He similarities and differences between autosomal recessive and Essay

He similarities and differences between autosomal recessive and sex-linked recessive conditions - Essay Example Autosomal recessive conditions manifest themselves only when an individual is homozygous for the affected allele that causes a certain condition The alleles that cause these conditions are not found on the sex genes (the X or Y chromosomes), and the affects are generally masked in the heterozygous parents who possess both a normal, dominant allele and the affected recessive allele. Only offspring with both recessive alleles, meaning both parents are heterozygous carriers of the recessive genes will be affected. These disorders are present in only about 2.5 per 1000 live births, and will not be manifested is the offspring receives a dominant allele from either parent. Sex-linked recessive conditions are found on the sex chromosomes. Females, who have two X chromosomes will only show the condition if, like autosomal recessive conditions, they inherit a recessive allele from both parents. Males, having only one X chromosome, are always affected by X-linked recessive alleles because they have no other dominant allele to mask the affects of the single affected X chromosome (Kumar and Clark 2009, p. 43). The primary difference between autosomal recessive and sex-linked recessive is how males and females are likely to be affected, and how likely each are to inherit, a condition. Examples of autosomal recessive conditions include cystic fibrosis and sickle cell disease. Examples of sex-linked recessive conditions include hemophilia and red-green color blindness.... This means that heterozygous parents may be carriers for certain conditions. Only if both parents pass the recessive allele onto the offspring will the offspring express the condition. This results in the chance that two heterozygous parents pass on an autosomal recessive condition of only 25%, whereas there is a 50% chance that a single heterozygous parents will pass on the condition to the offspring (Kumar and Clark 2009, p. 42-43). Examples of autosomal dominant conditions include Huntington’s disease. 3. Describe the differences seen between benign and malignant tumours. Use appropriate examples, with rationale, to support your points. Tumors arise from changes in a single cell that proliferate to affect areas of the body or even the whole body. Oncogenesis is a multistep process in which the malignant phenotype is expressed, which may occur due to both genetic and environmental factors. Anaplasia and metastatis are characteristics of malignant tumors, but no benign tumors . Anaplasia refers to the reversion of cellular differentiation and often includes an increased ability to multiply without differentiation. Metastatsis refers to the capacity of malignant tumor cells to spread across the body to adjacent and non-adjacent organs, often but not always through the bloodstream (Kumar and Clark 2009, p. 49). Benign tumors are nonprogressive and do not metastatis to other areas of the body. Some common examples of benign tumors include the common mole. Moles may sometimes develop malignancy over the course of an individual’s lifetime, however, so regular examinations by a physician are recommended. 4. Define with suitable examples, the following terms: aetiology,