Presentation is loading. Please wait.

Presentation is loading. Please wait.

Microbial Genetics (Micr340) Lecture 6 Genetic Analysis.

Similar presentations


Presentation on theme: "Microbial Genetics (Micr340) Lecture 6 Genetic Analysis."— Presentation transcript:

1 Microbial Genetics (Micr340) Lecture 6 Genetic Analysis

2 Isolating Mutants Genetic analysis: study of genes and their functions by creating and analyzing mutants Spontaneous mutation – mutations occur naturally – low frequency Artificial mutagenesis uses UV or chemicals to create mutations in DNA – increasing frequency Agents which cause mutations - mutagens

3 Selecting Mutants The process of finding mutants - screening Selective conditions – usually conditions under which either the mutant or the wild type will not be able to multiply to form a colony or a plaque. Positive selection: the mutant but not the wild type can multiply Negative seletion: wild type but not the mutant can multiply

4 Positive selection

5 Selecting Mutants Enrichment

6 Complementation Complementation – a method to determine if mutations are in different genes (allelism)

7 Complementation

8 Cloning by Complementation

9 Recombination Tests Complementation reveals how many genes can be mutated to give a particular phenotype and something about the nature of the mutations Recombination tests give information about where mutations are located in the chromosome Recombination: breakage and rejoining of two DNA molecules in new combinations

10

11 Recombination Most common type of recombination is generalized recombination (or homologous recombination); it occurs between two DNA regions that have same (homologous) sequences This requirement of homologous nature ensures the same order of genes before and after recombination Recombination frequency: the number of recombinant-type progeny over the total progeny

12 Marker Rescue Definition: recombination between a piece of introduced DNA and the corresponding region in the chromosome containing a mutation can “rescue” the mutation in the chromosome, restoring the wild type phenotype.

13 Marker rescue

14

15 Gene replacement and transgenics Gene replacement: replacement of a normal gene in an organism with a particular mutated allele of the same gene via recombination The process of introducing a predetermined mutation into the DNA of an organism is called “reverse genetics”, the reverse of normal genetic analysis

16

17

18


Download ppt "Microbial Genetics (Micr340) Lecture 6 Genetic Analysis."

Similar presentations


Ads by Google