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Chapter 3

Chapter 3- Genetics 2480-Huron

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Department
Psychology
Course
Psychology 2410A/B
Professor
Christine Tsang
Semester
Fall

Description
Chapter 3: Heredity and the Environmenth Some Basic Definitions  Genotype a person’s particular set of genes that are inherited from his or her parents. Aside from identical twins, no sets of genotypes are the same. Genotypes interact with the environment to produce the phenotype  Phenotype the visible expression of individual’s genetic traits. Characteristics include motor abilities, intellectual skills, and social behavior.  Gene’s parts of a chromosome that codes for the production of proteins, enzymes, that underlies characteristics that are inherited from on generation to the next. o How do chromosomes carry units of hereditary information? Gene chromosome and codes for the production of certain kinds of protein. o Each protein serves a different function. Some give characteristic physical properties (ex- bone cells get their hardness) other triggerchemical reactions, carrying chemical messages, fighting foreign invaders, regulating genes  Alleles, which are an alternative forms of gene. Typically a gene has two alleles, on inherited from the mother and one from the father. Ex- you have a gene that codes for eye color, one allele is blue eyed color. Sex chromosomes do not have two alleles Cell Division and Chromosome Duplication  Human body contains roughly 10 trillion cells, majority containing a nucleus  Chromosomes are thread like structures located in the nucleus of a cell that carries genetic information to help direct development and tell the cell to produce certain protein types. These protein types are strands of DNA.  Deoxyribonucleic acid (DNA) is a molecule that acts as the binding element of a chromosome.  DNA is made up of nucleotides Adenine and thymine form a bond, cytosine and guanine bond  Two Proceses:  Mitosis refers to the replication of autosomes (non sex chromosomes. You have a mother cell where a cell duplicates its chromosomes and ends up splitting to the north and south pole of the cell, and then divides into daughter cells with the exact same number of chromosomes as their parent. The zygote divides and continues to have the full complement of 46 chromosomes, and gradual becomes a multicellular organism.  Meiosis relates to sex chromosomes only. the process y that the germ cell divides to produce new germ cells in which the 23 chromosome pairs are halfed so that each contains on 23 chromosomes. Thus, went the egg and sperm unite, the new organism will have 46 chromosomes, half from each parent. The mixing of the chromosomes is random, allowing for a random assortment of 8 million different chromosome combinations  Genetic variability is further enhanced during meiosis with the process of crossing over  Crossing over: when equivalent sections of homologous chromosomes switch places so that genetic information is shuffled even more.  The zygote, develops in the mother body becoming an embryo, then a fetus and then a living infant  Mitosis the occurs in all autosome (non sex chromosomes) as well as sex chromosomes where a cell duplicates its chromosomes and then divides into daughter cells with the exact same number of chromosomes as their parent. The zygote divides and continues to have the full complement of 46 chromosomes, and gradual becomes a muticellular organism.  Meiosis the process y that the germ cell divides to produce new germ cells in which the 23 chromosome pairs are halfed so that each contains on 23 chromosomes. Thus, went the egg and sperm unite, the new organism will have 46 chromosomes, half from each parent. The mixing of the chromosomes is random, allowing for a random assortment of 8 million different chromosome combinations Crossing Over  Crossing over: when equivalent sections of homologous chromosomes switch places so that genetic information is shuffled even more. The two strands of dna wind aound aeach other and swap genes.  The zygote, develops in the mother body becoming an embryo, then a fetus and then a living infant  Genetic variability is further enhanced during meiosis with this process o If it was simply the case that one mother and father each passed on one chromosome, siblings would have the same characteristics. Because of crossing over, there are 64 trillion possibilities. o However, crossing over is limited. WE tend to hang out with people who have similar culture. Thus, we tend to marry people within the same social group. Previously it was not common that mixed racial marriages would take place. Gene expression  Work by Gregor Mendel, he crossbreed a short and tall pea plant, during his time it was thought that a combination of these traits should occur, thus a medium plant. However a tall plant was the result. By breeding the next generation, a short stem plant was the above  He worked out two principles: principles of segregation (each inherited trait comes from ones parent as a separate unit) and principle of independent assortment (inheritance of various traits occur independently. Inheritance of color has nothing got do with inheritance of height)  How do mendles principles correspond to the disappearance and reappearance o short and tall stems? o Homozygous is if the alleles for a particular trait from each of the parent are the same (AA, aa) o Heterozygous is when an individuals alleles from each parent are different. (Aa, or aA which is the same thing)  Why do certain characteristics disappear and then reappear? o If it is homozygous, the plant will inherit that characteristic o However, it is heterozygous, the more powerful, the dominant gene will be expressed. o Dominant the more powerful of the two alleles in a heterozygous combination- ex- angelinas lips o Recessive the weaker of two alleles in a heterozygous combination- ex- brad pitt lips  most harmful genes are recessive. one of the reasons why the voidance of intermarriages as it will be less likely for the recessive gene to be passed down.  Co-dominance is a pattern where heterogeneous alleles express those variants of the trait for which they code simultaneously and with equal force. They exist togther but in a non blended way. Ex – blood type. If a person inherits the allele from blood type A and one from blood type B , they will be blood type AB with bother A and B antigens  Incolomplete omincance where neither gene is dominant, and the two alleles become blended o Sickle cell anemia- a disorder henre the circulular form of blood cells tthat allows them to move through the circulatory system easily is mis shappenn, and is in the form f sickles. Thus, it creates a problem for movement through the circulatory system. If homozygous, you end up with ighly mishappen lood cells, and the disease is often terminal. However, if heterozygous, the individuals manifes some sympotoms ofcicle cell anemia but not to the same degree o If it is terminal, why does it still exist?  Because of the individuals who are heterozygous. Those who are heterozygous are provided with an dvantage over other people in the world.  Pleiotropism occurs when one gne influences multiple phenotypic traits. Conseuqentually,a mutation in thegene might have an affect on some or all of the traits o Polygenetic inheritance when many genes cn code for the same trait. Ex- we have found a gene that is linke to al timers, but have not been able to stop it showing there are other things that affect it. o Many characteristics are determined by a combination of multiple pairs of genes acting together. Ex- intelligence, creativity. The development of these traits depends on the configuration of many genes, and is generally not passed down to children. Ex- Genius o Modifier genes: genes that exert their influence indirectly, by affecting the expression of still other genes. Genetic Abnormalities  Mutation o A sudden change in the molecular structure of a gene. o It can occur spontaneously. Or as the resut of an envrionement even such as bein exposed to radiaition. They are not necessarly negative, just the echnaisi of mutation. o The majority of mutatitionals are detrmilntal but because of their detrimental nature do not get passed down o Darwing: darm mothsand ight moths, because of a mutation. When thte trees were lights, the lighter ones were more successful but when the indiustrial revolusion came around darm moths survived o •Mutation- the british royal family. Victoria and her conert had a number of childeren. Whern you look at the liniage, victoria has the gene for hemophelia. However, no on ebefore her had this gene. Well how did she get it? She was a genetic mutant. Somehow the gene was mutated in her, and she passed it to many of the royal houses. In the russia royal house, one was a carrier. That daughter ended up passing the gene and the full disorder onto the son. None of those childeren had childeren as they were killed in the first world war. The current royal family come from a linenage that does not have the gene  Inheritance o Resessive defective genese  •Ressesive defective genes- in order to exhibit these traits, you have to be homozygous recessive. Yu have to get one from fathe, one from mother As long as the individual has one normal allele, they will not be effected. This is why potnentially harmful alleales survive  •Cystic fibrosis: it’s a disorder that is masked by the allele that is not the disorder. Mucas is filling up in the lungs  phenylketonuria PKU which is a disorder of an enzyme which causees problems in breaking down phenylanin which is present in milk. If they are not treated, substances will build up and damage the nervous system cause mental retardation.  Tay sahcs- remains in the jewish people. It is a disease that usually happens to sons, where the child is born normal, but over the course of the first two to three years, the o Dominant defective genes  •his means you can be hetrozgous for the disorder, but you will still express the disorder.  •Hungtingso chorea- motor disease  Williams syndrome- the amethysts of downsydrome, asdie form improved language  •How do these dominent deffective genes remain in the gene pool as they would kill you?  •With huntingtons chorea, they don’t know they have it until later. Thus, they have kids before they know it o Sex-linked defective genes  genes that require or are linked to the x chromosome. The interesting thing is that often times women are carriers for the disorder, and the males express the disorder.  Because the X chromosome is larger than the Y chromosome it carries more genes. Thus, the genes on a male X chromosome will not be equivalent to the genes on his Y chromosome and any recessive xlinked genes will be expressed, and the male’s y genes will have no counteracting dominant genes. X Linked genes genes that are carried on the X chromosome that ma have no analogous genes on the Y chromosome of the male  In females, the xlinked recessive genes are expressed less frequently because the female usually has a dominant allele on the X chromosome  Colour Blindness  Hemophilia is a disorder in which the blood fails to clot. It is an example of an x related recessive characteristic. a female will have normally clotting blood, unless she is homozygous for the recessive gene. males have a greater likelihood of getting it as they can receive another hemophilia allele on his Y chromosome, or the genes on his Y chromosome might not have an allele to counter the gene on his y chromosome. rd o Sex chromosomes chromosome in both males and females, the 23 pair of chromosomes, which determine the individuals gender and are responsible for sex related characteristics n females (XX) and males it has either an X chromosome from the other or a Y chromosome from his father, the pattern is referred to as XY Chromosomal abnormalities  Some disorders are not caused by single genes or gene groups, but rather defects in entire chromosomes  Parts of chromosomes are deleted, duplicated or relocated.  Chromosomal affects arise during meiosis, not present in parent  Generally, the aberration proves lethal and the zygote aborts. However, if the zygote is able to survive the abnormal condition, they will be born with a chromosomal defect Down Syndrome  Down syndrome aka trisomy 21 is characterized by mental retardation, and a distinctive physical appearance. They generally have short stature almond shaped eyes with a fold in their eyelid and one or more other unusual characteristics. They are also highly more susceptible to illnesses such as leukemia, heart disorders, and respirator infections, and severe to moderate mental retardation  Caused by a deviation in the chromosomes labeled number 21, instead of having a pair there are three  With advances in treatment, 70% live into there 60s. However, they have a great risk of developing Alzheimer’
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