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Genetics Terminology

Genetics Terminology. Trait -characteristic or quality EX: Tongue rolling. The gene codes for the trait. There are 2 versions of the gene called Alleles. Can roll tongue = Dominant = T Cannot roll tongue. = Recessive = t

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Genetics Terminology

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  1. Genetics Terminology • Trait-characteristic or quality • EX: Tongue rolling. • The gene codes for the trait. There are 2 versions of the gene called Alleles. • Can roll tongue = Dominant = T • Cannot roll tongue. = Recessive = t Each trait receives two alleles, one from the mother, one from the father.

  2. Homozygous: all of the same alleles. • TT or tt • Heterozygous: Different alleles • Tt • Genotype: Phenotype • TT : Rolls Tongue • Tt : Rolls Tongue • tt : cannot roll • Phenotype: Physical/feel • Genotype: Genes • Trait-characteristic or quality • EX: Tongue rolling. • The gene codes for the trait. There are 2 versions of the gene called Alleles. • Can roll tongue = Dominant = T • Cannot roll tongue. = Recessive = t Each trait receives two alleles, one from the mother, one from the father.

  3. Genetic Crosses • Monohybrid: one trait • Dihybrid: two traits • Working backwards with you -grandparents: P generation - parents : F1 Generation -You: F2 generation Test Cross: used to determine if a phenotypically dominant individual is homozygous or heterozygous True-breeding: homozygous for a trait. • Homozygous: all of the same alleles. • TT or tt • Heterozygous: Different alleles • Tt • Genotype: Phenotype • TT : Rolls Tongue • Tt : Rolls Tongue • tt : cannot roll • Phenotype: Physical • Genotype: Genes

  4. Test Cross • Unknown dominant x known recessive • See example on the board • Look at the offspring of the test cross to determine if it is heter or homozygous. • Monohybrid: one trait • Dihybrid: two traits • Working backwards with you -grandparents: P generation - parents : F1 Generation -You: F2 generation Test Cross: used to determine if a phenotypically dominant individual is homozygous or heterozygous

  5. 9,10,11 • 10. • B ½ • C. ¼ • 11. • A. 1/8 • B. 1/32 • C. 1/32 • D 1/32

  6. Complete Dominance • “Normal” dominance • The dominant allele is completely expressed over the recessive allele.

  7. Incomplete Dominance • Incomplete = IN between • The heterozygous genotypes have a phenotype that is IN between the two homozygous genotypes • Red-Pink-White • RR – Rr - rr

  8. Codominance and Multiple Alleles • Co dominant= Co-captains of equal strenth on a team. • The heterozygous alleles are equally expressed • Multiple alleles. An additional allele can represent the recessive.

  9. Pleiotropy-one gene has many effects Epistatis-one gene affects the expression of another gene  BbCc BbCc Sperm 1/4 1/4 1/4 1/4 BC bC Bc bc Eggs 1/4 BC BBCc BBCC BbCC BbCc 1/4 bC bbCC bbCc BbCC BbCc 1/4 Bc BBcc Bbcc BBCc BbCc 1/4 bc BbCc bbCc Bbcc bbcc : 4 9 : 3 More non-Dominant Inheritance

  10. Polygenic Inheritance-Many alleles develop a trait. Example: Skin Color Role of the environment  AaBbCc AaBbCc Sperm 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 Eggs 1/8 1/8 1/8 1/8 Phenotypes: 1/64 6/64 15/64 20/64 15/64 1/64 6/64 Number of dark-skin alleles: 2 6 0 3 4 5 1 Non-Dominant Inheritance

  11. Law of Segregation Law of Independent Assortment The 2 alleles that each parent has for a trait separate to make sex cells The alleles will be random in the sperm and egg. Ch 15-mostly review

  12. Grasshoppers = two x is female, one x is male Z-W system is opposite humans, females determine Bees-diploid are females, haploid are males. 44 + XX 44 + XY Parents 22 + X 22 + X 22 + Y or + Sperm Egg 44 + XX 44 + XY or Zygotes (offspring) (a) The X-Y system 22 + XX 22 + X (b) The X-0 system 76 + ZW 76 + ZZ (c) The Z-W system 32 (Diploid) 16 (Haploid) (d) The haplo-diploid system Not all like humans

  13. W+ is wild type, usually dominant always homozygous. • Only male flies can have white eyes if they receive their only x from the mutant x.

  14. XnY XnY XNXN XNXn  XNY XNXn   Sperm Sperm Sperm Xn Y XN Xn Y Y Eggs Eggs XNXN Eggs XNXn XNY XN XNY XN XNXn XNY XN XnXn XnY XNXn XNY XnXN XnY Xn Xn XN (a) (b) (c) Colorblindness: males are more affected than females. Gene is located on X chromosome, heterozygous females are carriers.

  15. Fig. 15-15 A B C D E F G H A B C E F G H Deletion (a) A B C D E F G H A B C B C D E F G H Duplication (b) A B C D E F G H A D C B E F G H Inversion (c) A B C D E F G H M N O C D E F G H (d) Reciprocal translocation M N O P Q R A B P Q R

  16. Quiz on Wednesday:chapter 16 • A, T, C, G bonds • Purines vs. Pyrimidine • 5’-3’ order • Replication, Transcription, Translation • Helicase, Leading and Lagging strand,

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