Download Bacterial Genetics Summary

Bacterial Genetics Summary
A. Genetic Terms
1. Genetics
2. Genome
3. Gene
4. Allele
5. Locus
6. Genotype
7. Phenotype
8. Heredity
B. Structure of DNA
1. Polymer of Nucleotides
Each Nucleotide:
a. 5 carbon sugar - deoxyribose
b. phosphate group
c. nitrogen base
(1) adenine
(2) guanine
(3) cytosine
(4) thymine
2. Double stranded - antiparallel
a. sugar and phosphates form side rails of a ladder
b. nitrogen bases paired in center forming rungs of a ladder
(1) complementary bases
(a) Adenine and Thymine
(b) Guanine and Cytosine
(2) complementary strands
C. Semi-conservative Replication
1. Overview of Process
a. Two parental strands uncoil and unzipper
b. Replication starts at 3' end of parental strand
c. Complementary deoxyribonucleotides brought in
(1) hydrogen bond to complementary base
(2) covalent bond to adjacent nucleotide on growing
strand
d. When finished, have two molecules of DNA formed from one
molecule
e. Bacteria replication involves methylation of daughter stands, in
which a methyl group is added to one or two bases in a specific
nucleotide sequence- typically an adenine base.
f. semi-conservative process
(1) each daughter molecule contains one of original parent
strands and one newly synthesized strand
2. Enzymes of DNA Replication:
a. helicase
b. gyrase
c. Single Stranded Binding Protein
d. RNA primase
e. DNA polymerases
f. Topoisomerase
g. Ligase
h. Methylase
3. Leading Strand
a. open 3' end of DNA
b. continuous replication
c. replication proceeds in same direction as the replication fork
4. Lagging Strand
a. open 5' end of DNA
b. discontinuous replication; Generates Okazaki fragments
c. replication proceeds in direction opposite the replication fork
D. Protein Synthesis
1. Transcription
a. Information in one gene of DNA copied into sequence of RNA
b. Overview of Process
(1) one gene on DNA uncoils and unzippers
(2) only one strand of DNA is copied
(3) other strand of DNA is inactive
(4) transcription begins at promoter
(5) complementary ribonucleotides brought in
(a) hydrogen bond to complementary base
(b) covalent bond to adjacent nucleotide in growing RNA
molecule
(6) when terminator sequence is reached one gene has been copied
into RNA
(7) RNA leaves DNA
(8) DNA rezippers, recoils into double helix
c. Enzyme used - RNA polymerase
2. Three kinds of RNA formed
a. Ribosomal RNA (rRNA)
(1) composes ribosome
(2) ribosome contains small subunit with binding site for mRNA
(3) ribosome contains large subunit with 2 binding sites for tRNA
b. Messenger RNA (mRNA)
(1) carries information for sequencing one protein
(2) sequence of codons
(a) three nitrogen bases that specify an amino acid
(b) 64 different codons
(3) start signal - initiation codon (AUG)
(4) stop signal - termination codon (one of three)
c. Transfer RNA (tRNA)
(1) picks up and carries amino acids to ribosome
(2) anticodon complementary to codon on messenger
3. Translation
a. Information in mRNA used to produce one protein
b. Events of Translation
(1) Initiation
(a) various components assembled
(b) when start codon enters "p" site
(c) mRNA and first tRNA attach to ribosome at “p” site
(2) Elongation
(a)
(b)
(c)
(d)
(e)
with one tRNA in "p" site
second tRNA occupies "a" site
peptide bonds form between adjacent amino acids
tRNA in "p" site leaves ribosome
tRNA in "a" site and mRNA shift one position
(3) Termination
(a) when stop codon enters "a" site
(b) ribosome releases finished protein
(c) tRNA leaves, mRNA leaves, large and small subunits
separate
(d) new protein (polypeptide) is released