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Genetics Research

Extracts from this document...

Introduction

Mitosis-The process of cell division producing daughter cells with exactly the same number of chromosomes as the mother cell. Self-bleeding, Human skin cells do this, they are Autosomes Interphase-period before Mitosis, where the cell gets ready for cell division. Interphase G1-Normal cell functions continue, the cell grows and protein synthesis occurs. Can last as little as 8-12 hours or as long as a few months. Skin cells take 8-12 hours. Interphase-Synthesis phase-Lasts 6-8 hours, the cell duplicates its chromosomes. Humans have 23 pairs of chromosomes, so after S phase there's 46 pairs of chromosomes. G2 Phase-lasts 2-5 hours, and protein synthesis occurs. Prophase- Longest phase. Chromosomes (made up of 2 sister chromatides that are connected by the centromere) coil up and become visible. The nucleus and the Nuclear membrane begin to disappear. Centrioles begin moving to the poles of the cell. Microtubules and Spindle Fibers begin to extend between the centrioles, and chromatins begin attaching to the spindle fibers/microtubules. Metaphase- Shortest phase, spindle fibers connect the centromere, of each of the 46 pairs of chromosomes, to the centrioles. Chromosomes also line up in the middle of the cell. Anaphase- Each chromosome pair splits up, pulling a chromatid with it, forming two daughter chromosomes (Once the paired sister chromatids separate from one another, each is considered a "full" chromosome. They are referred to as daughter chromosomes.). The two daughter chromosomes begin to move to the poles. Telophase- The separate cells begin to separate, and returns to Interphase mode. The Nucleus and the Nuclear membrane reappear. Chromosomes uncoil, and the Nucleas enlarges. Cytokinesis- The cytoplasm divides, creating two daughter cells from the mother cell in this step. Completion of cytokinesis marks the end of mitoses. It begins in late Anaphase stage. Cytokinesis is when the cell starts to split up through a cleavage furrow. Chromosomes- Pieces of Chromatin wraped around each other, they are organized. ...read more.

Middle

Occurs in all ethnic groups. 95% is due to meiotic non-disjunction(When a chromosome pair fails to separate correctly during meiosis, resulting in reproductive cells which have missing or extra chromosomes). Most of the time the extra chromosome is inherited from the mother. A transfer of a chromosomal segment to a new position is seen in 3-4% of cases, about half of which are new, and half are relating to the family. Mosaicism(A condition in which tissues of genetically different types occur in the same organism) is seen in 1-2% of children. The recurrence risk depends upon the etiology(cause or origin of disorder as determined by medical diagnosis) In cases with non-disjunction and de novo translocation the risk is about 1% plus the maternal age risk. Familial 21/21 translocation have 100% recurrence risk. Theres a 2-5% risk if the carrier is the father and 10-15% risk if the carrier is the mother. Individuals with Down syndrome have characteristic faces and typical minor anomalies (Deviation or departure from the normal). In this day and age people with Trisomy 21 have lived healthier and longer lives and are better integrated into society. And can be cared for better. Fragile X Syndrome-Most common cause of inherited mental retardation with incidence of 1 in 2000 males, and 1 in 2500 females. The carrier frequency in females is 1/259 and in males is 1/755. Fragile X is an X-linked disorder in all ethnic groups. Responsible for 10% of all cases of inherited mental retardation and 30% of X-linked mental retardation. Gene responsible for Fragile X is located on the X chromosome. Within the FMR1 gene is a specific region of CGG repeats. Individuals with fewer than 40 repeats are not at risk to pass fragile X syndrome to their offspring. Individuals with 55-200 repeats are said to carry FMR! Permutation. Male's with over 200 repeats have fragile X syndrome. Females with more than 200 repeats have 50-70% risk to have a low or borderline IQ and 30-50% chance to have a normal IQ. ...read more.

Conclusion

Sudden vision change Tay Sachs Disease- What is Tay-Sachs Disease? Tay-Sachs disease is a fatal genetic disorder in which harmful quantities of a fatty substance called ganglioside GM2 accumulate in the nerve cells in the brain. Infants with Tay-Sachs disease appear to develop normally for the first few months of life. Then, as nerve cells begin to swell and expand with fatty material, a relentless deterioration of mental and physical abilities occurs. The child becomes blind, deaf, and unable to swallow. Muscles begin to deteriorate and paralysis sets in. A much rarer form of the disorder which occurs in patients in their twenties and early thirties is characterized by unsteadiness of gait and progressive neurological deterioration. Patients with Tay-Sachs have a "cherry-red" spot in the back of their eyes. The condition is caused by insufficient activity of an enzyme called hexosaminidase A that catalyzes the biodegradation of acidic fatty materials known as gangliosides. Gangliosides are made and biodegraded rapidly in early life as the brain develops. Patients and carriers of Tay-Sachs disease can be identified by a simple blood test that measures hexosaminidase A activity. Both parents must be carriers in order to have an affected child. When both parents are found to carry a genetic mutation in hexosaminidase A, there is a 25 percent chance with each pregnancy that the child will be affected with Tay-Sachs disease. Prenatal monitoring of pregnancies is available if desired. Is there any treatment? Presently there is no treatment for Tay-Sachs. What is the prognosis? Even with the best of care, children with Tay-Sachs disease usually die by age 5. Dominant or Recessive? Hair color-Dominant-dark hair. Recessive-Blond Hair, red hair Eye color-Brown or Hazel-Dominant..... Recessive-blue or gray Height-Short-dominant Tall-recessive Tasters PTC-Tasting is Dominant, not tasting is recessive Hemophilia-Is sex-linked recessive Hair texture-Curly Hair-Dominant Recessive-straight hair Ear lobe attachment-Attached is recessive, Free earlobes are dominant. Widows peak-Dominant, straight hair line is recessive. Deaf Mutism-Is recessive Brachydactyly-Is dominant Siamese Twins Video- 1 in a million to 1 in a half million are Siamese twins. Dyne has more control Seperation depends on which organs they share. ...read more.

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