Slide 1 Chapter 15: The Chromosomal Basis of Inheritance

Figure 15.1

Figure 15.2 P Generation F 1 Generation Yellow-round seeds (YYRR) Green-wrinkled seeds (yyrr)  Meiosis Fertilization Gametes Y Y R R Y R y y r y r All F 1 plants produce yellow-round seeds (YyRr). Meiosis Metaphase I Anaphase I Metaphase II R R R R R R R R R R R R rr r r rr r r r r r r YY Y Y Y Y Y Y Y Y Y Y y y y y y y y y y y y y Gametes LAW OF SEGREGATION The two alleles for each gene separate during gamete formation. LAW OF INDEPENDENT ASSORTMENT Alleles of genes on nonhomologous chromosomes assort independently during gamete formation /41/4 1/41/4 1/41/4 1/41/4 YR yr Yr yR F 2 Generation 3 3 Fertilization recombines the R and r alleles at random. Fertilization results in the 9:3:3:1 phenotypic ratio in the F 2 generation. An F 1  F 1 cross-fertilization 9 : 3 : 1 r

Figure 15.3 Thomas Hunt Morgan and his Fruit Flies

Figure 15.4 All offspring had red eyes. P Generation F 1 Generation F 2 Generation F 1 Generation P Generation Eggs Sperm X X X Y ww ww ww ww ww ww ww ww ww ww ww w w w w ww RESULTS EXPERIMENT CONCLUSION Morgan’s Experiment

Figure 15.6 Parents or Sperm or Egg Zygotes (offspring) 44  XY 44  XX 22  X 22  Y 22  X 44  XX 44  XY 22  XX 22  X 76  ZW 76  ZZ 32 (Diploid) 16 (Haploid) (a) The X-Y system (b) The X-0 system (c) The Z-W system (d) The haplo-diploid system Sex Determination

Figure 15.5 X Y Human Sex Chromosomes

Figure 15.7 Eggs Sperm (a) (b) (c) XNXNXNXN XnYXnY XNXnXNXn XNYXNY XNXnXNXn XnYXnY XnXn Y XNXN Y Y XnXn XnXn XnXn XNXN XNXN XNXN XNXN XNXnXNXn XNYXNY XNYXNY XNYXNYXNYXNY XnYXnY XnYXnY XNXnXNXn XNXnXNXn XNXnXNXn XNXNXNXN XnXnXnXn Sex Linked Genes

Figure 15.8 Early embryo: X chromosomes Allele for orange fur Allele for black fur Two cell populations in adult cat: Cell division and X chromosome inactivation Active X Inactive X Active X Black fur Orange fur X Inactivation

Figure P Generation (homozygous) Wild type (gray body, normal wings) b  b  vg  vg  b b vg vg Double mutant (black body, vestigial wings) EXPERIMENT

Figure P Generation (homozygous) Wild type (gray body, normal wings) F 1 dihybrid (wild type) TESTCROSS b  b  vg  vg  b  b vg  vg b b vg vg Double mutant (black body, vestigial wings) Double mutant EXPERIMENT

Figure P Generation (homozygous) Wild type (gray body, normal wings) F 1 dihybrid (wild type) Testcross offspring TESTCROSS b  b  vg  vg  b  b vg  vg b b vg vg Double mutant (black body, vestigial wings) Double mutant Eggs Sperm EXPERIMENT Wild type (gray-normal) Black- vestigial Gray- vestigial Black- normal b  vg  b vg b  vgb vg  b  b vg  vg b b vg vgb  b vg vgb b vg  vg b vg

Figure P Generation (homozygous) Wild type (gray body, normal wings) F 1 dihybrid (wild type) Testcross offspring TESTCROSS b  b  vg  vg  b  b vg  vg b b vg vg Double mutant (black body, vestigial wings) Double mutant Eggs Sperm EXPERIMENT RESULTS PREDICTED RATIOS Wild type (gray-normal) Black- vestigial Gray- vestigial Black- normal b  vg  b vg b  vgb vg  b  b vg  vg b b vg vgb  b vg vgb b vg  vg If genes are located on different chromosomes: If genes are located on the same chromosome and parental alleles are always inherited together: : : : : : : : : : b vg

Figure 15.UN01 Most offspring F 1 dihybrid female and homozygous recessive male in testcross or b + vg + b vg b + vg + b vg

Figure 15.UN02 Gametes from green- wrinkled homozygous recessive parent (yyrr) Gametes from yellow-round dihybrid parent (YyRr) Recombinant offspring Parental- type offspring YR yr Yr yR yr YyRr yyrr Yyrr yyRr

Figure Testcross parents Replication of chromosomes Gray body, normal wings (F 1 dihybrid) Black body, vestigial wings (double mutant) Replication of chromosomes Meiosis I Meiosis II Meiosis I and II Recombinant chromosomes Eggs b  vg  b vg b  vg  b  vg b vg  b vg b  vg  b  vg b vg b vg  Testcross offspring 965 Wild type (gray-normal) 944 Black- vestigial 206 Gray- vestigial 185 Black- normal Sperm Parental-type offspring Recombinant offspring Recombination frequency 391 recombinants 2,300 total offspring  100  17%  b  vg  b vg  b  vg b vg

Figure 15.10a Testcross parents Replication of chromosomes Gray body, normal wings (F 1 dihybrid) Black body, vestigial wings (double mutant) Replication of chromosomes Meiosis I Meiosis II Meiosis I and II Recombinant chromosomes Eggs b  vg  b vg b  vg  b  vg b vg  b vg b  vg  b  vg b vg b vg  Sperm b vg

Figure 15.10b Testcross offspring 965 Wild type (gray-normal) 944 Black- vestigial 206 Gray- vestigial 185 Black- normal Sperm Parental-type offspringRecombinant offspring Recombination frequency 391 recombinants 2,300 total offspring  100  17%  b  vg  b vg  b  vg b vg Eggs Recombinant chromosomes b  vg  b vg b  vg b vg 

Figure Chromosome Recombination frequencies 9% 9.5% 17% b cn vg RESULTS

Figure Mutant phenotypes Short aristae Black body Cinnabar eyes Vestigial wings Brown eyes Long aristae (appendages on head) Gray body Red eyes Normal wings Red eyes Wild-type phenotypes

Slide 21 Chromosomal Mutations Alteration of chromosome numberAlteration of chromosome number AneuploidyAneuploidy Monosomic (2n – 1)Monosomic (2n – 1) Trisomic (2n + 1)Trisomic (2n + 1) PolyploidyPolyploidy Alteration in chromosome structureAlteration in chromosome structure

Slide 22 Chromosomal Mutations Alteration of chromosome numberAlteration of chromosome number AneuploidyAneuploidy Monosomic (2n – 1)Monosomic (2n – 1) Trisomic (2n + 1)Trisomic (2n + 1) PolyploidyPolyploidy Alteration in chromosome structureAlteration in chromosome structure

Figure Meiosis I Meiosis II Nondisjunction Non- disjunction Gametes Number of chromosomes Nondisjunction of homo- logous chromosomes in meiosis I (a) Nondisjunction of sister chromatids in meiosis II (b) n  1 n  1 n  1 n  1 n  1 n n

Figure 15.15

Slide 25 Aneuploidy in Sex Chromosomes

Slide 26 Chromosomal Mutations Alteration of chromosome numberAlteration of chromosome number AneuploidyAneuploidy Monosomic (2n – 1)Monosomic (2n – 1) Trisomic (2n + 1)Trisomic (2n + 1) PolyploidyPolyploidy Alteration in chromosome structureAlteration in chromosome structure

Slide 27 Chromosomal Mutations Alteration of chromosome numberAlteration of chromosome number AneuploidyAneuploidy Monosomic (2n – 1)Monosomic (2n – 1) Trisomic (2n + 1)Trisomic (2n + 1) PolyploidyPolyploidy Alteration in chromosome structureAlteration in chromosome structure

Figure (a) Deletion (b) Duplication (c) Inversion (d) Translocation A deletion removes a chromosomal segment. A duplication repeats a segment. An inversion reverses a segment within a chromosome. A translocation moves a segment from one chromosome to a nonhomologous chromosome. ABCDEFGH ABCEFGH ABCDEFGH ABCDEFGHBC ABCDEFGH ADCBEFGH ABCDEFGH MNOPQR G MNOC HFED ABPQ R

Figure Normal chromosome 9 Normal chromosome 22 Reciprocal translocation Translocated chromosome 9 Translocated chromosome 22 (Philadelphia chromosome)

Slide 30 Exceptions to Chromosome Theory Genomic imprintingGenomic imprinting Organelle genesOrganelle genes