1. Notes: Chapter 13: RNA & Protein Synthesis
2 steps:
Transcription (DNA is made into mRNA in the nucleus)
Translation (mRNA is made into proteins by ribosomes in the cytoplasm or ER)

2. RNA Structure Similar to DNA, but with some important differences:
Single strand (DNA double)
Ribose is the sugar (not deoxyribose like DNA)
Uracil matches adenine (instead of thymine like DNA)
Shorter than DNA

3. RNA Functions Three different types of RNA:
mRNA (messenger) used as template to make proteins
rRNA (ribosomal) makes up ribosomes
tRNA (transfer) matches amino acids to mRNA to help make proteins

4. Transcription transcribe (to copy) happens in the nucleus
DNA’s code is copied onto RNA
1. RNA polymerase binds to beginning of a gene (promoter) and unwinds DNA
2. Complementary bases copied from 1 side of DNA
3. Termination (end) signal reached, mRNA and DNA free 

5. Translation
RNA’s “language” is translated into amino acids (which will become a protein)
RNA’s language is set of three nucleotides called a codon…3 nitrogen bases in a row
Codons match with specific amino acids to make polypeptide chain (which will be modified to make a protein)
20 amino acids all together
More than 20 codons, so some amino acids have more than one codon. There is also 1 start codon and 3 stop codons.

6. Translation

7. Translation
1. ribosome attaches to start codon 2. tRNA with amino acid matches mRNA codon (area on tRNA that matches called an anticodon). This process is called initiation. 2 tRNAs can fit at one time. 3. ribosome moves down and matches next codon. 4. Amino acids form peptide bond and protein continues to grow, 1 amino acid at a time. This process is called elongation. 5. ribosome reaches stop codon, mRNA, tRNAs, protein and ribosome released. This process is called termination. The product is called a polypeptide. Modified in ER or Golgi to make a protein.

8. Translation
Each mRNA can be used more than once, by more than 1 ribosome at a time, so many proteins can be translated from 1 transcribed piece mRNA.

9. Gene expression
The whole process of going from DNA to RNA to a protein that runs a cell process is called gene expression

10. Gene expression
After the polypeptide chain is made, it is often modified in the ER or Golgi Apparatus
The finished product is a protein and it has a three dimensional shape that decides its function

11. Mutations
Certain things can cause changes to the DNA/RNA code. They are called mutagens and cause mutations.
e.g. UV light, smoking, X rays, exposure to chemicals
Not all are bad…some allow for adaptation and evolution

12. Point mutations
Occur to one base or a small number of bases on DNA or RNA
Most are harmless, as many codons often code for the same amino acid.
3 kinds:
Substitution: one base is used instead of another
Insertion*: one base is added
Deletion*: one base is left out
* lead to a frameshift mutation, where everything is “off by one” base.

13. Point mutations

14. Chromosomal mutations
Change to a gene, series of genes or an entire chromosome
These are often helpful in plants, e.g. polyploidy…chromosomes do not separate during meiosis. Leads to seedless fruit that are bigger
In animals, they are often harmful or even lethal. You might be researching one disorder in the next unit on genetics…

15. Chromosomal mutations
Deletion: one or more genes is/are left out when copied
Duplication: one or more genes is/are copied more than once
Inversion: one or more genes is/are copied backwards
Translocation: one or more genes is/are moved from 1 chromosome to another
Nondisjunction (not shown): homologs fail to separate during meiosis

17. Transcription