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Microbial Genetics and Genetic Engineering (Terminology (Genetics (The…
Microbial Genetics and Genetic Engineering
Terminology
Genetics
The structure and function of the genetic material
Expression and variation of those traits
How this material changes
Transmission of traits from parent to offspring
Definition: the study of the inheritance (heredity) of living things and gene function
Genetic material
Definition: controls the inheritance of traits, formation and functioning of traits from one generation to the next.
DNA is the genetic material in prokaryotic and eukaryotic microbes
The building blocks of DNA are A, G (purines), T, and C (pyrimidines, along with U)
Known exceptions to this rule are the RNA viruses
Genome: sum total of genetic material of an organism
some appear as plasmids or in certain organelles of eukaryotes
genome of cells compose entirely of DNA
most of the genome exists in the form of chromosomes
genome of viruses can contain either DNA or RNA
Chromosome
Eukaryote
diploid (in pairs) or haploid (single)
linear appearance
DNA would around histone in the nucleus
Prokaryote
Single, circular chromosome
DNA condensed into a packet by means of histone-like proteins
Viruses
can contain either DNA or RNA
Definition: discrete cellular structure composed of neatly packaged DNA molecule
Genes
Molecular and biochemical sense
site on the chromosome that provides information for a certain cell function
Traditionally
a certain segment of DNA that contains the necessary code to make a protein or RNA molecule
Classical genetics
The fundamental unit of heredity responsible for a given trait in an organism
Recently
a gene can be defined as a segment of DNA that contains the code to make a group of related RNAs or proteins
Three Categories
regulatory genes that control gene expression
genes that code for RNA machinery used in protein production
structural genes that code for proteins
Genotype
the sum of all gene types; an organism's distinctive genetic makeup
Phenotype
The expression of an organisms genotype creates a trait
Three Process of DNA
Transcription
Translation
Introns
sequences that do not code for protein
Exons
coding regions that will be translated into protein
DNA replication
Definition: the process of duplicating DNA
semiconservative replication
one strand serves as a template is original parent on the DNA strand
Steps
hydrogen bonds between the base pairs are unzipped Nucleotide sequence of each strand serves as templates
two new strands are synthesized by attachment of the correct complementary nucleotides to each single-standee template
Parent DNA molecule uncoils
Origin of replication
rich in adenine (A) and thymidine (T)
held together by only two H bonds rather three
short sequence
less energy to separate the two strands
Helicases
bind the DNA at the origin
Helicases break the H bonds resulting in two separate strands
Untwist the helix to access helicases which bind dsDNA at the ori
Single stranded binding proteins keep strands apart
During replication, topoisomerases
DNA Polymerase III
Gene regulation
Reasons
Gene regulation ensures that the appropriate genes are turned on/off at the appropriated times
Prevents the waste of energy and materials
Enzymes are produced as they are needed
Antisense RNAs, micro RNAs, and riboswitches provide regulation in prokaryotes and eukaryotes
Correct protein are made
Help organism response to its environment
starve i sarcity
Hibernation
Operons
Types
Induction of gene expression
lactose catabolism
Repression of gene expression
arginine anabolism
Constitutive gene expression
glucose catabolism
Benefits of study Microbial Genetics to Human
Biofuels
Food
Medicines
Decomposers
DNA transfer in bacteria
Transfection
Transduction
Transformation
Conjugation
controlled by genes carried by plasmids, such as the fertility (F) factor
involves the transfer of the plasmid from donor to recipient cell
requires cell-to-cell contact between two bacteria
DNA
Nucleotides
Definition: the basic unit of DNA structure
Structure
Phosphate
Deoxyribose sugar
nitrogenous base
Nitrogenous bases attach along a strand by covalent bonds at the 1’ position of the sugar
purines and pyrimidines join with complementary bases using weak hydrogen bonds
molecule can easily be unzipped to gain access to the information encoded by the bases
Pairing of bases can be dictated by the formation of hydrogen bonds between bases
Guanine (G) always pairs with Cytosine (C)
Adenine (A) always pairs with Thymine (T)
2 purines – adenine (A) and guanine (G)
Double ring structures
2 pyrimidines – thymine (T) and cytosine (C)
Single ring structures
In RNA, thymine is replaced by uracil
Purines stabilized by 2 H bonds
Pyrimidines stabilized by 3 H bonds
each sugar attaches to two phosphates
Order of phosphate and sugar bonds differ between strands
from 5’ carbon to 3’ carbon on one side and 3’ to 5’ on the other
Antiparallel Arrangment
One side of the helix runs in the opposite direction of the other
Strands of nucleic acids have direction
All DNA strands are read from the 5' to the 3' end where the 5' end terminates in a phosphate group and the 3' end terminates in a sugar molecule
Significance of DNA structure
Provides variety or variation in the population
Maintains the code during reproduction (conservative replication of DNA)