1. How Proteins are Made
Biology I: Chapter 10

2. Decoding the Information in DNA
Traits, such as eye color, are determined by proteins that are built according to instructions coded in DNA
Proteins are not built directly from DNA
RNA is involved

3. RNA (ribonucleic acid)
A nucleic acid
Made of linked nucleotides

4. RNA versus DNA Single Stranded Sugar Ribose Nitrogenous Bases
Adenine (A)
Guanine (G)
Cytosine (C)
Uracil (U)
Double Stranded
Sugar Deoxyribose
Nitrogenous Bases
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)

6. Transcription
The process of synthesizing RNA by using one strand of DNA molecule as a template
Prokaryotes
Occurs in the cytoplasm
Eukaryotes
Occurs in the nucleus

8. Messenger RNA (mRNA)
The form of RNA that carries the instructions for making a protein from a gene and delivers it to the site of translation

9. Transcription: Step 1 RNA polymerase binds to the gene’s promoter
RNA polymerase: An enzyme that adds and links complementary RNA molecules during transcription
Promoter: a specific sequence of DNA that acts as a “start” signal for transcription

10. Transcription: Step 2
RNA polymerase unwinds and separates the two strands of the double helix
This exposes the DNA nucleotides on each strand

11. Transcription: Step 3
RNA polymerase adds and links complementary RNA nucleotides
RNA polymerase moves along the nucleotides of the DNA pairing G and C and A and U (not T)

12. Codons
RNA instructions
A series of 3 nucleotide sequences on the mRNA

13. Codons: Amino Acids The codons make amino acids
Linked amino acids: proteins!
Genetic Code: the 64 possible mRNA codons with “start” and “stop” signals

14. Transcription: End
RNA polymerase eventually reaches a “stop” signal in the DNA
Stop signal: A sequence of bases
Marks the end of each gene in eukaryotes
Marks the end of a set of genes in prokaryotes

15. Protein Synthesis in Eukaryotes
The human genome is about 30,000 genes
Regulatory proteins are used to determine if transcription should occur “transcription factors”

16. Transcription Factors
Help arrange RNA polymerases in the correct position on the promoter
Enhancer: sequence of DNA that can be bound by a transcription factor that can activate transcription

17. Introns and Exons
Introns: long segments of nucleotides that have no coding information
“junk”
Exons: the portions of a gene that are translated (expressed) in proteins

18. Spliceosomes
After a eukaryotic gene is transcribed, the introns in the resulting mRNA are cut out
Spliceosomes cut out introns and “stitch” exons together

19. Translation
The transfer of genetic material in the form of DNA fragments from one cell to another or from one organism to another

20. Translation
Eukaryotes and Prokaryotes
Takes place in the cytoplasm

21. Transfer RNA (tRNA)
Single strands of RNA that help in the synthesis of proteins
Folded into a particular shape with an anticodon
Anticodon: a 3-nucleotide sequence complementary to an mRNA codon

22. Ribosomal RNA (rRNA)
RNA molecules that are part of the structure of ribosomes
Ribosomes temporarily hold 1 mRNA and 2 tRNA

23. Translation
The ribosomal subunits, the mRNA, and the tRNA carrying methionine (Met) bind together

24. Translation
The tRNA carrying the amino acid specified by the codon in the A site arrives
A peptide bond forms between adjacent amino acids
The tRNA in the P site detaches and leaves its amino acid behind

25. Translation The tRNA in the A site move to the P site
The tRNA carrying the amino acid specified by the A site arrives
A peptide bond is formed
The tRNA in the P site detaches and leaves its amino acid behind

26. Translation The process is repeated until a stop codon is reached
The ribosome complex falls apart
The newly made protein is released

27. Gene Expression
The manifestation of the genetic material of an organism in the form of specific traits
Also known as protein synthesis

28. Protein Synthesis in Prokaryotes
Prokaryotes have about 2,000 genes
Operator: on-off switch for protein synthesis
Operon: the combined promoter and operator regions

29. Protein Synthesis in Prokaryotes
lac operon: operon that controls the metabolism of lactose
Repressor: protein that binds to an operator and blocks RNA polymerase from binding to the promoter site
If lactose is present it binds to the repressor and changes the repressor’s shape
The repressor falls off the operator and lactose can be metabolized

30. Protein Synthesis in Prokaryotes
By producing the enzyme only when the nutrient is available, the bacterium saves energy

31. Mutations A change in the DNA of a gene Gene rearrangements
Transposition or chromosomal rearrangement
Point mutation
A single nucleotide changes
Insertion mutation
A sizeable length of DNA is inserted into a gene
Deletion mutation
Segments of genes are lost, often during meiosis

32. Major Types of Mutations