EDP Chapter 2.docx

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Educational Psychology
EDP 3326
Janet Bagby

Chapter 2 9/1/2013 6:29:00 PM Distinguish between genotypes and phenotypes.  Phenotypes- directly observable characteristics; way you look  Genotypes- the complex blend of genetic information that determines our species and influences all our unique characteristics; genetic makeup Describe the structure and function of chromosomes and DNA molecules.  Chromosomes- rod-like structures which store and transmit genetic information o 23 matching pairs o each member of a pair corresponds to the other in size, shape and genetic functions o one set of 23 is inherited from the mother, and the other set of 23 is inherited from the father o store and transmit genetic information  DNA (deoxyribonucleic acid)- chemical substance that chromosomes are made up of o Forms a twisted ladder like structure o Each rung has a pair of bases (chemical substances) o Bases A and T are always paired together o Bases C and G are always paired together o DNA can duplicate itself through mitosis Describe the genetic events that determine the sex of the new organism. rd  The 23 chromosomal pair determines the sex of the organism and is referred to as the sex chromosomes  in females this pair is XX  in males this pair is XY  the X chromosome is relatively large, while the Y chromosome is short and carries little genetic material  when gametes form in males, the X and Y chromosomes separate into different sperm cells  the gametes that form in females all carry an X chromosome  therefore, the sex of the new organism is determined by whether an X-bearing or a Y-bearing sperm fertilizes the ovum Identify two types of twins, and explain how each is created.  Fraternal, or dizygotic, twins- the most common type of multiple birth, resulting from the release and fertilization of two ova o Genetically no more alike than regular siblings o Fraternal twins account for 1 in about every 60 births o Fraternal twinning often runs in families, causing women to be more genetically predisposed to produce two ova at one time  Identical, or monozygotic, twins- occurs when a zygote that has started to duplicate separates into two clusters of cells that develop into two individuals, thus the twins have the same genetic make-up o Identical twins account for 1 in every 330 births o In a minority of identical twin births, identical twinning runs in families Describe major chromosomal abnormalities.  Down syndrome o The most common chromosomal disorder, 1 out of every 770 live births st o 95% of cases, results from a failure of the 21 pair of chromosomes to separate during meiosis, so the new baby receives 3 of these chromosomes instead of 2 o sometimes called trisomy 21 o or an error occurs during the early stages of mitosis, causing some but not all body cells to have the defective chromosomal makeup (symptoms are often less extreme because this involves less genetic material) o consequences:  mental retardation  memory and speech problems  limited vocabulary  slow motor development o physical features  short, stocky build  flattened face  protruding tongue  almond-shaped eyes  an unusual crease running across the palm of the hand (occurs in 50% of cases) o infants with down syndrome are often born with  eye cataracts  hearing loss  heart and intestinal defects o many survive into their 50s, and a few into the 60s to 80s, but more than half the individuals who lived past age 40 show symptoms of alzheimer’s disease  genes on the 21 chromosome are linked to this disorder o infants with downs smile less readily, show poor eye-to-eye contact, have weak muscle tone, and explore objects less persistently o the older the mother, the more likely down syndrome is possible  abnormalities of the sex chromosome o disorders on autosomes, other than down syndrome, usually disrupt development so severely that miscarriage occurs; if they survive to birth, they rarely survive past early childhood o on the other hand, disorders of the sex chromosome usually leads to fewer problems, and are often not recognized until adolescence when puberty is delayed o most common problems involve the presence of an extra chromosome (either X or Y) or the absence of one X in females o XYY syndrome  Extra Y chromosome  Above average height  Large teeth  Sometimes severe acne  Intelligence, male sexual development and fertility are normal  1 in 1,000 male births  no special treatment necessary o triple X syndrome (XX
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