1306 Patterns of Inheritance Spring 2022.pptx
- 5. Table 17.1
- 6. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Chromosomes are packets of genetic information Section 10.1 Recall that a chromosome is a piece of DNA containing many different genes. Each gene’s locus is its location on a chromosome. When two haploid sex cells fuse during fertilization, a diploid zygote with two full sets of chromosomes is formed. Figure 10.1 (a): ©CNRI/Science Source
- 8. Figure 17.9
- 13. Figure 17.16
- 14. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Offspring gave Mendel clues about the genes of the parents Section 10.2 Figure 10.3 True-breeding plants produce offspring identical to themselves. a.True-breeding: Self- fertilization yields offspring with same seed color as parent plant Hybrid plants outwardly resemble true-breeders but produce mixed offspring. b.Hybrid: Self- fertilization yields mix of seed colors
- 22. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Punnett squares represent gamete formation and fertilization A Punnett square uses the genotypes of the parents to reveal which alleles the offspring may inherit. Figure 10.6
- 23. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Punnett squares show how the alleles separate during meiosis Section 10.3 When germ cells divide by meiosis, the gametes receive one allele per gene. For the seed-color gene, there is an equal chance of receiving either allele Y or y. Figure 10.6
- 24. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Punnett squares show expected proportions of offspring Section 10.3 This Punnett square is a prediction that shows the relative proportion of the offspring phenotypes and genotypes. Figure 10.6
- 25. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Punnett squares help us answer Mendel’s questions Section 10.2 If yellow seed color is dominant, why are some seeds green when a yellow-seed plant is crossed with a green-seed plant? Figures 10.4, 10.5 Genotyp e Phenotyp e Homozygous dominant (YY) Yellow Heterozygous (Yy) Yellow Homozygous recessive (yy) Green
- 26. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Offspring can reveal parental genotypes: If a cross between a yellow- seed pea plant (YY or Yy) and a green-seed pea plant (yy) yields all yellow seeds, the yellow-seed parent is homozygous dominant. If a cross between a yellow- seed pea plant (YY or Yy) and a green-seed pea plant (yy) yields some green seeds, the yellow-seed parent is heterozygous.
- 27. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Punnett squares summarize meiosis and fertilization Section 10.3 The two alleles for the seed color gene are packaged into separate gametes, which then combine at random. Figure 10.9
- 28. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Mendel’s law can be applied to human traits Section 10.3 Punnett squares are also useful for tracking the inheritance of genetic disorders, such as cystic fibrosis. Figure 10.10 Health noncarrier (FF): 25% chance Healthy carrier (Ff): 50% chance Affected (ff): 25% chance
- 33. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Dihybrid crosses track the inheritance of two genes at once Section 10.4 Two genes on different chromosomes can be combined into one large Punnett square. Figure 10.11
- 34. Figure 17.11
- 36. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Not all genes follow Mendelian inheritance patterns Section 10.6 So far we’ve discussed genes with two alleles, in which the dominant allele masks the recessive allele. But alleles do not interact this way for all genes, which leads to alternative patterns of inheritance. Figure 10.17
- 37. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Incompletely dominant alleles create a blended heterozygote phenotype Section 10.6 When the red allele (r1) and white allele (r2) are both present, the heterozygote (r1r2) phenotype is an intermediate pink. The white allele encodes a nonfunctional pigment protein. Figure 10.17
- 40. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Codominant alleles do not mask each other Section 10.6 In codominance, more than one allele encodes a functional protein. Figure 10.18 Genotype s Phenotypes Surface molecules Phenotypes ABO blood type 𝐼𝐴 𝐼𝐴 𝐼𝐴 𝑖 Only A Type A 𝐼𝐵 𝐼𝐵 𝐼𝐵 𝑖 Only B Type B 𝐼𝐴 𝐼𝐵 Both A and B Type AB ii None Type O
- 41. Table 17.2
- 42. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Codominant alleles create a double phenotype Section 10.6 If two dominant alleles are present, both proteins encoded by those alleles will be represented in the phenotype. Figure 10.18 Genotype s Phenotypes Surface molecules Phenotypes ABO blood type 𝐼𝐴 𝐼𝐴 𝐼𝐴 𝑖 Only A Type A 𝐼𝐵 𝐼𝐵 𝐼𝐵 𝑖 Only B Type B 𝐼𝐴 𝐼𝐵 Both A and B Type AB ii None Type O
- 43. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Human blood type alleles A and B are both dominant over the O allele Section 10.6 The I gene also has a recessive allele, i, which encodes a nonfunctional protein. But the two dominant alleles, 𝐼𝐴 and 𝐼𝐵, make the I gene codominant. Figure 10.18 Genotype s Phenotypes Surface molecules Phenotypes ABO blood type 𝐼𝐴 𝐼𝐴 𝐼𝐴 𝑖 Only A Type A 𝐼𝐵 𝐼𝐵 𝐼𝐵 𝑖 Only B Type B 𝐼𝐴 𝐼𝐵 Both A and B Type AB ii None Type O
- 46. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. One gene, many phenotypes Section 10.6 In pleiotropy, one gene has multiple effects on the phenotype. For example, a gene might affect more than one biochemical pathway. Marfan syndrome is an example of pleiotropy. Figure 10.19 Photo:©Roger Kisby/Getty Images
- 47. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Products of different genes can interact with each other Section 10.6 Epistasis occurs when one gene’s product affects the expression of another gene. Expression of the h allele (gene 1) affects the expression of A and B alleles (gene 2). Figure 10.20
- 48. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Sex-linked genes have unique inheritance patterns Section 10.7 In humans, females have two X chromosomes (XX). Males have one X chromosome and one Y chromosome (XY). This Punnett square shows that each fertilization event has a 50% chance of producing a female and a 50% chance of producing a male. Figure 10.21 Girl (XX): 50% chance Boy (XY): 50% chance ©Andrew Syred/Science Source
- 51. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Sex-linked genes disorders can be dominant or recessive TABLE 10.2 Some X-Linked Disorders in Humans Disorder Genetic Explanation Characteristics X-linked recessive inheritance Duchenne muscular dystrophy Mutant allele of gene encoding dystrophin Rapid muscle degeneration early in life Fragile X syndrome Unstable region of X chromosome has unusually high number of CCG repeats Most common form of inherited intellectual disability Hemophilia A Mutant allele of gene encoding blood-clotting protein (factor VIII) Uncontrolled bleeding, easy brusing Red-green color blindness Mutant alleles of gene encoding receptors for red or green (or both) wavelengths of light Reduced ability to distinguish between red and green Rett syndrome Mutant allele encoding DNA-binding protein expressed in nerve cells Multiple severe development problems; occurs almost exclusively in females; affected male fetuses rarely survive to birth X-linked dominant inheritance Extra hairiness (congenital generalized hypertrichosis;some forms) Mechanism unknown Many more hair follicles than normal Hypophosphatemic rickets (some forms) Mutant allele of gene involved in phosphorus absorption Defective bones caused by low blood phosphorus Retinitis pigmentosa (some forms) Mutant allele of cell-signaling proteins; mechanism unknown Partial blindness caused by defects in retina
- 52. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. X-inactivation prevents double dosing of gene products and produces unique inheritance patterns Section 10.7 Each cell in an XX individual, such as these female cats, randomly inactivates one X chromosome. Figure 10.24 ©Siede Preis/Getty Images RF If one X chromosome has an allele for orange fur, and the other has an allele for black fur, color patterns emerge when X chromosomes are randomly inactivated.
- 53. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. X-linked dominant disorders are less severe in females Section 10.7 In humans, an X-linked disorder called Rett syndrome is lethal to boys and has varying effects on girls, depending on how many cells inactivate the X chromosome carrying the Rett allele. Figure 10.25 (a) : ©Andy Cross/The Denver Post via Getty Images; (b) : ©Moof/Cultura/Getty Images RF
- 54. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. A pedigree depicts family relationships and phenotypes Section 10.8 Figure 10.26 This pedigree tracks achondroplasia, an autosomal dominant disorder. (a) : ©Rick Wilking/Reuters/Corbis
- 55. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Pedigrees show modes of inheritance Section 10.8 Figure 10.26 This pedigree tracks an autosomal recessive disorder. This pedigree tracks an X- linked recessive disorder. Note that more males are affected than females
- 56. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. The environment can alter phenotype Section 10.9 Many genes are affected by the environment. For example, the enzyme responsible for pigment production in Siamese cat fur is active only in cool body parts. In warm body parts, no color is produced. Figure 10.27 ©Carolyn A. McKeone/Science Source
- 57. ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Some traits depend on multiple genes Section 10.9 Skin color is a polygenic trait; it is affected by more than one gene. Figure 10.29 ©Sarah Leen/National Geographic Stock