Chapter 9 Flashcards
Advantages of using bacteria and viruses for genetic studies
rapid reproduction
many progeny produced
genomes are small
the haploid genome allows all mutations to be expressed directly
describe bacterial chromosomes
bacteria have one circular chromosome per cell
the chromosome has an origin on replication, but no centromeres or telomeres
F+ cells
have a plasmid containing the F fertility factor
F- cells
cells do not have a plasmid
Hfr cells (high frequency of recombination)
have the F factor within their chromosome as a result of recombination between the chromosome and a plasmid
F’ cells
cells that had the F factor incorporated in their genome, but it exercised from the chromosome to reform the plasmid and carried chromosomal genes with it
F+ x F-
two F+ cells
Hfr x F-
one Hfr and one F-
F’ x F-
two F’ cells
what is a plasmid
a small, usually circular DNA molecule that is distinct from the bacterial chromosome
characteristics that make bacteriophages ideal organisms for many types of genetic studies
they have small and easily manageable genomes, reproduce rapidly, and produce large numbers of progeny
what types of genomes do viruses have
viruses can have DNA or RNA genomes that can either single stranded or double stranded
lytic cycle of virulent phages
infect, multiply, burst
lysogenic cycle of temperate phages
infect, incorporate themselves into host DNA, excise, enter lytic cycle
when DNA is transferred from one organism to another, what is required for the DNA to be stably inherited
the DNA must be incorporated into the recipient cells genome (the chromosome or a plasmid)
what did Joshua Lederberg and Edward Tatum demonstrate with their experiment
demonstrated that bacteria undergo genetic exchange
what did Bernard Davis demonstrate with his experiment
through his U tube experiment he concluded that genetic exchange requires direct contact between bacterial cells
what is a sex pilus
slender extensions of the cell membrane
connects F+ and F- cells during bacterial conjugation
do F+ cells have an F factor before conjugation
yes
do F- cells have an F factor before conjugation
no
