Exam 1 Study Guide Flashcards
1
Q
What is required for cell division?
A
Replication and segregation of genetic material, and division of cytoplasm. Must be controlled and responsive to environmental conditions.
2
Q
What is an example of a prokaryote?
A
Bacteria
3
Q
What is an example of a eukaryote?
A
Plants, animals, protists, and fungi
4
Q
What is the size of a prokaryote?
A
Small (.2-2 um)
5
Q
What is the size of a eukaryote?
A
Large (10-100 um)
6
Q
Do prokaryotes have a nucleus?
A
No
7
Q
Do eukaryotes have a nucleus?
A
Yes
8
Q
Do prokaryotes have membrane-bound organelles?
A
No
9
Q
Do eukaryotes have membrane-bound organelles?
A
Yes
10
Q
How is DNA arranged in prokaryotes?
A
Circular chromosomes (genophores) compacted by supercoiling
11
Q
How is DNA arranged in eukaryotes?
A
Linear chromosomes
12
Q
How do prokaryotes divide?
A
Binary fission
13
Q
How do eukaryotes divide?
A
Mitosis and meiosis
14
Q
What is binary fission?
A
Asexual cell division which requires duplication and segregation of genetic material (contained in nucleoid region of compacted DNA, also RNA and proteins)
15
Q
What are the steps of binary fission?
A
- Single, circular bacterial chromosome is replicated 2. Replication begins at the origin of replication and
proceeds in two directions at site of termination - New chromosomes are partitioned to opposite
ends of the cell - Septum forms to divide into two cells (septation)
- Cell pinches off into two daughter cells
16
Q
What are the steps of septation?
A
- Formation of a ring of FtsZ proteins (in most
prokaryotes) - Accumulation of others follows
- Structure contracts radially to pinch cell into two
17
Q
What must happen during bacterial chromosome compaction?
A
Chromosome must be compacted and twisted, complexed with proteins
18
Q
What are cyanobacteria?
A
Photosynthetic bacterium with a circadian cycle (active 19 hours/day for division)
19
Q
What do genes Kai A, B and C do?
A
Regulate the expression of FtsZ to time division with light availability
20
Q
What are chromosomes?
A
Condensed molecules of DNA and associated proteins and RNAs
21
Q
What are centromeres?
A
Visible constrictions, area of repetitive DNA sequence
22
Q
What do kinetochore and cohesion proteins do?
A
Associate with each chromatid at the centromere during cell division, site of microtubule attachment
23
Q
What are telomeres?
A
Repeated short sequences of DNA at the end of chromosomes
24
Q
Through what enzyme do telomeres replicate?
A
Telomerase
25
What causes the shortening of telomeres?
Age and disease
26
What is DNA's net electrical charge and what causes it?
Negative (phosphate backbone)
27
What is histone proteins' net electrical charge?
Positive
28
What is a nucleosome?
146 base pairs of DNA wrapped around 8 histone proteins (most basic level of chromatin)
29
What is the metaphorical expression for chromatin?
Beads on a string
30
What is the metaphorical expression for selenoid?
Folded beads on a string, can be further folded into more and more structures
31
When is selenoid most compacted?
Mitosis
32
What is the G1 phase and what takes place?
First gap phase (pre-replication), carries out metabolic activity
33
What is the S phase and what takes place?
DNA synthesis/replication
34
What is the G2 phase and what takes place?
Second gap phase (post-replication), metabolize and prepare for segregation and cell division
35
What is the M phase and what takes place?
Mitosis/meiosis, DNA is segregated
36
What is cytokinesis?
The division of the cytoplasm into two cells
37
What phases make up interphase?
G1, S, and G2
38
What is interphase?
The metabolically active period between nuclear divisions
39
Mitosis and cytokinesis are:
Sometimes loosely called mitosis, but are separate events
40
What is the cell cycle an oscillation between?
Mitosis and interphase
41
What is the G0 phase?
An alive and metabolizing, but non-dividing state
42
What are cyclins?
Regulatory proteins that accumulate and degrade in a cell-cycle specific fashion
43
What do cyclins regulate?
Kinases (enzymes that phosphorylate other molecules)
44
What do phosphatases do?
Dephosphorylate other molecules
45
What are cyclin-dependent kinases (CDKs)?
Kinases that complex with cyclin to regulate other molecules by phosphorylating them, phosphorylate transcription factors necessary for gene expression, result in increased synthesis of cell cycle-specific proteins
46
What must CDKs be complexed with to be active?
Cyclin
47
Different stages of the cell cycle are triggered by what?
Different CDK/cyclin complexes
48
How do CDK/cyclin complexes activate other molecules?
By phosphorylating them
49
What are the expression of cyclins sensitive to?
Internal and external factors (e.g. nutritional state for single-celled yeast, hormones and growth factors in multicellular organisms)
50
Under what conditions would cell division probably be lethal?
Insufficient environmental conditions, incompletely-replicated DNA, or damaged DNA
51
What is the start checkpoint?
The commitment to divide at all; growth factors, nutritional state of cell, size of cell
52
What is the G2/M checkpoint?
Regulated by cyclin/CDKs; replication completed, DNA integrity
53
What is the APC checkpoint?
Anaphase promoting complex; no chromatid separation; chromosomes attached at metaphase plate
54
What are located on the sides of DNA helices?
Covalent phosphodiester bonds
55
What are in the middle of DNA helices?
H bonds (weak and can be easily broken to separate the strands to allow for replication)
56
What is the anatomy of a double helix?
Antiparallel, 5' end with phosphate and 3' end with sugar, H bonds between nitrogenous bases on interior
57
What is the template mechanism in DNA replication?
Strands separate, a new DNA strand is synthesized via complementary base pairing using the old DNA strand as a template (Chargaff), new nucleotides added by phosphodiester bond to the 3' end of a preexisting nucleotide by DNA polymerase
58
What enymes are required to replicate DNA?
Primase, helicase, DNA polymerase, and ligase
59
What is the initiation phase?
Starting, bring together necessary components for DNA replication
60
During initiation, what does the replication complex (RC) do?
Interacts with template strands
61
How does the RC know where to bind the DNA?
All chromosomes have DNA regions called origin of replication (ori); usually more than one; where replication begins. Proteins in RC bind to a DNA sequence in ori
62
Why are there multiple oris?
Eukaryotic chromosomes are very big
63
Why does DNA replication begin with a starter strand of RNA made by primase?
DNA polymerase has to add bases onto an existing nucleotide strand (in contrast with RNA polymerase)
64
What is the RNA primer complementary to?
DNA template
65
How is DNA polymerase positioned to carry out elongation?
By adding nucleotides to 3' end
66
What is elongation?
Actual replication of DNA. Helicase unwinds, binding proteins prevent bases from reforming hydrogen bonds
67
What is termination?
Making sure the process is appropriately stopped
68
What is the replication fork?
Site where DNA unwinds to expose bases with helicase's help
69
What happens during Leading Strand (Continuous) Elongation?
Synthesized continuously 5' to 3' until a primer/end of template is reached. RNA must be removed
70
What happens during Lagging Strand (Continuous) Elongation?
Occurs in small discontinuous DNA stretches (Okazaki), each Okazaki requires its own RNA primer synthesized by primase.
71
What does the lagging strand have more of than the leading strand?
RNA primers
72
What replaces primer with DNA?
DNA Polymerase (I)
73
What catalyzes the final phosphodiester linkage between fragments?
DNA Ligase
74
DNA polymerase has a high processivity...what is it?
An enzyme's ability to catalyze consecutive reactions without releasing its substrate
75
How is DNA polymerase helped in catalyzing polymerizations each time it binds to DNA?
Polymerases stabilized by sliding clamp proteins
76
DNA polymerase has a proofreading function as it adds nucleotides to a growing DNA strand...what does it do?
Polymerase can remove incorrect nucleotide and replace it with the correct one
77
What do excision repair enzymes do?
Detect mismatches and DNA damage (like thymidine dimers) and remove incorrect or damaged DNA.
78
After excision repair enzymes remove DNA, what does DNA polymerase do?
Fills in the gap
79
What is xeroderma pigmentosum?
Rare genetic disorder of DNA repair enzymes in which the ability to repair damage caused by UV light is deficient (NER enzymes have reduced ability)
80
How many chromosomes are in G1?
46 one-chromatid
81
How many chromosomes are after replication?
46 two-chromatid
82
What happens in mitotic prophase?
Chromosomes condense, nuclear membrane breaks down, spindle poles begin to form
83
What are spindle poles?
An array of microtubules at each pole that are involved in chromosome movement during the rest of mitosis
84
What happens in mitotic metaphase?
Chromosomes line up at center, cohesion proteins still exist so no separation yet, chromatids under tension
85
What is tubulin?
Protein dimer of alpha and beta subunits that can polymerize to form a microtubule with hollow cord
86
What allows microtubules to grow/shorten in length?
Polymerization/depolymerization of tubulin
87
What do motor proteins CENP-E and dynein do?
Located in kinetochore, physically move the chromosome forward and backward along the microtubules as they polymerize and depolymerize
88
What happens during mitotic anaphase?
Centromeres and chromatids are separated, chromosomes per cell double
89
If a spindle checkpoint is passed during anaphase, what is activated?
Anaphase promoting complex (APC); will dissolve cohesion proteins holding centromeres together
90
What happens during Anaphase A?
Chromosomes move to opposite poles (depolymerization of microtubules)
91
What happens during Anaphase B?
Poles move apart
92
What are are polar microtubules?
Extend from spindle pole to spindle pole
93
What are aster microtubules?
Connect spindle poles to cell membrane
94
What are kinetochore microtubules?
Connect chromosomes to spindle poles
95
What happens during mitotic telophase?
Chromosomes decondense, nuclear membrane reforms around chromosomes and spindle apparatus disappears. One chromatid per chromosome
96
Chromosomes after S phase?
One cell with 46 two-chromatid
97
Chromosomes after mitosis?
Two cells with 46 one-chromatid
98
What is mitotic cytokinesis?
Actual process of dividing one cell and its cytoplasmic contents into two
99
During cytokinesis, what do animals use?
A contractile ring, a highly evoluntionarily conserved structure
100
What two structures contract radially to pinch the cell into two (cleavage furrow)?
Actin microfilaments and myosin motor proteins
101
What is formed between dividing plant cells?
Cell plate
102
How many homologs do humans have for each chromosome?
2
103
After replication, how many sister chromatids does each homolog have?
2
104
What is ploidy?
How many sets of chromosomes are in a cell
105
What is a diploid cell?
Two complete sets of chromosomes, one from each parent, 2n (46 chromosomes, 23 homologous pairs)
106
What is a haploid cell?
One complete set of chromosomes, n or 1n (23 chromosomes, no homologous pairs)
107
What are ovum and sperm?
n, 23 chromosomes, haploid, combine to create a 2n zygote with 46 chromosomes
108
What is meiosis?
Cell division that produces n gametes from 2n cells
109
What are gametes?
Sex cells (sperm, ovum)
110
What is meiotic S phase?
46 two-chromatid chromosomes (diploid)
111
What is meiosis 1?
The first cell division, homologous chromosome pairs separate
112
What happens after meiosis 1?
Two cells with 23 two-chromatid chromosomes (haploid)
113
What is meiosis 2?
Second cell division, chromatids separate
114
What happens after meiosis 2?
Four cells with 23 one-chromatid chromosomes (haploid)
115
What is gametogenesis?
Gamete formation
116
What does spermatogenesis result in?
Four viable sperm cells (haploid)
117
What does ovogenesis result in?
One viable ovum cell and 3 nonviable ovum called polar bodies (haploid)
118
During prophase 1, what do homologous chromosomes do?
Pair and form a complex (tetrad)
119
What is crossing over?
When paired chromosomes exchange genetic material; rearranges chromosomes and increases genetic variation
120
When are the only conditions in which crossing over occurs?
Prophase 1 when homologs are paired, between non-sister chromatids
121
What is chiasamata?
The points at which the exchange of genetic material (crossing over) occur between homologous chromosomes
122
During metaphase 1, each haploid cell will contain a mixture of genes from the organism's mother and father called what?
Independent assortment
123
What happens during anaphase 1?
Homologs separate
124
What happens during meiotic cytokenesis?
One diploid divides into two haploid cells
125
What is interkinesis?
No replication, period of rest in which a cell prepares for meiosis 2
126
What does meiosis produce?
Haploid sperm and ovum
127
What does fertilization produce?
Diploid zygote
128
What does mitosis produce?
Whole organism
129
What did Mendel establish?
Laws of Mendelian inheritance, quantitative approach, particulate unit of inheritance (now genes), Law of Segregation, Law of Independent Assortment
130
What are genes?
Portions of DNA with information necessary to specify a trait (multiple genes may govern one trait)
131
What is a locus?
Physical location of a gene on a chromosome...pair of alleles has genes at same loci
132
What is an allele?
Genes that occupy the same spot on homologous chromosomes
133
What is a genotype?
The particular set of genes carried by an individual
134
What is the Principle of Segregation?
Maternal and paternal alleles segregate during gamete formation, 1 allele in each gamete
135
What did Mendel generate his Principle of Segregation from?
Homologs disjoin during Anaphase 1, so alleles must as well
136
What assumptions do Punnett squares make?
Equally likely gametic types combine randomly and each outcome is equally probable
137
Why are alleles for each locus segregated independently?
Because chromosomes segregated independently during meiosis
138
What does Mendel's model of inheritance assume?
Each trait is controlled by one gene, each gene has only two alleles, clear dominant-recessive relationship (most genes don't meet this criteria)
139
What is incomplete dominance?
Heterozygote has phenotype intermediate between the two homozygotes
140
What is codominance?
Similar to incomplete dominance, but subtle differences; heterozygote may show both phenotypes (think blood types)
141
What is black/brown coat color caused by?
Eumelanin
142
What is yellow coat color caused by?
Phaeomelanin
143
What is epistasis?
Latin for "to stand on"; one gene controls or stands on the other
144
What is heterogametic sex?
Two kinds of sex chromosomes
145
What is hemizygous?
Only one copy of an allele in an otherwise diploid organism
146
What is homogametic sex?
One kind of sex chromosome has two copies of it, rest of chromosomes are autosomes
147
How did we learn about sex linkage?
Thomas Hunt Morgan found naturally-occurring sex linked alleles in fruit flies (Drosophilia)
148
What is anthocyanin responsible for?
Shades of red and purple in foliage when chlorophyll production stops
149
What does the IA allele code for?
Transferase that adds galactosamine to the surface of RBCs
150
What does the IB allele code for?
Transferase that adds galactose to the surface of RBCs
151
What does the i allele code for?
An enzyme that is non-functional
