Cell Cycle and Meiosis

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How many chromosomes are in a human somatic cell?
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46
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Are somatic cells haploid or diploid?
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diploid
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Are germ cells haploid or diploid?
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diploid
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Are sperm haploid or diploid?
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haploid
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Are gametes haploid or diploid?
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haploid
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What are the 2 phases of the cell cycle?
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interphase and mitosis
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What are the parts of cell division
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PMAT and cytokinese
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A certain cell that has 6 chromosomes in the G1 phase will have _____ chromosomes in the G2 phase.
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12
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If a cell has 14 chromosomes at the start of prophase, how many will it have after cytokinesis?
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7
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How is cell division different in animal and plant cells?
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animal: has centrioles and cleavage furrow plant: formation of cell plate
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If a germ cell with 38 chromosomes undergoes meiosis, how many chromosomes will the resulting cells have? If a germ cell with 38 chromosomes undergoes meiosis, how many chromosomes will the resulting cells have?
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19, gametes
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Meiosis divides one diploid cell into 4 _____ cells.
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haploid
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A human sperm has _____ chromosomes.
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23
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What is crossing over?
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Exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring
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Summarize what happens during interphase?
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G1 S G2, DNA replication, preparing cell for mitosis
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Why do cells divide instead of just getting larger? Be specific and explain how you could model this?
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bc of the surface area to volume ration cells divide instead of getting larger in order to ensure molecules can diffuse across the cell in a timely manner, could be modeled with dialysis tubing and a variety or molecules (iodine and starch)
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Meiosis and sexual reproduction contribute to variation within a species. State the sources of variation in a these processes and why a species benefits from the variation that they allow for.
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crossing over, random movements of homologous chromosomes (independent assortment) and random fertilization contribute to variation, variation leads to increase survival of species
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What is the first phase of meiosis? The last phase?
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prophase I, telophase II
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In meiosis I, __________________ separate during anaphase I. In meiosis II, _______________ separate during anaphase II.
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homologous chromosomes, sister chromatids
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What phase is skipped during meiosis?
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interphase after meiosis I
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In which phase does crossing over occur?
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metaphase I
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Chromosome #4 that you inherit from your mom and chromosome #4 that you inherit from your dad are said to be _________. When each of these chromosomes (#4 from your mom OR #4 from your dad) is duplicated, the two exact copies of each chromosome are called ___________
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homologous, sister chromatids
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What is nondisjunction?
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gametes contain an abnormal/incorrect # of chromosomes due to failure of spindle fibers to separate or move more chromosomes during meiosis
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Why do unicellular organisms need to undergo cell division?
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to reproduce
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Why do multicellular organisms need to undergo cell division?
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to replace old and dying cells, or to repair
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What is the role of growth factors?
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to trigger cell division from molecular signals
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What is differentiation?
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when cells stop diving, specializes in structure and function
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What is apoptosis?
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the process of eliminating unnecessary cells during development, removes unhealthy and damaged cells
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What are cell cycle regulators?
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molecular signals either stimulating or halting divison
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In general, what is the purpose of a checkpoint in the cell cycle?
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to make sure none of the DNA is damaged
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What is one potential outcome when errors occur in this highly regulated cell cycle process?
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cancer can form
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What type of protein that regulates the cell cycle is encoded by proto-oncogenes?
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stimulating proteins
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What type of protein that regulates the cell cycle is encoded by tumor suppressor genes?
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inhibitory proteins
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The most important cell cycle regulators are the ______
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cyclin-dependent kinases (CDKs)
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What is kinase, and what does it do?
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enzymes that add a phosphate to other proteins to activate or inhibit their function—a process known as phosphorylation
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When are the cyclin-dependent (CDKs) present inside the cell during the cell cycle?
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always
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When are cyclins present inside the cell during the cell cycle?
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always
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What do activated CDK-cyclin complexes do?
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they stimulate or inhibit cell cycle progression
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Summarize what is happening in G1 phase
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cell increases in size and prepares to replicate its DNA
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Summarize what is happening in S phase
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cell replicated DNA, at the end of the phase, cell has two sets of chromosomes
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Summarize what is happening in G2 phase
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cell continues growth and prepares for divison
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Summarize what is happening in mitosis overall
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cell stops growing and divides into two daughter cells
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What three factors determine whether a cell enters G0 phase?
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development, type of cell, available resources
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Name two reasons why cells can form tumors
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too much cell division, too little death
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What cause uncontrolled cell division at the genetic level?
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mutations affecting proteins that normally regulate the cell cycle
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Explain what occurs if the APC gene is mutated
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cells starts to accumulate because of struggle to differentiate
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What do mutated proto-oncogenes cause?
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oncogenes (mutated proto-oncogenes) increase stimulation of cell cycle
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What do mutated tumor suppressor genes cause?
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loss of inhibition, they decrease suppression
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To cause cancer, proto-oncogenes require (1 or 2) allele(s) to be mutates and are therefore considered (dominate/recessive) This results in ___ of function.
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1, dominant, gain
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To cause cancer, tumor suppressor genes require (1 or 2) allele(s) to be mutates and are therefore considered (dominate/recessive) This results in ___ of function.
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2, recessive, loss
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Explain the impact on the cell cycle of proto-oncogene versus an oncogene
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proto-oncogenes are driving cell growth while oncogene are acting as an accelerator
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Explain the impact on the cell cycle of one mutate tumor suppressor gene allele versus two mutated tumor suppressor gene alleles
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normal tumor suppressor genes act as breaks, but when broken, the cell cycle goes more quickly without break
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When dies interphase occur?
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before meiosis
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What occurs during interphase?
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cell duplicated DNA and prepares for mitosis
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Uncoiled stringy DNA is called ___
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chromatin
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DNA has ____ that determines traits of an organism
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genes
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Different forms of a gene are called ____
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alleles
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What are made during meiosis?
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gametes ie) sperm and eggs
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Homologous chromosomes pair up during prophase I to form a ___
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tetrad
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What happens in prophase during mitosis?
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DNA and proteins start to condense into chromosomes, nuclear envelope starts to break, microtubules are assembled and move one of two centriole pairs to opposite end of cells
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What happens in metaphase during mitosis?
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all chromosomes line up at equator of spindle
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What happens in anaphase during mitosis?
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attachment between two sister chromatids of each chromosome break, the two are now separate chromosomes that move to opposite spindle poles
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What happens in telophase during mitosis?
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chromosomes de-condense, nuclear envelope is formed
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What happens in cytokinesis during mitosis?
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two daughter cells are formed, each is diploid, it had two of each type of chromosomes.
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What are somatic cells?
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replacement cells
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What are germ cells?
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a cell lineage set aside for the formation of gametes (such as sperm and egg)
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What are chromosomes?
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DNA molecules with its attached proteins
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What are sister chromatids?
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duplicates of chromosomes
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What is the centromere?
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small region with attachment sites for microtubules that move the chromosome during nuclear division
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What are amoebas?
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free-living cells that do not leave interphase
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What is a cleavage furrow?
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indentation in its plasma membrane

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