Download Chapter 3, Section 4 Notes (p.97-103)

Chapter 3, Section 4 Notes (p.97-103)
I.
The Genetic Code
a. Proteins determine traits (size, shape, color, etc.)
b. Chromosomes are made of DNA
c. DNA molecules made of four nitrogen bases
i. Adenine
ii. Thymine
iii. Guanine
iv. Cytosine
d. Genes are made up of a series of nitrogen bases
e. Order of nitrogen bases determines the protein that is produced
II.
How Cells Make Proteins
a. Protein synthesis: the production of proteins
i. Chromosomes found inside nucleus in a cell
ii. Proteins are produced in ribosomes (outside nucleus)
b. RNA – ribonucleic acid i. Made of one strand of nitrogen bases
ii. Contains uracil INSTEAD of thymine
c. Types of RNA
i. Messenger RNA – copies coded message from DNA (in nucleus) and carries
it to ribosome (in cytoplasm)
d. Transfer RNA – carries amino acids to the ribosome and adds them to a growing
protein
e. Translating the Code
i. DNA molecules “unzip” between base pairs, creates messenger RNA to pair
up with DNA strand, genetic info. is transferred from the DNA to the
messenger RNA
ii. Messenger RNA travels to cytoplasm and attaches to a ribosome (where
protein production begins); ribosome moves along the messenger RNA
strand
iii. Transfer RNA attaches to messenger RNA by matching up with three-letter
codes of bases; amino acids are added to the growing protein chain
iv. Protein chain continues to grow until the ribosome reaches the “stop” code;
the ribosome releases the completed protein
III.
Mutations
a. Mutations: cause cells to produce an incorrect protein during synthesis. The
protein may cause an organism’s traits to change because of this
i. Only mutations occurring in a parent’s sex cells can be passed on to the
offspring.
b. Types of mutations:
c.
i. Single nitrogen bases being substituted for other bases (can occur during
DNA replication)
ii. Chromosomes fail to separate correctly (offspring could end up with too
many or too few chromosomes)
Effects of Mutations
i. Mutations can be helpful, harmful, or no positive or negative effect on the
organism
ii. Mutations are harmful when they reduce the organism’s chance for
survival or reproduction
iii. Helpful mutations improve an organism’s chance for survival