Chapter 3 Flashcards
1
Q
What are chromosomes?
A
The structures within living cells that contain the genetic material. Genes are physically located within the structure of chromosomes. Biochemically, chromosomes contain a very long segment of DNA, which is the genetic material, and protein, which are bound to the DNA and provide it with an organized structure.
2
Q
What is a chromatin?
A
The association between DNA and proteins that is found within chromosomes.
3
Q
Bacteria and achaea are referred to as what?
A
Prokaryotes
4
Q
What are prokaryotes?
A
Another name for bacteria and archaea. The term refers to the fact that the chromosomes are not contained within a separate nucleus of the cell.
5
Q
Prokaryotes usually have a _________ in a region of the cytoplasm called the _________.
A
Single type of circular chromosome in a region of the cytoplasm called the nucleoid.
6
Q
What is the nucleoid?
A
A darkly staining region that contains the genetic material of mitochondria, chloroplasts, or bacteria.
7
Q
In bacteria, the cytoplasm is enclosed by what?
A
A plasma membrane that regulates the uptake of nutrients and the excretion of waste products.
8
Q
What’s outside the plasma membrane in bacteria?
A
A rigid cell wall that protects the cell from breakage.
9
Q
Eukaryotic cells exhibit compartmentalization. Define compartmentalization.
A
Cells have membrane-bound compartments.
10
Q
What are eukaryotes?
A
Have a defining feature that their cells contain nuclei bounded by cell membranes. Some simple eukaryotic species are single-clled protists and yeast; more complex multicellular species include fungi, plants and animals.
11
Q
The compartment of eukaryotic species form what?
A
Membrane-bound organelles.
12
Q
What are organelles?
A
Large specialized structure within a cell, which is often surrounded by a single or double membrane.
13
Q
Lysosomes play a role in what?
A
The degradation of macromolecules
14
Q
The endoplasmic reticulum and golgi body play a role in what?
A
In protein modification and trafficking.
15
Q
What is the nucleus?
A
A membrane-bound organelle in euikaryotic cells where the linear sets of chromosomes are found.
16
Q
The nucelus is bounded by what?
A
Two membranes that constitute the nuclear envelope.
17
Q
Which organelles in eukaryotic cells contain a small amount of their own DNA?
A
Mitochondrion
Chloroplast
18
Q
What is the DNA found in other organelles referred to as?
A
Extranuclear or extrachromosomal DNA
19
Q
What is the role of mitochondrion?
A
Functions in ATP synthesis
20
Q
WHat is the role of the chloroplasts?
A
In plant and algal cells, which function in photosynthesis.
21
Q
The DNA found in the organelles such as Mitochondrion and chloroplsats are referred to as what? WHY?
A
Extranuclear or extrachromosomal DNA To distinguish it from the DNA that is found in the cell nucleus
22
Q
What is cytogenetics?
A
The field of genetics that involves the microscopic examination of chromosomes
23
Q
What is a cytogeneticist?
A
A scientist who studies chromosomes under the microscope
24
Q
Observations of eukaryotic species is usually accomplished how? WHy?
A
Observing the chromosomes as they are found in actively dividing cells.
When the cell is preparing to divide, the chromosomes become more tightly coiled, which shortens them and increases their diameter.
25
Why does the tightly coiled chromosomes make it easier to observe?
There is a distinctive shape and the number of chromosomes are visible with a light microscope
26
What are somatic cells?
Any cell of the body except for germ-line cells that give rise to gametes.
27
What's a gamete?
A reproductive cell (usually haploid) that can unite with another reproductive cell to create a zygote. Sperm and egg cells are types of gametes.
28
Gametes are also called what?
Germ cells
29
How do you think the end results would be affected, in eukaryotic cell observation, if the cells were not treated with a hypotonic solution?
The chromosomes would not be spread out very well and would probably be overlapping. It would be difficult to see individual chromosomes
30
After the eukaryotic cells have been removed from the body, they are treated with what? Which will do what?
Chemicals that stimulate them to begin cell division and halt cell division during mitosis
31
The actively dividing cells are subject to what?
Centrifugation to concentrate them
32
The concentrated preparation during eukaryotic cell division and observation is then mixed with what? which causes what?
Hypotonic solution
| It makes the cells swell
33
The cells swelling causes what, after the addition of hypotonic solution?
The chromosomes to spread out within the cell, making it easier to see individual chromosomes.
34
What occurs after the chromosomes have spread out during eukaryotic cell observation?
They are treated with a fixative that chemically freezes them so that the chromosomes will no longer move around.
35
After be treated with a fixative, what happens to the chromosomes?
The cells are treated with a chemical dye that binds to the chromosomes and stains them. They are then placed on a slide and examined.
36
What is karyotype?
A photographic representation of all the chromosomes within a cell. It reveals how many chromosomes are found within an actively dividing somatic cell.
37
Most eukaryotic species are what?
Diploid
38
What is a diploid?
An organism or cell that contains two copies of each type of chromosomes
39
What is a homolog?
One of the chromosomes in a pair of homologous chromosomes
40
What are alleles?
An alternative form of a specific gene.
41
What is locus? (pl. loci)
The physical location of a gene within a chromosome.
42
How are homologs similar to each other and how are they different?
Similar in size, banding pattern, and carry the same types of genes.
THe alleles of a given gene may be different.
43
Which of the following is not found in a prokaryotic cell?
a. plasma membrane
b. ribosome
c. cell nucleus
d. cytoplasm
c. cell nucleus
44
When preparing a karyotype, which of the following steps is conducted?
a. treat the cells with drugs that cause them to begin cell division.
b. treat the cells with a hypotonic solution that causes them to swell.
c. expose the cells to chemical dyes that bind to the chromosomes and stain them.
d. All of the above.
d. All of the above.
45
How many sets of chromosomes are found in a human somatic cell, and how many chromosomes are within one set?
a. 2 sets, with 23 in each set
b. 23 sets, with 2 in each set.
c. 1 set, with 23 in each set
d. 23 sets, with 1 in each set.
a. 2 sets, with 23 in each set
46
What is asexual reproduction?
a form of reproduction that does not involve the union of gametes; at the cellular level, a preexisting cell divides to produce two new cells.
47
The original cell in asexual reproduction is usually called what?
The mother cell.
48
The two new cells that are produced from the asexual reproduction are called what?
Daughter cells
49
When species are unicellular, the mother cell is judged to be one _________ and the two daughter cells are what?
One organism
| Daughter cells are two separate organisms.
50
How do bacterial cells proliferate?
Asexual reproduction.
51
How do unicellular eukaryotes such as amoeba and baker's yeast reproduce?
Asexually
52
What is multicellularity?
The property by which an organism consists of more than one cell.
53
What species have undergone multicellularity?
Plants
Animals
most Fungi
some Protists
54
Bacteria have what type of chromosomes?
Single Circular chromosomes
55
How do bacteria divide?
Bacteria duplicate their circular chromosome; they then distribute a copy into each of the two daughter cells, which is called binary fission.
56
The circular chromsomes in bacteria are in direct contact with what?
The cytoplasm.
57
Escherichia coli, a common bacterium of the intestine can divide every ________ minutes.
20-30 minutes
58
Prior to cell division, bacterial cells do what?
Copy, or replicate their chromosomal DNA.
59
What is binary fission?
The physical process whereby a bacterial cell divides into two daughter cells, during this event, the two daughter cells become divided by the formation of a septum.
60
What is the function of the FtsZ protein during binary fission?
FtsZ assembles into a ring at the future site of the septum and recruits other proteins to this site that produce a cell wall between the two daughter cells.
61
FtsZ is evolutionarily related to a eukaryotic protein called what?
Tubulin
62
Tubulin is the main component of what?
Microtubules, which play a key role in chromosome sorting in eukaryotes.
63
Both FtsZ and tubulin form structures that provide what?
Cells with organization and play key roles in cell division.
64
Why is binary fission a asexual form of reproduction?
Because it does not involve genetic contributions from two different gametes.
65
What is the common outcome of prokaryotic cell division?
To produce two daughter cells that have the same number and types of chromosomes as the original mother cell.
66
What is the cell cycle?
A series of stages through which a cell progresses in order to divide in eukaryotic cells. The phases are G for growth or gap, S for synthesis ( of the genetic material), and M for mitosis. There are two G phases, G1 and G2.
67
What is the interphase?
The series of phases G1, S, and G2, during which a eukaryotic cell spends most of its life.
68
What happens to a cell in the G0 phase?
The cell is temporarily not progressing through the cell cycle or, in the case of terminally differentiated cells, such as most nerve cells in an adulat mammal, will never divide again.
69
What is the difference between the G0 and G1 phases?
The G1 phase is a phase of the cell cycle when a cell may make the decision to divide. By comparison, the G0 phase is a phase in which a cell is either not progressing through the cell cycle or has made a decision to never divide again.
70
A cell in the G1 phase may accumulate what?
Molecular changes that cause it to progress through the rest of the cell cycle.
71
What is a restriction point?
A point in the G1 phase of the cell cycle that causes a cell to progress to cell division.
72
What happens in the S phase?
The chromosomes are replicated.
73
What are chromatids?
Following chromosomal replication in eukaryotes, the two copies that remain attached to each other in the form of sister chromatids.
74
What is the centromere?
A segment of eukaryotic chromosomal DNA that provides an attachment site for the kinetochore.
75
What are sister chromatids?
Pairs of replicated chromosomes that are attached to each other at the centromere. Sister chromatids are genetically identical.
76
What's another name for sister chromatids?
Dyad
77
What is a monad?
The single chromatid within a dyad
78
What can also be called a monad?
An unreplicated chromosome
79
What is the kinetochore?
A group of cellular proteins that attach to the centromere durng meiosis and mitosis.
80
Kinetochore help to do what?
Hold the sister chromatids together and also play a role in chromosome sorting.
81
After chromosome replication what happens?
The two copies are called chromatids and are joined to each other at the centromere to form a unit known as a sister chromatids or dyad.
82
What is the difference between homologs versus the chromatids within a pair of sister chromatids?
Homologs are gentically similar; one is inherited from the mother and the other from the father. By comparison, Chromatids are the product of DNA replication. The chromatids within a pair of sister chromatids are genetically identical.
83
When the s phase is completed, a cell has twice as many what as what in the G1 phase.
Twice as many chromatids as chromosomes.
84
The term chromosome is a bit confusing, why?
It originally meant a distinct structure that is observable with the microscope. Therefore, the term Chromosome can refer to either a pair of sister chromatids (a dyad) during G2 and ealy stages of M phase or to a structure that is observed at the end of M phase and during G1.
85
What structure is observed at the end of M phase and during G1?
A monad.
86
A monad contains the equivalent of what?
One chromatid.
87
During the G2 phase, the cell accumulates what?
The material necessary for nuclear and cell division.
88
What occurs in the m phase?
Mitosis
89
What is mitosis?
A type of nuclear division into two nuclei, such that each daughter cell receives the same complement of chromosomes.
90
What is the primary purpose of mitosis?
To distribute the replicated chromosomes, dividing one cell nucleus into two nuclei, so each daughter cell receives the same complement of chromosomes.
91
When was mitosis first obserbed and by who?
In 1870
| By German biologist Walther Flemming.
92
How was the word mitosis derived?
From the greek word mitos, meaning thread.
93
Binary fission
a. is a form of asexual reproduction
b. is a way for bacteria to reproduce.
c. begins with a single mother cell and produces two genetically identical daughter cells.
d. all of the above.
d. all of the above.
94
Which of the following is the correct order of phases of the cell cycle?
a. G1, G2, S, M
b. G1, S, G2, M
c. G1, G2, M, S
d. G1, S, M, G2
b. G1, S, G2, M
95
What critical event occurs during the S phase of the eukaryotic cell cycle?
a. cells make a decision of whether or not to divide.
b. DNA replication produces pairs of sister chromatids.
c. the chromosomes condense.
d. The single nucleus is divided into two nuclei.
b. DNA replication produces pairs of sister chromatids.
96
What is the mitotic spindle apparatus?
The structure that organizes and separates the chromosomes during M phase of the eukaryotic cell cycle.
97
What is another name for mitotic spindle apparatus?
Mitotic spindle
98
The spindle apparatus is formed from what?
Microtuble-organizing centers (MTOCs)
99
What are microtuble-organizing centers (MTOCs)?
A site in a cell where microtubles begin to grow.
100
Microtubles ar produced from what?
The rapid polymerization of tubulin proteins.
101
In animal cells, the mitotic spindle is fromed from what?
Two MTOCs called Centrosomes.
102
What are centrosomes?
A cellular structure from which microtubules emanate.
103
Each centrosome is located at what?
A spindle pole.
104
What is a spindle pole?
One of the two sites in the cell where microtubules originate during cell division in eukaryotes.
105
What is found within each centrosome of animal cells?
A pair of centrioles at right angles to each other.
106
What are centrioles?
A pair of structures within the centrosome of animal cells.
107
Are centrosomes and centrioles found in all eukaryotic species?
No, They are found in animal cells.
108
Where are the two ends of a kinetochore microtubule?
1. Kinetochore on a chromsome.
| 2. Within the centrosome.
109
What are the three types of microtubules of the mitotic spindle of a typical animal cell?
Aster microtubles
Polar microtubles
Kinetochore microtubles
110
Where are the aster microtubles?
Emanating outward from the centrosome toward the plasma membrane.
111
Aster microtubles are important for what?
Positioning of the spindle apparatus within the cell and later in the process of cell division.
112
Polar microtubles are where?
Projecting toward the region where the chromosomes will be found during mitosis-- the region between the two spindle poles.
113
Polar microtubles that overlap with each other play a role in what?
The separation of the two poles.
| They help to push the poles away from each other.
114
Kinetochore microtubles are located where?
They attach to a kinetochore, which is a complex of proteins that is bound to the centromere of individual chromsomes.
115
Mitosis is subdivided into what phases?
```
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
```
116
During which phase are sister chromatids separated and sent to opposite poles of mitosis?
Anaphase
117
What phase is prior to mitosis?
Interphase
118
What occurs during interphase?
Chromosomes decondensed and found in the nucleus.
119
What occurs at the start of prophase of mitosis?
The chromosomes already replicated, into sister chromatids.
120
As prophase proceeds what happens in mitosis?
The nucleus membrane dissociates into small vesicles.
The chromatids become more condensed.
Centrosomes move apart.
Mitotic spindle begins to form.
121
As mitosis progresses from prophase to prometaphase, what happens?
The centrosomes move to oppsoite ends of cell.
| Shows edge of two spindle poles
122
What occurs during prometaphase of mitosis?
Nuclear membrane completely disrupted into vesicles.
| Allowing spindle fibers to interact with sister chromotids.
123
How do sister chromatids become attached to the spindle during prometaphase of mitosis?
Microtubules grow out from the two poles. If end of microtubule touches kinetochore, it's captured.
Alternatively, if end does not touch kinetochore, the microtubule depolymerizes and retracts to the centrosome.
124
What occurs at the end of prometaphase of mitosis?
Kinetochore on sister chromatids attached to kinetochore microtubules from opposite poles.
Sister chromatids are pulled, between two poles.
The mitotic spindle is completely formed.
125
The pair of sister chromatids eventually align themselves along what in mitosis?
A plane called the metaphase plate.
126
When does a cell reach metaphse in mitosis?
When the cell reaches alignment along the metaphase plate.
127
What occurs during metaphase of mitosis?
Pair of chromatids are attached to both poles and become organized into a single row along the metaphase plate.
128
What happens when the organization of the chromatids is finished in metaphase of mitosis?
The chromatids equally distributed into two daughter cells.
129
What occurs during anaphase of mitosis?
The connection broken between chromatids. Each chromatid an individual chromosome linked to only one pole.
130
As anaphase proceeds, what happens in mitosis?
The chromosomes move toward pole they are attached. Involving shortening of kinetochore microtubles.
The two poles move farther apart due to polar microtubules.
131
What occurs during telophase of mitosis?
The chromosomes reach respective poles and decondense. The nuclear membrane re-forms for two separate nuclei.
The nucleoli will also reappear.
132
In most cases, what follows mitosis?
Cytokinesis
133
What is cytokinesis?
The two nuclei are segregated into separate daughter cells. It also segregates cell organelles, such as mitochondria and chloroplasts, into daughter cells.
134
In animal cells cytokinesis begins shortly after what?
Anaphase.
135
What occurs in cytokinesis in animal cells?
A contractile ring, composed of myosin motor proteins and actin filaments, assembles at the cytoplasmic surface of the plasma membrane.
Myosin hydrolyzes ATP, shortens the ring, constricting the plasma membrane forming cleavage furrow that ingresses, or moves inward. Ingression continues until the cell divides.
136
What causes the cleavage furrow in an animal cell to ingress?
Myosin motor proteins shorten the contractile ring, which is formed from actin proteins.
137
In plants, how are the two daughter cells separated?
By the formation of a cell plate.
138
What is a cell plate?
A structure that forms between two daughter plant cells that leads to the separation of the cells by the formation of an intervening cell wall.
139
In plant cells, what happens at the end of anaphase of mitosis?
Golgi-derived vesicles carrying cell wall materials are transported to the equator of a dividing cell. The fusion of these vesicles gives rise to the cell plate, which is a membrane-bound compartment. The cell plate begins in the middle of the cell and expands until it attaches to the mother cell wall. Once this attachement has taken place, the cell plate undergoes a process of maturation and eventually separates the mother cell into two daughter cells.
140
What is the results of mitosis and cytokinesis?
The production of two daughter cells having the same number of chromsomes as the mother cell. The two daughter cells are genetically identical.
141
What is the function of microtubules during mitosis?
a. aster microtubules are important for the positioning of the spindile apparatus within an animal cell and in the process of cell division.
b. polar microtubules play a role in the separation of the two poles.
c. kinetochore microtubules aid in the alignment of chromosome during metaphase and the movement of individual chromsomes toward a pole during anaphase.
d. all of the above.
d. all of the above.
142
Which phase of mitosis is depicted in the drawing below?
| the chromatids have divided and are being separated
Anaphase.
143
Diploid eukaryotic cells may also divide by an alternative process called what?
Meiosis
144
What is meiosis?
A form of nuclear division in which the sorting process results in the production of haploid cells from a dipolid cell.
145
What are haploid cells?
The phenomenon that gametes contain half the genetic material found in somatic cells. For a speccies that is diploid, a haploid gamete contains a single set of chromosomes.
146
For meiosis to happen, what must occur?
The chromosomes mut be correctly sorted and distributed in a way that reduces the chromosome number to half its original value.
147
How is meiosis similar to mitosis?
Meiosis begins after a cell has progressed through the G1, S, and G2 phases of the cell cycle.
148
How is meiosis different to mitosis?
Meisosis involves two successive diisions rather than one
149
In meiosis, the single replication event is followed by what?
Two sequential cell divisions called meiosis I and II.
150
What are the subdivisions of meiosis I and meiosis II?
```
Prophase
Prometaphase,
Metaphase
Anaphase
Telophase
```
151
What are the subdivisions of prophase of Meiosis I?
```
Leptotene
Zygotene,
Pachytene
Diplotene
Diakinesis.
```
152
What occurs during the leptotene stage of prophase of meiosis I?
The replicated chromosomes begin to condense and become visible with a light microscope.
153
What occurs in the zygotene stage of prophase of meiosis I?
The recognition process known as synapsis, which involves the formation of a synaptonemal complex that forms between the homologous chromosomes.
154
What is synapsis?
The event in which homologous chromosomes recognize each other and then align themselves along their entire lengths.
155
What occurs in the pachytene stage of prophase of meiosis I?
The homologs have become completely aligned. The bivalents contain two pairs of sister chromatids, or four chromatids.
When synapsis is complete crossing over occurs. The connection that results from crossing over is called a chiasma
156
What are bivalents?
A structure in which two pairs of homologous sister chromatids have synapsed with each other.
157
What is another name for a bivalent?
A Tetrad
158
What is a tetrad?
The association among four sister chromatids during meiosis.
| A groups of four fungal spores contained within an ascus.
159
What is crossing over?
A physical exchange of chromosomes pieces that most commonly occurs during prophase of meiosis I.
160
What does crossing over involve?
A physical exchange of chromosome pieces.
161
Depending on the size of the chromosome determines What?
The number of crossovers.
| (ex. An average eukaryotic chromosome incurs a couple dozen crossovers.
162
Crossing over is usually critical for what?
Proper segregation of chromosomes.
163
Abnormalities in chromosome segregation may be related to what?
A defect in crossing over.
164
What is a chiasma?
The site where crossing over occurs between two chromosomes. It resembles the greek letter chi, X.
165
What happens in the diplotene stage of prophase of meiosis I?
The synaptonemal complex has largely disappeared. The bivalent pulls apart slightly, and microscopically it becomes easier to see that it is actually composed of four chromatids.
166
What occurs in diakinesis of prophase of meiosis I?
The synaptonemal complex completely disappears.
167
What occurs in prometaphase of meiosis I?
The spindle apparatus is complete, and the chromatids are attached via kinetochore microtubules .
168
How do the four cells at the end of meiosis differ from the original mother cell?
The cells are haploid, whereas the mother cell is diploid.
169
What occurs during metaphase of meiosis I?
The bivalents are organized along the metaphase plate, in a double row instead of a single row like in mitosis and within the double row the sister chromatids are random in regards to red and blue homologs.
Also, one pair of sister chromatids is linked to one of the poles, and the homologous pair is linked to the opposite pole. This is different from mitosis in which a pair of sister chromatids is linked to both poles.
170
How is the attachment of chromosomes to kinetochore microtubules different from their attachment during metaphase of mitosis?
In mitosis, each pair of sister chromatids is attached to both poles, whereas in metaphase of meiosis I, each pair of sister Chromatids is attached to just one pole.
171
What occurs in anaphase of meiosis I?
The two pairs of sister chromatids within a bivalent separate from each other, however the connection that holds the sister chromatids together does not break. Instead, each joined pair of chromatids migrates to one pole, and the homologous pair of chromatids moves to the opposite pole.
172
What occurs in telophase of meiosis I?
Decondensation occurs, in most species.
The nuclear membrane re-forms to produce two separate nuclei. The end result of meiosis I is two cells, each with three pairs of sister chromatids. This is considered reduction division.
173
Why is meiosis I considered reduction division?
The original diploid cell had its chromosomes in homologous pairs, but the two cells produced at the end are considered to be haploid; and do not have pairs of homologous chromosomes.
174
Why does the reduction division occur in meiosis I?
The connection holding the sister chromatids together does not break during anaphase.
175
Meiosis II is similar to what, but what is different?
The sorting events that occur during meiosis II are similar to mitosis, but the starting point is different.
176
Explain the different starting points of Meiosis II and mitosis?
For a diploid organism with six chromosomes, mitosis begins with 12 chromatids that are joined as 6 pairs of sister chromatids.
By comparison, the two cells that begin meiosis II each have six chromatids that are joined as three pairs of sister chromatids; meiosis II begins with three dyads.
177
What is the resulting difference between meiosis and mitosis?
Mitosis produced two diploid daughter cells with six chromosomes each, whereas meiosis produced four haploid daughter cells with three chromosomes each.
In other words, meiosis has halved the number of chromosomes per cell.
Mitosis produces genetically identical results, Meiosis does not produce gentically identical haploid cells.
178
When does crossing over usually occur, and what is the end result?
a. It occurs during prophase of meiosis I, and the end result is the exchange of pieces between homologous chromosomes.
b. it occurs during prometaphase of meiosis I, and the end result is the exchange of pieces between homologous chromosomes.
c. it occurs during prophase of meiosis I, and the end result is the separation of sister chromatids.
d. It occurs during prometaphase of meiosis I, and the end result is the separation of sister chromatids.
a. It occurs during prophase of meiosis I, and the end result is the exchange of pieces between homologous chromosomes.
179
What is sexual reproduction?
The process whereby parents make gametes that fuse with each other in the process of fertilization to begin the life of a new organism.
180
What is gametogenesis?
The production of gametes.
181
Haploid cells are represented by what and diploid cells are represented by what?
1n
| 2n
182
WHat is isogamous?
A species that makes morphologically similar gametes.
183
What are examples of isogamous organisms?
Species of fungi and algae
184
Most eukaryotic species are what?
Heterogamous
185
What is heterogamous?
A species that produces two morphologically different types of gametes.
186
What are sperm cells?
A male gamete. Sperm are small and usually travel relatively far distances to reach the female gamete.
187
What is an egg cell?
Also known as an ovum; it is a female gamete that is usually very larage and nonmotile.
188
The sperm cell of most animal species usually contain what?
A single flagellum that enables them to swim.
189
In fern and nonvascular plants, the sperm may have what?
Multiple flagella
190
In flowering plants, the sperm are contained within what?
Pollen grains.
191
Where does spermatogenesis occur?
The testes
192
What is spermatogenesis?
The production of sperm cells.
193
The testes contain what, which do what?
Spermatogonial cells that divide by mitosis to produce two cells. One remains a spermatogonial cell, and the other cell becomes a primary spermatocyte.
194
The spermatocyte progresses through what?
Meiosis I and II to produce four haploid cells, which are known as spermatids.
195
Spermatids mature into what?
Sperm cells.
196
What is the structure of a sperm cell?
A long flagellum and a head.
| The head contains little more than a haploid nucleus and an organelle at its tip, known as an acrosome.
197
What does the acrosome do?
It contains digestive enzymes that are released when a sperm meets an egg cell.
These enzymes enable the sperm to penetrate the outer protective layers of the egg and gain entry into the cell's cytosol.
198
What are polar bodies?
Small cells produced during oogenesis that degenerate.
199
What is oogenesis?
The production of egg cells.
200
Where does oogenesis occur?
Within specialized diploid cells of the ovary known as oogonia.
201
oogonia initiate what?
Meiosis to produce primary oocytes.
202
The primary oocytes are what and remain this way until what?
The oocytes are arrested-enter a dormant phase- at prophase of meiosis I, until the female reaches sexual maturity.
203
After sexual maturity, what happens to the oocytes?
Primary oocytes are periodically activated to progress through the remaining stages of oocyte development.
204
Meiosis of oocytes does what?
The first meiotic division is asymmetrical and produces a secondary oocyte and a much smaller cell, known as a polar body. Most of the cytoplasm is retained by the secondary oocyte and very little by the polar body, allowing the oocyte to become a larger cell with more stored nutrients. The second oocyte then begins meiosis II.
205
What is ovulation?
In mammals, the secondary oocyte is released from the ovary and travels down the oviduct toward the uterus.
206
During ovulation, what can happen?
If a sperm cell penetrates the secondary oocyte, it is stimulated to complete meiosis II; the secondary oocyte produces a haploid egg and a second polar body. The haploid egg and sperm nuclei then unite to create the diploid nucleus of a new individual.
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Plant species alternate between what?
Haplid and diplid generations.
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The haploid generation of plant cells is called what?
The gametophyte
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The diploid generation of plant cells is called what?
Sporophyte
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Certain cells in the sporophyte undergo what?
Meiosis and produce haploid cells called spores, which divide by mitosis to produce a gametophyte.
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The gametophytes of most plant species are what? Produced within what?
Very small structures produced within the much larger sporophyte.
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Meiosis occurs where in plants?
Within cells found in two different structures of the sporophyte: the anthers and the ovaries, which produce male and female gametophytes.
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Are all of the cells nuclei in the embryo sac haploid or is just the egg haploid?
All the nuclei in the embryo sac are haplid. The central cell has two haploid nuclei and all of the others, including the egg, have just one.
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What occurs in the anther?
Diploid cells called microsporocytes undergo meiosis to produce four haploid microspores. These separate into individual microspores. Each microspore undergoes mitosis to produce a two-celled structure containing one tube cell and one generative cell, both of which are haploid. This structure differentiates into a pollen grain. The generative cell undergoes mitosis to produce two haploid sperm cells. This mitosis only occurs if the pollen grain germinates.
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Female gametophytes of plant cells are produced where?
Within ovules found in the plant ovaries.
216
Megasporocyte undergoes what in the ovules of plant ovaries?
Meiosis to produce four haploid megaspores. Three of the four megaspores degenerate. The remaining haploid megaspore then undergoes three successive mitotic divisions accompanied by asymmetrical cytokinesis to produce seven individual cells--one egg, two synergids, three antipodals, and one central cell.
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What is the embryo sac in a plant cell?
The seven celled structure which containes: one egg, two synergids, three antipodals, and one central cell.
It is the mature female gametophyte.
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How does fertilization occur in a plant cell?
A pollen grain lands on a stigma, this stimulates the tube cell to sprout a pollen tube the grows through the style and eventually makes contact with an ovule. As this is occurring, the generative cell undergoes mitosis to produce two haploid sperm cells. The sperm cells migrate through the pollen tube and reach the ovule. One of the sperm cells enters the central cell, which contains the two polar nuclei. This results in a cell that is triploid. This cell divides mitotically to produce endosperm, which acts as a food-storing tissue. the other sperm enters the egg cell. the nuclei of both fuse to creat a diploid cell.
219
What is the different between animal production of gametes and plant production of gametes?
Animals produce gametes through meiosis, while plants produce them through mitosis.
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In animals, a key difference between spermatogenesis and oogenesis is that
a. only oogenesis involves meiosis
b. only spermatogenesis involves meiosis
c. spermatogenesis produces four sperm, whereas oogenesis produces only one egg cell.
d. none of the above.
c. spermatogenesis produces four sperm, whereas oogenesis produces only one egg cell.
221
Which of the following statements regarding plants is false?
a. meiosis within anthers produces spores that develop into pollen
b. meiosis within ovules produces spores that develop into an embryo sac.
c. the male gametophyte is a pollen grain, and the female gametophyte is an embryo sac.
d. meiosis directly produces sperm and egg cells in plants.
d. meiosis directly produces sperm and egg cells in plants.
222
What is x-linked inheritance?
An inheritance pattern in certain species that involves genes that are located only on the x chromosome.
223
What is the chromosome theory of inheritance?
A theory of Sutton and Bovaeri that the inheritance patterns of traits can be explained by the transmission patterns of chromosomes during gametogenesis and fertilization.
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What is the first fundamental principle for the chromosome theory of inheritance?
Chromosomes contain the genetic material that is tranmitted from parent to offspring and from cell to cell.
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What is the second fundamental principle for the chromosome theory of inheritance?
Chromosomes are replicated and passed along, generation after generation, from parent to offspring. They are also passed from cell to cell during the development of a multicellular organism. Each type of chromosome retains its individuality during cell division and gamete formation.
226
What is the third fundamental principle for the chromosome theory of inheritance?
The nuclei of most eukaryotic cells contain chromsomes that are found in homologous pairs-- they are diplid. One member of each pair is inherited from the mother, the other from the father. At meiosis, one of the two members of each pair segregates into one daughter nucleus, and the homolog segregates into the other daughter nucleus. Gametes contain one set of chromsomes-- they are haploid.
227
What is the fourth fundamental principle for the chromosome theory of inheritance?
During the formation of haploid cells, different types of chromosomes segregate independently of each other.
228
What is the fifth fundamental principle for the chromosome theory of inheritance?
Each parent contributes one set of chromsomes to its offspring. The maternal and paternal sets of homolgous chromosomes are functionally equivalent; each set carries a full complement of genes.
229
At which stage do homolgous chromosomes separate from each other?
Anaphase of meiosis I.
230
Let's suppose a pea plant is heterozygous for three genes, Tt Yy Rr, and each gene is on a different chromosome. How many different ways could the three homologous chromosomes line up during metaphase of meiosis I?
8 different ways.
231
What is the difference between the X-Y and X-0 systems of sex determination?
In the X-Y system, the presence of the Y chromosome causes maleness, whereas in the X-) system, it is the ratio between the number of X chromosomes and number of sets of autosomes that determines sex. A ratio of 0.5 is male and 1.0 is female.
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What are autosomes?
Chromosomes that are not sex chromosomes.
233
What gene on the Y chromosome plays a key role in the devleopment of male characteristics?
The Sry gene
234
The X-0 system determines sex in what types of organisms?
Insects mostly
235
The Z-W system determines sex in what organisms?
Birds and some fish
236
In the Z-W system what determines male or female?
Male is homogametic, and female is heterogametic, which is opposite of the X-Y
237
The haploidiploid system determines the sex in what organism?
Bees.
238
How does the haploidiploid system work?
Males are produced from unfertilized haploid eggs.
| Female bees, are preoduced from fertilized eggs and are diploid.
239
In certain reptiles and fish, how is sex determined?
By environmental factors such as temperature.
For alligators, if the fertilized eggs are at 33 degrees C they produce males, if below or above 33 degrees then they produce females.
240
What was one of Thomas Hunt Morgan's most famous studies?
Raised fruit flies in the dark to see if atrophy or mutation of the eyes would occur. Eventually a fruit fly with white eyes was breed contrast to the normal red eyes.
He then cross bred that fruit fly with many others. The F1 offspring all had red eyes when mixed with a red eyed female. So red eye is dominant.
The white allele is located on the X chromosome.
241
What type of science was Thomas Hunt Morgan's experiement?
Discovery-based science, rather than hypothesis testing.
242
Which of the following is not one of the tenets of the chromosome theory of inheritance?
a. chromosomes contain the genetic material that is transmitted from parent to offspring and from cell to cell.
b. chromosomes are replicated and passed along, generation after generation, from parent to offspring.
c. chromosome replication occurs during the S phase of the cell cycle.
d. Each parent contributes one set of chromosomes to its offspring.
c. chromosome replication occurs during the S phase of the cell cycle.
243
A pea plant has the genotype TtRr. The independent assortment of these two genes occurs at ___________ because chromosomes carrying the ________ alleles line up independently of the chromosomes carrying the ________ alleles.
a. metaphase of meiosis I, T and t, R and r
b. Metaphase of meiosis I, T and R, t and r
c. metaphase of meiosis II, T and t, R and r
D. metaphase of meiosis II, T and R, t and r.
a. metaphase of meiosis I, T and t, R and r
244
In mammals, sex is determined by what?
a. the Sry gene on the Y chromosome
b. having two copies of the X chromosome
c. having one copy of the X chromosome.
d. Both a and c.
a. the Sry gene on the Y chromosome
245
An abnormal fruit fly has two sets of autosomes and is XXY. Such a fly would be
a. a male
b. a female.
c. hermaphrodite
d. none of the above.
b. a female.
246
What is a homolog? With regard to genes and alleles, how are homologs similar to and different from each other?
The members of a chromosome pair. Homologs are usually the same size and carry the same types and order of genes. They may differ in that the genes that carry may be diffeent alleles.
247
With regard to sister chromatids, which phase of mitosis is the organization phase, and which is the separation phase?
Metaphase
| Anaphase
248
How does the attachment of kinetochore microtubules to the kinetochore differ in metaphase of meiosis I from metaphase of mitosis? Discuss what you think would happen if a sister chromatid was not attached to a kinetochore microtubule.
In metaphase I of meiosis, each pair of chromatids is attached to only one pole via the kinetochore microtubules. In metaphase of mitosis, there are two attachements. If the attachement was lost, a chromosome would not migrate to a pole and may not become enclosed in a nuclear membrane after telophase. If left out in the cytoplasm, it would eventually be degraded.
249
Describe the key events during meiosis that results in a 50% reduction in the amount of genetic material per cell.
The reduction occurs because there is a single DNA replication event but two cell dividions. Because of the nature of separation during anaphase I, each cell receives one copy of each type of chromosome.
250
The arrangement of homologs during metaphase of meiosis I is a random process. In your words, expalin what this means.
The maternally derived and paternally derived chromosomes are randomly aligned along the metaphase plate during metaphase I.
251
If a diploid cell contains six chromosomes, how many possible random arrangments of homologs could occur during metaphase of meiosis I?
There are three pairs of chromosomes.
2^n
n= the number of chromosomes per set. So 2^3=8
252
Why is it necessary for the chromosomes to condense during mitosis and meiosis? What do you think might happen if the chromosomes were not condensed?
If they didn't condense they might get tangled with each other and not sort properly. The condensation process occurs so that the chromosomes easily align along the equatorial plate during metaphase without getting tangled up.
253
The period between miosis I and meiosis II is called interphase II. Does DNA replication take place during interphase II?
No, the chromosomes at the end of telophase I have already replicated.
254
At puberty, the testes contain a finite number of cells and produce an enormous number of sperm cells during the life span of a male. Explain why testes do not run out of spermatogonial cells.
One cells reamins a spermatogonial cell to maintain the population of spermatogonial cells.
