Bio 2 Review Test 2The Cell Cycle, Mitosis & Meiosis (cell division)I. Types of Cells and Chromosomesi. Somatic: diploid = 2n (2 sets of chromosomes: mom plus dad) Muscle cells, skin cells, liver cellsii. How many chromosomes in a diploid human cell?iii. How many autosomal chromosomes do we have? #s?iv. Go through Mitosis NOT Meiosis!1. No crossing over; start and end with the same # of chromosomes2. One round of Interphase (G1 SG2) a. G1: cell is growing in order to accommodate 2x organelles/DNA- Cell is 2nb. S: DNA REPLICATION!!!**SISTER CHROMATIDS ONLY PRESENT AFTER S PHASE**- cell is still 2n but now sister chromatids are present!- Cell is 2nc. G2: Preparing to divide; protein synthesis and structure syn-thesis for cell division- MPF signal- G2 checkpoint!d. What are the 3 checkpoints of Interphase? CHEMICAL SIG-NALS- G1, if pass, cell continues to S phase; if doesn’t pass,goes to G0 what happens here? 2 things (apoptosisor repair)- G2 – MPF = cyclin + CDK a. Cyclin must be in a high enough concen-tration in order for CDK to bind- M 3. One round of Mitosis (PPMMATC)a. PROPHASE: - Centrosomes move to opposite pole- Spindle formation- Chromatin condensing forming distinct chromo-somesb. PRO-METAPHASE:- Kinetochore appears: location? Function?1. In centromere2. Attaches sister chromatids to the spindle fibersc. METAPHASE: - Chromosomes align SINGLE FILE along M-plate- Sister chromatids face opposite polesd. ANAPHASE- SISTER CHROMATIDS SPLIT FROM EACHOTHER- Now each is a distinct chromosomee. TELOPHASE AND CYTOKINESIS: - Nuclear membrane reforms, cell membrane pinches in and forms TWO separate cells- Each with identical DNA as parent cell1. Don’t need variation of alleles, i.e. do not need crossing over to occur when just forming new somatic cells; skin cells are all the same, doesn’tmatter, however, you may still have different al-leles on homologous chromosomes!4. cancer cells do not exhibit these two things: a. density dependent inhibition:- they will not be signaled to stop dividing if they touch another cell next to themb. anchorage dependence:- they do not need to attach to a substrate so they willgrow on top of each other and not in one uniform layer- cancer cells have telomerase activity: why does this help them to survive?1. What are telomeres? Just know definitiona. non-coding repetitive nucleotide se-quences at the ends of eukaryotic chro-mosomesb. When normal cell’s telomeres decrease, sign that cell will commit apoptosisc. Difference between proto-oncogenes and tumor suppressinggenes- normal tumor-suppressing genes (TSGs) restrict cell division1. suppress = depress = slow down2. P53- normal proto-oncogenes (POGs) stimulate cell divi-sion1. pro = lets go!- mutations in these types of genes cause cancer/tu-mors1. result in uncontrolled cell division2. p53 mutation – cell cannot be told to slow cell division3. proto-onco gene mutation – cell is told to speed up cell divisiond. Difference between centrosome, centrioles and centromere?1. Centrosome: this is a “microtubule orga-nizing center”; where the centrioles are housed2. Centrioles these contain microtubules needed for spindle formation 3. Centromere: holds together 2 sister chro-matidsb. Germ(Gametes: eggs and sperm): haploid = n (1 set of chromosomes: mom or dad)i. How many chromosomes in a haploid human cell?ii. How many sex chromosomes do we have? #s?iii. Go through Meiosis NOT Mitosis1. Begin as a diploid cell and end as haploid cells2. Meiosis I: REDUCTION DIVISION (reduce/divide # of chromosomes by ½)a. After meiosis 1 is the cell haploid or diploid?- VERY IMPORTANT TO UNDERSTAND!b. Prophase 1: How does it differ from Prophase of mitosis??- 2 main ways: 1. CROSSING OVER occurs here @ chiasma be-tween homologous chromosomes NOT sister chromatids2. Homologous chromosomes pair up c. Metaphase 1: How does it differ from Metaphase of mitosis??- 1 main way: 1. TETRADS formed and are on the metaphase plate; homologous chromosomes are NOT stacked one on top of another like mitosis. 2. LAW OF INDEPENDENT ASSORTMENT – genetic variationd. Anaphase 1: HOMOLOGOUS CHROMOSOMES SEPARATE ANDGO TO OPPOSITE POLES e. Telophase and Cytokinesis: - Result is 2 HAPLOID cells: Sister chromatids still at-tatched at centromere3. Meiosis II: Exactly the same process as Mitosis however, 4 haploid cells are formed and they are GENETICALLY DIFFERENT DUE TO CROSSING OVER!!a. Crossing over = trading of allelesc. Alleles are different versions of the same KIND of gene: i. Example: Flower color: 2 alleles (red or white)ii. For any chromosome, alleles may be the same or different: 1. i.e. can have either two red, two white, or 1 white and 1 redd. What can a Karyotype tell/show us?i. Definition: an orderly organization of chromosomesii. Give 3 things1. # of chromosomes2. any chromosomal abnormalities or chromosomal breakage(downs syndrome, aneuploidy, cri du chat)3. sex of individual (XX or XY)MENDELIAN GENETICS: I. What does True Breeding mean?a. Difference between Dominant (uppercase) and Recessive (low-ercase) allelesi. What does a dominant genotype look like? 2 possibilities1. PP2. Ppii. What does a recessive genotype look like? 1 possibility1. ppb. BB or bb – think pure bred = HOMOZYGOUSc. P generation = 1st parental generationd. F1 is first offspring generatione. F2 is second offspring generationf. In a True Breed cross PP X pp (homozygous DOMINANT x ho-mozygous RECESSIVE)i. F1 generation PHENOTYPIC ratio is 1:1 ii. F1 generation GENOTYPIC ratio is 1:1 ; resultant offspring are all HETEROZYGOUS = Pp iii. F2 generation PHENOTYPIC ratio is 3:1 (Pp x Pp)iv. F2 generation GENOTYPIC ratio is 1:2:1 ; resultant off-spring are PP, Pp and ppII. Trick!! FOR SINGLE GENE CROSSES ONLY!a. When question asks for how many GENOTYPE combinationsi. Homozygous X Homozygous = 1 combination (PP or pp or Pp) ii. Homozygous X Heterozygous = 2 combinations (PP or Pp) (Pp or pp) OR iii. Heterozygous X Heterozygous = 3 combinations (PP, Pp, and pp) b. When question asks for how many PHENOTYPE combinationsi. Homozygous X Homozygous = 1 combination (all domi-nant or all recessive) ii. Homozygous dominant X Heterozygous = 1 combination (all dominant)iii. Homozygous recessive X Heterozygous = 2 combinationsiv. Heterozygous X Heterozygous = 2 combinations (3 domi-nant and 1 recessive) c. When question asks for possible gamete combinationsi. If trait is homozygous PP or pp: use 1ii. If trait is heterozygous Pp:
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