1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 10 Patterns of Inheritance

2. Learning Outcomes Explain how genetic traits are passed from one generation to the next Describe the role of chromosomes in inheritance Explain the relationship between dominant and recessive alleles of a gene Differentiate between a gene, allele, locus and chromosome Compare and contrast genotype and phenotype Differentiate between homozygous and heterozygous Explain how meiosis and the production of gametes are associated with inheritance

3. Learning Outcomes Use a punnet square to diagram and explain a monohybrid cross Use a punnet square to diagram and explain independent assortment in a dihybrid cross Explain how meiosis contributes to independent assortment of alleles Diagram meiosis to indicate how genes can be linked Explain how linked genes can be used to create a genetic map Compare and contrast dominant, recessive, incomplete dominant, and codominant

4. Learning Outcomes Explain how pleiotrophy can influence phenotype Diagram and explain why males show X-linked recessive traits more than females Explain why one X chromosome is typically inactivated in female cells Analyze a pedigree to determine what pattern of inheritance a trait displays Explain how the environment can influence phenotype

5. 10.1 Chromosomes Are Packets of Genetic Information: A Review Gene – portion of DNA coding for a protein Chromosomes Diploid – 23 pairs Homologous pairs Meiosis produces haploid cells Figure 10.1 Homologous Chromosomes. AA BB dd AA bb dd a. b. 10 µm Sister chromatids Gene A locus Gene B locus Alleles at one locus Homologous pair of chromosomes Centromeres LM Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © CNRI/ Photo Researchers

6. 10.1 Mastering Concepts How do meiosis, fertilization, diploid cells, and haploid cells interact in a sexual life cycle?

7. 10.2 Experiments Uncovered Basic Laws of Inheritance Gregor Mendel – 19 th century A. Why Peas? Easy to grow, develop quickly, and produce many offspring Many traits in 2 forms Easy to control matings – Self-fertilization or cross- fertilization

8. Figure 10.2 Mendel’s Experimental Approach for Breeding Peas. 234. 2. 3.4. 11.Stamens (male parts) removed from flowers of short pea plant to prevent self-pollination. Pollen from tall pea plant flower transferred to female part of short pea plant flower. Pod from cross-pollinated plant contains seeds, each representing an independent offspring. Mature plants developed from seeds can reveal inheritance pattern for gene controlling plant height. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

9. 10.2 Experiments Uncovered Basic Laws of Inheritance B. Dominant Alleles Appear to Mask Recessive Alleles True-breeding - self-fertilization always produced offspring identical to the parent plant Dominant allele – exerts its effects whenever it is present Recessive allele – one whose effect is masked

10. Clicker Question Which is TRUE of dominant alleles? A.Always the most common trait B.Always the best trait to have C.Replaces the recessive allele in the DNA D.None of the above are TRUE

11. Figure 10.3 All Possible Crosses. a. Self-fertilizationb. Cross-fertilization True breeding: all green seeds True breeding: all yellow seeds Some yellow, some green seeds All yellow seedsSome yellow, some green seeds Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

12. 10.2 Experiments Uncovered Basic Laws of Inheritance C. For Each Gene, a Cell’s Two Alleles May Be Identical or Different Diploid cell only carries 2 alleles for a gene at one time Genotype – Homozygous dominant – Homozygous recessive – Heterozygous

13. Clicker Question There is a gene for flower color where the dominant allele F is blue and the recessive allele f is white. What is this individuals genotype? FF A.Heterozygous B.Homozygous dominant C.Homozygous recessive D.Heterozygous dominant

14. 10.2 Experiments Uncovered Basic Laws of Inheritance C. For Each Gene, a Cell’s Two Alleles May Be Identical or Different Phenotype – Observable characteristic – Interaction between genes and environment – Wild-type or mutant

15. 10.2 Experiments Uncovered Basic Laws of Inheritance D. Every Generation Has a Name P generation – Parental F 1 generation – First filial F 2 generation – Offspring of F 1

16. 10.3 The Two Alleles of Each Gene End Up in Different Gametes A. Monohybrid Crosses Track the Inheritance of One Gene Mating between two individuals that are both heterozygous for the same gene Punnet square 3:1 phenotypic ratio

17. Figure 10.4 Punnett Square. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. YY Yyyy Yy Y Male parent y Female parent Yy Female gametes (1:1) Male gametes (1:1) Y y Genotypic ratio 1:2:1 (1 YY: 2 Yy: 1 yy) Phenotypic ratio 3:1 (3 yellow: 1 green)

18. R 12 3 4 6 5 7 r Y y V v Ff G g L l a A * Each ratio deviates slightly from the expected 3:1 because inheritance refl ects the rules of probability. Repeating each experiment would likely yield slightly different ratios, each very close to 3:1. Mendel’s Monohybrid Crosses Table 10.2 ExperimentTotal Plants Expressing Dominant Allele Plants Expressing Recessive Allele Ratio* 1. Seed form 2. Seed color 3. Pod form 4. Pod color 5. Flower position 6. Seed coat color 7. Stem length 7324 8023 1181 580 1064 929 858 787 tall (L) 705 gray (A) 651 axial (F) 428 green (G) 882 inflated (V) 6022 yellow (Y) 5474 round (R) 277 short (l) 224 white (a) 207 terminal (f) 152 yellow (g) 299 restricted (v) 2001 green (y) 1850 wrinkled (r) 2.84:1 3.15:1 3.14:1 2.82:1 2.95:1 3.01:1 2.96:1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

19. 10.3 The Two Alleles of Each Gene End Up in Different Gametes A. Monohybrid Crosses Track the Inheritance of One Gene Test cross – Homozygous recessive x unknown individual Figure 10.5 Test cross. yy Y y Y Male gametes y Y y y y If plant is homozygous dominant (YY): YY Female gametes Yellow seeds (Yy): 100% chance Yy yy If plant is heterozygous (Yy): Yy Female gametes Yellow seeds (Yy): 50% chance Green seeds (yy): 50% chance Yy yy Yy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

20. 10.3 The Two Alleles of Each Gene End Up in Different Gametes B. Meiosis Explains Mendel’s Law of Segregation 2 alleles of each gene are packaged into separate gametes They “segregate” during gamete formation During meiosis I, homologous pairs of chromosomes separate

21. Figure 10.6 Mendel’s Law of Segregation. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Y y Y Y Y Y Y Y y y Y Y Y Y Y Y Y Y y y Replicated homologous chromosomes Parent1 (heterozygous) Segregates alleles into gametes Replicated homologous chromosomes Parent2 (homozygous dominant) Segregates alleles Into gametes Gametes or Gametes combine at random. Offspring (F 1 ) (equal probability) MEIOSIS FERTILIZATION Gametes

22. 10.3 The Two Alleles of Each Gene End Up in Different Gametes B. Meiosis Explains Mendel’s Law of Segregation Applies to all diploid species Cystic fibrosis – recessive condition – Same probabilities as Mendel’s peas Figure 10.7 Mendel’s Law Applied to Humans. Ff Healthy carrier F F f Female gametes Mother: healthy carrier Male gametes Father: healthy carrier f FF Healthy non- carrier Affected ff Healthy carrier Ff Healthy noncarrier (FF): 25%chance Healthy carrier (Ff): 50%chance Affected (ff): 25%chance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Pat Pendarvis

23. Clicker Question Using the cystic fibrosis example, if a carrier (Ff) has children with an affected person (ff). What are the odds of having healthy children? A.100% B.50% C.25% D.0% Ff f f