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Transcript
Ch. 10 Mendel and Meiosis I. Gregor Mendel’s Laws of Heredity A. Why Mendel Succeeded - “The Father of Genetics”, used ___________ to understand heredity a). _______________ – the passing on of characteristics from parents to offspring b). _______________ – studies heredity c). _______________ - characteristics that are inherited 1. Mendel chose his subject carefully – Mendel studied heredity in ______ plants. Garden pea plants reproduce sexually, which means they have two distinct _______________ a). Gametes – ________ _______. Ex: sperm in males, and eggs in females b). _______________ – the transfer of male pollen grains to the pistil of a flower c). _______________ – the uniting of male and female gametes Human Egg Human Sperm pollination 2. Mendel was a careful researcher. He only studied ____ variable at a time. B. Mendel’s Monohybrid Crosses – He crossed 6ft. tall plants with short plants Human Fertilization (zygote) a). _______ ________ – offspring with same parental traits b). _______________ – offspring of parents that have different forms of a trait 1. The first generation (“Parent”) 2. The second generation (“1st Filial”) 3. The third generation (“2nd filial”) EX: (P) (P) (F1) (F2) _______________ (hand fertilized) _______________ (self fertilized) _______________ (self fertilized) 4. The rule of unit factors – Mendel concluded that each trait has 2 factors that control it a). _______________ – a genetic factor that controls a trait R R b). _______________ – different versions of a gene for the same trait r c). _______________ – the observed trait Ex: tongue rolling d). _______________ – the trait that disappeared Ex: nonr roller 5. Mendel’s Laws: a). The Law of b). The Law of _______________ – c). The Law of _______________ _______________ when 2 alleles are different, 1 allele _______________ – gene pairs – each pair of can control the trait and 1 can be segregate into gametes randomly and alleles separates hidden (ex: tall vs. short plants) independently of each other C. Phenotypes and Genotypes a). _______________ – b). _______________ the way an organism – the actual genetic looks and behaves makeup Ex: tongue rolling Ex: TT or Tt Ex: non-roller Ex: tt c). _______________ – when 2 alleles for a trait are the same Ex: TT Ex: tt d). _______________ – When 2 alleles for a trait are different Ex: Tt D. Mendel’s Dihybrid Crosses – a test cross that looks at 2 traits at a time 1. The first generation cross – 2. The second generation E. Punntt Squares and Probability (P) Round Yellow (RRYY) vs. Wrinkled Green (rryy) (F1) 9:3:3:1 ratio Genes on 10.2 Meiosis chromosomes A. Genes, Chromosomes, and Numbers – genes are lined up on _________________________ 1. Diploid and haploid cells a). ___________ (2N) – a cell with 2 of each kind of chromosome Ex: human body cells (ex: cheek) ________________ b). _________ (N) – a cell with 1 of each kind of chromosome Ex: human sex cells (ex: eggs or sperm) N =23 Homologous 2. __________________ _____________________– The 2 chromosomes of each pair in a diploid cell. Humans have 23 pairs. 3. Why ________________? Sexual reproduction ensures that no offspring is exactly like its parent. By sharing genetic information, populations share favorable characteristics that allow them to survive and reproduce a). Meiosis – cell division that produces _____ the number of chromosomes as the parent’s body cells. b). ________________– male gametes c). ________________– female gametes Sexual reproduction d). ________________– a fertilized egg e). _____________ ___ ________________ – produces and fuses haploid cells B. The Phases of Meiosis 1. ________________– cells replicate chromosomes 2. ________________I – Tetrads (homologous chromosomes) condense and pair-up closely a). ____________ ____________– the exchange of genetic information between nonsister chromatids 3. ________________I – homologous chromosomes line-up in the middle of the cell 4. ______________ I - homologous chromosomes separate chromosomes 5. ________________I – the cell divides into two diploid cells 6. The phases of Meiosis II – the cell divides again producing _________ haploid gametes prophase II metaphase II Anaphase II Telophase II C. Meiosis Provides for Genetic Variation 1. ____________ _____________– the recombination of genetic information by crossing over or independent assortment of chromosomes D. Mistakes in Meiosis a). ________________– the failure of homologous chromosomes to separate during meiosis 1. ________________ (2N + 1)- when nondisjuction causes a extra chromosome in a haploid cell Ex: Down’s syndrome is trisomy of the 21st pair. The individual has 47 chromosomes 2. ________________ (2N – 1) - when nondisjunction causes a missing chromosome in a haploid cell, the zygote usually dies Ex: Turner’s syndrome (female with 1 X ) 3. _____________________- when nondisjunction occurs in all the chromosome pairs (deadly in animals) Ex: some bananas, lilies, wheat