UNIT 4 STUDY QUESTIONS
Fall 0123 CELL CYCLE AND MITOSIS 1. Why do cells reproduce? Cells reproduce for organismal development, create a new organism or for cellular maintenance and repair. 2. What is binary fission? A type of asexual cell division involving prokaryotic cells. 3. What is the eukaryotic cell cycle? The Eukaryotic cycle is an ordered sequence of events that extends from the instant a cell is first formed from a dividing parent cell until its own division into two cells consisting of three stages: Interphase, Mitosis & Cytokinesis. 4. What happens to DNA as the cell progresses through the cell cycle? It is in its loose chromatin form in interphase, condenses in prophase at the start of mitosis and it loosens back up in telophase once daughter cells have been produced. 5. What exactly is “mitosis”? Distinguish between karyokinesis (mitosis) and cytokinesis. Mitosis divides the nucleus 6. What is a chromosome? What macromolecules are present in a chromosome? Distinguish between chromatin, chromosomes and chromatids. Draw and label a replicated chromosome. Macromolecules that are present in a chromosome are proteins, nucleic acid. REGULATION OF THE CELL CYCLE 7. What is a cell cycle checkpoint? Describe the major checkpoints in the cycle, and label them on your mitotic cell cycle diagram. A cell cycle checkpoint is a critical point where stop and go signals regulate the cycle. The major checkpoints in the cycle are during the G1 and G2 sub-phases of interphase and in the M phase. 8. Describe quiescence, and give some examples of quiescent cells in your body. Quiescence is the G0 phase that occurs when a signal never arrives to signal the cell to divide, putting it in a permanent non dividing state. Some examples of quiescent cells are Mature nerve and heart muscle cells. 9. What cellular senescence? Cellular senescence is the irreversible loss of the ability to divide—cells cease to divide. Associated with aging. 10. What is apoptosis, and why might it occur? Apoptosis is programed cell death or cell suicide. It may occur as a response to DNA damage in cells. 11. What happens if the cell cycle is NOT properly controlled? If a cell cycle is not properly controlled, it can bring on the onset of cancer. 12. What are proto-oncogenes and tumor suppressor genes (what is their normal function)? How are these genes and their function altered in cancer cells? Proto-oncogenes are normal genes that have the potential to become cancerous or oncogenes. Tumor suppressor genes are genes whose normal products inhibit cell division. In cancer cells, gene mutations in genes cause the onset of cancer. Mutations that decrease normal activity of a tumor-suppresser protein may contribute to the development of cancer.1 UNIT 4 STUDY QUESTIONS
Fall 0123 13. What influences whether or not a cell will continue to divide? Growth factors are the main signals that tell the cell to divide. MEIOSIS AND GAMETE PRODUCTION 14. What is meiotic cell division (aka meiosis)? Define meiosis using the terms diploid and haploid. Is meiosis happening in your body now? If yes, in which tissue or organ? Meiosis is a type of cell division that produces haploid gametes in diploid organisms. Meiosis is not happening in my body right now. 15. What is the meaning of the terms haploid and diploid? Define these in terms of homologous chromosomes. Are somatic cells haploid or diploid? Are gametes haploid or diploid? A haploid cell contain one complete set of homologous chromosomes. A diploid cell contains two complete sets of homologous chromosomes. Somatic cells are diploid. Gametes are haploid. 16. What are homologous chromosomes? How many pairs of homologous chromosomes are present in your body cells? How many of these are “autosomal” chromosomes? How many of these are sex chromosomes? Distinguish between autosomal chromosomes and sex chromosomes. Homologous chromosomes are a set of one maternal and one paternal chromosomes that pair up with each other inside a cell during meiosis. There are 22 pairs of autosomal chromosomes and 1 pair of sex chromosomes per person. 17. Does the presence of homologous chromosome pairs depend on DNA replication? yes 18. Distinguish between somatic cells and gametes in animals and provide examples of each. How many chromosomes (in total) would you expect to find in a human somatic cell? In a human gamete? Do somatic cells and gametes exist in plants? If yes, provide an example of each. Somatic cells and gametes do exist in plants. Example of a plant somatic cell is a plant cell. 19.
A typical body cell
Cell Division Used
Sets of Chromosomes
2N= 2(23) = 46 chromosomes
N= (23) = 23 chromosomes
Identical or Unique?
Haploid or Diploid?
For growth, repair, or asexual reproduction
Skin cells and liver cells
Sperm and egg cell
Why do cells reproduce?
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20. Draw the meiotic cell cycle. Label each stage and explain the most important events that occur in each stage. Focus on events that contribute to the distribution of the DNA to the daughter cells. What is separated in the first meiotic division? What is separated in the second meiotic division? Although you drew this as a cycle, is it really a CYCLE? Explain. Homologous chromosomes are separated in the first meiotic division. Sister chromatids separate in second meiotic division. 2 UNIT 4 STUDY QUESTIONS
21. Complete a meiosis diagram (blank diagram on BBD) to illustrate the major events that occur in each stage of meiosis, focus on events that contribute to the distribution of the cell’s DNA to the daughter cells. 22. What is a tetrad? Why is it so central to meiotic division? Do tetrads also occur in mitosis? A tetrad is four chromosomes during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids. Tetrads do not occur in mitosis. 23. How does meiosis differ from mitosis? Are there any similarities? If yes, explain.
Each duplicated chromosome remain separate
Chromosomes are associated with their homologous pair
Nuclear membrane breaks down
Duplicated chromosomes line up singly
Chromosomes line up in a single file
What is binary fission?
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3 UNIT 4 STUDY QUESTIONS
chromosomes line up in pairs
Sister chromatids separate
Pairs of homologous chromosomes separate
Sister chromatids separate
Involves one division of the nucleus and cytoplasm
Two divisions in total of the nucleus and cytoplasm
Two divisions in total of the nucleus and cytoplasm
Two genetically identical diploid cells
Four genetically unique haploid cells
Four genetically unique haploid cells
Growth, tissue repair, asexual reproduction
Sexual reproduction Sexual
What is the eukaryotic cell cycle?
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MEIOSIS AND GENETIC VARIATION 24. Distinguish between asexual and sexual reproduction with regard to the number of parents (cells or organisms), and whether or not the offspring are genetically identical to the parents. Asexual reproduction involves a single organism or cell that produces genetically identical offspring. Sexual reproduction involves two organismal parents that produce genetically varied offspring. 25. A hallmark of sexual reproduction is the generation of genetic variation, such that each offspring is a genetically distinct individual, different from both parents. List and explain 3 ways in which this variation is generated during sexual reproduction. Genetic variation is generated by crossing over/genetic recombination (non-sister chromatids within a tetrad “cross over” or swap DNA) or independent assortment (random mixture of maternal and paternal chromosomes on either side of the metaphase plate) in the process of meiosis, and fertilization. 26. What is a chromosomal aberration? How do chromosomal aberrations arise? Give some examples of chromosomal aberrations in humans. A chromosomal aberration is a change in the structure and/or number of chromosomes in a cell. They are caused by nondisjunction or mistakes during “crossing over”. Some examples of chromosomal abberations in humans are down syndrome, Patau Syndrome, Edward’s Syndrome and Klinefelter’s Syndrome. 27. Distinguish between a chromosomal aberration and a gene mutation. Are there any similarities? If so, explain.
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4 UNIT 4 STUDY QUESTIONS
Change in the nucleotide sequence in a particular gene
Change in several genes in the chromosome
Considered large-scale alteration
Can sometimes be corrected
Slight structural alteration
Numerical or structural changes in entire DNA strand
MENDELIAN GENETICS 28. Define distinguish between the terms: “dominant” and “recessive”, “phenotype” and “genotype”, “gene” and “allele”, and “homozygous genotype” and “heterozygous genotype”.
Allele expressed that masks the effect of the recessive characteristic
Allele masked by A when present
Physical expression of alleles
Combination of alleles that cause the expression of a particular trait or disorder
A segment of DNA that codes for a protein
Alternate form of a gene (A or a)
Having two identical alleles of a gene
Having two different alleles of a gene
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29. Distinguish between monohybrid and dihybrid crosses. What is a test cross?
Cross between first generation offspring of parents who differ in one trait
Cross between first generation off spring of parents who differ in two traits
Useful in determining the dominance of genes
Useful in studying the assortment of the offspring
30. What question was Mendel asking in his monohybrid crosses? How many characterisitics inherited? 31. Diagram out Mendel’s monohybrid cross between a purple-flowered pea plant and a white-flowered pea plant. What are the F1 and the F2 genotypic ratios? 5 UNIT 4 STUDY QUESTIONS
Fall 0123 32. State and briefly explain Mendel’s two Laws of Genetics. What is the physical basis of each in terms of events in Meiosis? The Law of Segregation states that there are two alleles for each trait that reside on homologous chromosomes and that each offspring gets 1 allele from each parent. The Law of Independent Assortment states that pairs of alleles on different chromosomes assort independently of each other during meiosis. INHERITANCE PATTERNS 33. Distinguish between complete dominance, incomplete dominance, and codominance. Provide examples of each in humans.
Dominant allele completely masks recessive allele
Dominant allele doesn’t fully mask recessive allele
Neither allele masks the other
Heterozygous genotype shows as a dominant phenotype
Heterozygous genotype shows as a “blended” phenotype
Heterozygous genotype displays both phenotypes; additive phenotype
34. Be able to complete genetics problems for each of the above inheritance patterns in addition to Sex linked inheritance. Be able to calculate the genotypic and phenotypic frequencies of the offspring. Genotypic ratios are ratios that include each member of the Punnett square offspring. If there are 2 of the same offspring, then note that in the genotypic ratio. The phenotypic ratio expresses phenotypical characteristics. If all are the same, you put it as “[percentage] characterstic”. If they are Sex-linked alleles, then you must split the phenotypic ratios so that one references female gametes, and the other references male gametes. 35. Be able to read and interpret a pedigree. 36. How is gender determined in humans? It is determined by the male. 37. Why do human diseases that are controlled by genes carried on the X chromosome occur at a higher frequency in males than in females? Human diseases controlled by genes on the X chromosome occurs at a higher frequency in males than females because with males, they only have one X chromosome while females have two. Females can be a carrier of a disease and not have it while a male can either have it or not have it. So the chances of a male being affected is at a much higher chance. 6 UNIT 4 STUDY QUESTIONS
Fall 0123 38. From which parent do male offspring get their X chromosome? Male offspring get their X chromosome from the mother. Since they are males, the father must have donated his Y chromosome which leaves an X chromosome as the only chromosome the mother can donate. 39. What is a “carrier” of a genetic disease? Can a male be a carrier of an X-linked disease or genetic character? Can a male be a carrier of a Y-linked genetic character? A carrier of a genetic disease is someone that has the trait of a disease but is masked by a dominant allele so they do not express it. A male can not be a carrier of an X-linked disease because they only have one X, so they are either affected or not affected. A male can be a carrier of a Y-linked character because they are the only ones with the Y chromosome.7