Exploring Biological Anthropology The Essentials 3 rd Edition

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

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

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

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 (1822 -1884) 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 nontasting Copyright © 2013 Pearson Education, Inc. All rights reserved.

Mendelian Genetics in Humans (cont’d) • The Online Mendelian Inheritance in Man (OMIM) Web site: (http: //www. ncbi. nlm. nih. gov/entrez/quer 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 the environment

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 Copyright © 2013 Pearson Education, Inc. All rights reserved.