Sexual Reproduction and Genetic Transmission General points: chromosome-a threadlike structure made up of genes, in humans, there are 46 chromosomes in every cell, except sperm and ova Dna- (deoxyribonucleic acid) a long double-stranded molecule that makes up chromosomes Gene- The segments on a DNA molecule that act as hereditary blueprints for the organism?s development Zygote- the singe cell formed at conception from the union of the sperm and the ovum Mitosis: a process of cell replication (mitotic process- the process of cell duplication and division that generates all the individual?s cells except sperm and ova, somatic cells- all the cells in the body except the germ cells (sperm and ova)) Meiosis: a source of genetic variation (process of meiosis- the process that produces sperm and ova, each of which contains only half of the parent cell?s original complement of 46 chromosomes, germ cells- the sperm and ova, which are specialized for sexual reproduction and have half the number of chromosomes normal for a species, crossing over and variability- the process in which genetic material is exchanged between chromosomes containing genes for the same characteristic, monozygotic twins- twins that come from one zygote and therefore have identical genotypes, dizygotic twins- twins that come from two zygotes) Sexual determination as a source of variation (X and Y chromosomes) Women: XX, Men: XY all ova: X, sperm: half X, half Y. The two chromosomes that determine the sex of the individual. Normal females have two X chromosomes, while normal males have one Y chromosome inherited from their fathers and one X chromosome inherited from their mothers. Genotype (individual?s genetic makeup) and Phenotype (individual?s observable characteristics, created through genotype-environment interactions) Laws of genetic inheritance Dominant genes- the allele that is expressed when an individual possesses two different alleles for the same trait, recessive genes- the allele that is not expressed when an individual possesses two different alleles for the same trait, and codominace- alleles that do not dominate over one another, instead the trait produced shares traits from both of the original ones: alleles- the specific form of a gene coded for a particular trait, homozygocity outcomes- having inherited two genes of the same allelic forms for a trait, heterozygocity outcomes- having inherited two genes of different allelic forms for a trait, codominance outcomes- outcome in which a trait that is determined by two alleles is different from the trait produced by either of the contributing alleles alone; discrete traits- traits involving a single gene that operate as ?either-or? traits because a person either has one or does not and polygenetic traits- a genetic trait that is determined by the interaction of several genes Sex-linked genetic effects: sex-linked characteristics (generally carried on X chromosome); males more susceptible to genetic defects than females- traits determined by genes that are found on only the X or the Y chromosome Genes, the person, and the environment (genetic influence) Studying gene-environment interactions: principles 1st- that interactions between organisms and their environments need to be studied in a broad, ecological framework to account for differences in environment, 2nd- gene-environment interaction is a two-way process person -> environment, environment -> person, 3rd- genetic factors often play a role in the type of environment a person will inhabit Range of reaction Himalayan rabbit responding to the ice on his back and his fur turned black in order to trap and hold in heat, how well it can react to the environment that it is placed in Canalization the process that makes some traits relatively invulnerable to environmental events, like water running into a canal, the further it goes the more difficult it is to change Study of genectic influence on behavior (genetic influence) Heritability: what does it mean? A measure of the degree to which a variation in a particular trait among individuals in a specific population is related to genetic differences among those individuals Kinship studies: the use of naturally occurring conditions provided by kinship relations to estimate genetic and environmental contributions to a phenotypic trait use in estimating genetic and environmental contributions to phenotypic traits- family, adoption, and twin studies that determine how people are affected by their genes versus their environment, however these studies are really not that useful or accurate because there is nothing in them that rules out genetics or environment as the contributing factor to any condition Mutations and Genetic Abnormalities General: What is a mutation? An error in the process of gene replication that results in a change in the molecular structure of the DNA Why are mutations important for understanding development? So that it can be fixed or dealt with, to reduce the impact of the abnormality on the family, and to reveal how they work Examples of genetic abnormalities, observing gene-environment interactions (or: the influence of environmental events on the phenotypic expression of genotype; focus on why and how these examples illustrate the influence of environmental on genetic inheritance): Phenylketonuria: a treatable genetic disease if these disease is caught and treated early enough with a diet low in phenylalanine then there will not be any irreversible damage to the brain, the environment greatly affects the outcome of this, because the environment can change whether or not the person has brain damage or not Sickle-cell anemia: an example of gene-environmental interaction People in West Africa are much more likely to get sickle-cell anemia than those people in America because sickle-cell anemia makes you resistant to malaria, a disease that is highly prevalent in West Africa, so although some people die of sickle-cell anemia, there are still many heterozygous carriers of the mutation because it makes them more immune to malaria Klinefelter?s syndrome: a sex-linked chromosomal abnormality. A male with a chromosome configuration of XXY rather than just XY. Drawing on Chapter 2 and the New York Times article about Klinefelter?s syndrome, focus especially on the symptoms of Klinefelter?s syndrome as well as the physical and behavioral treatments for alleviating major effects of the syndrome. Symptoms: lack of facial hair growth, voices do not change, sex organs do not mature, they are sterile, sometimes begin to develop breasts Treatments: Physical: testosterone replacement therapy that allows more normal hair growth, sexual drive, libido, voice change, more manly distribution of fat, increased strength and bone density, removal of excess breast tissue is possible Behavioral: special education can help to compensate for their slowed learning abilities, and the testosterone can also help to relieve some depression and under-the-weather moods Biology and Culture: Biology, culture and survival strategies: ?cultural inheritance,? the role of culture in shaping the environment of human development Some things are culturally inherited such as how, where, and when to hunt food, how to speak, how to think logically about math, these ideas are passed on both culturally and genetically, but ?hazard preventing strategies? must be passed on in order for there to be a next generation. Biological and cultural factors have evolved somewhat together in a process called coevolution, culture has influenced biology (i.e. brains (frontal lobes) are larger now than they used to be due to more critical thinking and storage of knowledge
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