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Nucleic Acids DNA-RNA
- Nucleic acids are DNA and RNA
- They are responsible for cell growth and the storage of genetic information
- DNA- (deoxyribonucleic acid) carries the genetic code for cell reproduction and protein synthesis
- RNA-(ribonucleic acid) translates the genetic code into protein synthesis
DNA carries the genetic code of the organis located in nucleus of cells chromosomes-structures containing DNA when cells divide (mitosis) each copy of DNA must be copied (replication)
- RNA is responsible for protein synthesis
- RNA translates the genetic code from DNA
- RNA transfers the information outside of the
- nucleus to the ribosomes, where protein synthesis occurs.
- more RNA in cells than DNA
Nucleic acids are long repeating units of smaller subunits called nucleotides Each nucleotide itself is made up of three components pyrimidine or purine base a 5-carbon sugar (derived from ribose) a phosphate group
The Nitrogen Bases
- The nitrogen bases are the only components of nucleic acids that can have different identities.
- In this way, they are similar to the amino acids in proteins. There are only 5 nitrogen bases
- DNA consists of a double helix containing two chains consisting of a sugar- phosphate backbone containing pyrimidine and purine bases.
- The sugar in the backbone of DNA is deoxyribose (deoxyribonucleic acid)
- The amount of adenine (A) is equal to the amount of thymine (T)
- A on one chain is paired with T on the other chain
- The amount of cytosine (C) is equal to the amount of guanine (G)
- C on one chain is paired with G on the other
Enzyme 'helicase' begins to unwind double helix Specialized enzymes assemble nucleotides from smaller molecules within the cell Assembled nucleotides attach to single strand of DNA to compliment the original base DNA polymerase bonds the nucleotides together to complete the second DNA strand.
- Proteins are synthesized in the ribosomes
- ribosomes: cell structures outside of the nucleus
- Protein synthesis is carried out by RNA
- r-RNA (ribosomal RNA)
- m-RNA (messenger RNA)
- t-RNA (transfer RNA)
- In RNA U (uracil) takes the place of thymine.
Protein Synthesis Step 1-Transcription
- Start site
- RNA nucleotides attach to
- complementary bases
- Regulatory enzymes cause portion of DNA to uncoil
- After termination, RNA detaches
- from DNA and travels to ribosomes.
- This particular type of RNA is
- messenger RNA (m-RNA)
- Transfer RNA (t-RNA)
- Attaches serine to its 3' end
- 4) Ribosome moves down m- RNA chain and process repeats
- 3) Enzyme binds amino acid to growing chain. A t-RNA is released from the ribosome
- 2) t-RNA having complementary anti coden forms H-bonds with m- RNA coden
- 1) m-RNA binds to site in small ribosomal unit
Changes in the DNA code
- Alteration in the sequence of nucleotides
- Two major types
- substitution-single nucleotide is replaced by another
- frame shift- nucleotide is deleted or added
- Mutations can result in a change in the primary structure of proteins
- affects the activity of the protein
- may result in genetic disease