19,20,27.2 AHHHHHHH Flashcards
why are viruses not considered to be alive?
they can only reproduce with a host cell
describe the structure of viruses
they consist of nucleic acids (the DNA) enclosed in a protein coat and sometimes also an envelope
what is a capsid?
the protein shell that encloses the genome.
what are phages/bacteriophages?
viruses that infect bacteria
what is the structure of phages?
They have a capsid head that encloses the genome and a bunch of protein tailpieces that help attach to the host cell. (little robots)
what are the two reproductive mechanisms of phages?
the lytic cycle and the lysogenic cycle
describe the lytic cycle
The phage inserts its DNA/protein into the host cell and it self-assembles to create more phages. It then bursts the cell open and releases the phages. These are called virulent phages.
describe the lysogenic cycle
The viral DNA is integrated into the host’s DNA (prophage) which allows the host cell to make copies of the viral DNA. eventually, it uses the lytic cycle. These are called temperate phages.
what are retroviruses?
they use reverse transcriptase (an enzyme that catalyzes transcription of retrovirus RNA) to copy their RNA genome into DNA
What is the difference between a prophage and a provirus?
unlike a prophage, a provirus remains a permanent resident of the host cell.
Why is there a higher chance of mutations in RNA viruses?
because they lack proofreading enzymes.
what is a prion?
proteins that cause normal proteins to fold abnormally causing cellular death.
what are the 4 factors that increase genetic diversity in sexually reproducing organisms?
mutations, crossing over & recombination, random assortment of chromosomes in gametes, and random union of gametes in fertilization.
what is transformation in a bacterium?
the alteration of a bacterial cell’s genotype and phenotype by picking up foreign DNA from the surrounding environment
what is transduction?
a process in which phages carry bacterial genes from one host cell to another.
what is conjugation in bacteria?
the direct transfer of genetic material between bacterial cells that are temporarily joined through a sex pilus.
what are F plasmids and what happens?
F plasmids are found in F+ cells that function as DNA donors. cells with a built-in F factor are called Hfr cells.
What are R plasmids?
plasmids with resistance to various antibiotics.
how is recombinant DNA made?
when nucleotide sequences from two different sources are combined in vitro into the same DNA molecule.
what is gene cloning?
when scientists prepare gene-sized pieces of DNA in identical copies
what are restriction enzymes?
enzymes that cut DNA molecules at specific restriction sites (zig-zag shape) to make restriction fragments that are then used to make recombinant DNA.
What does DNA ligase do in this process?
seals the bonds between restriction fragments.
what is a cloning vector?
the original plasmid that can carry foreign DNA into a cell
what are the 6 steps to clone a human gene?
- vector and DNA are isolated, 2. DNA is inserted into the vector, 3. DNA fragments are mixed with cut plasmids, 4. recombinant plasmids are mixed with bacteria, 5. bacteria are plated and incubated, 6. cell clones are identified.
What is polymerase chain reaction (PCR)?
a process that produces many copies of a specific target segment of DNA
how is PCR done?
heat the DNA to separate strands. cool to allow primers to bind to the ends. Taq polymerase adds nucleotides to the 3’ ends. repeat cycle. every cycle produces 2^n DNA.
