Heredity & Evolution

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Exploring Biological Anthropology:
The Essentials, 3rd Edition

CRAIG STANFORD

JOHN S. ALLEN

SUSAN C. ANTÓN

As you work through this set of chapter slides, keep in mind the notations that are included from your instructor. Open, read carefully, download if necessary, and use in conjunction with your reading and video lesson study. All these components supplement each other. The wise student will keep this in mind.

Chapter 4
Genetics: From Genotype to Phenotype

How does an organism end up looking like it does? Read on and learn.

From Genotype to Phenotype

Structural Genes

Regulatory Genes

Structural genes contain the information to make a protein. Regulatory genes direct the expression of structural genes, without coding for a protein themselves. Think of the regulatory gene as the traffic cop.

From Genotype to Phenotype (cont’d)

Genotype

Phenotype

Think here of the blue print vs. the finished product. Architectural plan vs. completed structure.

Phenotype refers to one’s particular traits or characteristics. This individual has blue eyes, so he inherited a genetic marker for this trait.

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

The first here (ABO) refers to the genetic system for one of the proteins found on the surface of red blood cells. It consists of one gene with three alleles..A, B, and O.

The second item here is very well documented in our times. Go to chapter four and flesh out your understanding of it.

Mendelian Genetics

Gregor Mendel (1822-1884)
Experiments in particulate inheritance
Discovered dichotomous variation
Developed a series of postulates about inheritance

Simply put, genetics as understood by the pioneering scientist named Mendel (a priest), even though the term “gene” had not yet been coined. Figure that one out!

Look him up in the textbook and listen carefully to the video lesson as to who Mendel was and his amazing work in and around the time of Darwin, even though they did not even know each other existed.

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

Otherwise put, Mendel’s understanding of the laws of inheritance, genetically speaking.

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

You got it. The big boy’s laws continued.

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

Simply put, certain genes are said to be “linked” and are found very closely together on the chromosome. Crossing over is what happens when a gene migrates to another “homologous” chromosome during the first prophase of meiosis. Go for it…read the relevant page/s on this.

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

Any alteration of the DNA that may or may not alter the function of a cell. Mutations can be good, bad, or even neutral.

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

Yeah, here it is! The good, the bad, and the “innocent” type.

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.

Genetic conditions that are entirely x-chromosome based.

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

Follow up on this at pp. 62 and following. Very important! On earlobe form, think “hanging” vs. “attached” earlobe. Check out your own. What form do you have?

Mendelian Genetics in Humans (cont’d)

The Online Mendelian Inheritance in Man (OMIM) Web site: (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=OMIM ) provides an extraordinary database on genetic conditions in humans, from the most innocuous to the most lethal

Go for it! Check out the web site. Live and learn.

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

Rather self-explanatory. Correct?

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

Read up on pp. 72-73.

Genetics Beyond Mendel (cont’d)

Variability caused by genetics

Variability caused by genetics + Variability caused by the environment

Continuation of same reading location.

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

Keep reading. This continues the post Mendelian science of genetics. By the way, can you spot the misspelling up above here? Hint…see the final entry in the line up.

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

Very important to know so as to be understanding of unfortunate folks who, through no fault of their own, are born with this condition.

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

Smoke? Binge drink? Do drugs? Pay close attention to this topic and stay as healthy as possible.