exam 7 Flashcards
1
Q
T.H. Morgan
A
showed that genese exist as parts of chromosomes, the two chemical components of chromosomes–DNA and protein– emerged as the leading candidates for genetic material
2
Q
Frederick Griffith
A
studied two strains of the bacteria streptococcus pneumonia
concluded that the living R bacteria had been transformed into the pathogenic S bacteria by an unknown, heritable substance from the dead S cells that allowed R cells to make capsules
3
Q
transformation
A
change in genotype and phenotype due to the assimilation of external DNA by a cell
4
Q
bacteriophages
A
viruses that infect bacteria
5
Q
virus
A
little more than DNA enclosed by a protective coat, which is often simply protein
to produce more viruses, a virus must infect a cell and take over the cell’s metaboic machinery
6
Q
Hershey an Chase
A
used radioactive sulfur (protein) and phosphorus(DNA) to track the stuff of T2 phages that infect bacterial cells. they concluded that DNA was the heritable factor
7
Q
erwin chargaff
A
chargaff’s rules:
1) the base composition varies between species
2) within species, the number of A and T bases are roughly equal and the number of G and C bases are roughly equal
8
Q
Rosalind Franklin
A
X ray diffraction/crystolography to find shape of DNA
Watson and crick stole her thing
9
Q
double helix
A
shape of DNA that watson and crick coined
10
Q
antiparallel
A
their subunits run in opposite directions
11
Q
purine
A
2 ring
12
Q
pyrimidine
A
1 ring
13
Q
conservative model
A
the two parental strands reassociate after acting as template for new strands, thus restoring their parental double helix
14
Q
semiconservative model
A
the two strands of the parental molecule separate, and each functions as a template for synthesis of a new, complementary strand
15
Q
dispersive model
A
each strand of both daughter molecules conains a mixture of old and newly synthesized DNA
16
Q
Meselston and Stahl
A
cultured E. coli (details on experimient figure 13.11)
concluded that the semiconservative model was how DNA was replicated
17
Q
origins of replication
A
short stretches of DNA having a specific sequence of nucleotides to begin DNA replication
18
Q
replication fork
A
a Y shaped region where the parental strands of DNA are being unwound
19
Q
Helicases
A
enzymes that untwist the double helix at the replication forks, separating the two parental strands and making them available as template strands
20
Q
single-strand binding proteins
A
bind to the unpaired DNA strands and keep them from repairing
21
Q
topoisomerates
A
helps relieve the strain of twisting ahead of the replication fork
breaks, swivels, and rejoins DNA strands
22
Q
prokaryotic vs eukaryotic DNA replication
A
there is only 1 origin of replication and 1 replication fork in prokaryotic
there are multiple in eukaryotic
prokaryotic DNA is circular and the single replication fork moves in 2 directions
23
Q
primer
A
initial nucleotide chain that is produced during DNA synthesis is a short stretch of RNA
meant to attract DNA polymerase 3
24
Q
primase
A
enzyme that makes RNA primer
25
DNA polymerase III
synthesizes DNA opposite from the template strnad
| catalyzes the synthesis of new DNA by adding nucleotides to a preexisting chain.
26
leading strand
the strand made by this mechanism:
dna pol 3 remains in the replication fork on the template strand and continuously adds nucleotides to the new complementary strand as the fork progresses
5-3 direction
27
lagging strand
synthesized discontinuously, as a series of segments
28
okazaki fragments
piece of DNA between 2 RNA primers
| 1,000 to 2,000 nucleotides long
29
DNA ligase
enzyme that joins sugar phosphate backbones of all the Okazaki fragments into a continuous DNA strand
30
DNA pol 1
replaces the RNA primers with DNA, adding to the 3' end of fragment 2
31
mismatch repair
other enzymes remove and replace incorrectly paired nucleotides resulting from replication errors
32
nuclease
DNA cutting enzyme
33
nucleotide excision repair
teams of enzymes detect and repair damaged DNA which distorts the DNA molecule
a nuclease enzyme cuts the damaged DNA strand at 2 points, and the damaged section is removed
repair synthesis by a DNA pol fills in thee missing nucleotides
DNA ligase seals the free end of the new DNA to the old DNA, making the strand complete
34
telomeres
do not contain genes
the DNA consists of multiple repetitions of one short nucleotide sequence
buffer zone that protects the organism's genes
35
telomerase
catalyzes the lengthening of telomeres in eukaryotic germ cells, thus restoring their original length
not active in most human somatic cells but sows inappropriate activity in some cancer cells
36
nucleoid
dense region of DNA in bacterium is not surrounded by a membrane
37
chromatin
eukaryotic DNA and protein together in a complex called chromatin, fits into the nucleus through an elaborate, multilevel system of packing
38
palendrome
same forward as it is backwards
| favored to be cut by a restriction enzyme
39
heterochromatin
interphase chromatin, visible as irregular clump with a light microscope
40
euchromatin
less compacted more dispersed
41
levels of organization in chromosme
```
DNA, double helix
Histones
Nucleosomes
30 nm fiber
looped domains (300 nm)
metaphase chromosome
```
42
histones
proteins responsible for the first level of DNA packing in chromatin
small
43
nucleosome
chromatin resembling beads on a string
| each bead is a nucleosome, the basic unit of DNA packing; the string between beads is linker DNA
44
nucleic acid hybridization
the base pairing of one strand of a nucleic acid to a complementary sequence on another strand
45
genetic engineering
the direct manipulation of genes for practical purposes
46
plasmids
small circular DNA molecules that replicate separately from the bacterial chromosome
47
recombinant DNA
a DNA molecule formed when segments of DNA from 2 different sources--often different species--are combined in vitro (in a test tube) the plasmid is then returned to a bacterial cell, producing a recombinant bacterium. This single cell reproduces through repeated cell divisions to form a clone of cells, a population of genetically identical cell
48
gene cloning
the production of multiple copies of a single gene
49
restriction enzymes
enzymes that cut DNA molecules at a limited number of specific locations
50
restriction site
a specific particular short DNA sequence that is cut by a restriction enzyme at precise points
51
restriction fragments
fragments that yeild as a result of restriction enzymes making many cuts in a DNA molecule
52
gel electrophoresis
a process that separates a mixture of nucleic acid fragments by length
short fragments move further
long fragments move closer
53
sticky end
resulting double-stranded restriction fragments have at least 1 single stranded end called a sticky end
54
cloning vector
2 DNA molecules that are joined together in gene cloning
55
polymerase chain reaction
lots of copies of DNA
3 steps:
denaturation: heat briefly to separate DNA strands
Annealing: cool to allow primers to form hydrogen bonds with ends of target sequence
Extension: DNA polymerase adds nucleotides to the 3' end of each primer
56
DNA sequencing
once a gene is cloned, researchers can exploit the principle of complementary base pairing to determine the gene's complete nucleotide sequence
57
gene expression
process by which DNA directs synthesis of proteins
58
transcription
the synthesis of RNA using information in the DNA
59
messenger RNA
carries a genetic message from the DNA to the protien-synthesizing machinery of the cell
60
translation
synthesis of a polypeptide using the information in the mRNA
61
ribosomes
complex particles that facilitate the orderly linkage of amino acids into polypeptide chains
made of rRNA and proteins
62
primary transcript
the initial RNA transcript from any gene, including those specifying RNA that is not translated into protein
63
triplet code
the genetic instructions for a polypeptide chain written in the DNA as a series of non overlapping 3 nucleotide words
the series of words in a gene is transcribed into a complementary series of nonoverlapping three nucleotide words in mRNA whichis then translated into a chain of amino acids
64
templatestrand
the genetic instructions for a polypeptide chain are written in the DNAas a series of nonoverlapping-three nucleotide words
65
codons
mRNA nucleotide triplets
64 codons
61 code for amio acids
66
AUG
codes for Met and Start
67
RNA polymerase
pries two strands of DNA apart and joins together RNA nucleotides complementary to the DNA template strand, thus elongating the RNA polynucleotide. RNA polymerases can assemble a polynucleotide only in its 5'-3' direction
68
promoter
DNA sequence where RNA polymerase attaches and initiates transcription
69
terminator
in bacteria, the sequence that signals the end of transcription
70
trasncription unit
the stretch of DNA transcribed into an RNA molecule
71
start point
the nucleotide where RNA synthesis actually begins
72
stages of transcription
initiation
elongation
termination
73
initiation
after RNA polymerase binds to the promote, the DNA strands unwind, and the polymerase initiates RNA synthesis at the start point on the template strand
74
Elongation
the polymerase moves downstream, unwinding the DNA and elongating the RNA transcript 5'-3'. in the wake of transcrition, the DNA strands re-form a double helix
75
termination
eventually the RNA transcript is release, and the polymerase detaches from the DNA
76
transcription factors
proteins that mediate the binding of RNA polymerase and the initiation of transcription
77
transcription initiation complex
the whole complex of transcription factors and RNA polymerase 2 bound to the promoter
78
TATA box
crucial DNA sequence in the promoter that only has T and A nucleotides
79
RNA processing
both ends of the primary transcript are altered, also in most cases certin interior sections of the RNA molecule are cut out and the remaining parts are spliced together
these modifications produce an mRNA molecule ready for translation
80
5' cap
modified form of the Guanine nucleotide added onto the 5' end after transcription of the first 20-40 nucleotides
81
poly-A tail
at the 3' end, adds 50-250 more adenine nucleotides
82
functions of 5' cap and poly A tail
- facilitate the export of mature mRNA from the nucleus
- help protect the mRNA from degradation by hydrolitic enzymes
- help ribosomes attach to the 5' end of the mRNA once the mRNA reaches the cytoplasm
83
RNA splicing
removal of large portions of the RNA molecule that is initially synthesized
84
introns
noncoding segments of nucleic acid that lie between coding regions
intervening sequences
85
exons
other regions
| eventually expressed and translated into amino acid sequences
86
spliceosome
how is pre-mRNA splicing carried out? the removal of introns is accomplished by a large complex made of proteins and small RNAS called a spliceosome
this complex binds to several short nucleotide sequences along the intron
the intron is then released and rapidly degraded, and the splicosome joins ogether the two exons that flanked the intron
87
ribozymes
RNA molecules that function as enzymes
88
transfer RNA
transfer amino acids from the cytoplasmic pool of amino acids to a growing polypeptide in a ribosome
89
anticodon
the particular nucleotide triplet that base-pairs to a specific mRNA codon on tRNA
90
aminoacyl-tRNA synthases
enzymes that fit only a specific ombination of amino acid and tRNA
joins amino acid and tRNA through covalent bond
91
ribosomal RNA (rRNA)
make up ribosome
92
APE
A=arrival site
holds the tRNA carrying the next amino acid to be aded to the chain
P=protein building site
holds tRNA carrying the growing polypeptide chain
E=exit site
discharged tRNAs leave the ribosome from this site
93
release factor
protein shaped like a tRNA, binds directly to the stop codon in the A site
the release factor causes the addition of a water molecule instead of an amino acid to the polypeptide chain
this reaction hydrolyzes the bond between the completed polypeptide and the tRNA in the P site, releasing the polypeptide through the exit tunnel of the large subunit
94
phases of translation
codon recognition
peptide bond formation
translocation
95
free vs bound ribosome
free ribosomes are suspended in the cytosol and mostly synthesize proteins that stay in the cytosol and function there
bound ribosomes are attached to the cytosolic side of the ER or to the nuclear envelope
bound ribosomes make up proteins of the endomembrane system
96
signal peptide
the polypeptides of proteins destined for the endomembrane system or for secretion are marked by a signal peptide, which targets the protein to the ER.
97
signal-recognition particle
| SRP
recognizes the signal peptide and binds to it, which halts sythesis momentarily
this particle functions as an escort that brings the ribosome to a receptor protein built into the ER membrane
98
polyribosome
multiple ribosomes synthesizing the same mRNA strand into multiple versions of the same polypeptide
occurs in prokaryotic and eukaryotic cells
99
mutations
changes to the genetic information of a cell or virus
100
point mutations
small scale mutations of one or a few nucleotide pairs
101
silent mutations
no observable afect on the phenotype
102
missense mutations
change one amino acid o another
103
nonsense mutation
translation is terminated prematurely
104
nucleotide pair substitutions
least effect to most effect
silent
missense
nonsense
105
nucleotide-pair insertion or deletion
least effect to most effect
3 nucleotide pair deletion
frameshift causing missense
frameshift causing immediate nonsense
106
mutagens
number of physical and chemical angents that interact with DNA in ways that cause mutations
107
operator
on-off switch that can control the whole cluster of functionally related genes
108
operon
operator, promoter, and genes they control
109
repressor
binds to the operator and blocks attachment of RNA polymerase to the promoter, preventing transcription of the genes
110
regulatory gene
expressed continuously
| produces inactive repressors
111
corepressor
small molecule that cooperates with a repressor protein to switch an operon off
112
repressible operon
trp
| its transcription is usually ON but can be REPRESSED
113
inducible operon
lac
| transcription is usually OFF but can be INDUCED
114
inducer
inactivates repressor
| activates transcription
115
cyclic AMP (cAMP)
accumulates when glucose is scarce
| small organic molecule that binds to the regulatory protein CAP which is an activator
116
activator
a protein that binds to DNA and stimulates transcription of a gene
117
differential gene expression
the expression of different genes by cells with the same genome
118
histone acetylation
the addition of acetyl -COCH3
| promotes transcription by opening chromatin structure
119
DNA methylation
addition of methyl groups can lead to a condensation of chromatin and reduce transcription
once methylated, genes usually stay that way through successful cell divisions
120
epigenic inheritance
not directly involving nucleotide sequence
| things outside DNA can alter things that are inherited
121
control elements
segments of noncoding DNA having particular nucleotide sequences that serve as binding sites for the proteins called transcription
122
proximal control elements
control elements located close to the promoter
123
distal control elements
may be thousands of nucleotides upstream or downstream of a gene or within an intron
124
enhancers
groups of distal control elements
125
transcription initiation complex
formed on promoter and initiates transcription
126
alternative RNA splicing
different mRNA molecules are produced from the same primary transcript
figure 15.12
127
mRNA degradation
the life span of mRNA molecules in the cytoplasm is important in determining the pattern of protein
128
micro RNAs (miRNAs)
single stranded mRNA molecules that are capable of bining to complementary sequences in mRNA molecules
129
small interfering RNAs (siRNAS)
similar in size and unction to miRNAs
130
RNA interference
the blocking of gene expression by siRNAs
131
nucleic acid hybridization
the base pairing of one strand of a nucleic acid to the complementary sequence on another strand
132
nucleic acid probe
the complementary smolecule, a short single stranded nucleic acid that can be either RNA or DNA
133
in situ hybridization
probes dyed fluorescently to allow us to track mRNA
134
reverse transcriptase-polymerase chain reaction
| RT--PCR
turning sample sets of mRNAs into double-stranded DNAs with the corresponding sequences
135
complementary DNA (cDNA
resulting double stranded DNA fro RT--PCR
136
DNA microarray assays
a DNA microarray consists of tiny amounts of a large number of single stranded DNA fragments representing different genes fixed to a glass slide in a tightly spaced array, or grid. ideally these fragments represent all the genes in the genome of an organism
