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Gender Linked Diseases

Example of x-linked inheritance

Gender linked diseases affect both genders, but tend to be more common in males than females. While females can be carriers and still unaffected by a disease, males can only be infected or normal. These types of genetic diseases are due to defective sex chromosomes and are completely separate from other types of genetic diseases. Males only inherit y-linked diseases, while both females and males can inherit x-linked diseases; however, it can become more complicated. Genes can be influenced by hormonal levels, making them occur more frequently in a certain gender. Overall, Males are predominantly the ones affected because they only have one x and one y chromosome. If either one of these chromosomes are abnormal or don’t function properly, then males inherit a disease.

Depending on what the parents have, a child could be normal, a carrier, or infected. The only possible parents are XX and xY, Xx and XY, XX and Xy, Xx and xY, XX and XY, and Xx and Xy (the red letters represent the ‘bad genes’). If both parents are normal, then the child would be unaffected. If only one parent is a carrier then there is a 50% chance of a child being either a carrier or infected. If both parents are carriers/infected, then there is a 75% chance a child is a carrier or infected. The different incidences result in a variety of results. Even though genetic diseases are diagnosed on a daily basis, they still affect thousands out of the millions of people around the world.

In one of my labs, there was a case study dealing with sex-linked diseases called, ‘How many Chromosomes does my baby have?’. In this case, a karyotype was processed from a baby’s cells and abnormal results were found. The baby was diagnosed with xyy syndrome, which is when a person has an extra y chromosome. This is a y-linked disease, meaning that the baby is male, and the probability of this disease is 1 in every 1000 male births. This disease is not common among males, but it impacts their lives. This baby could possibly have developmental delays, behavioral problems, delayed speech, learning disabilities, poor motor control, and overall weakness. Technology today is trying to solve these genetic problems, and find a cure for those who inherit diseases.

Understanding more about how genes are inherited makes me realize how many things can affect genes. Dominance, recessive, linkage, mutation, and sex-linkage all affect genes and their inheritance. This makes me fascinated with the replication and creation of DNA. It is not simply take 1/2 from mom and 1/2 from dad, there is so much more involved. You could inherit a specific trait because it’s carried on the y chromosome, traits could be inherited because they’re linked, or you could not inherit a trait from your dad because it’s recessive. Gender linkage is a big factor in inheritance. It can decipher whether a person inherits a trait or not, or whether a person inherits a genetic disease or is just a carrier.

Over the years, genetic research has grown substantially and has impacted our society. Originally, there was no belief in genetics, and there was only the theory of creationism (in addition to other theories regarding other religions). The first hint at genetics was the “bricks and mortar” theory, which refers to the idea that physical characteristics are directly related to each specific part of the body. Debate occurred for years over this theory, then the idea of evolution rose from Charles Darwin. To build on this idea, Gregor Mendel brought up ideas about alleles through his pea plant experiment. Throughout these years, only the idea of genetics was forming, scientists still had no idea what they were dealing with and they still didn’t have all the components of genetics. It wasn’t until the early twentieth century when the idea of DNA and chromosomes was presented and proven. Once the basis of genetics was established, more complicated ideas were researched. Scientists began to look into genetic engineering and DNA sequencing. These revolutionary ideas would unlock the possibility of manipulating genetics. With our advanced technology and understanding today, modern scientists now know the identity of “more than 1800 genes that cause disease”. More accurate diagnostics are available to allow people to know what diseases they are in risk of and what to expect in their future. In addition, new treatments to ‘bad genes’ are available such as genetic engineering and medicine. Scientists have created chemicals and enzymes which are used as “gene therapy” in a sense. We are slowly gaining the power to turn on and off genes and alter genetic material.
This evolution in understanding and technology impacts our life in more than one way. It brings us a step closer to discovering the human genome in its entirety and curing genetic diseases. This could mean a new life for those diagnosed with a genetic disease. This would be a revolutionary breakthrough for geneticists to be able to save lives by just altering a gene. The future of genetics is heading in a direction that could change the world forever.

Haldeman-Englert, C., & Zieve, D. (Eds.). (2014, May 5). Sex-linked recessive: MedlinePlus Medical Encyclopedia. Retrieved May 5, 2015, from

Foley, M. (2013, May 29). Genetics: Past, Present, and Future. Retrieved May 5, 2015, from

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