genetics & experiment pt 5 & 6

What are the three ways DNA can be transferred from one bacterium to another?

Transformation, Conjugation, Transduction

What is transformation?

The ability of some bacteria to take up pieces of free DNA from their environment.

What is conjugation?

The transfer of DNA from one bacterium to another through direct cell-to-cell contact, usually involving an F pilus.

What is transduction?

The transfer of bacterial DNA from one bacterium to another by a bacteriophage.

What is the main difference between transformation, conjugation, and transduction?

Transformation: Bacteria take up free DNA from the environment. Conjugation: DNA transfers through direct bacterial contact. Transduction: DNA transfers through a bacteriophage.

Who performed the famous bacterial transformation experiment, and when?

Frederick Griffith in 1928.

What bacterium did Griffith study?

Streptococcus pneumoniae.

What are the two strains of Streptococcus pneumoniae used in Griffith's experiment?

Smooth (S) strain and rough (R) strain.

What is the smooth (S) strain of Streptococcus pneumoniae?

A strain that has a capsule and is virulent (disease-causing).

What is the rough (R) strain of Streptococcus pneumoniae?

A strain that lacks a capsule and is nonvirulent (does not normally cause disease).

Why is the smooth strain of Streptococcus pneumoniae virulent?

Its capsule helps protect it from being engulfed and destroyed by macrophages.

Why is the rough strain of Streptococcus pneumoniae nonvirulent?

It lacks a protective capsule and can be easily engulfed and destroyed by macrophages.

What happened when Griffith injected live smooth bacteria into mice?

The mice died, and live smooth bacteria were recovered.

What happened when Griffith injected live rough bacteria into mice?

The mice lived, and no bacteria were recovered.

What happened when Griffith injected heat-killed smooth bacteria into mice?

The mice lived, and no live bacteria were recovered.

What happened when Griffith injected live rough bacteria mixed with heat-killed smooth bacteria into mice?

The mice died, and live smooth bacteria were recovered.

What was the surprising discovery in Griffith's experiment?

Some live rough bacteria were transformed into live smooth bacteria by taking up genetic material from the heat-killed smooth bacteria.

What is the transforming principle?

The substance from dead smooth bacteria that entered rough bacteria and caused them to develop a capsule and become virulent. It was later identified as DNA.

How did transformation occur in Griffith's experiment?

Heat-killed smooth bacteria released DNA when their cells broke apart. Some live rough bacteria took up pieces of this DNA, including the gene for capsule production, and incorporated the DNA into their chromosomes.

What happened after rough bacteria incorporated the capsule gene from smooth bacteria?

They gained the ability to produce a capsule and became virulent smooth bacteria.

What did Griffith's experiment demonstrate?

Genetic information could be transferred between bacteria, causing a heritable change in their characteristics.