Inheritance - Inherited Disorders (GCSE Biology)
Inherited Disorders
Genetic Disorders
Some disorders can be inherited genetically. They can be transmitted from the parents to the offspring via the inheritance of different alleles. Here are some examples:
Polydactyly is the presence of extra fingers or toes. This is caused by a dominant allele, therefore, if any of the offspring inherit the allele for polydactyly, they will most definitely suffer from the condition, unless there is any mutation.
Cystic Fibrosis is another important genetic condition. Some cells produce a secretion known as mucus. This is a defence in the oesophagus for example. However, sufferers of Cystic Fibrosis have a mutation in their code for certain chloride channels in their cell membranes. This leads to a secretion of extra thick mucus. This can cause huge breathing difficulties to patients. It is caused by a recessive allele. Therefore, it can be passed on by unaffected heterozygous parents.
Sickle cell anaemia is another condition that can be inherited. It is a recessive condition so two HbS alleles are needed for the disease. The dominant allele is HbA . The disease itself is caused by the change in base sequence of the gene that codes for haemoglobin. This causes abnormal haemoglobin and sickle-shaped red blood cells. These can get stuck in blood vessels thus, hindering the delivery of oxygen to tissues. Hence, fatigue, fever and painful joints are symptoms of the disease.
However, being a carrier of the disease can be advantages. If you are heterozygous for the sickle cell allele (genotype HbS HbA), then you are less likely to get malaria as you are resistant to it. This is advantageous in places where the incidence of malaria is high e.g. in Africa. Hence, over time, this has caused an increase in the number sickle cell alleles in the population and also the number of carriers.
Screening
Embryonic screening can take place in order to test for alleles. This process can take place in many ways:
- Amniocentesis – A sample of amniotic fluid from the area surrounding the foetus can be tested.
- Chorionic Villous Sampling – A sample from the placenta is taken and checked.
In order to screen, DNA must be taken from the embryo and is tested.
When testing during IVF, the whole cell is removed from the embryo before implantation occurs.
Issues with screening:
- Ethics in Normal Pregnancy – Once the parent has their results, there is an ethical quagmire. They will be in the knowledge of a portion of the health of the child. This can lead to an element of choice in some cases. Parents may get the option of terminating the pregnancy. Some therefore, believe that this testing is unethical, as it could ruin the opportunity for an embryo to live a life. Others may not terminate the pregnancy, but use the result to prepare for pregnancy and the life of the child.
- Ethics in IVF – During IVF, if an embryo is found to have a genetic disorder, it is not implanted. There are questions regarding the ethics of this, as the embryo is then destroyed.
- Cost – One thing to remember is that all of this testing is very expensive, however the cost of the healthcare for the child who suffers from a disorder may be much greater.
- False results – If the results are a false positive or a false negative, they could lead to great trauma to a family.
Inheritance in biology refers to the passing down of traits or genes from one generation to another. These traits and genes can be physical characteristics, such as eye color or height, or they can be related to genetic disorders.
Inherited disorders are genetic conditions that are passed down from one generation to another. They are caused by changes or mutations in genes, and can lead to a range of health problems, including physical and intellectual disabilities.
Inherited disorders are passed down from one generation to the next through the transmission of genes from parents to their children. Genes are located on chromosomes in the cells of our bodies, and they carry the instructions for how our bodies develop and function. When a gene is mutated, it can lead to an inherited disorder.
Some common inherited disorders include sickle cell anemia, cystic fibrosis, Huntington’s disease, and Tay-Sachs disease. These disorders can cause a range of symptoms, including physical and intellectual disabilities, and can be life-threatening in some cases.
The risk of passing down an inherited disorder is determined by the pattern of inheritance of the disorder. Some disorders are passed down in a dominant pattern, which means that a person only needs to inherit one copy of the mutated gene to develop the disorder. Other disorders are passed down in a recessive pattern, which means that a person needs to inherit two copies of the mutated gene, one from each parent, to develop the disorder.
Inherited disorders can be diagnosed through a range of tests, including genetic testing, blood tests, and imaging tests. Genetic testing is often used to diagnose inherited disorders, as it can detect mutations in specific genes that are associated with the disorders.
The treatment and cure of inherited disorders depend on the specific disorder and the severity of the symptoms. Some inherited disorders can be managed with medication or other treatments, while others have no cure. In some cases, genetic counseling or pre-implantation genetic diagnosis may be recommended to help prevent the transmission of the disorder to future generations.
The role of genetics in inheritance and inherited disorders is critical, as it provides the underlying instructions for how our bodies develop and function. When a gene is mutated, it can lead to an inherited disorder, and a person’s genetic makeup plays a significant role in determining the risk of passing down an inherited disorder to future generations. Understanding the genetics of inheritance and inherited disorders is important for improving our ability to diagnose, treat, and prevent these conditions.
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