C6 - Bacterial Genetics Flashcards
discovered DNA
Frederick Miescher(1869)
discovered that DNA contained phosphates, five-carbon sugars (cyclic pentose), and nitrogen containing bases
Phoebus A. T. Levine (1920s)
→ discovered the helical structure by x-ray crystallography
Rosalind Franklin
described the three-dimensional structure of the DNA molecule
James Watson and Francis Crick (1950s )
What does genetics study?
Heredity and variation
What determines an organism’s ability to maintain viability, adapt, multiply, and cause disease?
Genetic composition
What are the three major aspects of microbial genetics?
Structure and organization of genetic material,
replication and expression of genetic information,
mechanisms of genetic information alteration and exchange
What is the structure of a DNA molecule?
Double helical chain of nucleotides
How is the DNA helix described?
Double strand twisted together, referred to as a “spiral staircase”
What determines the information contained in DNA?
Base sequence (Genetic Code)
What process involves DNA in the production of RNA?
Genetic information processing
What are the components of a nucleotide?
A phosphate group (PO4),
a cyclic five-carbon pentose sugar (deoxyribose),
and a nitrogen-containing base
What are the two types of nitrogen-containing bases in nucleotides?
Purine and pyrimidine
What is the structure and length of an RNA molecule compared to DNA?
RNA is single-stranded and short
What sugar is present in RNA molecules?
Ribose
What are the three major types of RNA?
Messenger RNA (mRNA),
Transfer RNA (tRNA),
Ribosomal RNA (rRNA)
A DNA sequence that encodes for a specific product (RNA or protein)
gene
What term refers to all the genes in an organism?
Genome
What organizes the genome into discrete elements?
Chromosomes
What type of chromosome do bacteria have?
Single, unpaired (haploid), double-stranded, closed, circular
What are double-stranded, closed, circular, autonomously replicating genetic elements called?
Plasmids
What are the size ranges of plasmids?
1 to 2 kilobases up to 1 megabase
What do plasmids encode for?
Replication and transfer products, specialized functions
Do plasmids encode essential viability products?
No
What are pieces of DNA that move between genetic elements called?
Transposable elements
What are the two types of transposable elements?
Simple Transposon, Composite Transposon
What do Simple Transposons (Insertion Sequences) contain?
Movement genes
What characterizes Composite Transposons?
Cassette flanked by insertion sequences
What do internal genes in insertion sequences often encode?
Accessory functions (e.g., antimicrobial resistance)
Extrachromosomal Elements
Plasmids
Transposable Elements
What is the complex process mediated by various enzymes for DNA replication?
Replication
What enzyme is crucial for DNA replication?
DNA polymerase
What is the first step in DNA replication?
Unwinding of the chromosome’s supercoiled DNA
What happens after unwinding the DNA in replication?
Separation of the complementary strands of the parental DNA
What is the third step in DNA replication?
Synthesis of the new DNA strands
What marks the end of the DNA replication process?
Termination of replication, releasing two identical chromosomes
How long does the replication process typically take in rapidly growing bacteria like E. coli?
Approximately 20 to 40 minutes
Expression of Genetic Information
Transcription
Translation
→processing of information encoded in genetic elements (i.e., chromosomes, plasmids, and transposons)
→results in the production of biochemical molecules, including RNA molecules and proteins
Gene expression
What is the synthesis of single-stranded RNA from a DNA template called?
Transcription
mRNA are considered as __________ due to their ability to encode for several gene products
Polycistronic
What process involves translating mRNA into amino acid sequences?
Translation
GENETIC EXCHANGE AND DIVERSITY
Three basic mechanisms:
Mutation
Genetic Recombination
Genetic Exchange
Genetic Exchange
Three mechanisms:
Transformation
Transduction
Conjugation
What is the alteration in the original nucleotide sequence of a gene called?
Mutation
What effect does a mutation have on an organism’s genotype?
It changes the genotype
What can induce mutations?
Chemical or physical factors (mutagens) or biologic factors
What is the process where a segment of DNA from one bacterial cell is exchanged with a segment of another cell’s DNA?
Genetic recombination
What type of recombination involves DNA segments with extensive nucleotide sequence similarities?
Homologous recombination
What protein plays a central role in homologous recombination?
RecA
What is the uptake of naked DNA from the environment by a recipient cell called?
Transformation
What happens to DNA during transformation after a bacterial cell dies and lyses?
It is released into the environment and can be incorporated into the recipient’s genome
What term describes cells that can take up naked DNA during transformation?
Competent
What is the transfer of bacterial genes by a bacteriophage from one cell to another called?
Transduction
What happens in generalized transduction?
Bacterial DNA may be randomly incorporated with viral DNA
What happens in specialized transduction?
Bacterial DNA is incorporated along with adjacent viral DNA
What mechanism involves the transfer of genetic material between two living bacterial cells through direct contact?
Conjugation
What structures are involved in the transfer of plasmids and transposons during conjugation?
Plasmids and transposons
What mediates contact between donor and recipient cells in conjugation?
Sex pilus
What does the sex pilus establish between the donor and recipient cells?
A conjugative bridge for DNA transfer
