Genetics as a phenomenon was discovered in the late 19th century. This can be considered as quite a late discovery in comparison to other medical advancements such as general anaesthesia which can be seen throughout recorded history around the world. Genes are the main factors that affect people with genetic conditions like the well-known Down’s syndrome or Huntington’s disease causing the person to sometimes have characteristic facial features or intellectual disabilities. A gene is a sequence of DNA bases that code for either a polypeptide chain or functional RNA; they can even exist in different forms called alleles – this is how organisms have variations within species like different eye colour or blood type. Genes can have random mutations which alter the base sequence of DNA through error.
There are two types of error: substitution and deletion. Substitution is when one base is substituted with another; deletion is when one base is deleted. Often these errors cause no effect on the organism due to the degenerate, non-overlapping nature of the genetic code but sometimes they do and thus cause genetic disorders. The two disorders I will investigate through the course of this report are 22q11 Deletion Syndrome and Turner syndrome. Both these disorders are genetically caused. Through my Work experience at Clinical Genetics, I have learn’t that it can be quite visually clear when a person has a specific genetic condition due to characteristic feature, for example, a short palpebral fissure, indistinct philtrum and micrognathia all indicate to the person having fetal alcohol syndrome or FAS.
These specific characteristics for specific genetic conditions are especially useful for clinical geneticists who help identify genetic causing conditions. However, for some genetic disorders, genetic doctors are faced with no outward, physical disabilities but a difference in other factors like puberty and sexual development, behaviour, fertility or even employment and education; these are all clinical features geneticist take into account when diagnosing. I will be specifically looking at the behavioural factors affected by the mutated gene that causes 22q11 deletion syndrome and Turner Syndrome. Genes cause 22q11 deletion syndrome and Turner Syndrome to come about, more specifically a mutation in a person’s gene causes these disorders.
These disorders can then have behavioural characteristics associated with them. Thus, I want to see whether these behaviour problems are due to the gene mutation, or other environmental factors. I also want to investigate the extent genes affect behaviour in the mentioned genetic disorders. Turner Syndrome:Turner syndrome’s features were described in 1938 and 1959 by Turner and he found that the cause of this syndrome is an absent X chromosome (45,X karyotype) in the 23rd chromosome pair. This mutation only happens in girls/ women and affects one in twenty-five thousand live female births. Girls who have this condition, do not have the second sex chromosome.
Statistics from the Oxford Desk Reference Clinical Genetics and Genomics (Second Edition) show us that 80% of the X chromosome in 45,X are of maternal origin meaning the origin of the mutation, is thought to be because of ‘paternal meiotic error’ that then cause ‘genetic abnormal sex chromosomes. ’ For this condition, there is help available through NHS approved groups that help the person themselves and those around them, family and friends that are affected.
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