Molecular Genetics and Genetics of Prokaryotic Cells

MCAT Prep: Biology Part 7

Basic unit

nucleotide (sugar, nitrogenous base, phosphate)

deoxyribose

DNA’s sugar

ribose

RNA’s sugar

adenine and guanine

double-ringed purines

cytosine, uracil, and thymine

single-ringed pyrimidines

DNA double helix

antiparallel strands joined by base pairs (A=T, C=G)

single-stranded

RNA is usually __________; A pairs with U, not T

Operon

transcription of prokaryotes is regulated by the ________

Structural genes

have DNA that codes for protein

Operator gene

repressor binding site

Promoter gene

RNA polymerase’s 1st binding site

Inducible systems

need an inducer for transcription to occur

Repressible systems

need a corepressor to inhibit transcription

Point

one nucleotide is substituted by another; they are silent if the sequence of amino acids doesn’t change

Frameshift

insertions or deletions shift reading frame. Protein doesn’t form, or is nonfunctional

viruses

acellular structures of double- or single-stranded DNA or RNA in a protein coat

Lytic cycle

virus kills the host cell

Lysogenic cell

virus enters the host genome

plasmids

many bacteria contain this; extragenomic material

episomes

plasmids that can be integrated into the genome

Transformation

occurs when a bacterium acquires a piece of genetic material from the environment and integrates that piece of genetic material into the host cell genome. This is a common method by which antibiotic resistance can be acquired

Conjugation

is the bacterial form of mating (sexual production). It involves two cells forming a cytoplasmic bridge between them that allows for the transfer of genetic material. The transfer is one-way, from the donor male (+) to the recipient female (-)

Sex pili

appendages that the bridge of conjugation is made of and is found on the donor male

Sex factors

plasmids that must be contained by bacteria to form the pilus for conjugation

Transduction

occurs when a bacteriophage acquires genetic information from a host cell. Sometimes, when the new virions are assembled in a host cell, some of the genetic material from the host cell is packaged along with the viral genetic material. Then, the bacteriophage infects another bacterium, resulting in transfer of bacterial genetic material