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 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 o 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 Meiosis 1 o Produces two diploid 2n daughter cells o Produces 2 haploid cells from one diploid o Occurs in cells that give rise to gametes Meiosis 2 o Cell division like mitosis but starting with the haploid chromosome complement 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 spindle cytoplasm each other a Nucleoli disappear Centrioles move away from b Chromatin condenses c Mitotic spindle forms from microtubules in d 4n chromatids e 4n DNA content f 2n chromosomes a Centrosomes at opposite poles b Chromosomes arranges at the mid plane of the c 4n chromatids d 4n DNA content e 2n chromosomes 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 e 2n chromatids f 2n DNA content g n chromosomes toward the poles 2 Metaphase 3 Anaphase 4 Telophase 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 2 Metaphase 1 to fibers going to the same pole e 4n chromatids f 2n chromosomes g 4n DNA content a Chromosome pairs align on equator of spindle b Kinetochores of sister chromatids are attached 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 d 2n chromosomes e 2n DNA content f 1n chromosomes 3 Anaphase 1 4 Telophase 1 Meiosis 2 o 1n chromatids o 1n DNA content o 5n chromosomes 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 No Are the genes for the ABO and Rh blood groups on the same chromosome Transfusions which combinations of donor and recipient blood groups are compatible A Can receive A and O B Can receive B and O AB Can receive all blood types O Can only receive O type blood 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 with 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 As stated before no they do not each have the same genes The X chromosome does not have the genetic code to produce sperm and also triggers the development of testicles during development You need to keep track of the sex chromosomes whereas for autosomal traits the sex chromosomes can be ignored Barr bodies Inactivated X chromosomes heterochromatin Be able to relate the number of Barr bodies observed to the number of X chromosomes an individual has XX sex chromosome there is one Barr body o Only one X chromosome is needed ergo in a normal female with Examples of X chromosome inactivation and the fur color patterns of
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