Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-1 Human Genetics Concepts and Applications Eighth Edition Powerpoint Lecture Outline Ricki Lewis Prepared by Dubear Kroening University of Wisconsin-Fox Valley

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-2 Chapter 4 Mendelian Inheritance

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-3 Inheritance A child inherits half of its genes from each parent How are traits assorted with each generation? Figure 4.1

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-4 Gregor Mendel Research in plant breeding Without knowledge of DNA, cells, or chromosomes Described the units of inheritance and how they pass from generation to generation Not recognized during his lifetime

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-5 Gregor Mendel Experimented from Developed the laws of inheritance Used Controlled plant breeding Careful recordkeeping Large numbers Statistics

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-6 Mendel Studied Transmission of Seven Traits in the Pea Plants Figure 4.2

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-7 True Breeding Plants Offspring have the same trait as parent Examples: Round seeded parents –produce all round seeded offspring Yellow seeded parents –produce all yellow seeded offspring Short parents –produce all short offspring

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-8 Monohybrid Cross True breeding plants with two forms of a trait are crossed Progeny show only one form of the trait The observed trait is dominant The masked trait is recessive

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-9 Monohybrid Cross Parental generation (P 1 ) Tall X Short F1F1 All Tall F2F2 ¼ Short ¾ Tall Figure 4.3

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Alleles Mendel’s units (or “elementen”) are alleles Versions of the same gene or DNA sequence. Differ in DNA sequence at one or more sites.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Mendel's Law of Segregation Each plant possesses two units (alleles) for each trait Alleles separate in the formation of gametes Gametes contain ONE allele for each trait

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Figure 4.4

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Mendel’s Data Table 4.1

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Genotype The alleles present in an individual –Homozygous carry the same alleles TT or tt –Heterozygous carry different alleles Tt Phenotype Indicates the trait observed Tall or Short Wild Type Most common phenotype Mutant phenotype A product of a change in the DNA Terms

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Punnett Square Represent particular genes in gametes and how they may combine Figure 4.5

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Test Cross Identifies parents with an unknown genotype Figure 4.6

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Autosomal Inheritance Human autosomal traits are located on the non sex chromosomes (1-22) They may be inherited as –Autosomal dominant or –Autosomal recessive

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Autosomal Dominant Homozygous dominant and heterozygotes exhibit the affected phenotype Males and females are equally affected and may transmit the trait Affected phenotype does not skip generation Figure 4.7

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Autosomal Recessive Only homozygous recessive individuals exhibit the affected phenotype Males and females are equally affected and may transmit the trait May skip generations Figure 4.8

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Reading 4.1, Figure 1

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Probability The likelihood that an event will occur The probability that a coin will land heads up is ½ The probability that a heterozygous individual (Bb) will produce a gamete with the B allele is ½

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Solving Genetics Problems List genotypes and phenotypes for the trait Determine the genotypes of the parents Possible gametes Possible genotypes of offspring Repeat for successive generations

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Meaning of Dominance and Recessive Whether an allele is dominant or recessive is important in determining risk and critical in medical genetics Reflect the characteristics or abundance of a protein Recessive traits have “loss of function” Dominant traits have “gain of function”

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Maintaining Detrimental or Lethal Alleles in a Population Recessive traits are maintained in a population in the heterozygotes How can a dominant lethal allele such as Huntington disease be maintained in a population?

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Mendel’s Second Law of Independent Assortment Two genes on different chromosomes segregate their alleles independently The inheritance of one does not influence the chance of inheriting the other

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Law of Independent Assortment Figure 4.9

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Independent Assortment of Two Traits Figure 4.10

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Independent Events The probability of simultaneous independent events = the product of the probability of each event Example: If both parents are heterozygous (Bb) what is the probability that they will produce a BB child? Probability of a sperm with B allele = ½ Probability of an ova with B allele = ½ Probability of a BB child is ½ X ½ = ¼

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Independent Events If both parents are heterozygous for two genes, what is the probability of having a homozygous recessive child? Figure 4.11

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Figure 4.12

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Dependent Events The probability of dependent events = the sum of probability of each event Example Parents are heterozygous for a trait, R. What is the chance that their child carries at least one dominant R allele? Probability of child carrying RR = ¼ Probability of child carrying Rr = ½ Probability of child carrying R_ = ¼ + ½ = ¾

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Pedigrees symbolic representations of family relationships and inheritance of a trait Figure 4.13

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display A Pedigree with Consanguinity Figure 4.14a

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Autosomal Recessive Inheritance Albinism Figure 4.15

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Autosomal Dominant Inheritance Brachydactyly-disproportionately short fingers and toes. Figure 4.16

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Genetic Predictions Ellen’s brother Michael has sickle cell anemia, an autosomal recessive disease. What is the probability that Ellen’s child has a sickle cell anemia allele?

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig Ellen and Michael’s parents must be heterozyg ous Assume Tim is not a carrier

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Applied Ques. 4.Chands Syndrome Text Figure 4.20

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Applied Ques. #6. Congenital insensitivity to pain

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Applied Ques. #8 Tay-Sachs Disease Autosomal recessive

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Applied Ques. #11 Sclerosteosis

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Applied Question #13 Kawasaki Syndrome- inflammation of the heart.