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The Causes of Individual Differences • Genes usually act in pairs • Humans posses chromosomes in pairs, with each chromosome containing genes for a particular characteristic, one gene can sometimes dominate. • Genes contain one or more alleles, which can be recessive or dominant. • An allele is one of the different forms of a single gene. • Dominant gene – is when that particular characteristic is expressed. • Recessive gene – when one gene has little or none of its characteristic expressed. • Eye colour is an example of dominant genes (pg 261 fig 10.4) • BB or bb are said to be homozygous as both genes are the same for a particular characteristic. • Bb or bB are said to be heterozygous as both genes for a particular characteristic are different. • Sometimes genes can be co-dominant where one gene is not entirely dominant over another gene. • Karyotype is a persons entire set of genetic material. • Genotype is used to describe the genetic code for those genetically determined characteristics that have the potential to be expressed. • Phenotype is the collection of traits of characteristics that are actually expressed by the individual. • Example looking at figure 10.4 from pg 262 • Genotype potential to have either blue or brown eyes yet Phenotype is expressed as having brown eyes. Achieving Maximum Potential • Both genetic and environmental factors play a part in determining whether or not a person eventually achieves their full genetic potential. • Genetic potential can be viewed from that it allows for an “upper” limit or optimal amount of various types of growth and development. • Example is that a very tall child has one short and one tall parent. It could be said that they are programmed to reach a maximum height predetermined by their genetics, however all must go to plan. • For example diet, exercise, illness etc… Ethnicity • Plays a significant role in determining an individuals overall pattern of growth and development. • Obvious differences that can be seen, skin, height, hair colour, eyes etc…. • Vary in the ethnic groups too • Blood disorder “Thalassemia” is common among certain population groups. It is an inherited disorder associated with the production of the haemoglobin that is used to carry oxygen around the body. Rate and Timing of Development • Genetically determined and hormone controlled. • Adolescent growth spurt differs among individuals on two bases: • 1) Sex (females and males) when it begins • 2) The difference in the AMOUNT and RATE of which growth occurs. (not only a change in height and weight but also in overall body proportion, size and function of several major organs in the body) • During the slow and steady phase of growth the pituitary gland is maturing, which is prompted by the hormones released by the hypothalamus • The pituitary gland produces its own hormones that also trigger an increase in hormone production by the adrenal glads as well as the male testes and the female ovaries. • The increase in hormone production results in growth spurt and pubertal changes. • Menarche also varies in timing and amongst different ethnic groups. (pg 265 Table 10.1) Longevity • Several factors are know to impact longevity, one of the most significant factor is sex. • Females live longer than men. • One reason for this maybe because of the hormone difference. • Different hormones levels may reduce the risk of certain diseases e.g./ men have a lower oestrogen level therefore have an increased risk of coronary heart disease. • Environmental factors have a major impact on longevity, diet, smoking, alcohol etc… Inherited Disease • Some individuals can be more susceptible to some forms of disease. • Genetically inherited disease can be the result of: • Mutation and/or • Defect of one or more genes/chromosomes • Expression of a recessive characteristic on the end of the X chromosome • Chromosomal abnormalities usually are the result of cell division gone wrong in the gametes or embryo. • This can lead to faulty chromosomes or cells that contain an incorrect number of chromosomes Inherited Disease • Gene abnormalities occur during the process of translocation (swapping of genes) during cell division. One normal gene (sometimes more than one) is replaced by an abnormal gene for a particular characteristic. • This can be inherited in future generations. • Genetically inherited disease can be transferred through sex-linked (sex chromosomes the X or Y) or autosomal (nonsex chromosomes), means. • Look at table 10.2 pg 266 • Do activity 10.5 from page 266-267 of text book. Genetic Predisposition to Disease • While someone may not experience any symptoms of a particular disease, it is possible for that person to be more susceptible to or at risk of developing that disease due to the fact that it runs in the family, (familial inheritance). • Coronary artery disease (CAD): increased risk due to a mutation in a number of genes that are responsible for controlling the action of low-density lipoproteins (LDL), which transport cholesterol around the body. • Mutation in a particular gene associated with one of the lipoproteins on chromosome 2 can lead to high levels of cholesterol and consequently an increase risk of CAD. Hypertension • Two consequences for hypertension are stroke and heart disease • Strong link of family history and the development of hypertension • Again chromosome 2 seems to be responsible • LUNG CANCER: There is a link between family members and the likelihood of development of lung cancer. • It has been discovered that there is a chromosome directly linked to the risk of the onset of lung cancer. • People with a family history and a next generation relative with early onset lung cancer were shown to have a greater risk of developing the disease • Black participants in the study were found to be more susceptible to the onset of lung cancer than their white counterparts. The Human Genome Project (HGP) • The HGP is an international research project investigating and mapping of the entire human genome. • It began in 1990 and completed in 2003. • It consists of somewhere between 30 000 and 35 000 human genes. • HGP hopes to map the location of each individual gene and its DNA subunit pattern. • The fact that they know the location of certain individual genes as well as what they do is very important. • Can develop new treatments for genetically inherited diseases, as well as partially environmentally influecned health problems. Hormonal Influences on development • Hormones: chemicals that are produced around various sites of the body. • Hormones influence the growth and development throughout the lifespan. • Each hormone has a particular structure and specific function(s) to perform. • Hormones form a communication system throughout the body. • Hormones are produced by a series of glands or production sites (endocrine system). • Cells are programmed to produce and secrete specific chemical substances • Some genetic influence on the rate and timing of the release of the hormones. Hormonal Influences on development • • Pituitary gland is the leader of the other glands in the endocrine system. It is located at the base of the brain and releases a range of hormones, which in turn trigger the production of hormones from other parts of the body. Hormonal Influences on development • Hormone production sites throughout the body Hormonal Influences on development • The pituitary gland is controlled by the hypothalamus, and it transmits messages via nerve cells to the pituitary gland to either release or not to release pituitary gland hormones. • The pituitary gland can be divided into two parts the anterior and the posterior pituitary gland. • They are responsible for the release of certain hormones. Hormonal Influences on development • Refer to page 271-272 for the table of hormones responsible for growth and development. • The END!