Chapter 11: Mechanisms of Microbial Genetics Flashcards
Gene Expression
The synthesis of a specific protein with a sequence of amino acids that is encoded in the gene.
Central Dogma
States that DNA encodes messenger RNA, which, in turn, encodes protein.
Semiconservative Replication
The two strands of the double helix separate during DNA replication, and each strand serves as a template from which the new complementary strand is copied.
DNA pol III
Adds deoxyribonucleotides each complementary to a nucleotide on the template strand, one by one to the 3’-OH group of the growing DNA chain.
DNA Gyrase/Topoisomerase II
Relaxes supercoiled chromosome to make DNA more accessible for the initiation of replication; helps relieve the stress of DNA when unwinding, by causing breaks and then resealing the DNA.
Helicase
Opens the DNA helix by breaking hydrogen bonds between the nitrogenous bases.
Primer
An RNA sequence 5-10 nucleotides long and complementary to the parental or template DNA that provides the free 3’OH end for DNA pol III.
RNA Polymerases
Do not need a free 3’-OH group to synthesize an RNA molecule.
Leading Strand
The continuously synthesized strand.
Okazaki Fragments
Small DNA fragments each separated by RNA primers.
Lagging Strand
The discontinuous strand with the Okazaki fragments.
Sliding Clamp
A ring-shaped protein that holds the DNA polymerase in place as it continues to add nucleotides.
Topoisomerase
Prevents the overwinding of the DNA double helix ahead of the replication fork as the DNA is opening up; it does so by causing temporary nicks in the DNA helix and then resealing it.
DNA pol I
Exonuclease activity removes RNA primer and replaces it with newly synthesized DNA.
DNA Ligase
Seals the gaps between the Okazaki fragments on the lagging strand to create one continuous DNA strand.
DNA pol II
Single-Stranded Binding Proteins
Bind to single-stranded DNA to prevent hydrogen bonding between DNA strands, reforming double-stranded DNA.
Topoisomerase IV
Introduces single-stranded break into concatenated chromosomes to release them from each other, and then reseals the DNA.
Translation/Protein Synthesis
The second part of gene expression, involves the decoding by a ribosome of an mRNA message into a polypeptide product.
Protein Sequence
Consists of 20 commonly occurring amino acids.
Codon
A triplet of nucleotides that makes up each amino acids within the mRNA.