biology II Flashcards
1
Q
The Genome
A
the entire genetic complement (DNA) of an organism
2
Q
Prokaryotes
A
a single double-stranded DNA molecule located in the nucleoid
3
Q
Eukaryotes
A
composed of multiple double-stranded DNA molecules bound to proteins called histones that form chromosomes.
4
Q
Chromosomes:
A
Located in the nucleus
5
Q
The Human Genome:
A
Composed of 46 chromosomes organized into two paired sets of 23 chromosomes
6
Q
Haploid
A
refers to one full set of chromosomes (n)
7
Q
What cells in humans are haploid?
A
in humans only sex cells (sperm and eggs) are haploid
8
Q
What are sex cells referred to as?
A
gametes
9
Q
Diploid
A
refers to two sets of chromosomes (2n)
10
Q
What cells in humans are diploid?
A
In humans, all non-sex cells are diploid
11
Q
What are matched pairs of chromosomes called in diploid organisms?
A
Homologous chromosomes
12
Q
Homologous chromosomes are…?
A
the same length and contain the same genes in the same locations or loci
13
Q
Gene:
A
the physical and functional unit of heredity or a sequence of DNA that codes for a specific peptide or RNA molecule
14
Q
Locus:
A
the position of a gene on a chromosome
15
Q
Homologous chromosomes contain…?
A
the same gene but may not contain the same variant
16
Q
What are sex chromosomes the exception to?
A
Sex chromosomes are the exception to homologous chromosomes. Genes on the X and Y chromosomes are not the same.
17
Q
How do cells reproduce?
A
The cell cycle
18
Q
The Cell Cycle:
A
an ordered series of events involving cell growth and cell division that produces two new genetically identical daughter cells. Two major phases Interphase and Mitotic phase
19
Q
What happens during interphase?
A
the cell undergoes normal processes and prepares for cell division with three phases: G1 S
20
Q
G1 Phase:
A
(first gap) First phase of interphase centered on cell growth where the cell accumulates building blocks of chromosomal DNA and the accumulation of energy reserves for chromosomal replication.
21
Q
S Phase:
A
(synthesis phase) Second phase of interphase during which DNA replication occurs With the formation of sister chromatids with mitotic spindles orchestrating the movement of chromosomes during mitosis.
22
Q
Formation of sister chromatids:
A
two identical copies of each chromosome during interphase
23
Q
Mitotic spindle:
A
the microtubule apparatus that orchestrates the movement of chromosomes during mitosis.
24
Q
Centrosome:
A
specialized organelle that is only active during cellular reproduction
25
Centrioles:
a paired rod-like structure constructed of microtubules at the center of each animal cell centrosome
26
G2 Phase:
(second gap) Third phase of interphase where the cell undergoes the final preparations for mitosis. Replenishes energy stores and synthesizes proteins for
27
chromosome manipulation.
Additional cell growth and duplication of organelles
28
Mitotic Phase:
the period of the cell cycle when duplicated chromosomes are distributed into two nuclei and the cytoplasmic contents are divided; includes mitosis and cytokinesis
29
Mitosis:
the period of the cell cycle at which the duplicated chromosomes are separated into identical nuclei. Includes prophase prometaphase
30
Prophase:
Chromosomes condense and become more visible. Expansion of mitotic spindle. Nuclear envelope breaks down. Centrosomes move toward opposite poles
31
Prometaphase:
Chromosomes continue to condense. Mitotic spindle fibers attach to kinetochores.
32
Kinetochores:
a protein structure in the centromere of each sister chromatid that attracts and binds spindle microtubules during prometaphase.
33
Metaphase:
Chromosomes are lined up at the metaphase plate and each sister chromatid is attached to a spindle fiber originating from opposite poles.
34
Metaphase plate:
the equatorial plane midway between two poles of a cell where the chromosomes align during metaphase
35
Anaphase:
Sister chromatids are separated from each other (now called chromosomes again) Certain spindle fibers begin to elongate the cell.
36
Telophase:
Chromosomes arrive at opposite poles and begin to decondense. Nuclear envelopes begin to reform. Mitotic spindle breaks down
37
Cytokinesis:
the division of the cytoplasm following mitosis to form two identical daughter cells
38
Cleavage furrow:
a constriction formed by the actin ring during animal-cell cytokinesis that leads to cytoplasmic division
39
Cell plate:
a structure formed during plant-cell cytokinesis by Golgi vesicles fusing at the metaphase plate
40
What does the cell plate lead to?
The formation of a cell wall to separate the two daughter cells.
41
G0 Phase:
Quiescent or inactive phase. Cell is not actively preparing to divide
42
G1 checkpoint:
makes sure all conditions are favorable for cell division to succeed. Once a cell passes this it is committed to dividing
43
G2 checkpoint:
checks for chromosome duplication and DNA damage
44
M Checkpoint:
occurs near the end of metaphase and checks that all sister chromatids are correctly attached to the mitotic spindle.
45
Cancer:
a collective name for many different diseases caused by uncontrolled cell division
46
What happens during S-phase to cause Cancer?
are several mechanisms that ensure proper DNA synthesis occurs. Small changes in DNA sequence can occur over time that can result in mutation in key genes.
47
What are the two types of genes that regulate the cell cycle?
Proto-oncogenes and Tumor suppressor genes.
48
Proto-oncogenes:
Positive regulators of the cell cycle meaning they push cells forward toward cell division. They act like a gas pedal for the cell cycle. Mutations in proto-oncogenes result in the formation of oncogenes
49
Oncogenes:
Genes that cause a cell to become cancerous. (Ex: Cdk protein pushes cells through division when all conditions are met) If mutated it can push cells through cell division when they are not ready.
50
Tumor suppressor genes:
Genes that code for negative regulators of the cell cycle meaning that they prevent the cell from progressing through the cell cycle
51
What do tumor suppressor genes do?
Act as brakes for the cell cycle signal cells to die
52
What are some common tumor suppressors?
Retinoblastoma protein (RB1) and p51
53
How do prokaryotes divide?
binary fission
54
Binary fission:
the process of prokaryotic cell division
55
Two forms of reproduction:
asexual and sexual
56
Characteristics of Asexual Reproduction:
Produces two daughters that are genetically identical to the parent. Faster. Simpler. Only requires one organism. Every organism is capable of reproducing independently. No energy required to find a mate
57
How is Asexual reproduction simpler?
Occurs via budding fragmentation
58
Sexual reproduction:
reproduction undergone by almost all eukaryotes.
59
Why do almost all eukaryotes reproduce via sexual reproduction?
Larger genetic diversity among individuals increases the flexibility and likelihood of survival of a species in an ever-changing environment.
60
Life Cycles in Sexual Reproduction:
life cycle and fertilization
61
Life cycle:
the sequence of events in the development of an organism and the production of cells that produce offspring
62
Fertilization:
the union of two haploid cells typically from two individual organisms
63
Germ cells:
a specialized cell that produces gametes such as eggs or sperm. Undergo mitosis and meiosis
64
Somatic cells:
all the cells of a multicellular organism except the gamete-forming cells. Only undergo mitosis
65
What does the development of gametes rely on?
Meiosis I and II
66
What does meiosis have in common with mitosis?
Interphase and subsequent phases.
67
G1 (interphase):
Focus is on cell growth
68
S Phase (interphase):
DNA synthesis and formation of sister chromatids
69
G2(interphase):
Final preparations for meiosis
70
What does meiosis 1 contain?
Prophase I Prometaphase I
71
Prophase I:
chromosomes are visible synapsis lines up homologous genes
72
Synapsis (prophase1):
tight pairings of homologous chromosomes.
73
Crossing over (prophase1):
(also recombination) the exchange of genetic material between homologous chromosomes resulting in chromosomes that incorporate genes from both parents of the organism forming reproductive cells.
74
Recombinant (prophase 1):
describing something composed of genetic material from two sources such as a chromosome with both maternal and paternal segments of DNA.
75
Tetrad (prophase1):
two duplicated homologous chromosomes (four chromatids) bound together by chiasmata during prophase 1.
76
Chiasmata (prophase1):
the structure that forms at the crossover points after genetic material is exchanged.
77
Prometaphase I:
A. Spindle fiber microtubules attach to the kinetochore proteins at the centromeres. B. microtubules assembled from centrosomes at opposite poles of the cell and grow toward the middle of the cell. C. each tetrad is attached to microtubules from both poles with one homologous chromosome attached at one pole and the other homologous chromosome attached to the other pole. D. The homologous chromosomes are still held together at the chiasmata.
78
Metaphase I:
A. the homologous chromosomes are arranged in the center of the cell (metaphase plate) with the kinetochores facing opposite poles. B. the orientation of each pair of homologous chromosomes at the center of the cell is random– the physical basis for second form of genetic variation during meiosis.
79
Anaphase I:
the spindle fibers pull the linked chromosomes apart. B. the sister chromatids remain tightly bound together at the centromere. C. Chiasmata connections are broken.
80
Telophase I:
the separated chromosomes arrive at opposite poles.
81
Cytokinesis:
physical separation and formation of 2 haploid daughter cells. Each haploid daughter cell contains 1 homologous chromosome composed of both sister chromatids.
82
Interkinesis:
a period of rest that may occur between meiosis I and meiosis II; there is no replication of DNA during this phase.
83
What comprises Meiosis II? Prophase II
Prometaphase II
84
Prophase II:
new centrosomes move to opposite ends of the newly formed daughter cells
85
Prometaphase II:
spindle formation; each sister chromatid forms its own kinetochore that attaches to opposite poles
86
Metaphase II:
sister chromatids are aligned at the metaphase plate
87
Anaphase II:
sister chromatids are pulled apart toward opposite poles
88
Telophase II:
chromosomes arrive at opposite poles
89
Cytokinesis:
separation and formation of 4 genetically unique haploid daughter cells.
90
Difference between Meiosis vs. Mitosis:
while mitosis produces two identical daughter cells with the same number of chromosomes as the parent cell; essentially meiosis produces four genetically distinct daughter cells with half chromosomes as the parent cell
91
Variations in Meiosis:
Karyotype and number of chromosomes
92
Karyotype:
the number and appearance of an individual’s chromosomes including the size
93
What are the variations in numbers of chromosomes called?
Euploid and Aneuploid
94
Euploid:
an individual with the appropriate number of chromosomes for their species
95
Aneuploid:
an individual with an error in chromosome number; includes deletion and duplications of chromosome segments.
96
Autosomes:
an individual with the appropriate number of chromosomes for their species.
97
Nondisjunction:
the failure of synapsed homologous chromosomes to completely separate and migrate to separate poles during the first cell division of meiosis.
98
Monosomy:
an otherwise diploid genotype in which one chromosome is missing
99
Trisomy:
an otherwise diploid genotype in which one entire chromosome is duplicated
100
Aneuploidy in Humans:
present in 20-40% of pregnancies; most incompatible with life. Chromosomal abnormalities are detected in 1 in 10 live births. No true autosomal monosomies are viable.
101
What are the 3 autosomal trisomies?
Trisomy 13 Trisomy 18
102
Trisomy 13:
patau syndrome
103
Trisomy 18:
edward syndrome
104
Trisomy 21:
down syndrome
105
Aneuploidy in sex chromosomes:
variation in the number of X chromosomes are more tolerable due to X inactivation.
106
X inactivation:
the condensation of X chromosomes into Barr bodies during embryonic development in females to compensate for the double genetic dose.
107
Types of Aneuploidy in Sex chromosomes:
Triple X syndrome Turner syndrome (X)
108
Structural variations in chromosomes:
these occur during S-phase of Prophase I (crossing over) partial duplications (partial trisomy)
109
Gregor Mendel and pea Plants created what?
the model system
110
The model system:
a species or biological system used to study a specific biological phenomenon to gain understanding that will be applied to other species
111
Trait:
a variation in an inherited characteristic
112
Continuous variation:
a variation in a characteristic in which individuals show a range of traits with small differences between them.
113
Discontinuous variation:
a variation in a characteristic in which individuals how two or a few
114
Hybridization:
the process of mating two individuals that differ with the goal of achieving a certain characteristic in their offspring.
115
P generation:
(Parental generation) the first generation in a cross
116
F1 generation:
the first filial generation in a cross; the offspring of the parental generation
117
F2 generation:
the second filial generation produced when F1 individuals are self-crossed or fertilized with each other
118
Dominant:
describes a trait that masks the expression of another trait when both versions of the gene are present in an individual. Represented by a capital letter
119
Recessive:
describes a trait whose expression is masked by another trait when the alleles for both traits are present in an individual. Represented by a lowercase letter
120
Allele:
one of two or more variants of a gene that determines a particular trait for a characteristic
121
Phenotype:
the observable traits expressed by an organism
122
Genotype:
the underlying genetic makeup consisting of both physically visible and non-expressed alleles
123
Homozygous-
having two identical alleles for a given gene on the homologous chromosomes
124
Heterozygous-
having two different alleles for a given gene on the homologous chromosomes
125
Law of dominance-
in a heterozygote one trait will conceal the presence of another trait for the same characteristic
126
Monohybrid-
the result of a cross between two true breeding parents that express different traits for only one characteristic
127
Law of segregation-
paired unit factors (i.e. genes) segregate equally into gametes such that offspring have an equal likelihood of inheriting any combination of factors
128
Test cross-
a cross between a dominant expressing individual with an unknown genotype and a homozygous recessive individual.
129
What does the offspring phenotypes indicate?
whether the unknown parent is heterozygous or homozygous for the dominant trait
130
Law of independent assortment-
genes do not influence each other with regard to sorting of alleles. Basis of independent assortment is during Metaphase I
131
Dihybrid-
the result of a cross between two true breeding parents that express different traits for two characteristics
132
Incomplete dominance
in a heterozygote expression of two contrasting alleles such that the individual displays an intermediate phenotype
133
Codominance-
in a heterozygote complete and simultaneous expression of both alleles for the same characteristic. Variation of incomplete dominance
134
X-linked-
a gene present on the X chromosome but not the Y chromosome
135
Hemizygous
the presence of only one allele for a characteristic as in X-linkage makes descriptions of dominance and recessiveness irrelevant
136
Linkage-
a phenomenon in which alleles that are located close together on the same chromosome are more likely to be inherited together due to recombination
137
Epistasis
an interaction between genes such that one gene masks or interferes with the expression of another
138
3 parts of a DNA nucleotide
Phosphate, deoxyribose sugar, nitrogenous base
139
Deoxyribose
the sugar component of DNA nucleotides
140
phosphate group
a molecular group consisting of a central phosphorus atom bound to four oxygen atoms
141
nitrogenous base
a nitrogen-containing molecule that acts as a base
142
what are the four types of nitrogenous bases?
Adenine (A)
Guanine (G)
Thymine (T)
Cytosine (C)
143
which nitrogenous bases are pyrimidines
cytosine and thymine
144
which nitrogenous bases are purines
guanine and adenine
145
How is DNA a double helix
- a sugar-phosphate group lines up to create a "backbone"
- strands run anti-parallel- 5'->3' and 3'->5'
146
What do nitrogenous bases form?
hydrogen bonds with complementary bases
C=G
A=T
147
factors DNA
Double-stranded helix
Contains Thymine (T)
148
factors of RNA
Single-stranded
Contains Uracil (U)
Pairs with Adenine
149
What does DNA form complexes with and why?
histones in the nucleus because histones contain basic proteins that bind with chromatin and become chromosomes.
150
Why is all DNA shape not the same?
The form DNA is in corresponds with what the cell is doing
Making proteins? Replicating?
less condensed and more accessible
Cell dividing?
highly compact to minimize damage
and ensure proper transportation
151
How do cells utilize the organization of DNA when replicating?
Cells use each strand of DNA as a template to construct a complementary strand
152
Semi-conservative model of DNA replication
Original double-stranded
molecule is separated and each
strand acts as a template for a
new strand to be synthesized
153
what is the result of the original double-stranded molecule being separated for new-strand synthesis?
Resulting DNA molecules are
composed of one new strand of
nucleotides and one old strand of nucleotides
154
Helicase
an enzyme that helps to open up the DNA helix during DNA replication by breaking the hydrogen bonds
155
Replication fork
the Y-shaped structure formed during the initiation of replication
156
DNA polymerase-
enzyme that synthesizes a new strand of DNA complementary to a template strand
157
Primer-
a short stretch of RNA nucleotides that is required to initiate replication and allow DNA polymerase to bind and begin replication
158
Leading strand
the strand that is synthesized continuously in the 5' to 3' direction that is synthesized in the direction of the replication fork
159
Lagging strand-
during replication of the 3' to 5’ strand, the strand that is replicated in short fragments and away from the
replication fork
160
Okazaki fragments
the DNA fragments that are synthesized in short stretches on the lagging strand
161
DNA ligase
the enzyme that catalyzes the joining of DNA fragments together
162
Telomeres
the DNA at the end of linear chromosomes
163
Telomerase
an enzyme that functions to maintain
telomeres at chromosome ends
164
which direction does DNA polymerase go?
5' to 3'
165
where is telomerase active, where is it absent?
* Active in germ cells and adult
stem cells
* Absent in adult somatic cells
(cellular basis of aging!)
166
What reduces mistakes in DNA replication?
DNA polymerase “proofreads” every nucleotide it adds
* Catches most mistakes in DNA replication
167
What repairs mistakes in DNA replication?
Mismatch repair enzymes recognize the wrongly incorporated base and excise it from the DNA, replacing it with the correct base
168
How does the mismatch repair enzyme fix the mistakes?
* DNA molecule is unwound
and separated in the region of
the nucleotide damage
* Damaged nucleotides are
removed and replaced with
new nucleotides using the
complementary strand
* DNA strand is resealed and
allowed to rejoin its
complement
169
basis of transcription
DNA --> RNA
170
mRNA-
messenger RNA; a form of RNA that carries the nucleotide sequence code for a protein sequence that is translated into a polypeptide sequence
171
Transcription bubble-
the region of locally unwound DNA that allows for transcription of mRNA
172
Promotor-
a sequence on
DNA to which RNA
polymerase and associated
factors bind and initiate
transcription
173
RNA polymerase-
an enzyme that synthesizes an RNA strand from a DNA template strand
174
Template strand-
the strand of DNA that specifies the complementary mRNA molecule
175
Non-template strand-
the strand of DNA that is not used to transcribe mRNA
* This strand is identical to the
mRNA except that T
nucleotides in the DNA are
replaced by U nucleotides in
the mRNA
176
What are the three processes from pre mRNA to mRNA
Exons
Introns
Splicing
177
exons
a sequence present in protein-coding mRNA after completion of pre-mRNA splicing
178
introns
non–protein-coding intervening sequences that are spliced from mRNA during processing
179
splicing
the process of removing introns and reconnecting exons in a pre-mRNA
180
rRNA
ribosomal RNA; molecules of RNA that combine to form part of the ribosome
181
tRNA
transfer RNA; an RNA molecule that contains a specific three-nucleotide anticodon sequence to pair with the mRNA codon and also binds to a specific amino acid
182
Codon
three consecutive nucleotides in mRNA that specify the addition of a specific amino acid or the release of a polypeptide chain during translation
183
start codon
the AUG on an mRNA from which translation begins
* always specifies methionine
184
stop codon
one of the three mRNA codons that specifies termination of translation
185
the central dogma of biology
DNA --> RNA --> Proteins
186
Epigenetics
describing non-genetic regulatory factors such as changes in modifications to histone proteins and DNA that control accessibility to genes in chromosomes
187
Post-transcriptional
control of gene expression after the RNA molecule has been created but before it is translated into protein
188
Alternative splicing
a post-transcriptional gene regulation mechanism in eukaryotes
189
What is the product of alternative splicing?
Multiple protein products are produced by a single gene through alternative splicing combinations of the RNA transcript
190
Post-translational
control of gene expression after a protein has been created
191
Control of gene expression in eukaryotic cells occurs at which level(s)?
a) epigenetic and transcriptional levels
b) epigenetic, transcriptional, posttranscriptional, translational, and posttranslational levels
c) only the transcriptional level
d) epigenetic, transcriptional, and translational levels
B) epigenetic, transcriptional, posttranscriptional, translational, and posttranslational levels
192
How long would the peptide be that is translated from this MRNA sequence: 5'-AUGGGCUACCGA-3'?
a) 0
b) 2
c) 4
d) 3
C) 4
(split the strand into sets of three and that's how many peptide's there would be)
193
DNA replicates by which of the following models?
a) conservative
b) dispersive
c) additive
d) semi-conservative
D) semi-conservative
194
Which of the following increases variation within a population?
Gene mutation
Mitosis
DNA replication
Sexual reproduction
1 and 4
195
The initial mechanism for repairing nucleotide errors in DNA is ________.
a) nucleotide excision repair
b) mismatch repair
c) DNA polymerase proofreading
d) thymine dimers
C) DNA polymerase proofreading
196
A promoter is ________.
a) an enzyme that synthesizes RNA
b) a specific sequence of RNA nucleotides
c) a specific sequence of DNA nucleotides
d) a protein that binds to DNA
C) a specific sequence of DNA nucleotides
