1.1 Congenital Birth Defects
Birth defects, congenital abnormalities are terms used to describe developmental defects that are present at birth. There are a lot of genetic and environmental interactions in the complex transition from a fertilised ovum to a fully formed human being. The stage of development that the interactions are affected influences the type of birth defects. Birth defect causes can be divided into two types, genetic and environmental causes. There are also birth defects which are caused due to multifactorial inheritance (George, 2007).
Genetic causes of birth defects
It has been estimated that 25% of all birth defects are caused due to genetic factors and out of these 85% causes are known (Brent, 2004). Birth defects can be caused due to chromosomal aberrations, mutations in single genes and interactions of both environmental and genetic factors. Chromosomal aberrations are seen frequently as the complex mechanisms such as meiosis or mitosis are prone to error. Another frequent causative factor of multiple birth defects is chromosomal aneuploidy (loss or gain of whole chromosome). Multiple congenital anomaly syndromes are caused due to single gene defects (Prescott, 2001).
Chromosomal abnormalities
They may be numerical or structural and are important causes of approximately 5-6% of all birth defects (Young, 2005). These abnormalities may arise newly or maybe inherited from a parent with same chromosomal aberration. Numerical abnormalities are caused due to any deviation from the human diploid number of 46 chromosomes which is called chromosomal aneuploidy. This leads to multiple birth defects as it disturbs the action of multiple genes. Usually, numerical chromosomal abnormalities are resu...
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...Synthetic lethality does indicate that when two genes have the same role and mutation occurs in them both making them non-functional only then it results in lethality. Moreover when both the genes have the same function in the pathway, each mutation in the genes diminishes the function of the pathway.
Even though genome sequencing of mouse and humans are completed the function of a major part of the genomes are still unknown. An effective way to discover the gene function is by determining the consequence of mutations in organisms. This study focuses on congenital birth defects by studying the mutations in mouse genome causing developmental abnormalities which serve as models for human congenital birth defects. In this study an attempt is made to identify the genes that cause developmental defects and lethality thus aids the study of congenital birth defects.
In 1990, the first great stride of genetics took place. This was called the Human Genome Project, a large-scale operation that was designed to understand the human genome (genetic structure). Since its commencement, there have been many leaps and bounds that have taken place. For certain genetic issues that we once knew nothing about, we no...
Twin studies have been used to distinguish between genetic and environmental factors for many disorders in the general population including ectodermal dysplasia, Ellis-van Creveld, and anencephaly. This review focuses on genetic disorders affecting monozygotic, dizygotic, and conjoined twins to gain a better understanding of them. Many studies focus on twins because they have a nearly identical genome, which eliminates environmental factors. In case studies, the concordance rates in monozygotic twins have supported that certain disorders were caused by genetics and not the environment. The discordant values in twins will also be evaluated briefly. Twinning studies have also shown linkages between specific disorders and the genes responsible for them. Knowing the location of these genes allows patients to be treated quickly and efficiently. This paper will discuss the possible causes of twinning and the various methods of identifying abnormalities in twins. These methods also allow preventive measures against the rise of birth defects during prenatal development. Epigenetics in twins is also viewed through the perspective of effects on them. Treatments for genetic disorders in twins are reviewed, ranging from the restoration of malformed teeth to the separation of conjoined twins. Support groups for twins in treatment, and their families are also briefly reviewed.
Genetic disorders can be caused by many of the 46 chromosomes in human cells. This specific disorder is linked to a mutation in the long arm of the X, or 23rd chromosome. The mutation is recessive, meaning a normal X chromosome can hide it. Females have two X chromosomes allowing them to hide the mutated recessive one, making them a carrier of the gene, while males only have one X chromosome, meaning that they are unable to hide the mutation and they become effected by the disease. Therefore if a male carries the gene, he is affected because he has no way of dominating the recessive gene, but if a female carries it, she is only a carrier and has a 50/50 chance of passing it on to her baby. This may seem like a high probability however, only one in every fifty thousand male births will have this immunodeficiency disease.
The birthmark is a compelling story of one man’s obsession with his scientific ability to produce perfection. Aylmer, a scientist, is married to a Georgiana who is a very beautiful woman. Not long after getting married Georgiana’s birthmark, which is in the shape of a tiny handprint on her check, really begins to bother Aylmer. He sees it as a flaw in an other wise perfect woman. Georgiana knows that her birthmark disgusts him and, having grown up not bother at all by it, begins to hate it herself. He asks if she has ever considered having it removed. This is not something she has considered since other people in her life, especially men, have always seen it as a “charm”. Aylmer being an amazing scientist almost sees himself as god and feels that he has the power to remove this imperfection. Georgiana, bothered by her husband’s reaction to her birthmark, agrees to let him try to rid her of it. She is taken to his laboratory and he immediately begins to experiment. After she finds Aylmer’s book of experiments, which all end in failure, she for the first time, has some doubt about how this will work and confronts him. He reassures her and begins to try a multitude of methods, with the help of his assistant Aminadab, which do not work. At one point, there are several experiments going on and he even refers to himself as a “sorcerer” (Hawthorne 232). Finally, he produces a potion, which she drinks, and the birthmark begins to disappear! Slowly though, even as the experiment is working, Georgiana is fading away. He finds that ultimately, the birthmark was connected to her very soul and in his trying to act god like he actually kills her. Really this short story just proves that science has its limits and no man should try to act like G...
Both of these methods can help determine and eliminate genetic disorders, as certain conditions can be screened out using these technologies. As discussed in Meseguer et al., more than 300 diseases have been related to sexual chromosomes till date. Case studies also argue the important role of these methods in family balancing for varied family dynamics who aim to compensate their family with a representation of the other sex (Meseguer et al., 2002). Critics have also mentioned that with an increase in demand, these methods could become more economical and widely available, including to couples who may need it due to medical
While pregnancies with a trisomy (a baby which has receive an extra chromosome) or a monosomy (have a missing chromosome) may go to full-term and result in the birth of a child with health problems, it is also possible that the pregnancy may miscarry, or that the baby is stillborn, because of the chromosome abnormality. In studies of first trimester miscarriages, about 60 percent (or more) are chromosomally abnormal. In studies of babies who are stillborn, 5 to 10 percent have a chromosome
Random mutations- genes that control brain development .Maternal infections that affect the developing fetus. Fetal stroke, a disruption of blood supply to the developing brain Lack of oxygen to the brain (asphyxia) related to diffic...
Boston: Bedford/St. Martin,. 304 - 316 mm. Print. The. Newman, Stuart A.. “The Hazards of Human Developmental Gene Modification.”
Lewis, Ricki, (2014), Human Genetics, 11th Edition, Chapter 12. Gene Mutation. [VitalSource Bookshelf Online]. Retrieved from
The type of mutation that occurs in Down syndrome is aneuploidy that is the irregular number of chromosomes in a cell. The most common of the three is the trisomy 21 that occurs in about 90% of people with the disorder. In this factor the human is given three copies of the chromosome 21 instead of the common two copies. This occurs due to the complications of the cell division in the process of the egg or sperm. The next case is mosaic which happen when there are inequality of cells with three copies of chromosome 21 and others with the original two copies. Mosaic appears when there is an unexpected cell division after fertilization. The last and the rarest form is translocation and that happens while the chromosome 21 in cell division is broken off and attached to another chromosome. Since the disorder is unexpected there are numerous amounts of risk factors that are possible based on the severity of the person.
For many hereditary diseases, cells deteriorate at a rapid pace, or they are mutated when they divide. However, with the use of cloning, scientists can study the diseased cell which causes the others have errors. By cloning a specific mutated cell, scientists can research the development in a disease (Jaenisch 1). Instead of allowing the cell to divide on its own and change its structure each time, exact replicas can be produced, which allows researchers to perform experiments on one independent variable at a time. By researching the inner workings of mutated cells, scientists can discover more information about healthy “monoallelic expression of imprinted genes… [and] the genomes of the sperm and the oocyte.... in the genome of the zygote” operate (Jaenisch 2). The zygote is a pre-fetus, and the healthy formation of it is vital for the healthy development of the human. By researching cloning, scientists can understand the harmful mutations of a cell and develop a cure or vaccination against them. Scientists can then, after finding how to stop mutations, accomplish a way to stop human cells from deteriorating, and discover a way to lengthen the lifespan of a typical human
According to Linda MacDonald Glenn, J.D., L.L.M., “The introduction of these diseases to the human population could have devastating consequences” (Glenn). Human genetic engineering may also cause the production of unwanted mutations, such as developmental issues. The procedures that would be used for genetically modifying human cells would include numerous alterations to sperm, eggs, stem cells, or embryos before entering a woman’s uterus. This could potentially modify the growth and development of the fetus in ways that have not yet been thoroughly explored (Genetics and Public Policy Center).... ...
A genetic mutation is a permanent change in the sequence of the DNA that makes up a gene. A mutation of these sorts can be caused by either inheritance from the parent or caused sometime during the life of someone. The mutation that has been inherited is called a germline mutation. Germline mutations affect virtually the entire body, and they seem to be present in every cell. A somatic mutation, or one that is caused in the DNA of a single cell sometime during the life, can be caused by an environmental factor or a wrong bonding in the DNA molecule. These cannot be passed down to the next generation of children because they occur in a specific cell as opposed to in a reproductive cell. Some mutations occur in the embryo as it is growing. These may occur during cell division, and some of the cells may or may not inherit this mutation. Some mutations are extremely rare, and others are incredibly common. Those that occur in more than one percent across a population are considered polymorphisms. Polymorphisms are considered normal variations in DNA, and they are known to cause simple changes such as variations in blood types and hair color. Although these are not typically fatal, they can influence the creation of some disorders (Lister Hill National Center for Biomedical Communications, U.S. National Library of Medicine, National Institutes of Health, Department of Health and Human Services, USA.gov, 2013).
...omosomes or genetic/chromosomal disorders. The most common type of genetic or chromosomal disorder is Down Syndrome or trisomy 21 (Cherry, n.d.). The condition occurs when a child has three chromosomes at the site of the twenty-first chromosome rather than the normal two. Some of the most common signs of Down Syndrome include round face, thick tongue, slanted eyes, hearing problems, heart defects, and intellectual impairment.