Genetics and Prenatal Development Child Development
A.  Genetics <ul><li>We each have 46 chromosomes (23 pairs from each parent).  </li></ul><ul><li>Chromosomes -threadlike s...
What is DNA (deoxyribonucleic acid): <ul><li>A long, double-stranded molecule that looks like a twisted ladder.  </li></ul...
What is a gene? <ul><li>A segment of DNA along the length of the chromosome.  </li></ul><ul><li>DNA can replicate itself, ...
Sex Cells (Gametes) <ul><li>Gametes- sperm and ova </li></ul><ul><li>Contain only 23 Chromosomes.  Formed through meiosis-...
Multiple offspring <ul><li>Monozygotic twins - a fertilized egg (zygote) separates into two distinct cell clusters that fo...
Is it a boy or girl? <ul><li>22 of our 23 chromosome pairs can be distinguished from one another.  These are called  autos...
Who determines the sex? <ul><li>Males- the X and Y-chromosomes separate into different sperm cells. </li></ul><ul><li>X- s...
What is the default? <ul><li>To be female!!! </li></ul><ul><li>A genetic male will only develop into a male infant if test...
Becoming male <ul><li>Testes in male fetuses:  Wolffian system to develop & Mullerian inhibiting hormone (MIH) is released...
Sex Chromosome anomalies <ul><li>Turner’s Syndrome:  When a male’s sperm fails to have an X or Y sex chromosome, the child...
Genetic inheritance <ul><li>2 or more forms of each gene occur at the same place on the chromosomes. </li></ul><ul><li>Eac...
Alleles <ul><li>If alleles from both parents are alike the child will be  homozygous (AA, aa) for that characteristic.  </...
What happens if a child is heterozygous? <ul><li>  e.g., eye color, Bb (B-brown, b-blue) </li></ul><ul><li>One   allele wi...
Possible Outcomes with heterozygous Allele patterns: <ul><li>1.  Dominant allele will be expressed, while the recessive al...
Carriers of recessive genes <ul><li>Heterozygous individuals with just one recessive allele (Bb) can pass that trait to th...
Dominant and Recessive Characteristics <ul><li>Dominant Recessive </li></ul><ul><li>Dark hair Blond hair </li></ul><ul><li...
PKU-a recessive disease <ul><li>Phenylketonuria – lack an enzyme that converts one of the basic amino acids that make up p...
What if a harmful recessive gene occurs on the X-chromosome? <ul><li>Females may have an extra allele that will cancel-out...
Chromosomal abnormalities <ul><li>Damage to the chromosomes may result in birth defects/disease. </li></ul><ul><li>Most co...
Down’s Syndrome   r esults in: <ul><li>mental retardation, speech difficulties, limited vocabulary, & slow motor developme...
Predisposing factors <ul><li>Maternal age (35 +)  </li></ul><ul><li>Paternal- Marijuana smoking increases likelihood of Do...
B.  Prenatal Diagnosis   <ul><li>Good News!!! </li></ul><ul><li>95 % of fetuses examined through prenatal diagnosis are  n...
Prenatal Diagnostic Tests   <ul><li>1.  Amniocentesis - A hollow needed is inserted through the abdominal wall to obtain a...
2.  Chorionic Villi sampling   <ul><li>A hollow probe is inserted through the vagina.  Sample collects chorionic villi, ha...
 
3.  Fetoscopy   <ul><li>A small tube with light source at one end is inserted into womb to inspect fetus for defects of th...
4.  Ultrasound <ul><li>High-frequency sound waves beamed at the uterus & their reflection is recorded. </li></ul><ul><li>P...
5.  Maternal Blood Analysis   <ul><li>A blood test done at 2 nd  month of pregnancy. </li></ul><ul><li>Looks for elevated ...
C. Prenatal Development <ul><li>Female releases a mature egg (ovum) once a month.  The egg travels from the ovaries to the...
Period of zygote:  from fertilization to Implantation (two week period). <ul><li>7 th  -9 th  day post conception.  </li><...
Period of the embryo <ul><li>Implantation -8 th  week of pregnancy.  </li></ul><ul><li>Period marks most rapid prenatal ch...
First Month <ul><li>Nervous system develops first -- neural tube or primitive spinal cord.  </li></ul><ul><li>At 3-4 weeks...
The Second Month <ul><li>Eyes, ears, nose, jaw, & neck form.  </li></ul><ul><li>Tiny buds become arms, legs, fingers,  </l...
Third Month <ul><li>Fetus can kick, bend its arms,  </li></ul><ul><li>forms a fist, curls its toes, & </li></ul><ul><li>op...
The Second Trimester: <ul><li>By end of 2 nd  trimester (6 months) all major organs are formed. </li></ul><ul><li>Baby con...
Third Trimester (6-9 mos.) <ul><li>Babies born during this time have a chance of survival (24 weeks-50% survival rate).  <...
Third trimester <ul><li>30 weeks </li></ul>
D. Childbirth: <ul><li>Stage 1:  Dilation and effacement of the cervix  (avg 12-14 hrs.) </li></ul><ul><li>Stage 2: Delive...
Complications <ul><li>Failure to progress </li></ul><ul><li>Fetal distress </li></ul><ul><li>Placental abruption </li></ul...
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Genetics and Prenatal Development Child Development

  1. 1. Genetics and Prenatal Development Child Development
  2. 2. A. Genetics <ul><li>We each have 46 chromosomes (23 pairs from each parent). </li></ul><ul><li>Chromosomes -threadlike structures--carry genetic information that directs development. </li></ul><ul><li>Chromosomes made up of DNA molecules (double helix) </li></ul>
  3. 3. What is DNA (deoxyribonucleic acid): <ul><li>A long, double-stranded molecule that looks like a twisted ladder. </li></ul><ul><li>Each of the latter consists of a specific pair of chemical substances called bases, joined together between the two sides . </li></ul><ul><li>Humans have 4 base pairs. </li></ul>
  4. 4. What is a gene? <ul><li>A segment of DNA along the length of the chromosome. </li></ul><ul><li>DNA can replicate itself, leading to the development of a human being from 1 cell. </li></ul><ul><li>This process is mitosis . </li></ul>
  5. 5. Sex Cells (Gametes) <ul><li>Gametes- sperm and ova </li></ul><ul><li>Contain only 23 Chromosomes. Formed through meiosis-which halves the # of chromosomes present in body. </li></ul><ul><li>In males- sperm produced throughout life, in a female-she is born will all ova she will have (350-450 during maturity). </li></ul>
  6. 6. Multiple offspring <ul><li>Monozygotic twins - a fertilized egg (zygote) separates into two distinct cell clusters that form into two genetically identical humans. </li></ul><ul><li>Odds (3 out of every 1,000 births). </li></ul><ul><li>Dizyogotic twins - two separate ova are fertilized by two different sperm cells. </li></ul>
  7. 7. Is it a boy or girl? <ul><li>22 of our 23 chromosome pairs can be distinguished from one another. These are called autosome s . </li></ul><ul><li>The 23 rd pair consists of sex chromosomes. </li></ul><ul><li>Females-XX and males-XY. The X is long, the Y short and carries less genetic material. </li></ul>
  8. 8. Who determines the sex? <ul><li>Males- the X and Y-chromosomes separate into different sperm cells. </li></ul><ul><li>X- sperm cells; Y-sperm cells. </li></ul><ul><li>Females-gametes carry X chromosomes only. </li></ul><ul><li>Male’s sperm determines baby’s sex. </li></ul>
  9. 9. What is the default? <ul><li>To be female!!! </li></ul><ul><li>A genetic male will only develop into a male infant if testosterone is presented during prenatal development. </li></ul><ul><li>Deficient male hormones will lead to development of female infant. </li></ul>
  10. 10. Becoming male <ul><li>Testes in male fetuses: Wolffian system to develop & Mullerian inhibiting hormone (MIH) is released. </li></ul><ul><li>Hormones—must be present during 3 rd and 4 th months of pregnancy. </li></ul>
  11. 11. Sex Chromosome anomalies <ul><li>Turner’s Syndrome: When a male’s sperm fails to have an X or Y sex chromosome, the child is an XO. She only has one X from her mother. These children will be short, have webbed necks, mouth/facial anomalies, and cognitive impairments. </li></ul><ul><li>Klinefelter’s syndrome: Occurs when a male child has an extra X chromosome (XXY), and displays female secondary sex characteristics and some cognitive impairments. </li></ul><ul><li>XXY males—appear to be significantly taller than normal males and may have cognitive impairments. </li></ul><ul><li>Fragile X- occurs in male children only in which the X is fragmented or broken. Leads to facial anomalies and mental retardation which gets progressively worse with age. </li></ul>
  12. 12. Genetic inheritance <ul><li>2 or more forms of each gene occur at the same place on the chromosomes. </li></ul><ul><li>Each different form of a gene is called an allele (1-mother, 1-father). </li></ul>
  13. 13. Alleles <ul><li>If alleles from both parents are alike the child will be homozygous (AA, aa) for that characteristic. </li></ul><ul><li>If alleles are different, the child will be heterozygous (Aa, aA) for that characteristic. </li></ul><ul><li>Here, relationships between alleles determine if trait will appear. </li></ul>
  14. 14. What happens if a child is heterozygous? <ul><li> e.g., eye color, Bb (B-brown, b-blue) </li></ul><ul><li>One allele will be dominant for a trait, whereas the other will be recessive. </li></ul><ul><li>This child will have Brown eyes! </li></ul>
  15. 15. Possible Outcomes with heterozygous Allele patterns: <ul><li>1. Dominant allele will be expressed, while the recessive allele will not (e.g., brown eyes winning out over blue.) </li></ul><ul><li>2. The trait expressed may be in between the dominant and recessive alleles (a dominant dark skin allele and recessive light skin allele, may yield a child with skin color in between the two). </li></ul><ul><li>3. Both alleles may be expressed simultaneously at full intensity (called codominance ). A child with an allele for A blood and an allele for B blood, may have both AB antigens expressed in their blood. </li></ul>
  16. 16. Carriers of recessive genes <ul><li>Heterozygous individuals with just one recessive allele (Bb) can pass that trait to their children. </li></ul><ul><li>These are carriers (blue eyes, blond hair, cystic fibrosis, PKU) </li></ul>
  17. 17. Dominant and Recessive Characteristics <ul><li>Dominant Recessive </li></ul><ul><li>Dark hair Blond hair </li></ul><ul><li>Normal hair Pattern baldness </li></ul><ul><li>Curly hair Straight hair </li></ul><ul><li>Nonred hair Red hair </li></ul><ul><li>Facial dimples No dimples </li></ul><ul><li>Normal hearing deafness </li></ul><ul><li>Normal vision myopia </li></ul><ul><li>Normally pigmented skin Albinism </li></ul><ul><li>Type A blood Type O blood </li></ul><ul><li>Type B blood Type O blood </li></ul><ul><li>Rh-positive blood Rh-negative blood </li></ul>
  18. 18. PKU-a recessive disease <ul><li>Phenylketonuria – lack an enzyme that converts one of the basic amino acids that make up proteins (phenylalanine). </li></ul><ul><li>phenylalanine quickly builds to toxic levels in brain </li></ul><ul><li>Will lead to mental retardation, but if caught early can be treated with diet restrictions. </li></ul>
  19. 19. What if a harmful recessive gene occurs on the X-chromosome? <ul><li>Females may have an extra allele that will cancel-out the effects of the harmful allele. </li></ul><ul><li>Males only have 1 X on 23 rd pair, so they don’t have any extra alleles to cancel-out effects. </li></ul><ul><li>(E.g, color blindness) </li></ul>
  20. 20. Chromosomal abnormalities <ul><li>Damage to the chromosomes may result in birth defects/disease. </li></ul><ul><li>Most common—Down’s Syndrome </li></ul><ul><li>Results when an extra chromosome is present on the 21 st pair. </li></ul>
  21. 21. Down’s Syndrome r esults in: <ul><li>mental retardation, speech difficulties, limited vocabulary, & slow motor development. </li></ul><ul><li>Down’s babies have more problems (breathing, feeding) than healthy infants. </li></ul>
  22. 22. Predisposing factors <ul><li>Maternal age (35 +) </li></ul><ul><li>Paternal- Marijuana smoking increases likelihood of Down’s syndrome. </li></ul>
  23. 23. B. Prenatal Diagnosis <ul><li>Good News!!! </li></ul><ul><li>95 % of fetuses examined through prenatal diagnosis are normal . </li></ul>
  24. 24. Prenatal Diagnostic Tests <ul><li>1. Amniocentesis - A hollow needed is inserted through the abdominal wall to obtain a sample of fluid in the uterus. </li></ul><ul><li>May be performed 11-14 </li></ul><ul><li>wks following conception. </li></ul><ul><li>1-2 weeks for results. </li></ul>
  25. 25. 2. Chorionic Villi sampling <ul><li>A hollow probe is inserted through the vagina. Sample collects chorionic villi, hairlike projections surrounding organism. </li></ul><ul><li>Performed (6 to 8 weeks following conception), results known within 24 hours. </li></ul>
  26. 27. 3. Fetoscopy <ul><li>A small tube with light source at one end is inserted into womb to inspect fetus for defects of the limbs & face. Blood may be taken. </li></ul><ul><li>Diagnoses- hemophilia, sickle-cell anemia, & neural tube defects. </li></ul><ul><li>Performed between 15 & 18 weeks post conception </li></ul>
  27. 28. 4. Ultrasound <ul><li>High-frequency sound waves beamed at the uterus & their reflection is recorded. </li></ul><ul><li>Provides picture of fetus. </li></ul><ul><li>Detects fetal age, multiple pregnancies, & identification of gross physical defects. </li></ul>
  28. 29. 5. Maternal Blood Analysis <ul><li>A blood test done at 2 nd month of pregnancy. </li></ul><ul><li>Looks for elevated levels of alpha-fetoprotein --may detect neural tube defects & Down’s Syndrome </li></ul>
  29. 30. C. Prenatal Development <ul><li>Female releases a mature egg (ovum) once a month. The egg travels from the ovaries to the fallopian tubes where it awaits a sperm cell to fertilize it. </li></ul><ul><li>When sperm meets egg, the egg is fertilized and travels down to the uterus. </li></ul>
  30. 31. Period of zygote: from fertilization to Implantation (two week period). <ul><li>7 th -9 th day post conception. </li></ul><ul><li>Zygote becomes a blastocyst , a hollow, fluid-filled ball. </li></ul><ul><li>Cells inside, form embryonic disk (will become baby). </li></ul>
  31. 32. Period of the embryo <ul><li>Implantation -8 th week of pregnancy. </li></ul><ul><li>Period marks most rapid prenatal changes (organ development). </li></ul><ul><li>Ectoderm-NS & skin </li></ul><ul><li>Mesoderm-muscle, skeletal </li></ul><ul><li>Endoderm-digestive tract, </li></ul><ul><li>(6 weeks) </li></ul>
  32. 33. First Month <ul><li>Nervous system develops first -- neural tube or primitive spinal cord. </li></ul><ul><li>At 3-4 weeks (brain & other </li></ul><ul><li>organs form </li></ul><ul><li>The Heart pumps blood!!! </li></ul><ul><li>(4weeks) </li></ul>
  33. 34. The Second Month <ul><li>Eyes, ears, nose, jaw, & neck form. </li></ul><ul><li>Tiny buds become arms, legs, fingers, </li></ul><ul><li>& toes. </li></ul><ul><li>Organs become more distinct </li></ul><ul><li>(heart) </li></ul><ul><li>Is 1 inch long, can move. </li></ul><ul><li>(8 weeks) </li></ul>
  34. 35. Third Month <ul><li>Fetus can kick, bend its arms, </li></ul><ul><li>forms a fist, curls its toes, & </li></ul><ul><li>opens it mouth. </li></ul><ul><li>By the 12 th week, the </li></ul><ul><li>external genitals are </li></ul><ul><li>well formed. </li></ul><ul><li> (12 weeks) </li></ul>
  35. 36. The Second Trimester: <ul><li>By end of 2 nd trimester (6 months) all major organs are formed. </li></ul><ul><li>Baby continues growing, </li></ul><ul><li>Is felt moving by mother. </li></ul>
  36. 37. Third Trimester (6-9 mos.) <ul><li>Babies born during this time have a chance of survival (24 weeks-50% survival rate). </li></ul><ul><li>Fetus gains weight (about 5 lbs.) </li></ul><ul><li>And continues growing. </li></ul><ul><li>Baby prepares for birth. </li></ul><ul><li>(24 weeks) </li></ul>
  37. 38. Third trimester <ul><li>30 weeks </li></ul>
  38. 39. D. Childbirth: <ul><li>Stage 1: Dilation and effacement of the cervix (avg 12-14 hrs.) </li></ul><ul><li>Stage 2: Delivery of the baby . </li></ul><ul><li>Stage 3: Birth of the placenta </li></ul>
  39. 40. Complications <ul><li>Failure to progress </li></ul><ul><li>Fetal distress </li></ul><ul><li>Placental abruption </li></ul><ul><li>Often results in C-section delivery, where baby is surgically removed from the mother. </li></ul>
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