(exam 1) chapter 8 microbial genetics Flashcards
what is genetics?
the study of genes, how they carry information, how information is expressed, and how genes are replicated
what are chromosomes?
contain DNA that carries hereditary information; contain genes
what do we know about bacterial chromosomes?
circular, has associated proteins, typically one
what do we know about eukaryotic chromosomes?
linear, wrapped around histones, arranged in pairs (number varies with organism)
what are Genes?
segments of DNA that encode functional products, usually proteins
what is the Genome?
all the genetic information in a cell
what is Genomics?
new field of sequencing and molecular characterization of genomes
what does genetic code describe?
how the four nucleotide bases (A,T,G,C) are read and converted by cellular machinery into amino acids
what central dogma of molecular biology?
DNA to RNA to Proteins
what is genotype?
the genetic makeup of an organism
what is phenotype?
expression of the genes
what is vertical gene transfer?
occurs mainly in eukaryotes; flow of genetic information from one generation to the next
(Occurs during replication)
what is Genetic recombination?
exchange of genes between two DNA molecules; creates genetic diversity
what is crossing over?
Two chromosomes break and rejoin, resulting in the insertion of foreign DNA into the chromosome
when does crossing over occur in eukaryotes?
occurs during production of reproductive cells
Vertical gene transfer
how does recombination work in prokaryotes (vertical gene transfer?)
vertical gene transfer to offspring
how does recombination work in prokaryotes (horizontal gene transfer)?
horizontal gene transfer is transfer of genes between cells of the same generation
what are four methods of horizontal gene transfer?
1) mobile genetic elements
2) transformation
3) conjugation
4) transduction
what are two types of mobile genetic elements?
1) plasmids
2) transposons
what is mobile genetic elements?
move from one chromosome to another or from one cell to another
what are plasmids?
Self-replicating circular pieces of DNA
(1 to 5% the size of a bacterial chromosome)
Often code for proteins that enhance the pathogenicity of a bacterium
what are three types of plasmids?
1) conjugative plasmids
2) dissimilation plasmids
3) Resistance factors (R factors)
what are conjugative plasmids?
carries genes for sex pili and transfer of the plasmid
what are dissimilation plasmids?
encode enzymes for the catabolism of unusual compounds (when trying to eat something unusual)
what are resistance factors (R factors) plasmids?
encode antibiotic resistance
what are transposons?
’ jumping genes that move on their own’ segments of DNA that can move from one region of DNA to another; Contain insertion sequences (IS) that code for transposase that cuts and reseals DNA; Complex transposons carry other genes (e.g., in antibiotic resistance) - humans have them but they are inhibited in us
what is transformation?
genes transferred from one bacterium to another as “naked” DNA; Cells must be “competent” meaning that the cell walls are altered for passage of large DNA molecules
what is one pit fall of transformation?
because the cells are altered so the cell wall becomes semi permeable this makes the cells susceptible to damage because they are very fragile in this state
what is conjugation?
genetic material transferred from one bacterium to another; Requires cell-to-cell contact via sex pili
what is specific about gram negative cells that use conjugation?
gram negative cells can be a little farther away because they use a sex pilus
what is specific about gram positive cells that use conjugation?
gram positive cells must be very close together because they use a mating bridge
what is transduction?
DNA is transferred from a donor cell to a recipient via a bacteriophage; relies completely on the bacteriophage
what do mutations and recombination create?
cell diversity
what is diversity the raw material for?
Evolution!
how does natural selection act on populations of organisms?
to ensure the survival of organisms fit for a particular environment (fit organisms survive and reproduce whereas nonfit organisms die off)
