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Genetics - Test A - Study Guide Sexual vs. Asexual 1. What is/are the difference(s) between sexual and asexual reproduction? Asexual—makes clones, identical, diploid (full set of chromosomes), fast, easier form of reproduction, takes less energy Sexual—makes genetically different organisms, diploidhaploid (half set of chromosomes), takes more time, takes more energy, and most importantly it increases genetic diversity 2. What does sexual reproduction help to create and maintain? How does this help a species if its environment changes for some reason? GENETIC DIVERISTY; this increases the chances that when an environment changes at least some of the organisms will be “best adapted” to this new environment and thus be able to survive and reproduce keeping the species alive 3. Are the offspring from asexually reproducing organisms genetically similar or different from their parent? Is this a good or bad trait? Explain your answer. Asexual reproduction produces clones, exact copies of the parent cell. It’s generally bad because all the species have the same exact traits. If the environment negatively changes, all the species will die out because everyone is the same. 4. What is alternation of generations? How does this process relate to sexual and asexual reproduction? Alternation of generations is a cycle where organisms alternate between mitosis and meiosis, asexual and sexual reproduction respectively. 5. Fill in the following chart: FORM OF ASEXUAL REPRODUCTION BINARY FISSION BUDDING DESCRIPTION Bi=2, fission=split, Asexual reproduction where the cell splits into 2, both are identical Budding is a form of asexual reproduction in which a new organism develops from an outgrowth or bud on another one due to cell division at one particular site. The new organism remains attached as it grows, separating from the parent organism only when it is mature, leaving behind scar tissue. Cloning is two identical organisms created from a single cell CLONING SPORE FORMATION VEGETATIVE PROPAGATION A spore is a unit of asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavorable conditions. A spore is a haploid cell that can form a new organism on its own. Vegetative Propagation is a form of asexual reproduction in plants. It is a process by which new organisms arise without production of seeds or spores. A new plant is produced from a plant’s own stems and roots. 6. Label each of the following as an advantage of sexual reproduction (S) or asexual reproduction (A): ___A__ Benefits isolated or simple organisms ___S__ Provides genetic diversity ___A__ Requires less energy ___A_ Rapid reproduction ___S__ Provides disease resistance ___S_ Increases adaptation Mitosis vs. Meiosis 7. What are the four (4) phases of mitosis (in order)? PMAT, Prophase, Metaphase, Anaphase, Telophase 8. What is the relationship between chromatin and chromosomes and chromatids? Chromatin is a condensed form of a chromosome, chromosomes are the full uncondensed form, and chromatids are one half of a chromosome 9. In which phase of Mitosis are the chromatids pulled apart? Which phase of Meiosis? Anaphase, Anaphase II 10. In which phase of Mitosis does the nuclear membrane DISSAPPEAR and then REDEVELOP? In Meiosis? Disappears—Prophase (Mitosis), Prophase I (Meiosis), Reappears—Telophase I (Mitosis), Telophase II (Meiosis) 11. Why is it important that DNA is replicated before division? During which phase of the cell cycle is DNA duplicated? So that each cell receives a full copy of DNA, S Phase of Interphase 12. You are looking at a cell under the microscope. You notice that the chromosomes are lined up in pairs in the middle of the cell. This would tell you that the cell is in which phase of cell division? Metaphase (Meta=Middle) 13. How are mitosis and cancer related? Cancer is uncontrolled mitosis (the cells will NOT stop dividing) 14. Why do humans need Mitosis? Why do humans need Meiosis? Mitosis is important for cell growth and repair of pre-existing cells, whereas Meiosis is only for sexual reproduction (sperm and egg) 15. What is the difference between n and 2n ? N= Haploid (half set of chromosomes) and 2N= Diploid (full set of chromsomes) 16. What are homologous chromosomes? Which parent donates homologous chromosomes? Homologous chromosomes are chromosome pairs, one from each parent, that are similar in length, gene position and centromere location; both parents donate homologous chromosomes (1/2 from each) 17. What do the terms diploid and haploid mean? Haploid (half set of chromosomes) Diploid (full set of chromsomes) In humans, our diploid number is 46 and our haploid number is 23 18. Why is crossing over important? When does it happen? Crossing over is where the paternal and maternal chromsomes “cross over” each other and exchange genetic information to create a new chromosome, with some of both parent’s DNA. This occurs in Prophase I. 19. Why is meiosis important for the formation of gametes, or what would happen if meiosis didn’t occur in gametes? We would be a clone of one of our parents. 20. What is a polar body? There are 4 haploid cells produced at the end of Meiosis, but only one egg and sperm cell are needed, so the other 3 disintegrate and they are known as “polar bodies” 21. The following phases are not in order. Match each description to the correct picture: PHASES of MITOSIS ___13__ A. Stage of meiosis where crossing over occurs. ___8_ B. Metaphase I ___1__ C. Anaphase ___5__ D. Metaphase ___7__ E. Anaphase II ___12_ F. Telophase II ___2__ G. Prophase 22. Fill in the following chart PHASE INTERPHASE SKETCH SUMMARY G1= GROW S = SYNTHESIS (DNA COPIED) G2= GROW Chromosomes become more coiled and can be viewed under a light microscope. PROPHASE • Each duplicated chromosome is seen as a pair of sister chromatids joined by the duplicated but unseparated centromere. • The nucleolus disappears during prophase. • In the cytoplasm, the mitotic spindle, consisting of microtubules and other proteins, forms between the two pairs of centrioles as they migrate to opposite poles of the cell. • The nuclear envelope disappears at the end of prophase. This signals the beginning of the substage called prometaphase. • The centrosomes are at opposite poles of the cell. • The chromosomes, now at their most highly coiled and condensed, become arranged on a plane equidistant from the two poles called the metaphase plate. METAPHASE • For each chromosome, the kinetochores of the sister chromatids face the opposite poles, and each is attached to a kinetochore microtubule coming from that pole. • Anaphase begins when the duplicated centromeres of each pair of sister chromatids separate, and the nowdaughter chromosomes begin moving toward opposite poles of the cell due to the action of the spindle. • Depending where the centromere is located along the chromosome, a characteristic shape appears during chromosome movement. The two shown above give V and J shapes. ANAPHASE SEE PICTURE IN CYTOKINESIS TELOPHASE • At the end of anaphase, a complete set of chromosomes has assembled at each pole of the cell. • The chromosomes assemble in sets at the two poles. • The chromosomes begin to uncoil and eventually assume the extended state characteristic of interphase. • A nuclear envelope reforms around each chromosome set, the spindle disappears, and the nucleolus reforms. Nuclear division by mitosis is complete at this point. • Cytokinesis, the division of the cytoplasm, usually is in progress before nuclear division is complete. In animal cells, cytokinesis involves the formation of a cleavage furrow resulting in the pinching of the cell into two. CYTOKINESIS 23. Fill in the following chart: POINT OF COMPARISON MITOSIS HOW CHROMOSOMES ALIGN IN METAPHASE Chromosomes align in the middle # OF CHROMOSOMES AT THE END OF THE PROCESS Diploid Haploid # OF DAUGHTER CELLS FORMED FROM ONE (1) PARENT CELL 2 4 WHERE THE PROCESS TAKES PLACE (WHAT TYPE OF CELL?) Prokaryotes and Eukaryotes Eukaryotes Mainly (few exceptions) # OF PHASES 4 MEIOSIS Metaphase I—Homologous chromosomes align in the middle Metaphase II-Sister chromatids align in the middle 8 Genetics 24. “The Father of Genetics” = ________Gregor Mendel________________ 25. In your own words, explain his 3 principles/Laws: a. Independent Assortment - states that allele pairs separate independently during the formation of gametes. This means that traits are transmitted to offspring independently of one another. b. Dominant & Recessive traits – dominant traits mask the recessive traits c. Segregation of factors - states that allele pairs separate or segregate during gamete formation, and randomly unite at fertilization. 26. Humans have _46___ (2n) chromosomes in each ____body cell_____(somatic) cell. 27. Humans have _23___ (1n) chromosomes in each _____germ cell____ (sex cell). 28. ___Traits____________ – different forms of the same gene (flower color) 29. _____Crossing Over_______________ ______________ occurs when chromatids of homologous pairs become entangled. This happens during the phase called _Prophase I__________________. (It is the Homologous pair that is pulled apart during Anaphase I) 30. _Honozygous_____- when the traits/genes (alleles for the trait) are represented by letters (Tt, Aa, BB, dd) 31. Genotypic ratios are written in the following order: _____Homozygous Dominant_________ : _____Heterozygous_________: _____Homozygous Recessive_________ 32. ____Phenotype______________– the physical appearance or what the offspring looks like. (Tall : short, curly hair : straight hair) Phenotype ratios are reported from the Dominant to the Recessive trait showing. The physical appearance of The physical appearance of Homozygous Dominant & Heterozygous : Homozygous Recessive 33. __ Homozygous Dominant ________________- both capital letters/dominant for genotype (TT , AA, BB) 34.____ Heterozygous _________________ - One letter is capital/dominant & one is small/recessive (Tt, Aa, Bb) 35. ___ Homozygous Recessive ______________________ – both letters are small/recessive (tt, aa, bb) 36. ____Punnett Square__________________– diagram showing probability of traits Parental alleles – from the gametes (genotype) go on the outside of the box 37. Dominant___________ (capital letter) trait will always show if present (covers any recessive traits) 38. Recessive___________ (lower case letters) – trait is masked or covered by the dominant. Recessive traits only show up if homozygous recessive (lower case letters) 39. Solve the Punnett square below: T t T t TT Tt Tt tt 40. Complete the ratios below based on the Punnett square in #39. 1 : 2 : HD: He : hr 1 Genotypic ratio 3 : 1 Phenotypic ratio show trait : don’t show trait DON’T FORGET TO LOOK AT EVERYTHING IN YOUR LOGBOOK! GO OVER INCOMPLETE AND CODOMINANCE PUNNETS AND PEDIGREES!