Learning Objectives Number 3 Cell Division Centromeres o Part of a chromosome that links sister chromatids and where the spindle fibers attach during mitosis Kinetochores Chromatids o The protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart o One of the two identical chromosomal strands into which a chromosome splits longitudinally prior to cell division Spindle apparatus o The subcellular structure of eukaryotic cells that segregate chromosomes between daughter cells during cell division CELL CYLCE AND CONTROL CHECKPOINTS Why are there checkpoints What do they check for o The checkpoints are in place to ensure proper division of each cell o G1 is the restriction checkpoint where the cell decides if it will begin the division process or not by seeing if there are any defects within the cell o G2 is the second checkpoint after the S phase where the cell undergoes growth to prepare for division this phase also ensures that nothing was damaged during the previous 2 years Interphase The M checkpoint is the last checkpoint and it s where everything is checked to ensure the cell is ready to divide What occurs in G1 S and G2 phases o DNA replication and cell growth What is Go o A resting phase in which the cell is neither dividing nor preparing to divide What is the purpose of the different types of cell division Mitosis chromosomes 46 total o Produces one chromatid per chromosome o And for a human cell 23 pairs of homologous o The cell is diploid o Ends with two chromatids per chromosome o Cell is haploid Meiosis 1 Meiosis 2 o Ends with 1 chromatid per chromosome o The cell is still haploid o Sister chromatids separate Haploid Diploid Mitosis Events in each phase o A cell that has only one set of chromosomes o A cell that has 2 sets of chromosomes What is the number of chromatids DNA content number of chromosomes 1 Prophase each other a Nucleoli disappear Centrioles move away from b Chromatin condenses c Mitotic spindle forms from microtubules in cytoplasm 2 Metaphase spindle 3 Anaphase a Centrosomes at opposite poles b Chromosomes arranges at the mid plane of the 4 Telophase toward the poles a Sister chromosomes separate and move b Cells split a Nuclear envelope returns b Spindle breaks down c Nucleoli returns d Chromatids become less densely wiled Mitosis has 1 chromatid per chromosome and only for a human cell it would have 23 pairs of homologous chromosomes 46 total Meiosis 1 Events in each phase What is the number of chromatids DNA content number of chromosomes 1 Prophase 1 a Chromosomes become visible b Spindle forms c Nucleolus disappears d Crossing over occurs a Chromosome pairs align on equator of spindle b Kinetochores of sister chromatids are attached to fibers going to the same pole 2 Metaphase 1 3 Anaphase 1 4 Telophase 1 c Homologous pairs line up a Homologous chromosome pairs separate b Sister chromatids remain together a Depending on the species b Nuclear membrane may reform c Cytokinesis may occur Meiosis 1 ends with two chromatids per chromosome and the cell is haploid Meiosis 2 o Cell division like mitosis but starting with the haploid chromosome complement o Sister chromatids separate o Ends with 1 chromatid per chromosome and cell is still haploid ABO and Rh blood groups Know the genetics inheritance of these phenotypes Human ABO blood groups RBC Antigens A polysaccharide on the RBC Both type A and type B polysaccharides expressed o Blood type A an A Antigen o Blood type AB A antigen and B antigen on the surface of the red blood cell RBC o Blood type O no antigen No A or B polysaccharides Man of blood type A o Phenotype A o Genotype I A o Ambiguous Man of blood type AB o Phenotype AB o Genotype must be I AI B Man of blood type O o Phenotype O o Genotype must be ii Man of blood type A Genotype A Phenotype ambiguous o Either IAIA or IAi o One parent must have an IA allele o And the other parent must have IA or i Example if a person has type A blood then you know that they Same reasoning for must have the genotype IA IA OR IA i type B However if a person has type AB or type O blood you know FOR SURE that their genotype is IA IB and i i respectively So if a person with AB blood has a kid set up the Punnett Square with IA and IB as the gametes The A B blood types alleles are codominant the i allele is recessive this fact helps you figure out the genotypes phenotypes Are the genes for the ABO and Rh blood groups on the same chromosome o No Transfusions A Can receive A A O and O A can receive A and O B Can receive B B O O B Can receive B and O AB Can receive all blood types AB can receive AB B A O O Can receive O and O O Can receive O FIGURE 14 11 Sex Linkage Autosomal versus sex linked genes Sex linked genes are genes carried on the sex chromosomes Chromosomal sex determination o XX homogametic sex XY heterogametic sex o XX females o XO males not an O chromosomes it just means nothing o ZW ZZ female bird male bird o Sex Chromosome Punnett square Gametes from the father Gametes from mother X Y All X s Father determines the sex of the child o Allele occurs on one of the sex chromosomes o In humans for the most part we are concerned with the X linked traits Mother determines if her son will display an X linked trait Inheritance of X linked and Y linked traits Examples from lecture e g color blindness hairy ear rims hemophilia X linked recessive for color blindness o Two alleles o N dominant allele for normal vision o n recessive allele for color blindness Phenotypes o XNXn Female with normal vision XNXN Female with color blindness XnXn Male with normal vision XNY Male with color blindness XnY Harry Pinnae o Hairy ear rims o Y linked trait Always passed from father to son Few examples Estimates 78 genes on the Y chromosome o 1 helps testis formation o 1 is for hairy ear rims o 99 encode proteins expressed in testis o 168 Mendelian diseases have been Estimates 1 098 gene identified and in various tumor types explained by mutation in x linked genes o Transmitted from mother to son o Primarily males are affected Color blindness hemophilia What are the differences between X and Y chromosomes o As shown in the image below the Y chromosome is considerably smaller in size than the X chromosome but this is not only the main difference The basics is that only males have the Y chromosome and this is what gives males the genetic code to generate sperm and produce testosterone properly Do they each have the same genes o
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