biologyfinalexamreview

Regulation checkpoints to fail o a benign tumor is a

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regulation (checkpoints) to fail o A benign tumor is a large, but normal, mass of cells that is stationary o Can be removed surgically o Only dangerous if it damages surrounding healthy tissue o Some stay benign forever o Some have the ability to become dangerous: malignant o Sometimes cells in a tumor change form & can break off to move around the body: malignant tumor Can move via the blood stream or lymphatic system (“immune system”) These moving cells invade other parts of the body & begin new masses/tumors: metastasis Chapter 10: Homo- vs. heterozygous; dominant vs. recessive; genotype vs. phenotype - If both chromosomes carry the same allele, the organism is homozygous - If both chromosomes carry different alleles, the organism is heterozygous - When 2 different alleles are present in an organism (heterozygous), a dominant allele may mask a recessive allele o e.g. In peas the purple-flower trait is dominant to the white-flower trait o (purple allele + white allele = purple flower) - The particular combination of the 2 alleles carried by an individual = the genotype (what you have ) - The physical expression of the genotype = the phenotype (what you show ) o e.g. Purple flowers (Dominant: P) + White flowers (recessive: p) = Purple flowers o Genotype = Pp (Purple; White) o Phenotype = Purple flowers Punnett square: % chance for offspring - The Punnett square method: - Predicts the probability of offspring genotypes & phenotypes using combinations of parental gametes o Genotype: 50% chance offspring are Ll 50% chance offspring are ll o -Phenotype: -50% chance offspring have short hair -50% chance offspring have long hair Sex chromosomes, sex-linked genes - Mammals have a set of sex chromosomes that dictate gender - Females have two X chromosomes
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- Males have an X chromosome and a Y chromosome - So how is the sex of offspring determined? - Sex-linked genes o Found only on the X or on the Y (not both) sex chromosomes o Some genes found only on the X chromosome are important to both sexes e.g. genes for color vision, blood clotting, & certain proteins in muscles ABO blood groups A single gene may have multiple alleles The human blood types are an example of multiple alleles of a single gene Human blood group genes have three alleles: A, B, and O These can produce FOUR possible blood phenotypes: A, B, AB, and O 3. Some alleles are codominant : both are expressed in entirety e.g. Blood types A and B are codominant over O, which is recessive The genotype A-A = phenotype A (homozygous) The genotype B-B = phenotype B (homozygous) The genotype O-O = phenotype O (homozygous) The genotype A-O = phenotype A (heterozygous) The genotype B-O = phenotype B (heterozygous) The genotype A-B = phenotype AB (heterozygous & codominant ) (6 possible genotypes, 4 possible phenotypes) Carriers, risk of disease for recessive vs. dominant genetic disorders (not examples) - Some genetic disorders are caused by recessive alleles o Heterozygous parents can show unaffected phenotypes but be carriers of the recessive allele o
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