Unit 3 review Flashcards by Annabel Chambers

used Pea Plants in 1866 to
conclude that characteristics are passed
from generation to generation. Coined the terms “dominant” and
“recessive”

Gregor Mendel

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Who first discovered DNA in 1869? His lab in Germany was investigating tissue
composition, was tasked to observe white blood cells (lymphoid cells)
* Isolated a molecule, which later came to be known as a component of DNA

Friedrich Miescher

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in 1882 spent time looking at
“units” passed from generation to generation
(chromosomes)
* Discovered Mitosis occurs through the
duplication of chromosomes

Walther Flemming

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In 1928, showed that DNA could be transferred
“horizontally”, rather than only by descent. Discovered that the bacteria exchanged
information across the surviving DNA

Frederick Griffith

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From 1944-1950, discovered that DNA was made by equal ratios of Adenine:Thymine and Cytosine:Guanine. Also found that these numbers differ between AND among species
* His research indicates that DNA is
responsible for heredity

Erwin Chargaff

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In 1952, provided additional
evidence of DNA being the genetic
material, not proteins  using a bacteriophage (virus that infects bacteria.)

Martha Chase, Alfred Hershey

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In 1950s, discovered the structure of DNA
using X-ray crystallography. Maurice Wilkins already worked on
crystallography here, and assumed Franklin was hired to “assist him” –
yikes
* Franklin took her own image and presented – James Watson was in
attendance and admitted to not paying attention to her lecture
* Wilkins showed Franklin’s image to
Watson and Crick, later, which confirmed their 3D model of DNA

Rosalind Franklin

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the study of inheritance and inheritable traits

Genetics

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The blank of a cell is all the genetic material. composed of DNA in all
living organisms (so far) while viruses can
have either RNA or DNA

Genome

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specific sequences of
nucleotides that code for proteins

Genes

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What are DNA’s functions?

Replicate faithfully so
somatic cells can divide
for growth, repair.
(Mitosis)
Replicate faithfully so
sex cells can divide to
make new organisms.
(Meiosis)
*Direct the production of
proteins. (Transcription,
Translation, and Gene
Control)

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Which nucleic acid found in organisms? * Double chain of polynucleotides arranged as a double helix
* Deoxyribose sugar phosphate backbone from which the nitrogenous bases protrude
* Uses the nitrogenous bases: Adenine, Cytosine,
Guanine, and Thymine
* Chains are connected by hydrogen bonds between
the bases giving the structure a ladder appearance

Deoxyribonucleic acid (DNA)

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Which nucleic acid found in organisms? * Single polynucleotide chain
* Some RNA viruses are the exception with
double stranded RNA
* Ribose sugar phosphate backbone from which
the nitrogenous bases protrude
* Uses the nucleotides: Adenine, Cytosine,
Guanine, and Uracil

Ribonucleic acid (RNA)

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what are nucleic acids (DNA and RNA) made of?

nucleotides

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what are the 3 parts of nucleotides?

the nitrogenous base,
a 5 carbon sugar,
and one or more
phosphates.

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In DNA, who pairs with who?

Adenine always pairs with
Thymine via two hydrogen bonds and
Cytosine always pairs with Guanine via
three hydrogen bonds.

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In RNA who pairs with who

Uracil pairs with Adenine and
Cytosine pairs with Guanine.

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Attraction between a Hydrogen atom and a Nitrogen or Oxygen
atom

strong enough
bond to hold the two strands of DNA together yet weak enough
to let it be separated for
replication and transcription

Weaker bond than an ionic or covalent

Hydrogen bonds

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What does 3’ (3 prime)
and 5’ (5 prime) mean?

One end of a DNA
strand is called the
5’ end because it
has a phosphate
group attached to
a 5’ carbon.

The opposite end
has a hydroxyl
group attached to
a 3’ carbon.

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is able to carry instructions for
the synthesis of proteins

is able to be replicated and passed on to progeny

DNA

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Allow the bacterial cell to transfer DNA to
another cell via conjugation.

Fertility (F) plasmids

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Carry genes for resistance to antimicrobial
drugs or heavy metals.

Resistance (R) plasmids

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Carry instructions for structures, enzymes,
or toxins that enable a bacterium to
become pathogenic.

Virulence plasmids

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basic unit of heredity.
Forms the fundamental or functional unit of genetic
material
* Simplified one gene has all the necessary
information to code for one protein

gene

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the location of a gene on a chromosome or plasmid.

Locus

different versions of the gene found at a single locus (examples are eye color, blood type, etc.)

Allele

heritable change in the sequence of nucleotides in the sequence of DNA

mutation

Certain DNA sequences signal a “Start” location

Origin of Replication

“unwinds” DNA, beginning at origin of replication  breaks Hbonds

Helicase

formed as DNA strands are split apart

Y-shaped replication forks

coat the DNA near replication forks to prevent re-winding into double helix

Single strand binding proteins

an enzyme which alters the supercoiled form of a DNA molecule

topoisomerase

lays down the RNA primer (first 5- 10 nucleotides) to give DNA polymerase a 3’ end to build from

* RNA Primase

synthesizes new DNA strands complementary to the exposed template strands, in 5’  3’ direction (which causes leading strand)

DNA polymerase III

removes RNA primer nucleotides and fills in space with DNA nucleotides

DNA polymerase I

seals the break in the sugar phosphate backbone from RNA primer and Okazaki fragments made in lagging strand

Ligase

refers to the set of genes an organism contains.

Genotype

refers to the physical features and functional traits of an organism. Includes structures, morphology, and metabolism.

phenotype

Proteins are necessary for life processes

* Reproduction * Repair * Regulation of Metabolism

DNA  RNA

transcription

mRNA  protein

translation

Used in transcription to break hydrogen bonds and synthesize RNA in the 5’ to 3’ direction from a DNA template Is able to start without a primer * Adds complementary nucleotide to the growing strand according to the directions (existing nucleotide) on the template strand

RNA polymerase

-transcription and translation both in cytoplasm (nucleoid region)

prokaryotes

-transcription in nucleus and further processing of mRNA in nucleus

eukaryotes

Three types of RNA participate in protein synthesis:

Ribosomal RNA (rRNA) * Messenger RNA (mRNA) * Transfer RNA (tRNA) All 3 types play a role in translation. The region of protein synthesis is at the intersection of mRNA, rRNA, and tRNA.

Carries genetic information to direct the synthesis of one or more polypeptide chains

mRNA

Does not carry a genetic message * Binds closely to proteins to form the two ribosomal subunits (large and small) * A blank is made up of one large and one small subunit * blank is the site of protein synthesis in the cell The two subunits bind together around an mRNA and serve as a binding site for tRNA carrying the corresponding amino acids

ribosomal RNA (rRNA)

Transfers amino acids from the cytoplasm to the ribosomes for placement in a protein molecule * Has a 3-base anticodon on one end of the molecule that is complementary to a particular mRNA codon Has an amino acid binding site that binds the amino acid that corresponds to the tRNA anticodon and the mRNA codon * Serves as the link between the codons and the corresponding amino acids * Charging (adding the A.A.) tRNAs costs ATP!

transfer RNA (tRNA)

How can only 4 different nucleotide bases (A,T, C, and G) code for 20 amino acids?

Codes in sets of 3. With at least one codon for each amino acid.

is the start codon, tells the ribosome to start the polypeptide chain with methionine

AUG

* A system of “Reading” the different letter combinations The letters of mRNA are read as codons (amino acid triplets) Genetic code is repetitive and universal (used in all species)

Genetic code

Viruses that have RNA instead of DNA as their genetic material

Retroviruses

* How do retroviruses make more RNA?

Have special enzymes called reverse transcriptase which use RNA as a template to make DNA. The DNA can then be used to make more RNA. (not as accurate)(HIV)

refers to the movement of genetic information between organisms

gene transfer

When genes pass from parents to offspring

vertical gene transfer

When genes pass to other microbes of their same generation accounts for lots of genetic diversity

Horizontal/lateral gene transfer:

what are the mechanisms of horizontal gene transfer in bacteria

transformation, transduction and conjugation

DNA that has been released from an organism after the cell is lysed and DNA is no longer incorporated into chromosomes

Naked DNA: Cells able to take up Naked DNA are termed Competent

A change in an organism’s characteristics because of transfer of genetic information

TRANSFORMATION

A method of transferring genetic material using a bacteriophage (virus that infects bacteria)

transduction

composed of a core of nucleic acid covered by protein coat steal host protein synthesis systems in order to make more phages and phage DNA

phages

Genetic information is transferred from one cell to another, via conjugation pili (sex pili)

conjugation

circular, double-stranded DNA molecules carries the information to make an F pilus

fertility plasmids

A conjugation pilus bridge which it attaches to the F- cell

F pilus

Acellular, infectious agents that are too small to be seen with a light microscope (need electron microscope)

viruses *contain DNA or RNA but never both

states that viruses arose from genetic elements that gained the ability to move between cells

Progressive (escape) hypothesis

asserts that viruses are remnants of cellular organisms

Regressive (reduction) hypothesis

states that viruses predate or coevolved with their current cellular hosts

Virus-first hypothesis

Viruses are classified in the following order:

Type of nucleic acid  Presence of an envelope  Shape  Size

The 5’ to 3’ is blank sense

positive

the 3’ to 5’ is blank sense.

negative

Encases the nucleic acid core/genome of a virion o Protects nucleic acids from degradation o Gives shape to the virion o Can play a key role in the attachment of some viruses o Made up of protein subunits called capsomeres o Some have a single type of protein capsomere while others have different protein capsomeres thatmakeuptheircapsid

capsid

three basic types of capsids

Helical capsids are composed of capsomeres that bond together in a spiral fashion to form a tube around the nucleic acid. Polyhedral capsids are roughly spherical with many triangular faces. Complex capsid is the term used to describe the rest of viral shapes that do not readily fit into the helical or polyhedral categories.

= no symmetry, with flexible core wall, leaves envelope exposed closer to virus body (

Some viruses are amorphous

A lipid bilayer membrane that closely resembles that of its host cell and is found external to the viral capsid.

envelope

viral genome + the capsid

Nucleocapsid

composed of a nucleocapsid and no envelope

Naked (nonenveloped)

nucleocapsid + envelope

Enveloped viruses

are glycoproteins that extend from the viral envelope and may aid in attachment to the host cell

spikes

spectrum or range of hosts that a virus can infect

Host Range

is destructive. It replicates in large numbers and destroy

A Virulent phage

is not destructive initially. It integrates its genetic info into the host cell in the lysogenic cycle and is replicated when the host cell replicates

A Temperate phage

Phage must collide in correct orientation with host cells in order to attach or adsorb into the host cell  Usually to the cell wall but can also attach to the flagella or pili  It is a chemical attraction: requires specific protein recognition factors on the phage tail fibers that bind to specific receptor sites on the host cell  The tail fibers bend allowing the pins of the phage to touch the cell surface

adsorption

Enzyme lysozyme, found in the phage tails weakens the bacterial cell wall  When the tail sheath contracts, the hollow core penetrates the weakened cell wall and comes into contact with the bacterial cell membrane  The viral DNA then moves from the phage into the bacterial cell and the phage head remains outside

penetration

Viral genomes (2,000-25,000 nts) are too small to contain all genetic information necessary to replicate themselves  Must use raw materials and biosynthetic machinery of the host  Phage genes take control of the host’s metabolic machinery and disrupt the host DNA so that nucleotides of the hydrolyzed nucleic acids can be used to build new phage  Phage DNA is transcribed to mRNA which directs host ribosomes to make capsid proteins and viral enzymes

synthesis

Head of the T4 phage is assembled in the host cell cytoplasm from the newly synthesized capsid proteins  A viral dsDNA molecule is packed into each head  Phage tails are assembled from newly formed base plates, sheaths, and collars  Filled heads are attached to complete tails and tail fibers are added to form mature, infective phages

maturation

Lysozyme is used again to weaken the bacterial cell wall, this time to let the phage escape  The bacterial cell lyses and the phages are released  The released phage then begin the cycle again by infecting new cells

release

Make a serial dilution of phage stock sample.  Each dilution is inoculated onto a plate containing a susceptible bacterial lawn (confluent growth.) * Use a Low enough dilution so only one phage infects one bacteria, grows and lyses that bacteria to infect surrounding bacteria, this continues for several rounds of lysis producing a plaque (clear area on the bacterial lawn).  Each plaque represents one phage and by counting plaques and multiplying by the dilution factor the initial stock concentration can be determined  Reported as plaque-forming units (pfu/mL)

Plaque Assay

Some DNA phages (temperate phages) undergo adsorption and penetration but don’t replicate  The viral genome inserts into bacterial genome and becomes an inactive prophage – the cell is not lysed  Prophage is retained and copied during normal cell division resulting in the transfer of temperate phage genome to all host cell progeny  Induction can occur resulting in activation of lysogenic prophage followed by viral replication and cell lysis

Lysogeny: The Silent Infection

needed to free the genetic information from the capsid once an animal virus has penetrated the host cell.

uncoating

The budding or new virions through a membrane may or may not destroy the host cell. Adenoviruses bud from host cell in a controlled manner (e.g. shedding) which does not lyse host cells

release

is the visible effects viruses have on cells  Cells in culture show several common effects, including changes in cell shape and detachment from adjacent cells or culture container

The Cytopathic Effect (CPE)

They are normal proteins that becomes folded incorrectly, usually found on the surface of mammalian brain cells  Once folded incorrectly, they stick together inside cells causing aggregates that eventually kill the cell  They also act as a template causing other normally folded proteins to misfold  Prion disease leads to slow neurological degeneration and eventual death  Prions are resistant to inactivation by heat up to 90 degrees C

Prion =Proteinaceous infectious particle

Unit 3 review Flashcards

(94 cards)