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What is genetics?
Study of heredity
What is molecular biology?
Study of DNA and protein synth
What is a genome?
Total DNA in a cell (chromosomes & plasmids)
What are genes?
Sections of DNA that code for traits
What is a DNA?
Macromolecule made of nucleotides
What does each DNA nucleotide consist of?
N base, deoxyribose sugar, phosphate
What shape is DNA?
Double helix
What is the base pairing rule?
A - T, C - G
How are nucleotides linked together?
Phosphodiester bonds
What is the flow of genetic information?
Replication
Gene expression
Recombination (DNA flow between 2 dif bacterial cells)
What happens during DNA replication?
Helicase unzips DNA while primase produces RNA primer, marking a start point for DNA polymerase to read each strand and create a complementary strand
What is the leading strand?
The strand that follows the replication fork
What is the lagging strand?
The strand that goes away from the replication fork; creates Okazaki fragments that is joined together by DNA ligase afterwards
What are the parts of gene expression?
Transcription
Translation
What are the 3 types of RNA?
mRNA
rRNA
tRNA
What is the first step in transcription?
RNA polymerase bond to promoter and copies the template strand
What is the second step in transcription?
As RNA polymerase synthesizes new RNA, DNA rewinds behind it
What happens during the third step in transcription?
RNA polymerase hits terminator, making it drop the newly synth RNA strand
What are codons?
Set of 3 nucleotides
What does mRNA do?
Info from DNA used to make proteins
What are stop codons?
UAA, UAG, UGA; signals end of protein synth
What happens in the first step of translation?
Ribosome assembles on mRNA; F-Met enters P-site, then next amino acid based on codons in A-site enters and F-Met binds to it using peptide bonds
What happens in the second step of translation?
Ribosome goes done mRNA, adding corresponding amino acids based on codons in A-site to the growing polypeptide chain in P-site, and releasing used tRNA at the E-site
Continues until stop codon
What happens in the third step in translation?
Ribosomes disassemble and releases polypeptide which then folds into its shape and becomes a protein
Disassembled ribosomes can be used again
How does genetic change happen in bacteria?
Mutation and horizontal gene transfer
What is mutation?
Change in nucleotide sequence of DNA which may change the original protein
What is horizontal gene transfer?
Gene info passed from one cell to another from the same gen
What is base substitution?
Single nucleotide is replaced by another, resulting in a base pair when DNA replicates
Missense mutation after translation (incorrect amino acid in protein)
What is frameshift mutation?
Insertion/Deletion of 1 or 2 nucleotides, changing reading frame of mRNA
Non-functional protein
How do mutations happen?
Spontaneous or induced mutations
What is spontaneous mutation?
Happens in absence of mutagens because of mistakes during DNA replication
What is induced mutation?
Happens because of mutagens - damages DNA and causes changes in its sequence
What is silent mutation?
No effect on protein - remaining functional
What is missense mutation?
Protein with a different amino acid sequence w/ dif function
What is nonsense mutation?
Incomplete protein because of early stop codon
What are plasmids?
Self replicating DNA molecules that have non-essential genes
What are F Plasmids?
Fertility factors - carry gene to make F pilus (sex factor) which is involved in conjugation
What is conjugation?
Transfer of gene material between bacteria
What are R plasmids?
Resistance factors - Genes for antibiotic resistance
What are Vir plasmids?
Virulence factors - Genes for toxin production
What are the steps in horizontal gene transfer?
Transformation
Transduction
Conjugation
What happens during the first step of horizontal gene transfer?
Pieces of “naked” DNA taken up by bacterial cell
Can be integrated into chromosome for recombination
What happens in the second step of horizontal gene transfer?
Fragments of DNA transfer between bacteria thru bacteriophage which attaches to the cell wall - injecting DNA inside so that phage DNA can replicate inside
Chance of transducing particles which can pass to another cell
What are transducing particles?
Bacteria DNA instead of phage DNA in newly made phages
What happens in the third step of horizontal gene transfer?
Transfer happens when donor (F+) cell forms F pilus to attach to recipient (F-) cell; Recipient cell becomes (F+)
What are viruses?
Acellular microbes that can infect and cause disease in host cells
Why do viruses need hosts?
Requires the host cell’s metabolic system to multiply, disrupting host’s normal function
What are some features that viruses have?
No plasma membrane
DNA or RNA with protein coat
What are viruses’ host range?
Most are single host species specific
What structures make up a virus?
Nucleic acid
Capsid
Envelope
What are capsids?
Protein coat that surround nucleic acid that is made up of capsomeres
What does the viruses’ envelope consist of?
Lipid bilayer from the host cell with spikes (viral proteins) inserted in it
What are the morphology of viruses?
Polyhedral
Helical
Enveloped
Complex
Describe the polyhedral shape of viruses
Icosahedral - shape with 20 triangular faces
Describe the helical shape of viruses
Long rods that can be rigid and flexible
Describe the enveloped shape of viruses
Roughly spherical
Describe the complex shape of viruses
Polyhedral head w/ helical tail; only in bacteriophages
Classification of viruses
Nucleic acid type
DNA or RNA
Single or double stranded
Segmented or single
Capsid structure
Polyhedral
Helical
Presence of envelope
What is the naming structure of viruses?
Family ends with -viridae; Genus ends with -virus; Descriptive name instead for species
Process of animal virus multiplication
Adsorption
Penetration
Uncoating
Biosynthesis
Maturation & Assembly
Release
What happens during adsorption?
Attach to host cell - virus attachment sites recognize protein/glycoprotein of host membrane
What happens during penetration?
Entry into host - enveloped viruses enter thru fusion, naked enter thru endocytosis
What happens during uncoating?
Viral nucleic acid freed from capsid
What happens during biosynthesis?
Viral nucleic acid replicated (DNA in nucleus, RNA in cytoplasm), viral proteins (capsomeres) synth in cytoplasm
What happens during maturation and assembly?
New virions assembled:
Capsid → Capsomeres
Nucleic acid enter capsid → Nucleocapsid
What happens during release?
Naked: Burst out → host cell dies
Enveloped: Bud out → host cell lives and steadily releases more
What are the different types of infections?
Acute
Persistent viral
Chronic viral
Latent viral
What is an acute infection?
Result from tissue damage, short, host may have long immunity
What is an example of an acute infection with late complications?
Measles → subacute sclerosing panencephalitis
What is a persistent viral infection?
Infection where virus is present with maybe no symptoms
Host can act as reservoir and transmit virus to others
What is a chronic viral infection?
After acute, virus remains with maybe no noticeable symptoms
What is a latent viral infection?
Acute with symptomless period; virus gives copy of DNA into host and remain dormant until reactivation years later
What is a provirus?
Virus that’s integrated into DNA of host cell
What is an example of a latent viral infection?
Varicella-Zoster virus (herpes) which causes chicken pox in children and can be reactivated later and cause shingles
What is a tumor?
Abnormal growth of tissue
What is a benign tumor?
A tumor that doesn’t spread
What is a malignant tumor?
Tumor that metastasize and invade nearby tissue (cancer)
Which genes control cell growth?
Proto-oncogenes
Tumor suppressor genes
What is a proto-oncogene?
Gene that stimulates cell growth
What is a tumor suppressor gene?
Gene that inhibit cell growth
What leads to tumor formation and cancer?
Mutations in proto-oncogene or tumor suppressor gene
What are oncogenes?
Genes that alter cell’s control mechanisms
What does Hepatitis B and C cause?
Liver cancer
What does the Epstein-Barr virus cause?
Infectious mononucleosis; may cause cancers of WBC (lymphoma) and of nose and throat
What does the Human Papillomavirus (HPV) cause?
Genital warts and cervical cancer
What are viroids?
Naked RNA w/o protein coat
Cause disease in plants
What are prions?
Infection protein particles w/o gene material that’s linked to human and animal diseases
What are the modes of infection?
Through food: destroyed at 480*C or autoclave in SOH-
What is innate immunity?
Immunity you’re born with; non-specific, no memory, and always present which means it responds fast
What defenses does innate immunity have?
First line defense (phys & chem barriers to prevent entry) and second line defense (eliminate microbe from body)
What are the physical barriers?
Skin, mucous membrane, fluid flow
What is the job of the skin?
Frequently sheds (remove microbes), dry (inhibit growth), rarely penetrated by microbes
What is the job of the mucous membrane?
Fluid/gas exchange, lines tracts and secrete mucous (glycoprotein) that traps microbes and cilia sweep it away
What is the job of fluid flow?
Bodily secretions that moves microbes away from the body
What are the chemical barriers?
Acidity of body fluids & skin, lysozome, lactoferrin, defensins, and normal microbiotaW
What is the job of acidity of body fluids and skin?
Stomach acid (pH 2) destroys bacteria & toxins
Skin fatty acid & lactic acid (pH 3-5) prevent growth
What is the job of lysozome?
Degrades peptidoglycan
What is the job of lactoferrin?
Iron binding proteins in mill & mucous that makes it slow microbe growth
What are the jobs of defensins?
Short polypeptide that poke holes in membranes
produced by epithelial cells
What are the jobs of normal microbiota?
Prevents growth of pathogens thru comp exclusion & microbial antagonism
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