During cell division of the cells reproduction, the 46 chromosomes should be divided into half having 23 chromosomes in each new cell. With the new cell having an extra or lacking chromosome, nondisjunction abnormalities occur. Down syndrome, being the most common abnormality, occurs with the presence of extra chromosome 21. It occurs in about 700 to 800 births. Langdon Down first described it but still with an unknown case.
Cri du chat is one of the most common syndromes caused by chromosomal deletion, affecting between one in twenty-thousand and one in fifty-thousand children. Eighty percent of children affected by the syndrome experience chromosome deletion that comes from their father's sperm rather than their mother's egg. When these deletions in the child's chromosomes occur during the formation of sperm or an egg it is caused by an unequal recombination during meiosis. Recombination usually happens between pairs of chromosomes during meiosis while there are lined up at the metaphase plate. If the pairs of chromosomes do not line up as they should or if the
Each chromosome in the DNA strand has a job or task that helps the body function, for chromosome 18 its job is to make proteins. When the chromosome 18 has three copies instead of two, then Edwards syndrome is formed. Edwards syndrome or trisomy 18 is the second most common trisomy disease with trisomy 21 being the most common. In every 5,000 babies born 1 will be born with Edwards syndrome. More than 20 to 30% of the infants that make it to full term will die within the first week to month.
Cri Du Chat Syndrome [pic] Occasionally chromosomal material is lost or rearranged during the formation of gametes or during cell division. This may be due to translocation or nondisjunction. Cri du chat is one of the most common syndromes caused by chromosomal deletion, affecting between one in twenty-thousand and one in fifty-thousand children. Eighty-percent of children affected by the syndrome experience chromosome deletion that comes from their father's sperm. When these deletions in the child's chromosomes occur during the formation of sperm or an egg, it is caused by an unequal recombination during meiosis.
One in four million newborns are affected by this disorder (Pollex). There is a case in India where a family had five out of seven children affected with HGPS in one generation. The average age a child with progeria lives is thirteen; most deaths from progeria are caused by progressive atherosclerosis (Pollex). Atherosclerosis is heart disease. A case of Hutchinson-Gilford progeria syndrome or simply progeria was first reported in 1886 by Hutchinson.
One aspect of the biological explanation of schizophrenia suggests that the illness is transmitted from parents to their children via genes. It has been found that a person has a 1% greater chance of developing the schizophrenia if they have a family relative suffering schizophrenia. Gottesman and Shields looked at the medical records of 57 schizophrenic twins. They found that if an MZ twin had schizophrenia their identical twin had a 42% chance of developing the disorder. There was also an increase for DZ twins as they discovered that if one twin had schizophrenia the likelihood of their twin developing the illness was as high as 9%.
It is shown that some individuals with Rubenstein-Taybi Syndrome can develop breathing problems and irregular heart beats when anesthesia or other muscle relaxers are administered. Rubenstein-Taybi Syndrome was first discovered in 1965 by doctors Jack Rubenstein and Hooshang Taybi. Rubenstein-Taybi Syndrome is a very uncommon disorder it only occurs in approximately 1 in every 300,000 births. Rubenstein-Taybi Syndrome may be recognized at birth by having a different physical appearance to family members but is not usually diagnosed until a child with Rubenstein-Taybi Syndrome is about 15 months of age. Rubenstein-Taybi Syndrome causes physical deformities some of which include an undersized head, a small mouth, down slanting eyes, a thick scalp, hair that extends to the fore head, a large nose.
Pearson syndrome is associated with a large deletion of the mitochondrial (mt) genome. The way the deletion containing mtDNA molecules are distributed during mitosis is not known. However, it is assumed that during cell division daughter cells randomly receive mitochondria carrying wild type (WT) or mutant mtDNA. Mitochondrial DNA is, theoretically, transmitted only to offspring through the mother via the large cytoplasmic component of the oocyte. Nearly all cases of Pearson syndrome arise from new mutational events.
This suggests that a genetic factor is involved. MZ twins share 100% of their genes; DZ twins share 50% of their genes. If genes are a factor we would expect more identical twins to share the disorder than non-identical. Rosenthal took a case study which had a set of female quadruplets. They all developed schizophrenia although the onset and symptoms were very different.
(13) Charcot Marie Tooth Disease is caused by a mutation within one of our genes and it can happen to any ethnic group and affects 1 out of every 3, 300 people worldwide. (3) Mutations within our genes are inherited and each of us carries two copies of each gene, one from each parent. There are many forms of Charcot Marie Tooth (CMT) disease; however, the one focused on for this research paper is CMT1A. (3, 6, 9) There are three main types of CMT1, which are all caused by abnormalities in the myelin sheath found on the neurons of the peripheral nerves. CMT1A is an autosomal dominant disease.