Unit II Study Guide Part A 1 Describe a duplicated or replicated chromosome a A replicated eukaryotic chromosome 2 sister chromatids joined at a centromere 2 To what does the cell cycle refer and what events stages steps etc are involved The cell cycle two components 1 Cell growth 2 Cell division 2 general phases interphase and mitotic phase Interphase 3 stages G1 S G2 G1 new cell gows S chromosomes replicate G2 the cell prepares to divide Mitotic mitosis and cytokinesis M nucleus divides by mitosis Cytokinesis cytoplasm divides into 2 daughter cells each containing the original number of chromosomes 3 Why do cells organisms need to regulate or control the cell cycle The cell cycle is regulated at various checkpoints G1 G2 and M there are molecular signals in the cytoplasm that regulate the cell cycle Cancer results when there are errors in control of the cell cycle The cell cycle effects could be uncontrolled cell growth and cause a tumor 4 How do cells organisms regulate or control the cell cycle Explain the role of checkpoints Explain the chemical control system that gets cells through the G2 checkpoint G1 restriction cell cycle pauses decides if it will go through the checkpoint depending on signals The signals will direct cell to enter S or to undergo apoptosis cell death G2 if preparations for cell division are ok then signal molecules will be directed to enter M phase Chemical control system to go through g2 cyclin accumulated cyclically through the cell cycle When cyclin gets high it binds with CDK and forms MPF signal which is needed to go through the G2 Check point CDK is always present and when it is combined to cyclin then it will create MPF Cyclin protein fluctuates in concentration CDK cyclin dependent kinases bind to and activate cyclin to get through checkpoint MPF needed to go through G2 checkpoint Cyclin is synthesized during S and G2 When the cyclin level is high it binds to CDK which is always present and creates MPF This signal puts the cell through G2 checkpoint and initiates mitosis There is internal and external control of cell cycle 1 Repeated internal synthesis and degradation of various cyclin clock molecules 2 Feedback from internal signals hormones and external signals growth factors to adjust cyclin levels as needed 5 What is the general purpose of mitotic cell division Describe the step wise process of mitotic cell division Compare the number of chromosomes before the start of mitosis at each step and at the end Mitosis division of the nucleus that preserves the parental chromosomes number in each daughter cell 1 Prophase centrosome move to opposite poles diffused DNA that is replicated during S begins to condense into distinct chromosome A replicated chromosome is 2 sister chromatids joined at a centromere 2 Prometaphase the nuclear membrane is gone and chromosomes are distinct The spindle apparatus is complete Kinetochores appear at each centromere Aster microtubules are at the cell edge a Kinetochore complex of proteins at the centromere that attach sister chromatids to spindle fibers Pole to kt b Non kinetochore pole to pole c Aster from centrosome to cell edge 3 Metaphase chromosomes line up in a single file at the midline or cell equator metaphase plate Sister chromatids of a replicated chromosome face opposite sides 4 Anaphase centromere splits Spindle microtubules pull apart sister chromatids and go to opposite sides Each separated chromatid is now its own distinct chromosome 5 Telophase spindle disassembles and a nucleolus reappears Mitosis is complete nuclear division 6 Cytokinesis last stage cell membrane pinches and invaginates at the cleavage furrow 2 daughter cells are created each with identical DNA as parent and same chromosome number as parent Cytokinesis is a little different in plants a cellulose cell plate forms between plant daughter cells At the start of mitosis if you start with 46 chromosomes even after duplication of DNA the number is still 46 chromosomes This is because before DNA replication each chromosome consists of one chromatid After replication chromatids are duplicated and each chromosomes has 2 chromatids This is the result of a X shaped chromosome The chromatids will be separated in mitosis There can be 92 chromatids but it is still 46 chromosomes 6 What do cancer and the cell cycle have to do with one another What do cancer and gene regulation has to do with one another Cancer results when there are errors in the control of the cell cycle Cancer is caused when there is a mutation to genes Tumor suppressing genes TSG restrict cell division Proto oncogenes POGs stimulate cell division Cancer causing mutations involve TSGs POGs and other gene regulation issues in the cell cycle When there are mutations in POGs it can result in cell cycle overstimulation which can create to many cells and create a tumor On the other hand there can be a TSG mutation which fails to restrict the bad cells from dividing A combination of both will result in a tumor Cells need anchorage dependence and density dependent inhibition Cancer looses these growth factors which can create tumors 7 Compare contrast somatic vs germ cells a k a sex cells or gametes with respect to location in an organism function how they are formed and chromosome number Somatic sex cells found in muscle and skin They are diploid come in pairs and are represented as 2n They contain 2 sets of chromosomes 1 maternal pair and 1 paternal pair Example human somatic cell is 2n 46 chromosomes 23 paternal and 23 maternal pair Germ cells gametes egg and sperm cells They are haploid represented as n 1 set Just one chromosome from each pair Example human gamete cell is n 23 chromosomes 8 Describe a karyotype What does a karyotype reveal Why are karyotypes useful Karyotype an ordered display showing the and types of chromosomes in a diploid cell display visible chromosomes undergoing mitosis This occurs in somatic cells only It will reveal maternal and paternal contributions of pairs You can look at the 23rd chromosome to see the sex 9 What does it mean when we say that in eukaryotes chromosomes exist in pairs What are the two chromosomes that make up a pair called How are they similar to each other How are they possibly different from each other 2 chromosomes in a pair are homologous They are similar to each other because they have the same number and kind of gene They can be different from each other because they can have different alleles An allele is a different version of
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