BIOL 1441 1st Edition Lecture 21 Outline of Last Lecture I Cell cycle II Cancer III Two main phases of the cell cycle IV Cellular division V Chromosomes VI Cell cycle VII Mitosis VIII Cell cycle regulation control system Outline of Current Lecture I Cyclins and Cyclin dependent kinases II Cell growth cancer genes III Meiosis IV Gamete production V nondisjunction Current Lecture I Cyclins Cyclin Dependent Kinases a Regulatory proteins involved in cell cycle control i Cyclins concentration varies cyclically ii Cyclin dependent kinases Cdks concentration constant b Concentration of cyclins activity of Cdks fluctuates during the cell cycle i Cdks always present in the cell at the same concentration inactive These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II ii Need to be attached to a cyclin to be active iii Cyclins concentration fluctuates iv Cdks enzymatic activity fluctuates c Cyclins concentration fluctuates cyclically d Cdks activity depends on whether or not they are attached to cyclin e Cdk activity rises and falls with changes in concentration of cyclins Cell Growth Cancer Genes a Oncogenes Mutated or amplified genes involved in cell growth and differentiation i Makes cells grow divide constantly its turned on when its not supposed to be ii Proto oncogene normal non mutated oncogene iii Dominant Gain of function b Tumor Suppressors i Function to inhibit cell growth cell cycle check points DNA damage repair ii Recessive Loss of function iii Tumor Suppressor Loss of Function 1 Two hit hypothesis must lose function of both alleles a Mutation deletion b Loss of Heterozygosity LOH i Missegregation ii Mitotic Recombination 2 Cell cycle check points 3 Check repair DNA sequences 4 Induce apoptosis iv Mutation p53 1 Transcription factor detects errors in DNA decides repair DNA damage or apoptosis live or die 2 Over 50 all cancers have p53 mutation v Internal External Signals at the Checkpoints 1 Internal signal kinetochores not attached to spindle microtubules send a molecular signal that delays anaphase 2 External signals growth factors proteins released by certain cells that stimulate other cells to divide a Density dependent inhibition crowded cells stop dividing b Anchorage dependence cells must be attached to a substratum in order to divide c Cancer Cells i Exhibit neither density dependent inhibition nor anchorage dependence 1 Grow on top of eachother and don t stop don t flatten out ii Loss of Cell Cycle Controls in Cancer Cells 1 Do not respond to the body s control mechanisms III 2 Form tumors masses of abnormal cells within otherwise normal tissue iii If abnormal cells remain at the original site benign tumor 1 Not secreting hormones not moving iv Malignant tumors invade surrounding tissues metastasize 1 Moves to other parts of the body 2 May form secondary tumors 3 Gets in blood stream lymphatic system d Cancer Stages i Stage 1 small localized ii Stage 2 larger starts invading iii Stage 3 Invading tissue angiogenesis grow in nutrients iv Stage 4 metastasis moved into other organs Meiosis a Cellular division of gametes i Egg sperm ii Each have 23 chromosomes b Fertilization joining of egg and sperm i Form 1 cell with 46 chromosomes ii Cell divides mitosis develops into fetus somatic cells iii Puberty meiosis occurs and gametes form c Two divisions i Meiosis I ii Meiosis II d Gamete Production i Produced in gonads testes or ovaries ii Males spermatogenesis 64 days 1 Doesn t occur until puberty iii Spermatogenesis affected by 1 Dietary deficiencies vitamins B E and A 2 Anabolic steroids 3 Cadmium and lead dioxin X rays 4 Alcohol infectious diseases e Gamete Production i Females oogenesis ii Born with as many oocytes as you will ever have iii 20 wks 7 million eggs f Gametogenesis differences i Gamete number 1 Spermatogenesis 4 gametes 2 Oogenesis 1 gamete 3 polar bodies ii Start of gamete development 1 Spermatogenesis occurs throughout adolescence adulthood 2 Oogenesis begins before birth IV iii Timing 1 Spermatogenesis occurs continuously 2 Oogenesis long interruptions cycles Nondisjunction a Normal separation of chromosomes in meiosis disjunction b Separation is not normal nondisjunction c Results in the production of gametes too many of too few of a particular chromosome i Common mechanism for trisomy or monosomy d Down Syndrome trisomy of chromosome 21 e Klinefelter s Syndrome extra X chromosomes in males XXY XXXY XXXXY 1 in every 500 males only 1 in 1 000 have syndrome f Turner s Syndrome lacking of one X chromosome in females XO 1 in every 2500 females g XYY Syndrome an extra Y chromosome in males