Genetics and Heredity “Why We Look the Way We Do” Genes: Our Biological Blueprint Genes basic units of heredity that maintain their structural identity from one generation to another. The biochemical units of heredity that make up the chromosomes a segment of DNA capable of synthesizing a protein Genes are aligned along chromosomes (strands of genes) and come in pairs.
Chromosomes threadlike structures made of DNA molecules that contain the genes DNA (deoxyribonucleic acid) a complex molecule containing the genetic information that makes up the chromosomes has two strands-forming a double helix”- held together by bonds between pairs of nucleotides A gene is a portion of a chromosome and is composed of deoxyribonucleic acid (DNA). DNA serves as a model for the synthesis of ribonucleic acid (RNA).
Genome the complete instructions for making an organism consisting of all the genetic material in its chromosomes outcomes: The 22 paired non-sex chromosomes. The Genetics of Behavior RNA is a single strand chemical that can serve as a template/ model for the synthesis of proteins. Proteins determine the development of the body by: forming part of the structure of the body. Irving as enzymes, biological catalysts that regulate chemical reactions in the body. Homozygous for a gene means that a person has an identical pair of genes on the two chromosomes.
Heterozygous for a gene means that a person has an unmatched pair of genes on the two chromosomes Genes are either dominant, recessive, or intermediate. Examples: eye color, ability to taste APT A dominant gene shows a strong effect in either the homozygous or heterozygous condition. A recessive gene shows its effect only in the homozygous condition. Types of genes include: Autocross genes – all other genes except for sex- linked genes. Sex-linked genes – genes located on the sex chromosomes. In mammals, the sex chromosomes are designated X & Y.
Females have two X chromosomes (XX). Males have an X and a Y chromosome (XX). During reproduction: Females contribute an X chromosome. Males contribute either an X or a Y chromosome that determines the sex of the child. If an X chromosome is contributed by the male, the off-spring is female. If a Y chromosome is contributed by the male, the off-spring will be male. 23 chromosomes – a gift from mom’s egg 23 chromosomes – a gift from dad’s sperm Modifier genes: Genes that influence a trait indirectly.
For example, a dominant gene affects whether people can get early cataracts, but modifier genes determine how serious the cataracts are likely to be. Often these modifier genes are located on different chromosomes. Genes work together. Most traits studied by psychologists are influenced by multiple genes (polygene) Most genes influence more than one trait (popularity). Sex-limited genes are genes that are present in both sexes but mainly have an effect on one sex (Chest hair, breast size, etc. ) Almost all behaviors have both a genetic component and an environmental component.
Researchers study minimization (“from one egg”) and fraternal (“from two eggs”) twins to infer contributions of heredity and environment Researchers also study adopted children and their resemblance to their biological parents to infer hereditary influences Heritability – refers to how much characteristics depend on genetic differences. Estimates of hereditary influences are often difficult to infer and are prone to error. Sources of error include the following: The inability to distinguish between the effects of genes and prenatal influences. Environmental factors can inactivate genes. Sources of error
Multiplier effect – genetic tendencies that guide behavior will result in a change in the environment that magnifies the original tendency. Traits with a strong hereditary influence can by modified by environmental intervention. Chromosome Problems Female xx sex chromosomes Male xx sex chromosomes At least one x chromosome is essential for life. A single y is never enough for development GENETICS OF BEHAVIOR Genes do not directly produce behaviors. Genes produce proteins that increase the probability that a behavior will develop under certain circumstances. Genes can also have an indirect affect.
Genes can alter your environment by producing behaviors or traits that alter how people in your environment react to you. Chromosomal disorders: Down syndrome Chromosomal disorders: Down syndrome is caused by non-disc]unction of the 21st chromosome during meiosis. As a result, the child has three 21st chromosomes instead of the normal two. Down Syndrome is a genetic disorder but it is not caused by having a harmful gene Many human disorders follow Madeline patterns of inheritance Cystic fibrosis, which strikes one out of every 2,500 whites of European descent but is much rarer in other groups.
One out of 25 whites (4% ) is a carrier. The normal allele (alternative versions of a gene)for this gene codes for a membrane protein that functions in chloride ion transport between certain cells and the extracurricular fluid. These chloride channels are defective or absent. The result is an abnormally high concentration of extracurricular chloride, which causes the mucus that coats certain cells to become thicker and stickier than normal. ATA-Cash disease is caused by a dysfunctional enzyme that fails to break down brain lipids of a certain class.
Is proportionately high incidence of ATA-Cash disease mongo Sneakiness Jews, Jewish people whose ancestors lived in central Europe Sickle-cell disease, which affects one out of 400 African Americans. Sickle-cell disease is caused by the substitution of a single amino acid in the hemoglobin protein of red blood cells Pattern Baldness In Humans: A Sex Influenced Trait Baldness is an autocross trait and is apparently influenced by sex hormones after people reach 30 years of age or older. In men the gene is dominant, while in women it is recessive.
A man needs only one allele (B) for the baldness trait to be expressed, while a bald woman must be homozygous for the trait (B). Human Genome Project, Findings Humans are 99. 95% identical Many human genes appear only in humans and appear to have come from bacteria. One gene makes 2 or 3 proteins, complex chains of amino acids that carry out the tasks of life. Every humans genome shows the residues of evolution. Dominant and Recessive Genes A dominant trait does not mean “more potent” and recessive does not mean “weaker. ” The terms refer to the visible trait. Is there a difference between female and male brains?
What do you think? What do we know? Evolutionary Psychology duty of the evolution of behavior using the principle of natural selection, which presumably favors genes that predispose behavior tendencies and information– processing systems that solved adaptive problems faced by our ancestors Evolutionary psychology (sociobiology) focuses upon functional explanations of how behaviors evolved. Assumes that behaviors characteristic of a species have arisen through natural selection and provide a survival advantage. Examples: differences in peripheral/color vision, sleep mechanisms in the brain, eating habits, temperature regulation.
How Evolutionary Psychology Works Many years of drought Finches evolved thicker beaks Enabled them to crack harder seeds Over many years of heavy rains Finches developed thinner beaks Enabled them to eat softer seeds E. P. , Children and Bedtime Why do young children resist going to bed? We say they are “spoiled. ” Is it true? In hunter-gatherer days, being alone in the dark was dangerous, monsters were real. Present day hunter-gathers consider allowing a child to sleep alone to be child abuse. Timothy Miller -Practical Implications of E. P. Humans strive for the prerequisites of reproductive success Wealth Status Love
From an evolutionary perspective there is no such thing as enough reproductive success. Genetic Effects on Taste The ability to taste Phenomenological (APT) Is an inherited trait. About 2/3 of Americans are tasters. Determined by one pair of alleles, T and t Ability to taste is dominant. Gender (in psychology) the characteristics, whether biologically or socially influenced, by which people define male and female What do we look for in mates? Countries with dots (OMG omitted plus refer to the PPTP) were surveyed as to their mating preferences, in all 10,047 people in 37 countries were asked.
Men – preferred attractive features, youth, and health preferred wealth, maturity, social status, health, attractive Natural Selection Women – the principle that, among the range of inherited trait variations, those contributing to reproduction and survival will most likely be passed on to succeeding generations Mutation a random error in gene replication that leads to a change in the sequence of nucleotides the source of all genetic diversity Four dimensions of sexuality on the Hendricks Sexual Attitude Scale 1. Remissness’s (items 1-21) = open, casual sexuality 2. Sexual practices (items 22-28) = expansible, tolerant sexuality 3. Communion in the relationship (items 29-37) = emotional, idealistic sexuality 4. Instrumentality (items 38-42) = sex as egocentric and very biological The Hendricks Sexual Attitude Scale Some findings about sex: 1 . Men identify a more casual, less conventional, and more manipulative approach. 2. Women are into love/sexuality – practical and conventional approach. 3.
Very religious people differed from most other’s responses. 4. Those who had been in love several times were more endorsing of “permissiveness” and some instrumentality. 5. Those currently in love were less permissive and instrumental and more endorsing of communion. Critiques of Evolutionary Psychology If men are committed to their mates, only those genes survived. If men are only interested in protecting their gene pool they would stay with the woman carrying their children. This evolutionary speculation “reinforces male-female stereotypes. We can be socialized to be monogamous or polygamous. Could be a result of acculturation into family and community structure. Behavior Genetics Identical Twins develop from a single fertilized egg that splits in two, creating two genetically identical organisms Fraternal Twins develop from separate eggs genetically no closer than brothers and sisters, but they share a fetal environment Behavior Genetics As you know striking similarities have sometimes been found between twins who are reunited after years of separation.
What does this mean? Social Implications Study of biological origins of behavior could lead to genocide and eugenics aimed at eliminating certain types of people Could also be used to create new categories of people, such as people bred to be good soldiers or manual laborers