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Human genetics


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Human genetics

  2. 2. Genes & Chromosomes <ul><li>Gametes </li></ul><ul><li>Male & female reproductive cells </li></ul><ul><li>Zygote </li></ul><ul><li>The new cell formed at conception </li></ul><ul><li>Genes </li></ul><ul><li>Basic units of genetic information </li></ul><ul><li>DNA </li></ul><ul><li>The biochemical basis of heredity </li></ul><ul><li>Chromosomes </li></ul><ul><li>Thread-like structures in the nucleus of a cell which contain genetic material </li></ul>
  3. 3. <ul><li>Inside the nucleus  chromosomes </li></ul><ul><li>Chromosome = 1000s of coils of genes </li></ul><ul><li>Gene = comprise ‘DNA’ that decides our characteristics </li></ul><ul><li>DNA = deoxyribose nucleic acid (chemical) </li></ul><ul><li>Each gene acts as a code for a particular characteristic </li></ul>
  4. 4. The Human Genome <ul><li>Genetic Compliment </li></ul><ul><li>Over 25,000 genes in human gename </li></ul><ul><li>Contribution of the Parents </li></ul><ul><li>Each parent gives 23 chromosomes at conception </li></ul>
  5. 5. Genes <ul><li>Each pair contains a gene from your mother, and a gene from your father for a particular characteristic </li></ul><ul><li>So each pair contains two “options” for a characteristic </li></ul><ul><li>These options are called alleles </li></ul><ul><li>e.g. gene = eye colour; </li></ul><ul><li>alleles = blue eye colour, brown eye colour </li></ul>
  6. 6. Alleles <ul><li>An Allele is an alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome. </li></ul><ul><li>Alleles are dominant or recessive </li></ul><ul><li>Homozygous = two same alleles (purebred) </li></ul><ul><li>Heterozygous = two different alleles </li></ul><ul><li>Dominant + recessive  dominant </li></ul><ul><li>Dominant + dominant  dominant </li></ul><ul><li>Recessive + dominant  dominant </li></ul><ul><li>Recessive + recessive  recessive </li></ul><ul><li>e.g. BB, Bb = brown eyes; bb = blue eyes </li></ul><ul><li>Two parents are Bb + bb; offspring has 50% chance of blue eyes </li></ul>
  7. 7. Basic Genetics <ul><li>Dominant Trait </li></ul><ul><li>Trait expressed when 2 traits compete </li></ul><ul><li>Recessive Trait </li></ul><ul><li>Trait that expresses itself only when paired with another of the same kind </li></ul><ul><li>Genotype </li></ul><ul><li>Underlying genetic material </li></ul><ul><li>Phenotype </li></ul><ul><li>Observable trait </li></ul><ul><li>Heterozygous </li></ul><ul><li>When genes for characteristics differ </li></ul><ul><li>Homozygous </li></ul><ul><li>When genes for characteristics are the same </li></ul>
  8. 8. Eye Colour A heterozygous brown-eyed father and a blue-eyed mother: 50:50 chance of being either brown eyed or blue eyed
  9. 9. DOMINANT AND RECESSIVE CHARACTERISTICS Characteristics in the left-hand column dominate over those characteristics listed in the right-hand column .     * sex-linked characteristic   DOMINANT TRAITS RECESSIVE TRAITS eye coloring brown eyes grey, green, hazel, blue eyes vision farsightedness normal vision normal vision normal vision normal vision nearsightedness night blindness color blindness* hair dark hair non-red hair curly hair widow's peak blonde, light, red hair red hair straight hair normal hairline facial features dimples freckles broad lips no dimples no freckles thin lips
  10. 10. Behavioral Genetics <ul><li>Study of the Effects of Genetics on Behavior </li></ul><ul><li>99% of all gene sequences is shared by ALL humans </li></ul><ul><li>Genetics produces predispositions </li></ul><ul><li>Personality Traits </li></ul><ul><li>Many personality traits have genetic links: shyness, sociability, moodiness, temperament, assertiveness, depression, AD/HD, schizophrenia </li></ul>
  11. 11. Heredity & Environment <ul><li>Heredity & Environment Work Together </li></ul><ul><li>Genetics is under the influence of the environment </li></ul><ul><li>e.g. height, language, & temperament </li></ul><ul><li>Interaction of Many Factors </li></ul><ul><li>Many traits reflect multifactoral transmission </li></ul><ul><li>Determined by a combination of genetic & environmental factors </li></ul><ul><li>Question is: How much is nature & how much is nurture? </li></ul><ul><li>All data suggests it’s a combination </li></ul>
  12. 12. Multi-Factorial Traits <ul><li>Physical traits influenced by both genes and environment . </li></ul><ul><ul><li>Height is an example: If a child is ill, poorly nourished, or emotionally neglected, s/he may be smaller than others her/his age. </li></ul></ul><ul><ul><li>Psychological traits (intelligence, personality) influenced by both nature and nurture (multi-factorial) </li></ul></ul>
  13. 13. Psychological Disorders <ul><li>Schizophrenia </li></ul><ul><li>Tends to run in families </li></ul><ul><li>Monozygotic twins have 50% chance of developing it </li></ul><ul><li>Sensitivity to stress </li></ul><ul><li>Other Disorders </li></ul><ul><li>Major depression, alcoholism, autism, AD/HD </li></ul><ul><li>Heredity & Environment </li></ul><ul><li>Influences of each changes over person’s life-time </li></ul>
  16. 17. Turner Syndrome Webbed neck – spaced nipples
  17. 18. Prenatal Diagnosis and Treatment <ul><li>Genetic Counseling </li></ul><ul><ul><li>Helps to assess the chances of inherited disorders. </li></ul></ul><ul><li>Prenatal Diagnosis </li></ul><ul><ul><li>Ultrasound is the use of soundwaves to produce a picture of the fetus. </li></ul></ul><ul><ul><li>Amniocentesis allows the taking of a sample of the amniotic fluid. </li></ul></ul><ul><ul><li>Chorionic Villus Sampling (CVS) is taken from the placenta and can be done earlier than amniocentesis. </li></ul></ul>
  18. 19. Chorionic Villus Sampling: Done in the first trimester for genetic studies. The cells obtained are identical to those of the fetus, grown and analyzed. Complications include pregnancy loss and limb abnormalities. Done as early as week 5 of pregnancy to detect any genetic disorders Amniocentesis: Amniotic Fluid (20 ml) is withdrawn under US guidance, and is analyzed for prenatal diagnosis of karyotypic abnormalities such as: congenital defects, fetal lung maturity, and NTD. Done at the 14 th -16 th week of pregnancy Complications include pregnancy loss, amniotic fluid leakage, fetal injury This process is indicated for: Women over 35 y. of age: ↑ risk of malformations- 21, 18, 13 trissomy Women who had a child with a chromosomal abnormality.
  21. 22. Threats to Development <ul><li>Taratogens </li></ul><ul><li>Drugs, chemicals, viruses, etc. </li></ul><ul><li>Timing & quantity of the exposure is important </li></ul><ul><li>Especially problematic during periods of rapid prenatal development </li></ul><ul><li>Poverty increases the chances of exposure </li></ul>
  22. 23. Threats to Development <ul><li>Mother’s Diet </li></ul><ul><li>Developing fetus needs the appropriate nutrients </li></ul><ul><li>Mother’s Age </li></ul><ul><li>Under 16, over 30, & over 40 greatest risk </li></ul><ul><li>Down’s Syndrome in 1 of 100 over 40 births </li></ul><ul><li>Adolescent pregnancies more likely to be premature & still-born </li></ul><ul><li>Prenatal Support </li></ul><ul><li>Younger mothers generally have adverse social & economic factors </li></ul><ul><li>Mother’s Health </li></ul><ul><li>Rubella prior to 11 th week can produce blindness, deafness, heart defects, or brain damage </li></ul><ul><li>Chicken pox & mumps increase miscarriage </li></ul><ul><li>Some STD can be transmitted to fetus </li></ul><ul><li>Mother’s Drug Use </li></ul><ul><li>Some OTC remedies can cause problems </li></ul><ul><li>Mother’s Use of Alcohol & Tobacco </li></ul><ul><li>FAS in 1 of 750 births of alcohol users </li></ul><ul><li>Smoking reduces oxygen content & increases carbon monoxide </li></ul>
  23. 24. Threats to Development <ul><li>Father’s Effects </li></ul><ul><li>2 nd hand smoke affects the mother’s health which affects the fetus </li></ul><ul><li>Use of alcohol & illicit drugs can damage sperm </li></ul><ul><li>Physical & emotional abuse affects the stress level of the mother </li></ul>
  24. 25. Key points about genetics <ul><li>Genetic disorders are disorders resulting from defect in the structure or number of genes or chromosomes. Genetics is the study of how and why such disorders occur. </li></ul><ul><li>A phenotype is a person’s outward appearance. Genotype refers to the actual gene composition. </li></ul><ul><li>A person’s genome is the complete set of genes present. </li></ul><ul><li>A karyotype is a graphic representation of the chromosomes that are present. </li></ul>
  25. 26. <ul><li>A person is homozygous if he or she has two like genes for a trait and heterozygous if he or she has two unlike genes for a trait </li></ul><ul><li>An important aspect of genetic counseling is respecting a couples right to privacy. Be certain that all information remains confidential. </li></ul><ul><li>People who are told that a genetic abnormality does exist in the family may suffer a loss of self- esteem. Offering support to help them deal with the feelings they experience is an important nursing intervention. </li></ul>
  27. 28. ........DESKTOPASSIGNMENT GENETICS.PPTX <ul><li>THANK YOU… </li></ul>