Module 16/17 Flashcards
Genome
genetic information of the cell
Genes
segments of DNA that code for functional products
Codon
a group of three nucleotides on mRNA
Genotype
genetic makeup, potential properties
Phenotype
expressed properties of the genotype, the manifestation of the genotype
Anticodon
complementary sequence on the tRNA (to codon on mRNA); decides which amino acid is brought to the ribosome
What is the genome of a bacterial cell?
1 chromosome total not a pair
- Single chromosome
- Haploid
- Low amounts of noncoding regions
- Circular chromosome
- No histones-other proteins used
- Attached to the plasma membrane
What is the typical genetic flow of information?
DNA to DNA (replication)
DNA to RNA (transcription)
RNA to Protein (translation)
codon
a group of three nucleotides on mRNA
anticodon
complementary sequence on the tRNA (to codon on mRNA); decides which amino acid is brought to the ribosome
What is replication? What is transcription? What is translation?
- DNA supercoiling relaxed and parental DNA strands unwound by enzymes
- RNA polymerase bonds gene promoter and DNA unwinds; mRNA is synthesized (with RNA nucleotides) using DNA as a template in 5’-3’ direction until reaching terminator
- Ribosome subunits form with mRNA; mRNA codons determine which tRNA (each carry a different amino acid) “docks’ in ribosome; tRNA leaves amino acid for the forming polypeptide; synthesis of polypeptide continues until reaching a stop codon on mRNA
What does semiconservative replication of DNA mean? What experiment demonstrated this?
Each new double-stranded DNA molecule is one parental (old) strand and one daughter (new) strand
Meselson and Stahl experiment
First step: grow E. coli with N15 isotope to incorporate it into DNA-heavy DNA
Second step: grow E coli with N14
List the general steps for DNA replication.
Leading strand- synthesized continuously by DNA polymerase in 5’-3’ direction toward fork (with DNA nucleotides)
Lagging strand- synthesized discontinuously via Okazaki fragments by DNA polymerase in 5’-3’ direction away from the fork (with DNA nucleotides)- more complex- fragments extending from RNA primers.
Replication in bacterial cells is bidirectional
Why does the DNA polymerase of replication have a low error rate?
It has proofreading capability- DNA polymerase
checks the work as it goes
Errors 1 in 10^10 bases incorporated
Why does HIV have a high error (natural mutation) rate?
It has reverse transcriptase, which mutates quicker and faster
List the three types of RNA and their importance?
rRNA
-ribosomal RNA
-makes up ribosome-important for protein synthesis
-protein makes up protein
tRNA
-transfer RNA
-molecule brings the amino acid into ribosome during protein synthesis
-one for every amino acid
mRNA
-messenger RNA
-brings the message from the DNA to the ribosome
List the general steps for transcription.
- RNA polymerase binds gene promoter and DNA unwinds
- mRNA is synthesized (with RNA nucleotides) using DNA as template in 5’-3’ direction until reaching terminator
List the general steps for translation
- ribosome subunits form with mRNA
- mRNA codons determine which tRNA (each carry a different amino acid) “docks” in ribosome
- tRNA leaves amino acid for the forming polypeptide
- synthesis of polypeptide continues until reaching a stop codon on mRNA
Where does transcription and translation occur in the prokaryotic cell?
Simultaneous transcription and translation going on in cytoplasm (no nucleus)
Where does transcription and translation occur in the eukaryotic cell?
Transcription- nucleus
Translation-cystoplasm
How are bacteria able to transfer DNA (define vertical vs. horizontal gene transfer)?
Genetic recombination- exchange of genes between two DNA molecules to form new combinations of genes
-Survivability of bacteria
-Somewhat like sexual reproduction, so it contributes to genetic diversity
Vertical gene transfer- genes are passed from parent to offspring- plants, animals. Bacteria
Horizontal gene transfer- genes are passed between different bacteria
-3 methods:
—Transformation
—Conjugation
—Transduction
What is transformation? What does competency mean?
Uptake of DNA from the environment
First discovered in 1928 with Federick Griffiths experiments- transforming principle
Cells must be competent- alterations in the cell wall that make it permeable to DNA
-Strains without DNase
-Haemophilus, bacillus, staphylococcus, and streptococcus are competent
-Can make E. coli cells competent
What is conjugation?
DNA transfer with plasmids through pili
Explain the mechanism of conjugation and all of the important factors involved (names of the cells, etc.)
With F factor- The first plasmid studied for conjugation in E. coli
Donor cell contains fertility plasmid, is F+, male cell
The recipient cell does not, is F-, female cell
After conjugation F- cell becomes F+ (receive copy of F+)
Factor has genetic information for transfer/pili
DNA transfer during conjugation
—Rolling circle-ssDNA is transferred than made into dsDNA in cell it was transferred to
What is Hfr conjugation?
F plasmid may combine with genome and thus have Hfr cell
Conjugation of some of the genome from Hfr leads to recombination in recipient cell
What is a plasmid? What are some characteristics of plasmids and functions they code for?
Plasmids- small extra-chromosomal element
i. 1-5% of bacterial genome size
ii. Self replicates-rates vary
iii. Mobile during conjugation
iv. Cured if nonessential
Functions of plasmids
i. Resistance genes
ii. Metabolic genes
iii. Virulence factors
iv. Fertility- has genes for conjugation
What is transduction?
DNA transfer with viruses
Mechanism
-Defective phage
—Phage introduces bacterial DNA into a different bacterial cell and then have chance for recombination
—Generalized vs specialized
