Bio 101 Exam 3 Flashcards
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Viruses
- infectious particles enclosed in protein coat (capsid)
-cellular parasites and have a specific host range
Infectious particle
nucleic acid
Capsid
- layer of proteins surrounding nucleic acid (virus genome- DNA or RNA)
- Some have a third layer- membrane phospholipid bilayer, called an envelope
viral envelope
Surrounds virus protien - a lipid bilayer membrane formed by the host cell
What can viruses infect
Plants, animals, people, and bacteria
Glycoproteins
receptors
- Sticks out of viruses outermost layer
- Glycoprotein sometimes called receptor spikes
- Must bind to a host cell
-Each virus has specific spikes with special chemistry
-Viruses have specific receptors that must bind to the host cell for attachment entry
Receptor spikes are on outside which lets them bump into host cells and bind
Triggers injection of DNA into host cell, capsid stays on outside
Lactic cycle
when you are sick
Lysogenic cycle
when you are sick, then goes dormant, then comes back
Viruses use receptors to
bind to the host cell for attachment and entry
A virus that has a dormancy phase
is able to integrate the genome of the virus into the host cell chromosome
the varicella-zoster virus infects many cells throughout the body and causes chickenpox, characterized by a rash of blisters covering the skin. About 10 to 12 days postinfection, the disease resolves and the virus goes dormant, living within nerve-cell ganglia for years.
Can viruses have DNA and RNA
No, a virus cannot have both DNA and RNA; a virus can only contain one type of nucleic acid, either DNA or RNA, not both within the same viral particle.
When a virus has an envelope (phospholipid bilayer, which is oil, which is liquid) it allows entry by fusion (instead of binding)
2 come together like merging oil droplets
Reverse transcriptase
transcribes RNA into DNA
Deoxyribonucleic acid
Deoxyribose (sugar)
■ Hereditary molecule that is passed from parents to offspring
■ Common to all living organisms
■ Sevres as the instruction manual for how to build an individual
■ Found i the nucleus of eukaryotic cells
- In the form of a chromosome ( Single DNA molecule wrapped around proteins)
● What is DNA?
Deoxyribonucleic acid
Why is each persons DNA different
- its structure to understand why
● Unique sequence of nucleotides, 4 different bases of nucleotides
● Each nucleotide has phosphate, sugar, and base
● Sugar backbone is sometimes drawn as a straight line with bases sticking off the sides
What are nucleotides?
Monomers that combine to make DNA
Nucleotides have one of four base
Adenine (A) ○ Thymine (T) Guanin (G) ○ Cytosine (C)
What are the complementary base pairings for DNA?
○ A-T, C-G
Adenine will always pair with thymine and guanine will always pair with cytosine
When referring to DNA, what is the “double helix”?
Two strands of linked nucleotides that are twisted around each other
Two strands of nucleotides pair up and twist around each other to form a spiral shaped double helix
Sugars and phosphates form the outside “backbone” ○ Bases form the internal “rungs”
Two strands of DNA double helix are held together by
base pairing ( hydrogen bonding ) between the bases of each stand
● Complementary base pairing
A always pairs with T
C always pairs with G
DNA Replication
Natural process by which cells make an identical copy of a DNA molecule
- Takes advantage of complementary base-pairing rules
Helicase
can open up and separate two strands- breaks hydrogen bonds, binds to DNA, separates two strands of helix
DNA polymerase
enzyme that builds new DNA polymer
DNA replication is semiconservative
holds onto each side of the parent strand in the new daughter strands - half old, half new
Understanding the structure and replication of DNA is crucial to using it in forensic applications
Specific sequence of nucleotides along a strand of DNA is unique to each individual
- Extract the DNA from the cells to create individual’s DNA profile (Visual representation of a person’s unique DNA sequence) (Need many copies of their DNA)
The polymerase chain reaction (PCR)
PCR is a laboratory technique used to replicate and amplify specific DNA segment
Primers
short segments of DNA that guide DNA polymerase to the section of DNA to copy
During each round of PCR
1- Heating separates DNA strands
2- Cooling allows DNA polymerase to pair new nucleotides with the original template strands
- New DNA binds to template strand and builds complementary strand
● PCR test used when
you gave a small sample and want to increase sample size in order to test
PCR
heating, strand separation (double helix separates), DNA replication
PCR amplification of DNA is useful when
There is limited sample to work with
PCR can be useful in
DNA profiling
DNA profiling takes advantage of
the fact that no two people have the exact same DNA sequence
Genome
one complete set of genetic material present in a cell or organism
Determining sequence of entire genome is extremely time consuming and expensive
Use shortcut
- Use PCR to amplify only specific segments of DNA
○ Short tandem repeats (STR) ● STRs are sections of a chromosome in which DNA sequences are repeated
○ For example, sequence AGCT may be repeated over and over again
What are short tandem repeats (STRs)?
Blocks of repeated DNA sequences (AGCT) that vary in length from person to person
STRs are in the same places along chromosomes
Exact length of STR varies from person to person
Making a DNA profile
- Collects cells and extract DNA
- Use PCR to amplify multiple STR regions
Making a DNA profile– how will you visualize the results?
Separate STRs using gel electrophoresis
■ Laboratory technique that separates fragments of DNA by size
■ Small piece of DNA move fastest and go to the bottom, longer piece are slower and stay closer to the top
DNA evidence is
more reliable than other forms of evidence
○ Error rates for bite mark identification can be as high as 91%
○ Hair analysis can exclude a suspect, not positively identify one
no two people share exactly the same DNA except for…
identical twins
DNA in crime
Uses DNA as evidence to free people wrongly convicted of crimes
● DNA testing is a standard part of court cases
● Extremely accurate way to math crime scene evidence of perpetrators
When performing gel electrophoresis, STRs are separated
by pipetting them into a gel and applying an electric field, with the smallest fragments moving the furthest distance and the longest fragments moving the shortest distance, to create a unique profile of banding pattern for each individual
Sickle cell disease is an
nherited genetic disorder that causes red blood cells to take on a sickled shape (crescent moon) and carry less oxygen