Mid Genetics I

Front 1

What is transformation?

Back 1

DNA from one species is taken up by another species through free DNA

Front 2

What is transduction?

Back 2

Genetic information is transmitted from bacteria to bacteria through a virus

Front 3

What is conjugation?

Back 3

Requires cell-to-cell contract between bacteria, but is much more efficient

Front 4

Describe bacterial chromosomes

Back 4

-Most bacteria contain a single chromosome + extrachromosomal elements
-Some bacteria have been found also to contain 2-3 replicones which can be considered either megaplasmids or minichromosomes
-A few bacterial genera contain >1 chromosome
-Some bacteria harbor large replicones essential for survival in a specific ecological niche but not under laboratory conditions

Front 5

Compare bacterial and eukaryotic chromosomes

Back 5

Bacterial chromosomes are very dense. There is not a lot of "wasteful" DNA. If you look at the locus of an RNA polymerase gene, around it you see many genes with very few spacers. If you look at the chromosome of a eukaryote, there are more intergenic regions. When you get to more complicated multicellular organisms there is a more drastic change.

Front 6

Describe plasmids

Back 6

-Extrachromosomal
-Circular or linear
-2 kb to hundreds of kb in size
-Non-essential
-May carry "supplemental" genetic information or may be cryptic
-Employ host functions for most of DNA metabolism

Front 7

What is a nonsense mutation?

Back 7

A change to a stop codon

Front 8

What are the effects of silent mutations?

Back 8

The effect of silent mutations depend on the abundance of the tRNA. If the new tRNA is rare that will affect the creation of the protein.

Front 9

What are insertion sequence (IS) elements?

Back 9

Insertion sequence elements are the simplest transposable element, they can move around in the chromosome or plasmid. They are small and they only encode genes that allow them to insert themselves into the DNA of the cell. We don’t know what they do. The inverted repeats have a targeting sequence which allow them to insert into the chromosome. They goes a transposable genes which mediates the insertion into the DNA.

1. Simplest type of transposable element found in bacterial chromosomes and plasmids
2. Encode only genes for mobilization and insertion
3. Range from 768 bp to 5 kb
4. Ends of all known IS elements show inverted terminal repeats (ITRs)

Front 10

Describe the time course of transmission

Back 10

Transmission is a simple method that allows cells to uptake naked DNA. This DNA sensitive to all the nucleases in the environment. This is a quick process or else the DNA would be destroyed. The cells need to be competent (need to be able to take up the DNA).

Front 11

What are the factors affecting transformation?

Back 11

-DNA size and state
-Sensitive to nucleases
-Competent of the recipient
-Competence factor
-Induced competence

Front 12

What does it take for a cell to be competent?

Back 12

For cells to become competent they have to set up these structures on their surface. These structures allow the uptake of DNA and incorporation into the chromosome. DNA is released through lysing or is secreted from the cell.

Front 13

What are the steps of transformation?

Back 13

-You start with double stranded donor DNA
-One strand of donor DNA enters the cell as the other gets degraded
-A triple strand forms
-There is recombination (strand displacement) by double crossover
-There is a chromosome with segement a+/a heteroduplex DNA and the remaining ragment is degraded