Genetics of Birth Defects

1. Genetics of Birth Defects Elizabeth Beeson Jessica Kraemer Tharindhie De Silva

2. Genetics • Homozygous: Both alleles are the same for a trait. • Heterozygous: Alleles are different for a trait. • There are 46 chromosomes in a normal human and 23 in the egg or sperm. • Allele: are genes that are carried on chromosomes. • Dominant alleles are always expressed if present. • Recessive alleles are expressed when there is no dominant alleles expressed. http://teachline.ls.huji.ac.il/72155/chromosome3.jpeg

3. Mitosis: Is when one cell divides to make two cells that are exactly the same with 46 chromosomes. http://genetics.gsk.com/index_flash.htm

4. Meiosis: When one cell copies it DNA and dived twice to form four genetically different daughter cells with 23 chromosomes. http://www.yksd.com/DistanceEdCourses/YKSDbiology/lessons/ThirdQuarterLessons/Chapter09/9-2.html

5. Nondisjunction: During cell division a pair of chromosomes does not separate. • One daughter cell will end up with 24 chromosomes while the other has 22.

6. Spina Bifida • Most common defect to Central Nervous System • Caused by the failure of the neural tube to close during development • Spinal cord may protrude from the back • Paralysis occurs in varying degrees http://www.gillettechildrens.org/default.cfm/PID=1.3.18

7. http://www.humanillnesses.com/Behavioral-Health-A-Br/Birth-Defects-and-Brain-Development.htmlhttp://www.humanillnesses.com/Behavioral-Health-A-Br/Birth-Defects-and-Brain-Development.html http://health.enotes.com/genetic-disorders-encyclopedia/spina-bifida

8. Down Syndrome • Caused by nondisjunction of the 21st chromosome. • If a sperm or egg with an abnormal number of chromosomes fertilize, the resulting fertilized egg will have an abnormal number of chromosomes. • This is called trisomy 21. • Physical features • A flatter face • Upward slanting eyes • A somewhat larger tongue • Possible heart defects. • They usually have some mental retardation. • May have trouble learning.

9. Turner's Syndrome • Turner syndrome is a chromosomal condition that girls and women have. Due to complete or partial absence of the second sex chromosome. • The syndrome is named after Dr. Henry Turner, who was the first to describe its features in the 1930s. • This occurs in about 1 in 2,000 live female births and as many as 10% of all miscarriages today. http://www.antenataltesting.info/images/karyotypeTurners.jpg

10. A normal female has two X chromosomes and males have one X and one Y. • People with Turner Syndrome are missing all or part of one of their sex chromosomes. • Half of girls with Turner syndrome have only one X chromosome. A third has two X chromosomes with part of one X missing • Characteristics: • Narrow, high-arched palate • Low-set ears • Low hairline • Webbed neck • Slight droop to eyes • lazy eye • Broad chest • arms that turn out slightly • Scoliosis • Flat feet • Small, narrow fingernails • toenails that turn up http://learn.genetics.utah.edu/units/disorders/karyotype/images/turner_person.jpg

11. Kleinfelter's Syndrome • Kleinfelter syndrome is a genetic disorder that occurs in males. • Normal person has 46 chromosomes and the one who has this syndrome has 47 chromosomes. • Two of the sex chromosomes are X chromosomes, and one is a Y chromosome. • This is also called XXY syndrome. • Mental retardation. • Lower IQ test scores. • Affected males look tall with long, skinny fingers and toes. • Poorly developed secondary sexual characteristics. • Delayed motor function, speech, and maturation development.

12. Duchenne Muscular Dystrophy Duchenne Muscular Dystrophy • X- linked disease that mainly affects boys. • Caused by a lack of the protein dystrophin. • Characterized by muscle weakness and progressive muscle wasting away of voluntary muscles • Distinctive posture and movement

13. http://www.dinf.ne.jp/doc/english/global/david/dwe002/dwe00212.htmhttp://www.dinf.ne.jp/doc/english/global/david/dwe002/dwe00212.htm http://www.humanillnesses.com/original/Men-Os/Muscular-Dystrophy.html

14. Neurofibromatosis • Neurofibromatosis: is a genetic disorder of the nervous system. They cause growth of noncancerous tumors along nerves. It can also cause abnormalities of skin and bone. • There are two types NF1 and NF2. They both had different levels of severity. • The gene for NF1 is located on chromosome 17. • The gene for NF2 is on chromosome 22. • The abnormal gene are inherited from one parent who has the disorder or can result from a new mutation in a normal gene. http://cc.oulu.fi/~anatwww/NF/Neurofibromatosis/plexiform.gif

15. People with NF1 normally have mild case and will life a normal life. There is not serious risk to their heath. • While NF2 can also cause hearing loss, ringing in the ears, dizziness, facial numbness, balance problems and headaches.These people will have a harder time living normal lives. http://www.sjxwl.com/pic/neurofibromatosis2.jpg • Characteristics: • Six or more tan spots on the skin • Freckles that appear under the arms or in the groin • Two or more benign tumors • tumor on the eye nerve • bowing of the legs

16. Questions?