Bacterial Genetics Flashcards
1
Q
What are the functions of DNA
A
- Inheritance: Genetic material is responsible for inheritance, passed from parent to offspring
- Replication: Great accuracy with minimal errors that introduce changes to DNA sequence, preserves integrity of genetic information
- Genome: Contains full complement of DNA within a cell and is organised into smaller, discrete units called genes that are arranged on chromosomes and plasmids
- Protein Synthesis: Directs and regulates the construction of proteins necessary to a cell for growth and reproduction in a particular cellular environment
2
Q
What is the central dogma and gene expression
A
- Central Dogma: Process of DNA being transcribes to mRNA which is translated to a protein
- Each stages includes initiation, elongation, termination
- Gene Expression: Processes of transcription and translation, synthesis of a specific protein with a sequence of AA that is encoded in the gene
3
Q
What is a genotype
A
- Genetic makeup, all its DNA, the information that codes for all the particular characteristics of the organism, potential properties
- Although a cell’s genotype remains constant, not all genes are used to direct the production of their proteins simultaneously
4
Q
What is a phenotype
A
- Observable / expressed properties, manifestation of genes, product of an array of proteins produced by a cell at a given time, influenced by genotype and interactions with environment
- Genes code for proteins that have functions in the cell
- Production of a specific protein encoded by an individual gene results in a distinct phenotype
- Cells carefully regulate expression of their genes, only using genes to make specific proteins when those proteins are needed
5
Q
Define genes, genetics and chromosomes
A
- Gene: A segment of DNA that encodes a functional product, transcribed to produce an RNA molecule during the process of transcription and eventually a functional product (protein)
- Genetics: The study of what genes are, how they carry information, how information is expressed, and how genes are replicated
- Chromosome: Structure containing DNA that physically carries hereditary information, contain genes
- Bacterial Chromosome: Singular circular model of DNA and associated proteins, looped, folded and attached at one of several points to cell membrane
6
Q
What are the 3 different replication models
A
- Semiconservative: Two strands of DNA separate, each serves as a template from which a new strand is copied
- Conservative: Two parental strands remain together after replication
- Dispersive: Strands broken into segments, even after second replication parental strand is somewhat present
7
Q
What is DNA vs RNA
A
DNA:
- Long antiparallel strands of nucleotides twisted together in pairs to form a double helix
- Strands held together by H bonds
- Each strand has a string of alternating sugar and phosphate groups (sugar-phosphate backbone), and a nitrogenous base is attached to each sugar in the backbone
- Nucleotide: 3 parts, nitrogen base (AT and CG), deoxyribose pentose sugar and phosphate
RNA
- Long strands of nucleotides, single stranded, nitrogenous bases (AU and CG), ribose sugar
8
Q
How does the flow of genetic information occur
A
- Vertical: Transfer of genes from an organism to its offspring, between generations of cells (replication)
- Horizontal: Transfer of genes laterally, to other microbes of same generation (recombination)
9
Q
Provide an overview of DNA replication
A
- “Parental” double-stranded DNA molecule is converted to two identical molecules, one strand serves as a template for the production of a second strand
- Topoisomerase / Gyrase: Relaxes supercoiling ahead of replication fork
- Helicase: Unwinds double-strand, replication fork created
- DNA Polymerase: Synthesise DNA, proofread and facilitate repair of DNA, add nucleotides to the growing DNA strand, in 5’ 3’ direction, removes RNA primer and joins okazaki fragments with ligase
- Leading Strand: Continuously synthesised
- Lagging Strand: Synthesised discontinuously, creating okazaki fragments
10
Q
What are okazaki fragments
A
- Relatively short fragment of DNA (with an RNA primer at the 5’ terminus)
- Created on the lagging strand during DNA replication
11
Q
Describe the steps in DNA synthesis / replication
A
- Enzymes (topoisomerase / DNA gyrase) unwind parental double helix
- Proteins stabilise unwound parental DNA
- Leading strand synthesised continuously from primer by DNA polymerase
- The lagging strand is synthesised discontinuously, primase (RNA polymerase) synthesises a short RNA primer which is then extended by DNA polymerase
- DNA polymerase digests RNA primer and replaces it with DNA
- DNA ligase joins discontinuous fragments of lagging strand
12
Q
How does replication of bacterial DNA occur
A
- Bidirectionally
- Around the chromosome, two replication forks move in opposite directions away from the origin of replication
13
Q
What is transcription
A
- Synthesis of a complementary strand of RNA from a DNA template
- rRNA (ribosomal subunit, integral part of ribosomes)
- tRNA (transfer, transports AA during protein synthesis)
- mRNA (messenger, carries coded information from DNA to ribosomes)
14
Q
Describe the steps involved in transcription
A
- RNA polymerase binds to promoter and DNA unwinds at the beginning of the gene
- RNA is synthesised by complementary base pairing of free nucleotides with the nucleotide bases on the template strand of DNA
- The site of synthesis moves along DNA, DNA that has been transcribed rewinds
- Transcription reaches the terminator (complete RNA strand produced)
- RNA and RNA polymerase are released and the DNA helix reforms
15
Q
What is translation
A
- Protein synthesis, decoding the “language” of nucleic acids (mRNA) and converting it into the “language” of proteins (codons)
- Multiple ribosomes attached per mRNA molecule, all at various stages of protein synthesis
- Codon: Language of mRNA, groups of three mRNA nucleotides that code for a particular AA
- Start / Stop: Translation begins at start codon (AUG) and ends at stop codon (UAA, UAG, UGA)
