Review questions 5 Flashcards
1] What is the difference between a gene and a genome? True or False: Most cells contain a copy of the entire genome of an individual. How does the information contained in the genome control the development, growth & activity of an individual? hint: recall the Central Dogma of genetic inheritance…be able to explain this concept (from Week 4 material). Are all of the genes present in the genome being actively transcribed into mRNA and then translated into protein? What is meant by gene expression? [see Chapter 9]
A gene is an inheritable sequence of nucleotides that codes for a protein which may have phenotypic effects on our body. However a genome is the whole genetic make up of an organism. T: almost every cell contains a complete copy of these instructions.The information is contained in the DNA, and most of these amino acids needed to control development is also in an individuals diet. Also, the proteins that help with this dictate cell function. Central Dogma is the main thesis for molecular inheritance, it states that DNA makes RNA which is protein. DNA acts as a template for its own replication and transcription to RNA. Translation is RNA to proteins. Gene expression is genes encode proteins and genes expressed in a particular cell determine what they can do
2] What is a chromosome? Where is the chromosome located in prokaryotes? In eukaryotes? What is the main structural difference between a typical prokaryotic chromosome and chromosome(s) in eukaryotic organisms? Do all eukaryotic organisms have 23 pairs of chromosomes? Are all eukaryotes diploid (2n)? For eukaryotes: How can you distinguish an unduplicated chromosome from a duplicated chromosome? What is meant by the term homologous chromosomes? True or False: one member of a homologous pair of chromosomes is derived from the maternal parent and the other from the paternal parent.
Located in the nucleus of each cell, it is DNA molecules packaged into thread like structure where hereditary information is transmitted from one generation to the next. In the prokaryote cell its in the cytoplasm, it is a single chrosome plus plasmids. A difference is that prokaryote has circular structure. Human Eukaryotic organisms have 23 pairs, not everything. Yes. Homologous chromosomes is two chromosomes, one of paternal, one of maternal, identical in appearance and pair during meiosis. T
3] What is meant by a ‘cell cycle’? Describe the stages beginning w/G1 (cells enter this stage immediately after mitosis). What happens in each stage? Include the three stages of Interphase as well as the stages of Mitosis. True or False: Mitosis ensures that each daughter cell receives an exact copy of each chromosome. How many daughter cells are produced during mitosis? If the original parent cell is diploid (2n) what is the ploidy of the new daughter cells? Are they genetically identical to each other? To the original parent? Why might it be important for mitosis to maintain the chromosome number (ploidy)?
Cell cycle is a series of events that take place in a cell leading to its division and duplication (replication) that produces two daughter cells. Cell with chromosome in the nucleus in G1, then DNA sytnthesis, chromosome duplication STAGE S then G2 cell with duplicated chromosome then Mitosis is where chromosome separation occurs and cell division finally occurs. T. 2 daughter cells is produced. They are all identical. The ploidy is haploid cells.
4] Refer to the figure showing the mitotic stages on page 181 of your text. Focus on the images of mitosis in onion cells and the accompanying diagram and follow the movement of the chromosomes as well as the changes in the nuclear membrane and the formation/dis-assembly of the mitotic spindle. Be able to describe what happens in each stage. [It would be a good idea to integrate this information with the simplified diagram you drew in class]. What is the function of centrosomes & centrioles in animal cells? How many of each are present in the cell? During Interphase? During Mitosis? Are these structures present in plant cells? If not, do plant cells utilize a mitotic spindle? What is the significance of the mitotic spindle—how & when does it ‘capture’, stabilize, and separate the sister chromatids of a chromosome?
Interphase-cell is engaged in activity and preparing its for mitosis. Prophase- chromatin in the nucleus begins to condense and become visible, centrioles begin moving to opposite ends of the cell and fivers extend from the centromeres. Some fibers cross the cell to form the mitotic spindle. ProMetaphase- nuclear membrane dissolves and proteins attach to the centromeres creating kinetochores. Microtubules attach at the kinetochores and the chromosomes begin moving. Metaphase- spindle fibers align the chromosomes along the middle of the cell nucleus. Line is referred as metaphase plate. Anaphase- the paired chromosomes separate at the kinetochores and move to opposite sides of the cell. Telophase- chromatids arrive at opposite poles of cell, a new membrane forms around the daughter nuclei. Spindle fivers disperse, and the cell is almost becoming two. Cytokinesis- results when fiber ring composed of a protein called actin around the center of the cell contracts pinching the cell into two daughter cells each with one nucleus. Centrosomes consist of two centrioles, the centrioles are needed to organize the centrosome for when they start duplicating. 2 centrioles in each cell. They are present in the S phase of the cell cycle which is the synthesis of DNA. The centrosome is also in plant cells but plant cells do not have centrioles. Mitotic spindle segregates chromosomes of two daughter cells during mitosis, which are done with the microtubule polymers whose intrinsic polarity and dynamic properties are cirtical for bipolar spindle organization and functions.
5] True or False: Chromosomes exist in a diffuse, thread-like stage during Mitosis, and undergo higher order packaging (formation of nucleosomes, coiling & super-coiling) to return to the condensed form during Interphase. You can refer to figure 8.2 to visualize the differences in structure.
During interphase (1), chromatin is in its least condensed state and appears loosely distributed throughout the nucleus. Chromatin condensation begins during prophase (2) and chromosomes become visible. Chromosomes remain condensed throughout the various stages of mitosis (2-5).
6] True or False: Chromosomes are replicated during G1-phase and consist of two identical sister chromatids held together by their centromeres (which replicate at the same time). At which stage of Mitosis are the sister chromatids separated? How are they separated? (What is the role of the microtubules of the mitotic spindle and the centromere? What is a kinetochore molecule?) Are motor proteins involved in this process? Once the sister chromatids have been separated, they are known as ________________________________ and enter Interphase.
False, they are duplicated in the S-phase. They are completely separated during cytokinesis. Microtubules align chromosomes. Mitotic spindle are how microtubules organize into, they are used to position the chromosomes at a specific position inside the cell. Centrosomes anchors one end, its duplicated during S phase and the two copies move to opposite sides of the cell. Also reffered to as spindle poles. Kinetochore is a protein structure that assembles in the centromere during mitosis. It assembles on each side of the chromosome of each chromatid. Yes, motor proteins utilize the energy of ATP to move along microtubules. They are known as daughter chromosomes.
7] How does cytokinesis occur in animal cells? Plant cells? What is the difference between a cleavage furrow and a cell plate?( Refer to Figure 11.7)
In animal cells a “cleavage furrow” appears as the cell is pinched in two from the outer edges. In plant cells, a cell plate begins at the center of the cell and grows out to the cell membrane. A cleavage furrow contractile microfilaments pull the plasma membrane inward, a cell plate uses vesicles containing building materials fuse with one another to from the dislike cell plate between the two new cells.
8] Multiple Choice: Which of the following is true of telomeres? A) these are non-coding DNA sequences that protect the coding portion of the chromosomes B) these non-coding DNA sequences shorten each time a cell replicates its chromosomes C) these non-coding DNA sequences act as a limit on the number of times a cell can replicate (a cell undergoes cell death when they become too short) D) All are true
D. All are true
9] What is the difference between a neoplasm and a tumor? Between an oncogene and a proto-oncogene? Between a growth factor and a tumor suppressor? True or False: Neoplasms and tumors are always cancerous. True or False: Only a malignant neoplasm or tumor is considered cancerous. What is meant by the term metastasis? What are the other two characteristics of malignant cells?
False. True. Neoplasm: a group of cells that lost control over how they grow and divide, a lump that grows from the neoplasm is called a Tumor.
Oncogene: is any gene that helps transform a normal cell into a tumor cell, Proto-oncogene: genes encoding proteins that promote mitosis.
Metastasis: when malignant tumors break loose and invade other parts of the body. (cancer spreading)
Two characteristics of malignant cells: capillary blood supply may increase abnormally, cytoplasm and plasma membrane may are altered.
10] True or False: Mitosis accounts for growth, repair & replacement of somatic cells (and for asexual reproduction) whereas Meiosis (in germ cells) is the basis for sexual reproduction. True or False: Mitosis halves the chromosome number in offspring (each daughter cell receives one half of the genetic information of the parent cell) True or False: Meiosis halves the chromosome number in offspring (each daughter cell receives one half of the genetic information of the parent cell) True or False: Mitosis follows a single DNA replication event and one nuclear division to result in four identical, haploid daughter cells. True or False: Meiosis follows a single DNA replication event and two nuclear divisions to result in four identical, diploid daughter cells. Why is Meiosis called reduction division? Which stage of Meiosis is responsible for the reduction? Which stage of Meiosis is similar to Mitosis?
True. False. True. False. False. Meiosis is called reduction division because the reduction in chromosome number occurs in Meiosis I, as we go from diploid to haploid cells.
Prophase I is responsible for reduction division. Prophase and Prophase I are similar.
11] What are alleles? True or False: Both member of a homologous pair of chromosomes always have the same alleles. True or False: Gametes are diploid (2n) and somatic cells are haploid (n). What are germ cells? Explain how the fusion of two gametes restores the diploid (2n) condition in a zygote. Refer to page 192-193 in your text. Follow the stages of Meiosis I and II in the animal cell and the accompanying diagram. [It would be beneficial to integrate this information with the simplified diagram of Meiosis that you were instructed to draw in Lab] What are the four stages of Meiosis I (reduction division); what happens in each stage? What are the four stages of Meiosis II; what happens in each stage? Describe the movement of the chromosomes, nuclear envelope and mitotic spindle. What is different about Meiosis I and Mitosis? What is similar about Meiosis II and Mitosis?
True. False. Meiosis I:
Prophase 1: Homologous chromosomes form tetrads and cross over. Mitotic spindle travels to opposite polls.
Metaphase 1: Tetrads line up at center, chromosomes attached to spindle fibers.
Anaphase 1: Homologous chromosomes separate
Telophase 1: Cell forms two haploid cells
Meiosis II:
Prophase II: Spindle fibers reform and attach to centromeres in prophase II.
Metaphase II: The chromosomes align on the metaphase plate during metaphase II in preparation for centromeres to divide in the next phase.
Anaphase II : chromosomes divide at the centromeres (like in mitosis) and the resulting chromosomes, each with one chromatid, move toward opposite poles of the cell.
Telophase II and Cytokinesis: Four haploid nuclei (containing chromosomes with single chromatids) are formed in telophase II. Division of the cytoplasm during cytokinesis results in four haploid cells. Note that these four cells are not identical, as random arrangements of bivalents and crossing over in meiosis I leads to different genetic composition of these cells.
Chromosomes: Condense, line up to equator, half of them gets dragged to the one pole by spindle fibers attached to asters and the other half gets dragged to the opposite pole. Then cytokinesis occurs
Similar/Different: Both mitosis and meiosis are associated with cytokinesis. The end result of both are daughter cells produced from a parent cell. The fundamental sequence of events in mitosis is the same as in meiosis (in meiosis it happens twice). Both processes include the breakdown of the nuclear membrane, the separation of genetic material into two groups, followed by cell division and the reformation of the nuclear membrane in each cells. The processes differ in two fundamental. Meiosis has two rounds of genetic separation and cellular division while mitosis only has one of each. In meiosis homologous chromosomes separate leading to daughter cells that are not genetically identical. In mitosis the daughter cells are identical to the parent as well as to each other.
12] Compare & Contrast Mitosis & Meiosis…address number of DNA replication events (chromosome duplication), number of nuclear divisions, ploidy of parent cell, number and ploidy of daughter cells; are the daughter cells genetically identical or unique? *Where is genetic variability introduced during Meiosis? Describe the formation of a tetrad—where does this occur? Why is this event significant? What is Cross-Over? (also called recombination) and how/where/when does this occur? True or False: Sister Chromatids undergo Cross-Over (if this is true, how can we tell? If this is false, why not?) True or False: Non-Sister Chromatids undergo Cross-Over (If this is true, what is the significance of this event? If this is false, what is wrong with this statement?) Explain the alternate patterns by which homologous pairs of chromosomes can be aligned on the equatorial plate of Meiosis I—what accounts for this pattern? Is it random? What is the significance of this event (in terms of genetic variability?) Refer to the diagram of Meiosis you drew in Lab—sketch out the results of Meiosis I and II if the tetrads lines up in the alternate pattern shown…how does this differ from your original results? Refer to Figure 12.7 in your text for an idea of the increasing complexity of random segregation of chromosomes as the number of chromosomes increases…this figure only shows 3 pairs of chromosomes—imagine 23 pairs!
Mitosis
Chromosomes are aligned at the equatorial plate in Metaphase in random order
Each Chromosome consists of two identical Sister Chromatids
During Anaphase, Sister Chromatids are separated
Meiosis
Homologous Chromosome Pairs form a Tetrad in Prophase I and ‘Cross-Over’
Homologous Chromosome Pairs are aligned at the equatorial plate in Metaphase I (alternative patterns)
Pairs are separated in Anaphase I
One homolog (2 Sister Chromatids each) to each pole
During Anaphase II, Sister Chromatids are separated
Genetic Variability: during meiotic metaphase I, and produces a gamete with a mixture of the organism’s chromosomes. Along with crossing over, independent assortment increases genetic diversity by producing novel genetic combinations
Tetrad: is the structure formed when the homologous double stranded chromosomes (4 chromatids) come together during the synapsis of meiosis. Crossing over is important because it results in new combinations of genetic material that were not found in the parent DNA. Recombination: The process of producing new genetic combinations not present in the original parent DNA is called recombination. It is an important process in genetics because it leads to offspring that have different genetic make-up from each other as well as different from either parent. Occurs in Prophase I.
We can tell that non-sister chromatids undergo cross over because they have a region called the pseudoautosomal region which is homologous between the X an Y chromosomes. The rest of the X and Y chromosomes, including the region around the centromere are not homologous.
13] In humans; what are germ cells? Gametes? How does Meiosis differ in male and female during the formation of gametes? How many sperm are formed? Are they haploid or diploid? How many ova are formed? Are they haploid or diploid? How many polar bodies are formed? Are they haploid or diploid? What ultimately becomes of the polar bodies? What is fertilization? True or False: A zygote is a single cell with two nuclei that arise from fertilization (one nucleus from the sperm, one from the ovum); an n+ n condition. True or False: The sperm and ovum that united to form the zygote are both diploid and arose through the process of Meiosis. True or False: The zygote is haploid (because of reduction division during Meiosis II). True or False: The diploid (2n) zygote will undergo Mitosis (NOT Meiosis) as it develops into an embryo.
False. True. False. True. Gametes: They are produced by germ cells through a special process of cell division known as meiosis.
Both males and females use meiosis to produce their gametes. In females, the process of meiosis is called oogenesis, since it produces oocytes and ultimately yields mature ova(eggs). The male counterpart is spermatogenesis, the production of sperm. While they occur at different times and different locations depending on the sex, both processes begin meiosis in essentially the same way. Both diploid, 23 ova 23 sperm (haploids) , the polar bodies ultimately become fertilized.
Fertilization: The diploid chromosome number is restored at fertilization, when two haploid gametes (one ovum and one sperm) fuse to form a diploid zygote, the first cell of a new individual (which then grows and develops through somatic cell division—mitosis)
15] True or False: Prokaryotes undergo Mitosis to produce clones (if this is false, what process IS utilized?) What is the difference between sexual reproduction and asexual reproduction? What is a potential benefit of each? True or False: Some animals (some insects, frogs & lizards, among others) produce viable offspring from unfertilized eggs via a process termed parthenogenesis. Multiple Choice: Which of the following is true of Asexual Reproduction? A) Occurs by parthenogenesis—a diploid egg develops into an individual via Meiosis B) Occurs by fragmentation—an organism can be regenerated from a part of an organism and grow via Meiosis (as in Sea Stars/Starfish) C) An immature organism can bud from a parent and grow via Mitosis D) A prokaryote can undergo Binary Fission E) More than one of these are true.
True. Should be haploid. B, C, D, are correct. Prokaryotes undergo Binary Fission, even though these organisms are clones, there are mechanisms for gene transfer.
Sexual Reproduction: offspring arise from two parents and a mixture of genes are inherited from both.
Offspring of sexual reproducers have a better chance of surviving the effects of a harmful mutation that arises in the population.
Asexual Reproduction: produces genetically identical copies of a single parent (clones)
