Final Flashcards
(247 cards)
1
Q
Chromosomes rearrangements are?
A
Changes in the structure of chromosomes.
2
Q
Aneuploidy is?
A
An increase or decrease in chromosomes number.
3
Q
Polyploidy is?
A
The presence of extra chromosomes.
4
Q
Types of chromosome rearrangements
A
Duplications, deletions, inversions, and translocations.
5
Q
In individuals heterozygous for a duplication…
A
The duplication region will form a loop when homologous chromosomes pairs in meiosis.
6
Q
In individuals heterozygous for a deletion…
A
One of the chromosomes will loop out during pairing in meiosis.
7
Q
Deletions may cause…
A
Recessive alleles to be expressed.
8
Q
Pericentric inversions
A
Include the centromere.
9
Q
Paracentric inversions
A
Do not include to centromere.
10
Q
In individuals heterozygous for inversions…
A
The homologous chromosomes forms inversion loops in meiosis and the reduced recombination takes place within the inverted region.
11
Q
In translocation heterozygotes…
A
The chromosomes form cross like structures in meiosis.
12
Q
Copy-number variations include…
A
Duplications and deletions.
13
Q
Why does aneuploidy cause dramatic phenotypic effects?
A
Because it leads to unbalanced gene dosage.
14
Q
Primary down syndrome is caused by…
A
The presence of 3 full copies of chromosome 21.`
15
Q
Familial down syndrome
A
Caused by the presence of 2 normal copies of chromosome 21 and 3rd copy that is attached to another chromosome through translocation.
16
Q
All chromosomes in autoploidy are from…
A
One species.
17
Q
Chromosomes in alloploidy come from…
A
Two or more species.
18
Q
Metacentric
A
The centromere is located in the middle, chromosomes arms are of equal length,
19
Q
Submetacentric
A
Centromere is displaced toward one end, creating a long and short arm.
20
Q
Acrocentric
A
The centromere is near one end, producing a long arm and a knob at the other end.
21
Q
Telocentric
A
Centromere is at or very near the end of the chromosome.
22
Q
Chromosome duplication
A
Part of the chromosome has been doubled.
23
Q
Tandem duplication
A
Duplicated segment is directly adjacent to the original segment.
24
Q
Displaced duplication
A
Duplication is far away from original segment, either on the same chromosome or on another chromosome.
25
Segmental duplications
Duplication greater than 1000 base pairs in length.
26
Deletion
The loss of a chromosome segment.
27
Pseudodominance
Expression of a normally recessive mutation. It is in indication that one of the homologous chromosomes has a deletion.
28
Haplo-insufficient gene
When a single copy of a gene is not sufficient to produce a wildtype phenotype.
29
Chromosome inversions
When a segment of a chromosome is inverted.
30
Position effect
If a genes position is altered by an inversion, their expression may be altered.
31
Dicentric chromatid
In a paracentric inversion, one of the four chromatids now has two centromeres.
32
Acentric chromatid
In a paracentric inversion, a chromatid will lack a centromere.
33
Translocation
Movement of genetic material between non homologous chromosomes or within the same chromosome.
34
Nonreciprocal translocation
Genetic material moves from one chromosome to another without any reciprocal change.
35
Reciprocal translocation
Two-way exchange of segments between the chromosomes.
36
Robertsonian translocation
The short arm of one acrocentric chromosome is exchanged with the long arm of another. Generates a metacentric chromosome with two long arms and another chromosome with two very short arms.
37
Nullisomy
Loss of both members of a homologous pair of chromosomes. 2n-2.
38
Monosomy
The loss of a single chromosome. 2n-1.
39
Trisomy
The gain of a single chromosome. 2n+1.
40
Tetrasomy
The gain of two homologous chromosomes. 2n+2.
41
Nondisjunction
The failure of homologous chromosomes of sister chromatids to separate in meiosis or mitosis.
42
Amphidiploid
Type of alloploidy consisting of 2 combined genomes.
43
DNA may be transferred between between bacteria by means of...
Conjugation, transformation and transduction.
44
What is conjugation controlled by?
The F factor, and episome.
45
The time is takes for individual genes to be transferred during conjugation provides info about...
The order of the genes and the distance between them on the bacterial chromosome.
46
Frequencies of the co transformation of genes provide...
Information about the physical distance between chromosomal genes.
47
Rates of cotransduction can be used to...
Map bacterial genes.
48
How can phages genes be mapped?
By infecting bacterial cells with 2 different phage strains and counting the number of recombinant plaques produced by the progeny phages.
49
What does a complete medium contain?
Leucine, required by bacteria for growth.
50
Plasmids
Small pieces of bacterial DNA that can replicate independently of the bacterial chromosomes. They carry genes that are not essential to bacterial function.
51
Episomes
Plasmids that are capable of replicating freely and able to integrate into the bacterial chromosomes.
52
F (fertility) factor
An episome that controls mating and gene exchange between E. coli cells. Contains a number of genes required for conjugation.
53
Conjugation
When genetic material is passed directly from one bacterium to another. Takes place more frequently in some species than others.
54
Transformation
When a bacterium takes up DNA from the medium in which it is growing.
55
Transduction
When bacterial viruses carry DNA from one bacterium to another.
56
Competent cells
Cells that take up DNA through their membrane.
57
Horizontal gene transfer
Genes can be passed between individual members of different species by non reproductive mechanisms.
58
Virus
Simple replicating structure made up of nucleic acid surrounded by a protein coat. Some have DNA as their genetic material, and others have RNA.
59
Virulent phages
Reproduce strictly through the lytic cycle and kill their host cells.
60
Temperate phages
Can undergo either the lytic or the lysogenic cycle.
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Plaque
A clear patch of lysed cells that appears after several rounds of phage reproduction.
62
Transducing phages
A piece of the bacterial chromosome, instead of phage DNA, gets packed into the phage coat,
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Retroviruses
RNA viruses capable of integrating into the genomes of their hosts.
64
Reverse transcriptase
An enzyme that synthesizes complementary DNA from either an RNA or a DNA template. Produced by the retrovirus.
65
Provirus
A viral genome incorporated into the host chromosome.
66
Avery, MacLeod and McCarty discovered what?
Evidence that DNA is the source of genetic information.
67
Hershey and Chase discovered what?
That viral DNA is passed onto progeny phages.
68
Nucleotide's are joined together by...
Phosphodiester linkages.
69
What is free at the 5' end of a polynucleotide strand?
A phosphate group.
70
What is free at the 3' end of a polynucleotide strand?
A hydroxyl group.
71
DNA consists of...
2 nucleotide strands that wind around each other to form a double helix.
72
What lies on the outside of the double helix?
The sugars and phosphates.
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What lies on the inside of the double helix?
The bases are stacked in the interior.
74
The central dogma of genetic biology proposes that...
Information flows in one direction, from DNA to RNA protein. There are some exceptions, such as reverse transcription in retroviruses.
75
Super coiling results from...
Strain produced when rotations are added to or removed from a relaxed DNA molecule.
76
A bacterial chromosome consists of...
A single circular DNA molecule that is bound to proteins and exists as a series of large loops.
77
The nucleosome consists of...
A core of 8 histone proteins and the DNA that wraps around the core.
78
What stabilizes the ends of chromosomes?
Telomeres.
79
B-DNA
Exists when plenty of water surrounds the molecule and there is no unusual base stacking.
80
A-DNA
Exists when the is less water present, right-handed helix like B-DNA, but shorter and wider.
81
Z-DNA
Forms a left-handed helix.
82
Positive supercoiling
Molecules that are over rotated.
83
Negative supercoiling
Molecules that are under rotated. Most DNA found in cells.
84
Topoisomerases
Enzymes that add or remove rotations from the DNA helix by temporarily breaking the nucleotide strands, rotating the ends around each other and then rejoining the broken ends.
85
Chromatin
The combination of DNA and protein.
86
Euchromatin
Undergoes the normal process of condensation and decondensation in the cell cycle.
87
Heterochromatin
Remains highly condensed during the cell cycle.
88
Epigenetics
Alterations of chromatin structure that are passed on the descendant cells or individuals.
89
All DNA is synthesized in which direction?
5' to 3'
90
Replication in bacteria begins when...
Initiator proteins bind to an origin of replication and unwind a short stretch of DNA to which helicase attaches.
91
DNA polymerases add...
New nucleotides to the 3' end of the growing polynucleotide.
92
Precise replication in multiple origins in eukaryotes is ensured by...
A licensing factor that must attach to an origin before replication can begin.
93
How are the ends of linear eukaryotic DNA molecules replicated?
The enzyme telomerase.
94
Homologous recombination takes place through...
Alignment of homologous DNA segments, breaks in nucleotide strands and rejoining of the strands.
95
Theta replication
A common type of replication that takes place in circular DNA.
96
Bidirectional replication
Occurs when there are two replication forks.
97
Initiator proteins
Bind to origin and separate strands of DNA to initiate replication.
98
DNA helicase
Unwinds DNA at replication fork.
99
SSB proteins
Attach to single stranded DNA and prevent secondary structures from reforming.
100
DNA gyrase
Moves ahead of the replication fork, making and resealing breaks in the double stranded helical DNA to release to torque that builds up as a result of unwinding at the replication fork.
101
DNA primase
Synthesizes a short RNA primer to provide a 3' OH group provided by the primer.
102
DNA polymerase III
Elongates a new nucleotide strand from the 3' OH group provided by the primer.
103
DNA polymerase I
Removes RNA primers and replaces them with DNA.
104
DNA ligase
Joins Okazaki fragments by sealing breaks in the sugar phosphate backbone of newly synthesized DNA.
105
G overhang
Single strand sticking out from end of telomere.
106
Telomerase
Extends G over hang.
107
Holliday junction
Pathway formed by merging of single strand breaks in each of 2 DNA molecules.
108
What is the template for RNA synthesis?
Single stranded DNA.
109
What does a transcription unit consist of?
A promoter, an RNA coding region and a terminator.
110
What are the substrates for RNA synthesis?
Ribonucleoside triphosphates.
111
What does the sigma factor control?
The binding of the core enzyme (RNA polymerase) to the promotor.
112
What are the 3 primary parts of an mRNA molecule?
A 5' untranslated region, a protein coding sequence, and 3' untranslated region.
113
Ribozymes
Catalytic RNA molecules. Can cut out parts of their own sequences, connect some RNA molecules, replicate others, and catalyze the formation of peptide bonds between amino acids.
114
mRNA
Carries the coding instructions for polypeptide chains from DNA to the ribosome.
115
pre-mRNAs
Immediate products of transcription in eukaryotic cells. Not in bacterial cells.
116
tRNA
Serves as a link between the coding sequence of nucleotides in an mRNA molecule and the amino acid sequence of the polypeptide chain.
117
snRNA
Participate in converting pre-mRNA to mRNA.
118
snRNPs
snRNA and small protein subunits combined.
119
snoRNAs
Take part in the processing of rRNA.
120
microRNA and siRNA
Carry out RNA interference, found in the cytoplasm of eukaryotic cells
121
piRNA
Has a role in suppressing the expression of transposable elements in reproductive cells.
122
crRNA
Assists in the destruction of foreign DNA, prokaryotic. Small RNA's with silencing functions.
123
Template strand
Nucleotide strand used for transcription.
124
Nontemplate strand
Not usually transcribed.
125
Promoter
DNA sequence that the transcription apparatus recognizes and binds. Not transcribed itself.
126
RNA coding region
Sequence of nucleotides that is coded into RNA.
127
Terminator
Signals the stop of transcription, is transcribed into RNA.
128
Core enzyme
At the heart of RNA polymerases, catalyzes the elongation of the RNA molecule by the addition of RNA nucleotides.
129
Sigma factor + core enzyme
Holoenzyme
130
RNA polymerase I
Transcribes large tRNA.
131
RNA polymerase II
Transcribes pre-mRNA, some snRNA, snoRNA, and some miRNA
132
RNA polymerase III
tRNAs, small rRNAs, some snRNAs and some miRNAs.
133
TATA
10 consensus sequence.
134
Rho-dependant terminators
Able to cause the termination of transcription only in the presence of the rho factor.
135
Rho-independant terminators
Able to cause the end of transcription in the absence of rho.
136
Hairpin
When inverted repeats are transcribed into RNA
137
Polysistronic RNA
A group of genes transcribed into a single RNA molecule.
138
Colinear
Suggests that there is a direct correspondence between the nucleotide sequence of DNA and amino acid sequence of a protein.
139
Exons
Coding regions
140
Introns
Non coding region
141
Shine dalgarno sequence
Serves as the ribosome binding site during translation. Found in the 5' untranslated region.
142
5' cap
Consists of extra modified nucleotide at the 5' end and methyl groups.
143
Spliceosome
Where intron splicing occur.
144
Alternative splicing
Enables exons to be spliced together in different combinations to yield mRNAs that encode for different proteins.
145
Anticodon
Set of 3 nucleotides on a tRNA molecule. Pairs with corresponding codon on mRNA.
146
RNAi
RNA interference. Used to limit the invasion of foreign genes and censor the expression of their own cells genes.
147
RISC
RNA induced silencing complex. siRNA and miRNA combine with proteins to form this.
148
What are some characteristics of the genetic code?
It is degenerate (more than one codon = one amino acid), it is non overlapping, and is almost universal.
149
What is required for the binding an an amino acid to tRNA?
The presence of a specific aminoacyl-tRNA synthetase and ATP.
150
Polyribsome
Structure created when mRNA are simultaneously translated by several ribosomes.
151
One gene one enzyme hypothesis
Suggested that genes function by encoding enzymes and that each gene encodes a seperate enzyme.
152
Peptide bonds
Join amino acid chains (polypeptide chains)
153
One gene one polypeptide hypothesis
Different polypeptide chains are encoded by separate genes.
154
Degenerate
The genetic code is redundant, the amino acids may be specified by more than one codon.
155
Isoaccepting tRNAs
Different tRNAs that accept the same amino acid but have different anticodons.
156
Reading frame
Each nucleotide sequence has 3 potential reading frames.
157
tRNA charging
The attachment of a tRNA to its appropriate amino acid. Requires energy.
158
Initiation factor 3
Binds to the small subunit of the ribosome and prevents the large subunit from binding during initiation.
159
Initiation factor 1
Enhances the dissociation of the small and large ribosomal subunit.
160
Initiation factor 2
Required for the attachment of the initiator tRNA to the initation codon, forms a complex with GTP.
161
Translocation
The movement of the ribosome down the mRNA in the 5' to 3' direction.
162
30S ribosomal subunit
Attaches to mRNA.
163
50S ribosomal subunit
Stabilizes tRNAs and amino acids.
164
70S initiation complex
Functional ribosome with A, P and E sites where protein synthesis takes place.
165
Elongation facotr Tu
Binds GTP and charged tRNA; delivers charged tRNA to A site.
166
Elongation factor Ts
Regenerates active elongation facotr Tu.
167
Elongation factor G
Stimulates movement of ribosome to next codon.
168
At what levels can gene expression be controlled?
Alteration of gene structure, transcription, mRNA processing, mRNA stability, translation and posttranslational modification.
169
Genes in bacterial cells are often clustered into...
Operons.
170
What happens in a negative control?
A repressor protein binds to DNA and inhibits transcription.
171
What happens in a positive control?
An activator protein binds to DNA and stimulates transcription.
172
The lac operon is...
A negative inducible operon.
173
How does the lac operon work?
When lactose is absent, a repressor binds to the operator and prevents the transcription of the genes that encode for B-galactosidase, permease, and transacetlyase. When lactose is present, some of it is converted into allolactose, which binds to the repressor and makes in inactive, allowing the structural genes to be transcribed.
174
How does positive control occur in the lac operon?
Through catabolite repression.
175
What is the trp operon?
A negative repressible operon that controls the biosynthesis of tryptophan.
176
What is different in eukaryotic gene regulation?
The absence of operons, the presences of chromatin and the presences of a nuclear membrane.
177
How can gene expression in eukaryotic cells be influenced?
By RNA processing and by changes in mRNA.
178
How does RNA interference play a role in gene regulation in eukaryotes?
siRNA and miRNA combine with proteins and bind to sequences on mRNA or DNA. These complexes cleave RNA, inhibit translation, affect RNA degradation and silence transcription.
179
Structural genes
Encode proteins that are used in biosynthesis.
180
Regulatory genes
Either RNA or proteins, interact with other DNA sequences and affect the transcription or translation of those sequences.
181
Constitutive genes
Not regulated, type of structural gene.
182
Regulatory elements
Affect the expression of DNA sequences to which they are physically linked.
183
Regulator gene
Helps control the structural genes of the operon, not considered part of the operon.
184
Inducible operons
Transcription is normally off and must be turned on.
185
Repressible operons
Transcription is normally on and must be turned off.
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Inducer
Turns transcription on when it binds to the repressor.
187
Corepressor
Binds to repressor and helps it bind to operator to turn transcription off.
188
Catabolite repression
Represses genes that participate in the metabolism of other sugars when glucose is present. Results in positive control in response to glucose.
189
CAP
Establishes positive control in catabolite repression.
190
General transcription factors
Bind with RNA polymerase to assemble into a basal transcription apparatus which binds to a core promoter.
191
Transcriptional regulator proteins
Are required to bring about normal levels of transcription, bind to the regulatory promoter.
192
Transcriptional activator proteins
Stimulate and stabilize the basal transcription apparatus at the core promoter.
193
Silencers
Effect transcription at a distance.
194
Enhancers
Regulatory elements found some distance from the gene.
195
Insulators
Block the effects of enhancers.
196
Heat shock proteins
Help prevent damage from stressing agents
197
Response elements
Binding sites for transcriptional activators.
198
What mutations occur spontaneously?
Mispairing of bases in replication, depurination and deamination.
199
How can insertions and deletions arise?
From strand slippage or from unequal crossing over.
200
What are the 2 common characteristics of transposable elements?
Terminal inverted repeats and the generation of short direct repeats in DNA at the point of insertion.
201
How can a transposon be transposed?
As a DNA molecule or through the production of an RNA molecule that is then reverse transcribed into DNA.
202
Germ line mutations
Arise in cells that produce gametes.
203
Somatic mutation
Occur in somatic tissues that do not produce gametes.
204
Base substitution
Alteration of a single nucleotide in the DNA.
205
Transition
Base sub where a purine is replaced with a different purine.
206
Transversion
Base sub where a purine is replaced with a pyrimdine. Number of possible transversions is twice the number of possible transitions.
207
Indels
Insertions and deletions
208
Indels that do not affect the reading frame
In frame insertions and deletions.
209
Forward mutation
A mutation that alters the wild type allele is called.
210
Reverse mutation
Changes a mutant allele back into the wild type allele.
211
Missense mutation
A base sub that results in a different amino acid in the protein.
212
Nonsense mutation
Changes a sense codon (one that specifies an amino acid) into a nonsense codon (a termination codon).
213
Silent mutation
Changes a codon to a synonymous codon that specifies that same amino acid.
214
Neutral mutation
Missense mutation that changes amino acid sequence but doesn't have a huge effect.
215
Suppressor mutation
A genetic change that hides or suppresses the effect of another mutation.
216
Intragenic suppressor mutation
Takes place in the same genes that contains the mutation being suppressed.
217
Intergenic suppressor mutation
Occurs in a gene other than the one bearing the orginal mutation.
218
Induced mutations
Those that result from changes caused by environmental chemicals or radiation.
219
Deamination
The loss of an amino group from a base.
220
Mutagen
Any environmental agent that significantly increases that rate of mutation above the spontaneous rate.
221
Intercalating agents
Produce mutations by sandwiching themselves between adjacent bases in DNA. Proflavin, acridine orange, ethidium bromide and dioxin.
222
Transposable elements
DNA sequences that can move about in the genome, are often a cause of mutations.
223
Flanking direct repeats
Present on both sides of most transposable elements.
224
Terminal inverted repeats
At the ends of many, but not all, transposable elements, inverted complements of one another.
225
Transposition
The movement of a transposable element from one location to another.
226
Retrotransposons
Elements that transpose through an RNA intermediate, majority of transposons.
227
What are restriction endonucleases?
Enzymes that make double stranded cuts in DNA at specific base sequences.
228
What is the CRISPR Cas9 system?
It can be used to cut and edit the genome. It combines a single guide RNA with a nuclease which together attach to DNA sequences and make double stranded cuts at specific locations.
229
How are plasmids often used?
As vectors to ensure that a cloned gene is stable and replicated within the recipient cells.
230
What do expression vectors contain?
Sequences necessary for foreign DNA to be transcribed and translated.
231
What is a cDNA library created from?
mRNA that is converted into cDNA.
232
What is positional cloning?
It uses linkage re.lations to determine the location of genes without any knowledge of their products.
233
What is the Sanger (dideoxy) method of DNA sequencing?
It uses special substrates of DNA synthesis that terminate synthesis after they have been incorporated into the newly made DNA.
234
What is used in DNA fingerprinting?
Short tandem repeats, or microsatellites
235
What is forward genetics?
Starts with a phenotype and conducts analyses to locate the responsible genes.
236
What is reverse genetics?
Starts with the DNA sequences and uses tests to determine the phenotypic effect.
237
What does sequencing the whole genome require?
Breaking it into small overlapping fragments whose DNA sequences can be determined in sequencing reactions.
238
Single nucleotide polymorphisms
Single base differences in DNA between individual organisms and are valuable as markers in linkage studies.
239
Where does cancer arise?
From somatic mutations in multiple genes that affect cell division and proliferation.
240
What happens if one or more mutations are inherited?
Fewer additional mutations are required for cancer to develop.
241
Oncogenes
Dominant mutated copies of normal genes that stimulate cell division.
242
Tumor-supressor genes
Normally inhibit cell division; recessive mutations in these genes may contribute to cancer.
243
What enzymes control the cell cycle?
Cyclins and cyclindepedent kinases.
244
Malignant
Cells that invade other tissues.
245
Metastasis
Cells that travel to other sites in the body and establish secondary tumors.
246
Loss of heterozygosity
Inactivation of the remaining wild-type allele in heterozygotes. Often caused by a deletion on the chromosome that carried the normal copy of the tumor-suppressor gene.
247
Apoptosis
Programmed cell death.
