1.28.10 - Chapter 3 Heredity& Environment Genes are...

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Unformatted text preview: 1/28/2010 Chapter 3: Heredity & Environment - Genes are pervasive and powerful Child & Adolescent Development . But often, they are also elusive and hidden Spring 2010 __,. . They provide the blueprint for our development, Dr. Christine Hughes but environmental forces can either hinder or University of Miami promote development in certain areas 1;... l—_— CHROMDSOME (DNA MOLECULE Genetic Code - Chromosomes - organized into genes - How many do we have? ,___.. :- 1—. Karyotype Human Genome Project . Human genome = full set of genes that are the instructions to make an individual member of a certain species - Project: an international effort to map the entire human genome - has already revealed a great deal about the nature of genes and genetic variations The Beginning of Life - Development begins at conception = sperm penetrates the ovum . Gamete = a reproductive cell (sperm or ovum) . The organism is first called a zygote: the single cell formed from the fusing of two gametes (a sperm and an ovum) . The genotype of the zygote is the genetic information on the 23 chromosome pairs Male or Female? XX is a 23rd chromosome pair XYis 21 23rd chromosome pair that consists of two X—shaped that consists of an X—shaped chromosomes, one each from chromosome from the the mother and the father. mother and a Y—shaped chromosome from the father. )Qr' zygotes become females XY zygotes become males Additive Heredity - Additive genes = their effects combine, or “add up" to influence the phenotype 0 Ex: Height— the inherited genes from mother and from father are added together Gene Pairs . First 22 pairs are autosomes, the same whether the 23rd pair is for a male or a female - On the 23rd pair: XX = female or XY = male r-——— Genotype —) Phenotype ~ Phenotype = actual appearance and behavior of a person - because some instructions on the genotype are ignored, others amplified . translation of genes into reality a Dominant-Recessive Heredity . A dominant-recessive pattern occurs when the influence of one gene is greater than the other gene 0 Ex: blood types Aand B, and brown eyes - This pattern may be X—linked (on the X chromosome), in which case males are more affected a Ex.color-b1indness 1/28/2010 4...— Hereditary Transmission . Carrier: 3 person whose genotype includes a gene not expressed in phenotype - Generally, only when inherited from both parents does characteristic appear in the phenotype TABLE 34 ' X indicates an X chromosome with the X-linked gene forcolor blindness 23rd Pair Himtype Genotype 1. XX Normal woman Not a carrier 2. XY Normal man Normal X from mother 3. XX Normal woman Carrier from father Normal woman Carrier from mother lnherited from mother Color—blind Inherited from woman trawl both patients Nm Mention No color hiindness from mother No color blindnm from father Hail her children will inherit her X. The girls with her X will be carriers,- the boys with her X Will be color—blind. Half her children will inherit her X. Thegirls with her X will be can'iers; the boys with Mr X will be color-blind. All his daughters will have his X. None afhis sons will have his X. All his children will have normal vision, unless their mother also had an X for color blindness. Every child will hove om: X from her. Therefore, every son will be color-blind. Daughters will be only carriers. unless they also inherit an x from the father, as their mother did. Twins & Clones ’ . Dizygotic (fraternal) twins result from two sperm penetrating two ova, and share 50% of their genes . Monozygotic (identical) twins originate from one zygote, and share 100% genes 0 A clone originates from a live organism n Artificially created by humans Multiple Births . The likelihood of multiple births vary by age and ethnicity . Fertility treatments may also cause them D in vitro fertilization a artificial insemination - Assisted Reproductive Technolo (ART); general term for techniques to he p infertile couples conceive and sustain a pregnancy Identical or Fraternal? 1/ 28/2010 Multiple Births - Complications and birth defects may increase with IVF a Low birthweight is a common complication . In the US. because of ART: n triplet births increased by 500 percent since 1970 a twin births have almost doubled in this time Research on Effects of Genes . Heredity = statistic representing the degree of genetic Influence for each trait - Twin studies D Estimate heritability by measuring both kinds of twins a Compare correlations of MZ & DZ twins . Adoption studies a Estimate heritability by studying adopted children, their biological parents & sibs, and their adoptive family D Compare children & their biological families, & with their adoptive families 1/28/2010 Complexity - Must Remember: cannot assume one specific phenotype results from only one genotype, or one genotype is responsible for only one phenotype - We do not know exactly how or why some genes are expressed and others are not a In females, only one X is dominant, the other inactive Psychopathology - Genes have been found to influence several mental disorders, including: a Schizophrenia n Addiction D Antisocial behavior a Compulsions - However, the environment also plays a key role in these disorders Genain quadruplets Schizophrenia . Rate: 1% of the population ¢ But, 12% if a parent or full sibling has it . If one monozygotic twin develops, about 65% of the time, the other develops it . Also means: 88% of children with a parent with schizophrenia do not'develop it, . And about 35% of identical twins with an affected twin do not develop it 4 Chromosomal Abnormalities - Chromosomal abnormalities = when the zygote’s cells have fewer or more than 46 chromosomes . Maternal age = most common correlate . Many zygotes with chromosomal abnormalities are spontaneously aborted 1 i Down Syndrome (Trisomy 21) - Down sKndrome occurs when a zygote as 3 copies of chromosome 21 - Characteristics: mental retardation, faster aging, and physical problems a specific facial features, easy temperament, deficits in language ability ~ Social support and a positive attitude a1 ows children and adults with Down Syndrome to live well Abnormalities of the 23rd pair - About 1 in 500 infants have either one too many or too few chromosomes on the 23rd pair - can lead to underdeveloped sexual organs (girls), breast development (boys), or other anomalies . Turner syndrome (in girls) a Girl has only 1 X (written: X0) - Klinefelter syndrome (in boys) a Boy has an extra X (written: XXY) Dominant Disorders . Dominant = traits that are much more likely to be expressed - Huntington disease a a fatal CNS disorder caused by a genetic miscode v inactive until middle adulthood . Other common traits: a detached earlobes a dimpled cheeks u arched feet a ability to roll your tongue Fragile X Syndrome . Fragile X syndrome: part of the X chromosome seems to be attached by very thin string of molecules - Characteristics: specific facial features, cognitive deficits, poor social- emotional skills - X—linked, so males are at greater risk Recessive Disorders - _Uniqi_1e situation: two recessive alleles must be inherited to show condition . Cystic Fibrosis: affects tissues that produce mucus SECTethHS a serious respiratory problems and lung infections - Sickle Cell Disease: affects hemoglobin n clots in blood vessels, causing damage to tissue - Ta S-Sachs Disease: damage to the brain & Genetic Counseling - Genetic counseling provides facts. It is recommended for: a Couples from the same ethnic group n Individuals with a close relative with a genetic condition 9 Couples with a history of infertility or miscarriage a Women 35 or older, men 40 or older 1/28/2010 1/28/2010 Genetic Counseling - Genetic Counseling . Techniques of prenatal screening - Genetic counselors, scientists, and general a Amniocentesis, Chorionic villus sampling (CVS) public usually favor testing . . . . a ' ' ' than ,9 - Genetic counseling raises a number of ethical ‘8 some mfomahon better "one and complicated issues - high risk individuals do not always want to know u Ex: What if a couple decides to abort a child of . a truth might jeopardize marriage, insurance coverage, abnormal height? ' or chance of parenthood - Results are an estimate of risk, not a guarantee that a disorder will or won’t occur ...
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