Test Three for Biology Chapter Eleven October 19th 2012 Cell Cycle Regulation Regulation is at the molecular level Cancer calls are not regulated normally An area of intense research Normal plant and animal cells have a cell cycle control system Proteins that integrate information and send stop or go ahead signals at key points in the cell cycle Both plant and animal cells can become cancerous which means they are growing out of control What is cancer A disease that claims the lives of 1 out of every 5 people in the US A disease of the cell cycle Cancer cells do not respond normally to the cell cycle control system Cancer cells can form tumors Abnormally growing masses of cells If a tumor is malignant It can spread to other parts of the body A person with malignant cancer cells is said to have cancer Cancer cells spread from a malignant tumor Metastasis is the spread of cancer A cell that is no longer responding to growth controls is said to be Transformation transformed Usually transformed cells are destroyed by the immune system If not a tumor forms A benign tumor the cells remain at the original site A malignant tumor the cells can spread to neighboring tissues or other parts of the body metastasis Types of Cancer Named according to where the originate 4 main categories 1 Carcinomas in external or internal coverings Intestine 2 Sarcomas in support tissues muscle or bone 3 Leukemia in the bone marrow 4 Lymphomas in the lymph glands Genetic Basis of Cancer In recent years scientists have learned more about the genetics of cancer As early as 1911 certain viruses were known to cause cancer Cancer causing viruses often carry specific genes called oncogenes Proto oncogenes Are normal genes that can become oncogenes Are found in many animals Code for growth factors that stimulate cell division For a proto oncogene to become an oncogene a mutation must occur in the cell s DNA KNOW THE THREE WAYS A PROTO ONCOGENE CAN BECOME CANCEROUS Inhibit cell division Tumor suppressor genes Prevent uncontrolled cell growth May be mutated and contribute to cancer Ex P53 is a tumor suppressor The p53 protein senses DNA damage and can halt progression of the cell cycle in G1 It also forces damaged cells to undergo apoptosis Programmed suicide Over 150 000 Americans will be stricken by cancer of the colon or The Progression of Cancer rectum this year Colon cancer Spreads gradually Is produced by more than one mutation The development of a malignant tumor is accompanied by a gradual accumulation of mutations that Convert proto oncogenes to oncogenes Knock out tumor suppressor genes Inherited Cancer Mutations that lead to cancer usually arise in the organ cancer starts in These mutations don t affect reproductive cells so not passed on to children Other changes must still occur Cancer is always a genetic disease because it always results from changes in DNA In some families mutations in one or more genes predisposing the recipient to cancer can be passed on Breast cancer has nothing to do with inherited mutations in the vast majority of cases In some families can be caused by inherited cancer genes Can be caused by mutations affecting the BRCA1 and BRCA2 genes Viruses and Cancer Some viruses have been shown to cause cancer Ex Human papilloma virus has been found in 99 7 of all cervical cancers Also associated with 40 of all cancers of the penis The mechanism is well understood HOW can viruses cause cancer Some viruses become part of the host cell s DNA In order to get copied These viruses can be involved in cancer if They carry an oncogene or a mutated tumor suppressor gene as part of their genome Probably picked up a human gene randomly during evolution 2 Or they alter expression of the host cell s copy of one of these genes Chapter Nine Genetics October 22 2012 Testing Your Baby Genetic testing allows expectant parents to test for possibilities in their unborn child Includes amniocentesis and CVS know what both stand for Has risks associated with it Heritable Variation and Patterns of Inheritance Various traits exist in organisms These traits are usually inherited in particular patterns Gregor Mendel Considered the father of genetics Was the first person to analyze patterns of inheritance Deduced the fundamental principles of genetics Mendel studied garden sweet peas These plants are easily manipulated These plants can self fertilize He created true breeding varieties of plants Mendel then crossed two different true breeding varieties creating hybrids The offspring from these crosses are called the first filial or F1 generation Figure 9 3 true breeding Monohybrid Crosses A monohybrid cross is a cross between parent plants that differ in only one characteristic P Generation true breeding parents purple flowers X white flowers F1 Generation All plants have purple flowers and Fertilization among F1 plants F1XF1 F2 Generation of plants have purple flowers and of plants have white flowers 1 There are alternative forms of genes the units that determine heritable traits Four hypotheses 2 For each inherited character an organism inherits 2 alleles 1 from each parent 3 If the 2 alleles of an inherited pair differ the one determines the organism s appearance and is called the dominant allele the other has no noticeable effect on the organism s appearance and is called the recessive allele 4 A sperm of egg carries only 1 allele for each inherited character because the 2 members of an allele pair separate from each other during the production of gametes Genetic Alleles and Homologous Chromosomes Homologous chromosomes have genes at specific loci Have alleles of a gene at the same locus When an organism has identical alleles for a gene When an organism has different alleles for a gene An organism s physical traits Homozygous Heterozygous Phenotype Genotype An organism s genetic makeup There should be 2 copies of each gene Pairs of alleles segregate separate during gamete formation the fusion of gametes at fertilization creates allele pairs again Mendel s principle of independent assortment Each pair of alleles segregates independently of the other pairs during gamete formation Using a Testcross to Determine an Unknown Genotype A testcross is a mating between an individual of unknown genotype and a homozygous recessive individual Human Disorders Controlled by a Single Gene Family Pedigrees Shows the history of a trait in a family Allows researchers to analyze human traits Know how to read a Pedigree Many human