Molecular Genetics

1. DNA Replication

\-happens during S phase of interphase

\-semi-conservative

\-DNA is replicated by an enzyme that matches complementary bases

Semi-conservative

each new DNA molecule = 1 original strand and 1 new strand

Complementary bases

\-A pairs with T

\-C pairs with G

Transcription

\-DNA contains the instructions to make proteins

\-information in DNA is used to make RNA

What makes RNA?

\-an enzyme

\-creates a strand of complementary bases

Translation

\-mRNA carries the instructions from DNA to the ribosome to make a protein

\-ribosomes read mRNA and create a polypeptide chain

Codons

\-contained in RNA

\-indicate which amino acid to add

Anticodons

\-contained in tRNA

\-match with codons-

What is tRNA’s job?

\-brings **amino acids** to the ribosome

Codon Chart

\-show which amino acids are coded by each codon

\-multiple codons can code for the same amino acid

\-one start codon

\-three stop codons

Mutations

Can arise from:


1. Mistakes in DNA replication
2. Exposure to mutagens

Point Mutations

a nucleotide is changed, inserted, or deleted

Insertion mutations

nucleotide(s) are added

Deletion mutations

nucleotide(s) are removed

Substitution mutations

one nucleotide is switched for another

Substitution mutations can result in…

1. a different amino acid
2. an early stop codon
3. no change in amino acid

Gel Electrophoresis

\-Shows DNA fragments separated by size

\-An electrical current pushes & pulls DNA through the gel

\-Large fragments don’t travel far

\-Small fragments travel far

\-We compare DNA bands to determine: paternity, evolutionary relatedness, and crime scenes

Comparing DNA bands to determine paternity:

\-The child is 50% mom; 50% dad

Comparing DNA bands to determine crime scenes:

\-DNA at the crime scene should match DNA from the criminal

Comparing DNA bands to determine evolutionary relatedness:

\-More DNA in common = closer evolutionary relatives