HG&D: Chapter 3 part 2 Pages 70-88

A person who has a gene in his or her genotype that is not expressed in the phenotype but that can be passed on to the person’s offspring is said to be a carrier of that gene.

The complexity of genetic interaction is particularly apparent in behavior genetics, which is the study of the genetic origins of psychological characteristics. These include traits such as personality…and sociability, assertiveness, moodiness, fearfulness...

…psychological disorders such as schizophrenia …psychological disorders such as schizophrenia...depression, ADHD; and cognitive traits such as memory of #s, spatial perception, and fluency of expression.

Most behavioral traits are affected by the interaction of large numbers of genes with environmental factors. Traits that are plastic early in life do not always remain plastic thereafter.

The most feared form of senility is Alzheimers disease, which occurs when the protein amyloid B accumulates in the brain and kills cells. When this disease occurs before age 50, which is referred to as early- onset, the cause is entirely genetic. More common is the late-onset form of the disease, which is more prevalent in people over 80 who inherited a particular allele of the ApoE gene.

Although the gene increases the risk of the disease, other health indicators are also factors, including hypertension, diabetes, and higher cholesterol.

Psychopathologies such as Psychopathologies such as *depression are genetically based traits that are also subject to environmental influence. *also include antisocial behavior, phobias, and compulsions.

Environmental influences do play an important role in the appearance of schizophrenia. One prediposing factor is birth during late winter, probably because a certain virus is more prevalent at this time of the year.

Alcoholism is partly genetic, furthermore, its expression is affected by the environment. Certain temperamental traits correlate with abusive drinking, including a quick temper, risk taker, and anxiety.

On a practical level, genes and environment affect every human characteristic.

Researchers study genetic and chromosomal abnormalities for three major reasons: -provide insight -knowledge of origin; maybe prevalent -understand them better; not misinformation

Chromosomal abnormalities occur during the formation of gametes, producing a sperm or ovum that does not have the normal complement of chromosomes.

The variable that most often correlates with chromosomal abnormalities is maternal age. When cells in a zygote end up with more or fewer than 46 chromosomes the result is a person who is mosaic.

Most fetuses with chromosomal abnormalities are spontaneously aborted (miscarriage). Nevertheless, about 1 in every 200 newborns has one chromosome too few or one too many, leading to a cluster of characteristics called a syndrome.

The most common extra-chromosome syndrome is Down’s, which is also called trisomy-21. People with this syndrome age faster than other adults. By middle age, people with Down syndrome almost invariable develop Alzheimers, which severely impairs their already limited communication skills.

Several of the physical and psychological characteristics associated with Down syndrome: -thick tongue -round face -slanted eyes -hearing problems -heart problems -short stature -mental slowness

About 1 in every 500 infants is either missing a sex chromosome or has two or more such chromosomes. One resulting syndrome is Klinefelter syndrome, in which a boy inherits the XXY chromosome pattern.

Most of the known genetic disorders are dominant Most of the known genetic disorders are dominant. Genetic disorders usually are not seriously disabling. It is much more likely that a person is a carrier of one or more harmful genes than that he or she has abnormal chromosomes.

Two exceptions are the central nervous system disease called Huntington’s and the disorder that causes its victims to exhibit uncontrollable tics and explosive outbursts, called Tourette syndrome.

In some individuals, part of the X chromosome is attached by such a thin string of molecules that it seems about to break off; this abnormality is called fragile X syndrome.

Genetic disorders that are recessive and multifactorial claim more victims than dominant ones. Three common recessive disorders are cystic fibrosis, thalassemia, and sickle-cell anemia.

Through prenatal genetic counseling, couples today can learn more about their genes and about their chances of conceiving a child with chromosomal or other genetic abnormalities.

Four situations in which genetic counseling is strongly recommended: -parent, sibling, child with serious genetic disease -history of spontaneous abortions; stillbirths -couples from same ethnic group -women over 35; men over 40

Among the many reproductive alternatives available to those who are carriers of a serious condition or at high risk because of their age or family history are: -avoid pregnancy -plan to adopt -in vitro

The innovative new prenatal therapy called genetic engineering involves the altering of an organism’s genetic instructions.