NSG 530 STUDY GUIDE Patho Quiz 1 Graded A+.

NSG 530 STUDY GUIDE Patho Quiz 1 Graded A+ . STUDY GUIDE FOR QUIZ #1 Advanced Pathophysiology Study the process of meiosis – specifically what occurs when homologous chromosomes fail to separate Human cell can be categorized into gametes (Sperm & egg cells) and somatic cells, which include all cells other than gametes. Each somatic cell nucleus has 46 chromosomes in 23 pairs. These are diploid cells, and the individual’s father and mother each donate on chromosome per pair. New somatic cells are formed through mitosis and cytokinesis. Gametes are haploid cells: they have only 1 member of each chromosome pair, for a total of 23 chromosomes. Haploid cells are formed from diploid cells by meiosis. A somatic cell has 23 pairs of chromosomes In meiosis I, chromosomes in a diploid cell resegregate, producing four haploid daughter cells. It is this step in meiosis that generates genetic diversity. DNA replication precedes the start of meiosis I. During prophase I, homologous chromosomes pair and form synapses, a step unique to meiosis. In meiosis a haploid cell is created from a diploid cell. What are the 8 stages of meiosis in order? Aneuploidy is caused by nondisjunction, which occurs when pairs of homologous chromosomes or sister chromatids fail to separate during meiosis. The loss of a single chromosome from a diploid genome is called monosomy (2n-1), while the gain of one chromosome is called trisomy (2n+1). Know the risk factors for down syndrome Nondisjunction occurs when homologous chromosomes (meiosis I) or sister chromatids (meiosis II) fail to separate during meiosis ..... The most common trisomy is that of chromosome 21, which leads to Down syndrome. Down syndrome is a chromosomal disorder Down syndrome Best known example of aneuploidy Trisomy 21 1:800 live births Mentally retarded, low nasal bridge, epicanthal folds, protruding tongue, poor muscle tone Risk increases with maternal age 35 People who have down syndrome are at a higher risk for developing Alzheimer disease because of involvement of chromosome 21. 1 in 800 to 1 in 1000 live births are affected with Down syndrome. RISK FACTORS – increases greatly with material age. Younger than 30 have a risk of 1 – 1000 to 1 in 2000. After 35 risk increases greatly. By 45 and older a risk of 3% to 5% of children born will have down syndrome. This increase in risk is caused by the age of maternal egg cells, which are held in an arrested state of prophase 1 from the time they are formed in the female embryo until they are shred in ovulations. Thus, an egg cell formed by a 45-year woman is inself 45 years old. This long suspended state may allow defects to accumulate in the cellular proteins responsible for meiosis, leading to nondisjunction. The risk of Down syndrome, as well as other trisomies, does not increase with paternal age. Genetic diseases caused by single genes usually are autosomal dominant, autosomal recessive or X-linked recessive X-linked recessive disease are seen more often in males than in females. If the cells have three copies of each chromosome triploidy is present. Loss of chromosome material usually has more serious consequences than duplication of chromosome material. A Barr body is an inactivated X chromosome that is seen in normal female cells. Study transmission factors associated with Huntington’s disease Recurrence risk for autosomal dominant inheritance like Huntington’s Disease. Recurrence risk for autosomal dominant inheritance would be 50% if one parent was heterozygous for the trait, 75% if both parents were heterozygous, and 100% if either parent was homozygous for the trait. Autosomal dominant inheritance pattern Huntington disease is a single-gene disorder. Huntington's disease is caused by an inherited defect in a single gene. Huntington's disease is an autosomal dominant disorder, which means that a person needs only one copy of the defective gene to develop the disorder.