Usually these instructions make a protein. There are many different types of proteins in our bodies which can perform multiple important tasks. For example, proteins form the basis of our organ tissues, bones, and nervous system.
They also guide how we digest food and medications. Although genetic factors play a part in nearly all health conditions and characteristics, there are some conditions in which the genetic changes are almost exclusively responsible for causing the condition. These are called genetic disorders, or inherited diseases. Since genes are passed from parent to child, any changes to the DNA within a gene are also passed. DNA changes may also happen spontaneously, showing up for the first time within the child of unaffected parents.
This is referred to as a new mutation, where the word mutation means change. Sometimes this change can cause mistakes in the protein instructions, leading to production of a protein that doesn't work properly or cannot be made at all.
When one protein is missing or not working as it should, it can cause a genetic disorder. The genetics of each disorder are unique. Cancer occurs when one or more cells in an organ develop a mutation, which can cause the cells to grow uncontrollably. Oncologists call these germline mutations. Some of the best-known germline mutations are the mutations in the BRCA1 and BRCA2 genes , which increase the risk for breast, ovarian, prostate, and pancreatic cancers. Experts estimate that they account for a small percentage of all cancers.
The Genetic Theory of Aging. Genetic vs. Was this page helpful? Thanks for your feedback! Sign Up. What are your concerns? Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles.
Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. What is a gene? Related Articles. Desmoid Tumor: Causes and Risk Factors. Is Schizophrenia Genetic? These are called inheritance patterns. Examples of inheritance patterns include:.
An allele of a gene is said to be dominant when it effectively overrules the other recessive allele. The allele for brown eyes B is dominant over the allele for blue eyes b. So, if you have one allele for brown eyes and one allele for blue eyes Bb , your eyes will be brown. This is also the case if you have two alleles for brown eyes, BB. However, if both alleles are for the recessive trait in this case, blue eyes, bb you will inherit blue eyes. For blood groups, the alleles are A, B and O.
The A allele is dominant over the O allele. Blood group A is said to have a dominant inheritance pattern over blood group O.
If the father has two O alleles OO , he has the blood group O. For each child that couple has, each parent will pass on one or the other of those two alleles. This is shown in figure 1. This means that each one of their children has a 50 per cent chance of having blood group A AO and a 50 per cent chance of having blood group O OO , depending on which alleles they inherit.
The combination of alleles that you have is called your genotype e. The observable trait that you have — in this case blood group A — is your phenotype. If a person has one changed q and one unchanged Q copy of a gene, and they do not have the condition associated with that gene change, they are said to be a carrier of that condition. The condition is said to have a recessive inheritance pattern — it is not expressed if there is a functioning copy of the gene present.
If two people are carriers Qq of the same recessive genetic condition, there is a 25 per cent or one in four chance that they may both pass the changed copy of the gene on to their child qq, see figure 2.
As the child then does not have an unchanged, fully functioning copy of the gene, they will develop the condition. There is also a 25 per cent chance that each child of the same parents may be unaffected, and a 50 per cent chance that they may be carriers of the condition.
Recessive genetic conditions are more likely to arise if two parents are related, although they are still quite rare. Examples of autosomal recessive genetic conditions include cystic fibrosis and phenylketonuria PKU. Not all genes are either dominant or recessive. Sometimes, each allele in the gene pair carries equal weight and will show up as a combined physical characteristic.
The A and B alleles are said to be co-dominant. Someone with one copy of A and one copy of B has the blood group AB. A cell reproduces by copying its genetic information then splitting in half, forming two individual cells. Occasionally, an alteration occurs in this process, causing a genetic change.
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