Bio 1113 - Unit 9 - Mitosis, Meiosis, and Cancer
List the phases of mitosis and describe the events that take place in each
*1) Prophase* - Chromosomes condense further, nuclear envelope breaks down, mitotic spindle begins to form, nucleolus disappears *2) Prometaphase*: Nuclear envelope completely fragments; Mitotic spindle fully formed, spindle fibers attach to chromosomes *3) Metaphase*: Chromosomes align on a plane in the center of the cell, called the metaphase plate *4) Anaphase*: Sister chromatids separate and move to opposite poles of the cell *5) Telophase*: Spindle dismantled, nuclear envelope forms around chromosomes at each pole, chromosomes begin to decondense, nucleoli reappear
Haploid
- 1 set of chromosomes; "n"
Sister Chromatids
- 2 copies of a duplicated chromosome that remain attached to each other
If a diploid cell goes through mitosis, how many daughter cells will be formed? Will the daughter cells be diploid or haploid?
- 2 daughter cells formed - daughter cells will be diploid
Diploid
- 2 sets of chromosomes; "2n"
What kinds of proteins can tumor-suppressor genes code for?
- 2 types: 1) Proteins that maintain genome integrity: either by DNA repair or prevention of damage 2) Proteins that negatively regulate cell division: either by repressing gene transcription, or by over-promoting cell division
What are the 3 phases of Interphase? During which phase does DNA Replication take place? Describe the chromosomes after replication
- 3 Phases of Interphase: 1) G1 Phase (First Gap) 2) S Phase (Synthesis) 3) G2 Phase (Second Gap) - DNA Replication takes place during S phase - After replication, the chromosomes are more dense and are attached at the centromere, forming Sister Chromatids, which are 2 identical copies of the same chromosome joined together
If a diploid cell goes through meiosis, how many daughter cells will be formed? Will the daughter cells be diploid or haploid?
- 4 daughter cells formed - daughter cells will be haploid
Kinetochore
- A group of proteins that bind to a centromere and are necessary for sorting each chromosome
Metaphase Plate
- A plate halfway between the poles of the spindle apparatus on which the sister chromatids align during the metaphase stage of mitosis
Cyclin
- A protein responsible for advancing a cell through the phases of the cell cycle by binding to a cyclin-dependent kinase
Fill in the blanks and then put the following events in order, starting with events that occur immediately after the cell was born. Use the following key for the blanks: M, G1, G2, S. A The ____________________phase occurs between chromosome replication and mitosis. B During ___________________ phase, the shortest phase, the cell undergoes both mitosis and cytokinesis. C During _______________phase, the genetic material undergoes replication. D The _________________phase is when most cell growth will occur; DNA is unreplicated.
A. G2 B. M C. S D. G1 Order: D, C, A, B
Humans have __________ different types of autosomes.? a. 46 b. 44 c. 23 d. 22 e. 11
b. 44
The cell cycle consists of several checkpoints at which the cycle can be stopped before restarting. Which of the following is not a function of these checkpoints?? a. Limiting the amount of daughter cells that might contain genetic abnormalities b. Supplying energy for the replication of chromosomes into pairs of sister chromatids c. Preventing the start of mitosis until all chromosomes are fully replicated d. Making sure chromosomes are correctly replicated before nuclear division is complete e. Ensuring that conditions are favorable for DNA replication and cell division
b. Supplying energy for the replication of chromosomes into pairs of sister chromatids
Homologous chromosomes are identical copies of each other. a. True b. False
b. false
Mitotic cell division is never used by organisms as a means of reproduction. a. True b. False
b. false
The life cycle of a sexual reproducing organism includes:?? a. mitosis and meiosis b. mitosis, meiosis, and fusion of the gametes. c. meiosis and fusion of gametes d. only mitosis e. only meiosis
b. mitosis, meiosis, and fusion of the gametes
Chromosomes are replicated during the ______ phase. a. G1 b. G2 c. S d. M e. meta-
c. S
Meiosis I produces ________, and meiosis II produces _________ cells. a. two diploid, two haploid b. two diploid, 4 haploid c. two haploid, 4 haploid d. two haploid, two haploid e. two somatic, two gametic
c. two haploid, 4 haploid
Answer to question above:
d. a pair of homologous chromosomes
The Ras protein normally regulates cell growth. A mutation that occurs in the gene encoding Ras can cause Ras to become overactive, which results in cancer. This means that Ras is an example of a/an a. retrovirus b. tumor-suppressor gene c. carcinogen d. proto-oncogene. e. enhancer protein
d. proto-oncogene
Which of the following statements is incorrect concerning sister chromatids? a. The formation of sister chromatids doubles the amount of DNA in a cell b. Sister chromatids consist of two identical copies of a single homologue c. Sister chromatids are held together at the centromere d. Sister chromatids are formed during the S phase of the cell cycle e. Sister chromatids separate during telophase
e. Sister chromatids separate during telophase (actually separate during anaphase)
At the end of meiosis I: a. cells are haploid b. cells are diploid c. sister chromatids are in separate cells d. the homologous pairs are in separate cells. e. a and d f. b and c
e. a and d
Sister chromatids separate during: a. prophase of meiosis I b. metaphase of meiosis I c. metaphase of meiosis II d. prometaphase of meiosis I e. anaphase of meiosis II
e. anaphase of meiosis II
Consider a diploid species where n=5 (n is the number of chromosomes per set). If an individual of this species was found to have 11 chromosomes, it would be categorized as a. polyploidy b. aneuploid c. trisomic d. monosomic. e. both aneuploid and trisomic
e. both aneuploid and trismoic
The first division of meiosis is called a reduction division. This is because a. the purpose of meiosis is to divide into four smaller cells b. the chromosomes are much more highly condensed than in mitosis c. the products of the first division are diploid but then discard some chromosomes d. the number of chromosomes per cell stays the same after the first division e. the mother cell is diploid, but the products of the first division are haploid
e. the mother cell is diploid, but the products of the first division are haploid
Cyclin-Dependent Kinase (cdk)
- A protein responsible for advancing a cell through the phases of the cell cycle. Its function is dependent on the binding of a cyclin
Somatic Cell
- All cells in the body other than germ cells and gametes; Diploid cells
Aneuploidy
- An alteration in the number of particular chromosomes so that the total number of chromosomes is not an exact multiple of a set - Either having too many or too few chromosomes
Oncogene
- An altered gene whose product can act in a dominant fashion to help make a cell cancerous - A type of mutant gene derived from a proto-oncogene. An oncogene is overactive, thus contributing to uncontrolled cell growth and promoting cancer.
How is cytokinesis different in an animal cell compared to a plant cell?
- Animal Cell: Involves a ring of actin filament that constricts; forming a cleavage furrow; which eventually splits the cells. - Plant Cell: Involves vesicles derived from Golgi Apparatus; vesicles fuse, forming a cell plate; Cell plate grows outward until reaching the membrane.
Autosome
- Any chromosome not involved in determining sex
Binary Fission
- Asexual reproductive method in prokaryotes - The process of cell division in bacteria and archaea in which one cell divides into two cells
How is asexual reproduction different from sexual reproduction? Binary fission in prokaryotes is an example of which form of reproduction?
- Asexual: One parent; offspring genetically identical to parent - Sexual: 2 parents; offspring genetically unique - Binary fission in prokaryotes is an example of Asexual Reproduction
Answer to question above:
c. centromere
Describe the cell cycle control system Describe how cyclins and cyclin-dependent kinases work in this system
- Cell Control System: Several checkpoints in the cell cycle in which the cycle can be arrested if previous events have not been completed 1) G1 Checkpoint: Is environment favorable? If so , enter S phase 2) G2 Checkpoint: Is all DNA Replicated? If so, enter M phase 3) Metaphase Checkpoint: Are all chromosomes attached to the spindle? If so, exit Metaphase - Cyclins: If present: bind to Cyclin Dependent Kinases - Cyclin Dependent Kinases: If have Cyclin bound to them, they trigger steps in Mitosis - M-Cdk: Triggers mitosis machinery - S-Cdk: Triggers DNA replication machinery
Germ Cell
- Cell that gives rise to gametes; Diploid cells
Draw a chromosome in metaphase during mitosis. Label and describe the following: Centromere and Kinetochore
- Centromere: Constricted Region of a mitotic chromosome that holds sister chromatids together. Site where kinetochore forms - Kinetochore: Protein complex that forms on the centromere; captures microtubules from the mitotic spindle which pull apart the chromosome
Sex Chromosome
- Chromosomes involved in determining sex (X and Y)
When does crossing over occur? Explain what occurs during crossing over?
- Crossing over occurs during Prophase I - During crossing over, homologous chromosomes synapse together, forming a bivalent/tetrad. Then similar segments of DNA switch between adjacent chromosomes. The chiasma is the area where crossing over occurs.
How many times is the DNA replicated before Meiosis? Is the DNA replicated another time during Meiosis?
- DNA replicated only once before meiosis - No, DNA is not replicated during meiosis
Zygote
- Diploid cell produced in fertilization; - Diploid cell the result of fertilization of 2 haploid gametes
Chromosome
- Discrete unit of genetic material composed of DNA and associated proteins - Eukaryotes have chromosomes in their cell nuclei and in plastids and mitochondria
Describe the different events that take place during interphase
- G1 (First Gap): Primary growth phase of cell; majority of time spent in G1 - S (Synthesis): DNA Replication; forms sister chromatids - G2 (Second Gap): Replication of mitochondria, condensation of chromosomes, synthesis of microtubules
What is the relationship between gametes and a zygote?
- Gametes are haploid reproductive cells, that when they fuse, form a zygote - Male (sperm) and Female (Ova) are gametes. When they fuse and fertilize, they produce a zygote (diploid) which will turn into a multi-cellular organism
Tumor Suppresor Gene
- Gene that appears to help prevent formation of a cancer. Loss-of-function mutations in such genes favor the development of cancer
What is the relationship between germ cells and gametes?
- Germ cells are the cells that give rise to the gametes. Diploid germ cells undergo meiosis to produce haploid gametes
Monosomic
- Having 1 too few chromosomes - Can only have a missing X chromosome; all other monosomies not viable
Trisomic
- Having 1 too many chromosomes - Only a few viable trisomies (down syndrome, etc)
Bivalent
- Homologous pairs of sister chromatids associated with each other, lying side by side - Complex formed when homologous chromosomes are synapsed together
Cleavage Furrow
- In animal cells, an area that constricts like a drawstring to separate the cells during cytokinesis
Cell Plate
- In plant cells, a structure that forms a cell wall between the two daughter cells during cytokinesis
Explain independent assortment. How many different alignments could occur during metaphase I?
- Independent Assortment: each pair of homologous chromosomes sorts independently of other pairs when lining up on metaphase plate of Metaphase I. This random sorting produces genetic variation - In a human cell, there are 8.4 million different ways that homologous chromosomes could align
What gets separated during meiosis I? What gets separated during meiosis II?
- Meiosis I: Homologous chromosomes separated - Meiosis 2: Sister chromatids separated
What aligns along the center of the cell during metaphase I and how is this different from metaphase II?
- Metaphase I: Paired homologous chromosomes align down the center of the cell - Metaphase II: Sister chromatids align down the center of the cell
Describe the Mitotic Spindle What are the 3 types of Microtubules that make up the Mitotic Spindle?
- Mitotic Spindle: - Growth of microtubules begins at the centrosomes (at each pole); - Two centrosomes formed during interphase move apart during prophase and prometaphase; - Each centrosome defines a pole of the mitotic spindle - Types of Microtubules: *1) Kinetochore Microtubules*: Attach to the centrosome at the Kinetochore protein; *play a role in separating the sister chromatids from each other* *2) Polar Microtubules*: Overlapping microtubules from each pole; *play a role in separating the two poles from each other* *3) Astral Microtubules*: *Play a role in correctly positioning the mitotic spindle within the cell*
What are the properties of a cancer cell?
- More self-sufficient than normal cells for growth/proliferation - Relatively insensitive to anti-proliferative extracellular signals - Less prone than normal cells to undergo apoptosis (cell suicide) - Defective in intracellular control mechanisms that normally stop cell division permanently in response to stress - Induce help from normal stromal cells in local environment - Induce angiogenesis (growth of new blood vessels from existing blood vessels) - Escape from their home tissues and survive and proliferate in foreign sites - Genetically unstable - Either produce telomerase, or acquire another way of stabilizing their telomeres
Do normal cells get converted into malignant cells by a single mutation?
- No. Several mutations needed to convert normal cells to cancer cells
Are all sexual life cycles the same?
- No. Vary across animals, plants, etc.
What is nondisjunction? How is it related to aneuploidy? What is the difference between a trisomic animal and a monosomic animal? What does it mean if a human has trisomy 21?
- Nondisjunction: Error in Meiosis where chromosomes fail to separate, resulting in abnormal number of chromosomes. 2 ways it can happen: 1) Homologous chromosomes fail to separate from each other in Meiosis 1 2) Sister chromatids fail to separate from each other in Meiosis II - Aneuploidy is having 1/few too many or 1/few too few chromosomes. It is a direct result of nondisjunction - Trisomic Animal: Has *1 too many* chromosomes - Monosomic Animal: Has *1 too few* chromosomes - Trisomy 21 in humans: 3 copies of gene 21, usually results in down syndrome
Proto-Oncogene
- Normal gene, usually concerned with the regulation of cell proliferation, that can be converted into cancer promoting oncogene by mutation - A normal gene that, if mutated, can become an oncogene
Homologous Chromosomes
- Pair of chromosomes that carry the same set of genes
What are the normal roles of some of the genes involved in cancer?
- Proto-oncogene: Normal gene, usually concerned with regulation of cell proliferation - Oncogene: Altered gene whose product can act in a dominant fashion to help make a cell cancerous - Tumor Suppressor Gene: Gene that appears to help prevent formation of a cancer. Loss-of-function mutations in such genes favor the development oc cancer. Have to have both copies of a gene lose their function to have development of cancer.
Sexual Reproduction
- Reproduction involving 2 parents; offspring not genetically identical to parents - A process that requires a fertilization event in which two gametes unite to produce a cell called a zygote
Asexual Reproduction
- Reproduction involving one parent; offspring genetically identical to parent - A reproductive strategy that occurs when offspring are produced from a single parent, without the fusion of gametes from two parents. The offspring are therefore clones of the parent.
Gamete
- Reproductive cells; haploid
Centrosome
- Single structure near the cell nucleus of eukaryotic cells that forms a nucleating site for the growth of microtubules; also called the MTOC
What aligns along the metaphase plate in Mitosis? How many of these things would align along the metaphase plate in a human cell? What separates during anaphase in Mitosis?
- Sister Chromatids align along the metaphase plate in Mitosis - 23? - Sister Chromatids separate during anaphase in Mitosis
Tetrad
- Synonym for bivalent; the complex formed when homologous chromosomes are synapsed together
Chiasma (pl: chiasmata)
- The connection at a crossover site of two chromosomes - Site of crossing over of homologous chromosomes
Crossing Over
- The exchange of genetic material between homologous chromosomes during meiosis; allows for increased variation in genetic information that each parent may pass to the offspring
Synapsis
- The process of forming a bivalent; homologous chromosomes "synapse" together
Independent Assortment
- The random sorting of each pair of homologous chromosomes when lining up on metaphase plate in Meiosis I. Provides genetic assortment because there is a 50% chance of homologous chromosomes lining up on either side of the metaphase plate. - To calculate: 2 to nth power (n = number of pairs of chromosomes)
Centromere
- The region where the two sister chromatids are tightly associated; the centromere is an attachment site for kinetochore proteins
Mitotic Spindle
- The structure responsible for organizing and sorting the chromosomes during mitosis; also called the mitotic spindle apparatus
Fill in the blanks: 1) The ends of eukaryotic chromosomes are called _____? 2) The parts of chromosomes where the spindle apparatus will attach are called ____? 3) When a single chromosome has undergone DNA replication, it consists of two ____? 4) Each pair of human chromosomes (for example, two copies of chromosome 17) is called a pair of ____? 5) A single, unreplicated chromosome consists of a single ____?
1) Telomeres 2) Centromeres 3) Sister chromatids 4) Homologous chromosomes 5) double stranded DNA molecule
Which of the following is a false statement about the haploid/diploid life cycles of animals, plants, or fungi? a. Meiosis is used to produce diploid cells when haploid gametes fuse b. In most animals, haploid sperm and eggs fuse to make a diploid zygote c. In multicellular fungi, somatic cells are haploid most of the time d. Some plants can have a haploid generation and a diploid generation e. Mitosis generates a multicellular organism in plants, animals, and fungi
a. Meiosis is used to produce diploid cells when haploid gametes fuse
Answer to question above:
a. Sister Chromatids
Fill in the blank with the correct term that applies to the following statements about Prophase I of meiosis. a. The process of pairing of homologous chromosomes is called ____________. b. A physical exchange of material between two homologous chromosomes is called _____________.
a. Synapsis b. Crossing over
Sexual life cycles include both haploid and diploid stages. a. True b. False
a. true
A gene encodes a protein that normally functions in promoting the programmed cell death of blood cells that have accumulated damage to DNA. A mutation in this gene can result in leukemia (cancer of the blood). This gene is an example of a/an?? a. tumor-suppressor gene b. epidermal growth factor c. cell cycle regulator d. sarcoma viral gene e. proto-oncogene
a. tumor-suppressor gene
Consider an organism whose karyotype shows it to have a total of 60 chromosomes. How many chromosomes would be contained in the sperm of this organism? a. 23 b. 30 c. 46 d. 60 e. 90
b. 30