Copyright © 2013 Pearson Education, Inc. All rights reserved. Exploring Biological Anthropology: The Essentials, 3 rd Edition CRAIG STANFORD JOHN S. ALLEN SUSAN C. ANTÓN

Copyright © 2013 Pearson Education, Inc. All rights reserved. Chapter 4 Genetics: From Genotype to Phenotype

Copyright © 2013 Pearson Education, Inc. All rights reserved. From Genotype to Phenotype Structural Genes Regulatory Genes

Copyright © 2013 Pearson Education, Inc. All rights reserved. From Genotype to Phenotype (cont’d) Genotype Phenotype

Copyright © 2013 Pearson Education, Inc. All rights reserved. From Genotype to Phenotype (cont’d) The ABO Blood Type System – Recessive, dominant and co-dominant alleles Obesity: A Complex Interaction – Genes, environment, and phenotype

Copyright © 2013 Pearson Education, Inc. All rights reserved. Mendelian Genetics Gregor Mendel ( ) Experiments in particulate inheritance Discovered dichotomous variation Developed a series of postulates about inheritance

Copyright © 2013 Pearson Education, Inc. All rights reserved. Mendel’s Postulates Hereditary characteristics are controlled by particulate unit factors that exist in pairs in individual organisms When an individual has two different unit factors responsible for a characteristic, only one is expressed and is said to be dominant to the other, which is said to be recessive

Copyright © 2013 Pearson Education, Inc. All rights reserved. Mendel’s Postulates (cont’d) Mendel’s Law of Segregation: during the formation of gametes, the paired unit factors separate or segregate randomly so that each sex cell receives one or the other with equal likelihood Mendel’s Law of Independent Assortment: during gamete formation, segregating pairs of unit factors assort independently of each other

Copyright © 2013 Pearson Education, Inc. All rights reserved. Linkage and Assortment Linkage: genes found on the same chromosome are said to be linked. The closer together two genes are, the greater the linkage Crossing Over: makes possible the independent assortment of linked genes

Copyright © 2013 Pearson Education, Inc. All rights reserved. Mutation Point Mutation and Sickle Cell Disease: when a single base in a gene is changed Trinucleotide Repeat Disease: involves the insertion mutation or deletion mutation of several bases in sequence of a gene – Huntington Disease: caused by the repeat of the sequence CAG (code for glutamine) 40 – 180 times on chromosome 4

Copyright © 2013 Pearson Education, Inc. All rights reserved. Mutation (cont’d) “Bad” Mutations – Reduction in the protein’s ability to function, causing mild reduction in fitness with lethal results Neutral Mutations: – No change in protein form of function or slight changes with no effect on reproduction (no contribution to phenotype) “Good” Mutations: – Increases protein’s ability to function; enhances fitness

Copyright © 2013 Pearson Education, Inc. All rights reserved. X-Linked Disorders Genetic conditions that result from mutations to genes on the X chromosome. They are almost always expressed in males, who have only one copy of the X chromosome.

Copyright © 2013 Pearson Education, Inc. All rights reserved. Mendelian Genetics in Humans Over the past century, hundreds of human disorders and diseases have been cataloged, which can be explained in terms of Mendelian genetic transmission – Earlobe form – Phenylthiocarbamide (PTC) tasting or non- tasting

Copyright © 2013 Pearson Education, Inc. All rights reserved. Mendelian Genetics in Humans (cont’d) The Online Mendelian Inheritance in Man (OMIM) Web site: ( y.fcgi?db=OMIM ) provides an extraordinary database on genetic conditions in humans, from the most innocuous to the most lethal

Copyright © 2013 Pearson Education, Inc. All rights reserved. Genetics Beyond Mendel Qualitative variation Phenotypic variation that can be characterized as belonging to discrete, observable categories Quantitative variation Phenotypic variation that is characterized by the distribution of continuous variation within a population

Copyright © 2013 Pearson Education, Inc. All rights reserved. Genetics Beyond Mendel (cont’d) Polygenic Traits, the Phenotype, and the Environment – Heritability The proportion of total phenotypic variability observed for a given trait that can be ascribed to genetic factors

Copyright © 2013 Pearson Education, Inc. All rights reserved. Genetics Beyond Mendel (cont’d) Variability caused by genetics Variability caused by genetics + Variability caused by the environment

Copyright © 2013 Pearson Education, Inc. All rights reserved. Genetics Beyond Mendel (cont’d) Heritability and IQ Test Score Performance – IQ Test Score Performance Exhibit continuous variation in human populations, with a normal distribution Genetics is an important factor in producing the variation observed within populations Both genetics and environment effect IQ score variation

Copyright © 2013 Pearson Education, Inc. All rights reserved. Phenylketonuria: Illustrating Mendelian and Post-Mendelian Concepts Autosomal recessive condition that leads to the accumulation of large quantities of the amino acid phenylalanine, which causes mental retardation and other phenotypic abnormalities – Screening in newborns – Nutritional prognosis

Copyright © 2013 Pearson Education, Inc. All rights reserved. Genes and Environments Environment – From a gene’s perspective the “environment” is made up of other genes The genetic environment is just as critical to the production of phenotypes as any other kind of environment