one polypeptide chain.
what is the purpose of tRNA molecules in translation?
tRNA molecules bring amino acids to the ribosome (every amino acid has it’s own tRNA molecule)
the mRNA provides the code for the correct order of amino acids
each tRNA molecule has an anticodon which matches the base triplets on the mRNA chain - base triple codons
