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Genetics - Exam 3 Flashcards

1
Q

What do the majority bacterial chromosomes consist of?

A

sequences that encode proteins

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2
Q

plasmids

A

small circular DNA molecules that are distinct from the bacterial chromosome

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3
Q

horizontal gene transder

A

the transfer of DNA between different genomes. This process is independent of reproduction

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4
Q

Mechanisms of horizontal gene transfer

A

Conjugation
Transformation
Transduction

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5
Q

prokaryotic genome

A

no nucleus, no nuclear membrane, no membrane bound organelles, single circular chromosome , haploid, many contain plasmids

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6
Q

how do prokaryotes replicate?

A

binary fision

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7
Q

what do plasmids contain genes for?

A

fertility factors, antibiotic resistance, and toxin genes

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8
Q

what does conjugation require?

A

a physical connection between cells which involves the transfer of DNA from one bacterium to another

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9
Q

What does conjugation depend on?

A

a F (fertility) factor

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10
Q

what are conjugating cells connected by?

A

a membrane extension called a sex pilus

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11
Q

How do plasmids replicate?

A

they replicate freely of the bacterial chromosome by theta replication.

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12
Q

episome

A

plasmids that can integrate into the bacterial chromosome that replicate independently of host chromosome

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13
Q

Which of the following statements is true of plasmids?

a. they are composed of RNA
b. they normally exist outside of bacterial cells
c. they posses only a single strand of DNA
d.
they contain an origin of replication

A

d.
they contain an origin of replication

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14
Q

In conjugation does the F factor or the bacterial chromosome replicate and transfer into the recipient cell?

A

the F factor plasmid

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15
Q

do bacteria exchange genetic material?

A

yes, by genetic exchange and recombination

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16
Q

conjugation between an F+ cell and a F- cell usually results in?

A

two F+ cells

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17
Q

what occurs when an F plasmid integrates into the bacterial chromosome?

A

produces an Hfr cell through a recombination event occurs between the insertion sites

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18
Q

what do Hfr strains behave like?

A

they behave like F+ cells

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19
Q

what is a F factor?

A

an episome that contains an origin of replication and a number of genes required for conjugation

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20
Q

how is transfer initiated in conjugation?

A

one of the DNA strands is nicked at the origin of transfer or oriT. This end separates from the circle and passes across the cytoplasmic bridge into the recipient cell leading with its 5’ end.

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21
Q

what is high frequency recombination?

A

in bacterial strains the F factor can sometimes be integrated into the bacterial chromosome

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22
Q

what occurs during conjugation between Hfr and F- cells?

A

the integrated F factor is nicked at the initiation of strand transfer which leads into the recipient cell. The bacterial chromosome follows the f factor into the cell.

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23
Q

what takes place after crossing over during conjugation between Hfr and F- cell?

A

the donated strand is degraded and the recombinant recipient remains.

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24
Q

F’ cells

A

cells containing an F plasmid with some bacterial genes

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25
what does conjugation between an F' cell and a F- cell produce?
a partial diploid
26
when does a Hfr cell become an F' cell?
when the F factor is excised from the cell and takes some bacterial chromosomal DNA with it
27
Describe the process of an Hfr cell turning into an F' cell
crossing over occurs within the Hfr cell by a single loop that creates a 8. The loop cuts off containing the whole F factor along wit a piece of the bacterial chromosome. The F' cell can then conjugate with a F- cell which produces 2 copies of the bacterial chromosome DNA.
28
transformation
cells pick up DNA from extracellular environment which involves the transfer of DNA from one bacterium to another
29
when the cell replicates and divides after undergoing transformation do both contain the adopted DNA fragment
no, one will be trasnformed and contain the integrated DNA into the bacterial chromosome and the other will be nontransformed
30
virus
replicating structure made up of nucleic acid surrounded by a protein coat
31
bacteriophage
virus that infects bacteria
32
virulent phage
reproduces only through lytic cycle and kill host cells
33
temperate phage
undergo either lytic or lysogenic life cycle
34
competent cells
cells that can take up DNA through their cell membrane
35
what kind of DNA can competent cells pick up?
any type; its not restricted to bacterial
36
transformants
cells that receive genetic material through transformation
37
auxotrophic
requires addition nutrients to grow as it cannot synthesize those nutrients on its own
38
prototrophic
derives nutrients from inorganic sources/ do not need specific nutrients to grow
39
lytic cycle
1. the phage enters the host cell 2. host DNA is degraded 3. phage DNA replicates 4. host cell transcribes and translates phage DNA producing phage proteins 5. a phage encoded enzyme causes the cell to lyse and new phages are released
40
lysogenic cycle
1. phage binds to bacterium and phage DNA enters host cell 2. phage DNA integrates into the bacterial chromosome and becomes prophage 3. prophage is replicated as part of bacterial chromosome which can continue through many cell divisions 4. the prophage can separate from the chromosome and the cell will enter the lytic cycle
41
transduction
requires a viral vector or intermediate and involves transfer of DNA from one bacteria to another
42
specialized transduction
only genes near insertion site are transferred - only a few genes are transferred
43
eukaryotic viruses can be?
1. virulent 2. temperate 3. the lytic cycle does not always lyse the cell
44
RNA viral mechanisms
RNA viruses have to replicate their genome and translate viral proteins
45
general transduction
any gene may be transferred
46
cotransduced
the act of closely located genes being transferred together by the viral phage
47
what type of phage is required for specialized transduction?
temperate bacteriophages that use specific prophage integration sites
48
retrovirus
RNA viruses that can integrate into the genome of their hosts
49
reverse transcriptase
an enzyme that synthesizes complementary DNA from wither RNA or a DNA template which is produced by a retrovirus
50
provirus
viral genome that is incorporated into host genome in eukaryotes
51
when is the provirus replicated?
it is replicated by host enzymes when the host chromosome is duplicated
52
How many copies of the RNA genome exist in a retrovirus?
two copies of single stranded RNA genome
53
how does the retrovirus produce new viruses within the host?
after complementary DNA is transcribed and the viral DNA is incorporated into the host chromosome the DNA is transcribed into RNA which is moved into the cytoplasm. This RNA codes for viral proteins and new virus are assembled
54
integrase
an enzyme that inserts the viral DNA into the host chromosome
55
example of virulent virus
Flu, coronavirus
56
example of temperate virus
HIV and AIDs
57
how do virulent viruses replicate?
replication and transcription via RNA dependent RNA polymerases - not transcribed to DNA
58
what is the basic structure of DNA?
triphosphate and sugar connected at the hydroxyl group, and one of four bases
59
what are the four bases? Which are classified as purines and which are classified as pyrimidine?
thymine and cytosine are pyrimidines and adenine and guanine are purines
60
what is DNA polymerase composed of?
a phosphodiester bond
61
differences between DNA and RNA?
DNA has a deoxyribose sugar whereas RNA has a hydroxyl group attached to the sugar. RNA also replaces thymine with uracil. The additional oxygen in RNA makes it less stable and more reactive than DNA.
62
what protein is responsible for bacterial DNA compaction?
scaffold proteins
63
is bacterial DNA circular or linear?
circular
64
how do scaffold proteins condense bacterial DNA?
the proteins stabilize the DNA as it is folded in loops to prevent free rotation of the ends where supercoiling takes place within the loops.
65
nucleotide
linked repeating units that contain a sugar, phosphate, and base
66
where is the phosphate group bonded to within DNA?
the phosphate is bonded to the 5' carbon of the sugar.
67
Describe the direction of the polynucleotide strands (nucleotides joined by phosphodiester linkages). (DNA)
At the 5' end, a free phosphate group is attached to the 5' carbon atom, while a free hydroxyl group is attached to the sugar's 3' carbon atom.
68
supercoiling
when the DNA helix is subject to being strained by overcoiling or undercoiling.
69
positive supercoiling
when the DNA helix is overrotated where it twists in on itself.
70
negative supercoiling
when the DNA helix is underrotated where the helix twists in itself in the opposite direction.
71
topoisomerase
the enzyme that facilitates supercoiling. The enzyme adds or removes rotations by temporarily breaking the nucleotide strands, twisting the loops around each other, and then rejoining the broken ends.
72
what type of supercoiling is typically found in cells?
Negative supercoiling is used to make the separation during replication easier.
73
what is the fundamental repeating unit of chromatin?
the nucleosome
74

Biology (8 decks)

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