Transcript Nucleic Acids: RNA

Nucleic Acids: RNA
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Ribonucleic Acid: RNA
RNA is a single strand, not double
The base Uracil is used instead of Thymine
The sugar molecule is ribose, not
deoxyribose
DNA vs. RNA
Double strand vs. Single strand
RNA
 There are 3 types of RNA
 Ribosomal RNA (rRNA) - makes up part of
the ribosome
 Messenger RNA (mRNA) - brings the code
or message of DNA from the nucleus to the
ribosome
 Transfer RNA (tRNA) - carries amino acids
to the mRNA at the ribosome
Protein Synthesis
 Protein synthesis - cells make different
kinds of proteins by using different
combinations of amino acids
 DNA determines which proteins are made.
 The sequence of DNA bases is a code for
proteins.
 RNA is needed to put proteins together.
Protein Synthesis: Transcription
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Transcription - process of making mRNA
DNA is used as a template, or pattern.
During transcription, the DNA “unzips”.
RNA nucleotides (in the nucleoplasm) go to
the DNA and bond to a complimentary base
on one strand of the DNA.
Protein Synthesis: Transcription
 3 bases in a strand of DNA form a “word”,
in the making of a protein.
 The 3 letters AUG are always used to start a
message.
 UAA, UAG, and UGA are always used to
end the message.
Protein Synthesis: Transcription
 Codon - 3 bases on the mRNA form a code
for one specific amino acid.
 Once a stop message is reached, the mRNA
separates from the DNA strand.
 The DNA zips back up.
 The mRNA moves out into the cytoplasm in
search of a ribosome.
Protein Synthesis: Transcription
Protein Synthesis: Translation
 Translation - the original code of DNA
carried by the mRNA is “translated” into a
protein.
 During translation, mRNA temporarily
binds to a ribosome.
 The ribosome appears to move along the
mRNA and “point out” each codon to
tRNA.
Protein Synthesis: Translation
 TransferRNA, picks up individual amino
acids and brings (transfers) them to the
mRNA.
 Each tRNA unit can bond to a
complimentary mRNA codon.
 3 tRNA bases are called an anticodon.
 After two amino acids are placed in the
proper order, a peptide bond is formed.
Protein Synthesis: Translation
 After the peptide bond has formed, the
weak bond between tRNA and the amino
acid is broken.
 The tRNA is free to find another amino
acid.
 This process continues until the protein is
complete.
Protein Synthesis: Translation