DNA, RNA, & PROTEIN SYNTHESIS
1. Organism’s may have 100’s to 1000’s of proteins in their makeup. DNA & RNA
work together to manufacture these proteins in a process called protein
synthesis.
2. Facts about DNA, deoxyribonucleic acid:
a) controls genetic mystery of what makes an organism unique
b) found in cell nucleus of eukaryotes & in cytoplasm of prokaryotes
c) 2 twisted strands called a double helix created by connecting nucleotides
d) each nucleotide is: 1 deoxyribose sugar + 1 phosphate + 1 nitrogen base
e) these 4 nitrogen bases always together in these pairs by hydrogen bonds:
1) adenine <----> thymine
2) cytosine <----> guanine
3. For cells to reproduce, each DNA molecule must first make an exact copy of
itself in a process called DNA replication.
a) the 2 strands of the double helix unwind & separate
b) free-floating nucleotides in the nucleus will bond with bases that are
exposed where strands separated
c) double helix rewinds as 2 exact copies of original DNA molecule
4. Facts about molecules of RNA, ribonucleic acid:
a) 3 types are produced by DNA for job of protein synthesis
1) messenger RNA (mRNA) - carries instructions from DNA to
ribosomes in cytoplasm
2) transfer RNA (tRNA) - carries amino acids to ribosomes to form
proteins
3) ribosomal RNA (rRNA) - found in ribosomes & help create proteins
b) only 1 strand of nucleotides - each 1 ribose sugar + 1 phosphate + 1
nitrogen base:
c) nitrogen bases are: cytosine, guanine, adenine, & uracil instead of DNA’s
thymine
5. DNA creates RNA during transcription.
a) double helix of DNA unwinds
b) enzymes signals free-floating RNA nucleotides to bond with exposed DNA
nitrogen bases
1) cytosine <----> guanine
2) adenine <----> uracil
c) completed RNA breaks away from DNA
6. Protein systhesis or translation is the formation of polypeptides. These are
functional proteins such as enzymes, hormones, muscles, & carrier molecules
that each perform a specific job in creating an organism.
7. Protein molecules are made up building blocks called amino acids held together
in chains by peptide bonds.
8. Amino acids appear in groups of 3 nitrogen bases called codons. Each codon
represents the name of 1 amino acid.
a) the start codon (AUG) begins the process of translation
b) one of the stop codons (UAA, UAG, UGA) brings the process to an end
9. The order of events leading to genetic expression in an organism is:
DNA -> RNA -> amino acid -> protein -> genetic expression
10. The translation of proteins:
a) mRNA travels to ribosome carrying instructions from DNA for making
proteins
b) tRNA carries a group of 3 nitrogen bases called an anticodon to ribosomes
c) ribosomes identify tRNA anticodon & bond it with its complementary
codon on the strand of mRNA
d) process is repeated until protein is complete & then released for use