How Are Genetic Mutations Passed From Parents To Offspring?

Genetic mutations can be passed from parents to offspring, and that’s one of the reasons why certain types of cancer or disease run in families.

Inherited genetic mutations came into the spotlight when Angelina Jolie, a Hollywood superstar, elected to have a prophylactic double mastectomy or surgical removal of both breasts. It was controversial because she had no breast tumors or cancer cells. She had undergone genetic screening showing the presence of BRCA1 pathogenic genetic mutation that indicates a genetic predisposition or likelihood of developing breast cancer. On top of that, her own mother died at age of 56 due to breast cancer. As a preventive measure, Jolie opted for surgical removal of both of her healthy breasts to reduce the overall risk of getting breast or ovarian cancer based on the presence of BRCA1 genetic mutation and the presence of strong family history of breast cancer as diagnosed in her mother, aunt and grandmother.

If you lost a parent to a certain cancer or disease, it could provide you with peace of mind to take preventive measures like Angeliina Jolie did. For example, if one of your parents passed away from colorectal cancer, it could ease your mind to get frequent colonoscopies at the earliest to find the tumor if present so that a surgery can be done to remove those polyps or tumor from the colon. It’s a very simple surgical operation if at all needed, and if you lost a parent to colorectal  cancer, it’s understandable why you’d consider this decision.

Many Different Genetic Mutations are Passed From Parents to Their Children

Because genetic mutations can be passed from the parents to offspring is why certain hereditary diseases run in families, some manifesting later in life like Alzheimer’s disease, various cancers, heart disease, psoriasis, or osteoporosis. Moreover, there are also certain hereditary mutations or chromosomal anomalies that are evident at the time of a baby’s birth. For instance, a single-gene disorder like Sickle Cell Anemia or a chromosome disorder such as Trisomy 13 are often diagnosed in newborn babies.

If you’re concerned about avoiding potential health complications from gene mutations as you age, being informed about your genetic health risks passed on from your parents is critical in mitigating issues to help prevent them. For example, those with a family history of breast  cancer could elect to have more screenings like mammography or breast MRI at frequent intervals to detect any presence of tumor and to remove them before they become cancerous cells. At the same time, if you’re planning a family, it is vital to talk about your family history with your partner because genetic mutations could be passed to your future children, and what if you’re both carriers of the same mutation or a mutation in the same gene? Learn more about this below:

How Do Genetic Mutations Happen?

Genetic mutations occur when there are modifications of an organism’s DNA sequence. A DNA molecule is composed of four base chemicals which are arranged into a sequence with billions of combinations. They determine an individual’s appearance, traits, behavior, and even health conditions. During cell division, cells make copies which include encoding the DNA sequence. However, with a genetic mutation, there is a change in the sequence which could be a deletion, insertion, duplication, or inversion of the base chemicals which affect the cell growth and function.

Are genetic mutations a bad thing? Not necessarily. One study stated that these mutations are a fundamental factor in driving evolution and they occur naturally throughout the world. Gene changes could even help with natural selection and help organisms survive with changing times and environments as parents pass off new genetic variants to their offspring during the reproduction process. For instance, farmers cultivating grapes could selectively grow hardy parent variants to reproduce fruits without seeds, that are sweeter, and naturally more resilient against pest infestations and soil changes.

However, genetic mutations that cause diseases like cancer, Huntington’s disease, Alzheimer’s disease or hemophilia are worrisome. Often, these diseases are seen to run in families, such as a family history of ovarian cancer on the mother’s side of the family with the mother, aunts, grandma, sisters, daughters, or cousins developing the same cancer at some point in time in their life. This shows that inherited genes could pass certain diseases from one generation to the next.

How Do Parents Pass Genetic Mutations to Their Children?

Genetic mutations occur when there is a change in one or many genes, rearrangement of genes or whole chromosome, or loss of one or more genes.

Many gene mutations are actually acquired due to environmental stimuli throughout a person’s lifetime, and therefore mutations are not always inherited. These changes to the genetic code could happen spontaneously or randomly. A perfect example of this is exposure to carcinogens that alter genes and affect cell growth leading to tumor growth and cancer. These are called somatic mutations, affecting only some cells. Since they are spontaneously acquired from the environment, you cannot pass this to your kids.

Germline Mutations

There are many mutations that people are born with because they acquire genetic mutations from one or both parents during conception. These are referred to as germline mutations or germline variants. The egg or sperm are called germ cells. During the germination or fertilization of a human being, 23 pairs of chromosomes from the mom and dad carrying billions of DNA codes combine. If a parent carries genetic mutations in any of those codes, they could pass them on to their offspring.

Common Genetic Disorders

These hereditary genetic mutations are found in every cell of the offspring for life as it is incorporated into the DNA sequence during the embryo’s formation and growth. When the offspring eventually reproduces, these mutated genes could be replicated and passed on to their own future kids. As a result, the baby may show symptoms of hereditary diseases caused by genetic mutations. These are the top five common genetic disorders:

• Down Syndrome
• Thalassemia
• Cystic Fibrosis
• Tay-Sachs Disease
• Sickle Cell Anemia

Do All Genetic Mutations Equate to Serious Health Issues?

Not all genetic mutations result in health disorders or genetic abnormalities. For example, having the genetic mutation associated with Alzheimer’s disease does not necessarily mean you’ll get Alzheimer’s disease.

Genetic mutations can occur throughout a person’s life as cells continually grow and replicate. Some genetic changes are silent mutations with no physical manifestations or effects on health. The body can even repair many mutations. Moreover, other genetic mutations are beneficial to make the organism survive and for the population to thrive. To illustrate, some children have genetic mutations in the SLC30A8 genes which make them 65% less likely to get diabetes even with a risk factor such as obesity.

That being said, there are genetic mutations that are responsible for genetic malformations such as Down’s Syndrome which is an abnormality in the chromosome 21 count, which contains genetic codes. If you’re wondering if both parents have to be carriers of the same genetic mutation to pass it onto their child, the answer is no. All it takes is one sperm or egg to pass on the altered gene during conception to the offspring.

However, this doesn’t necessarily mean that the genetic mutation will manifest immediately as a genetic disorder or illness in the child. When a family is diagnosed with a genetic disorder, members naturally want to know the likelihood of their kids developing a health issue from an altered gene. One important consideration in determining this likelihood is how the genetic condition is inherited. Take a look at the examples below:

Autosomal Dominant Inheritance

A study on genetic inheritance patterns stated that dominant genetic mutations could manifest as a genetic disorder even if only one copy of the mutation is present with the parent at the time of conception. Furthermore, a parent will have a 50% chance of passing the mutation to any of their offspring. An example of this mutation with high probability of being passed from parent to offspring is Huntington’s disease or familial hypercholesterolemia, which typically occurs in every generation. An affected child will have one parent who has the disease.

Autosomal Recessive Inheritance

Recessive inheritance needs two mutated gene copies from both the mother and father for the disease to develop as a genetic disorder in babies. A recessive variant is typically not seen in every generation. Hence, a recessive gene carrier with the mutated gene could be physically normal. If both parents are mutated gene carriers, the disease could manifest in their kids. But if only one parent is a carrier, the mutated gene could still be passed to the offspring but the baby will only be a genetic carrier and will show no symptoms of the disease. Examples of these are Tay-Sachs disease and cystic fibrosis.

X-Linked Dominant Inheritance

The chances of passing an X-linked Dominant condition like Rickets differs between male and female. A man has one X and one Y sex chromosome, while a woman has two X chromosomes. The man passes his Y chromosomes to his son and X chromosome to his daughter. Hence, a man with an X-linked Dominant disorder will have sons that are not affected but his daughters could inherit the condition. Meanwhile, a woman passes one or the other of her X chromosomes to a child. Hence, a woman with an X-linked dominant gene mutation has 50% chances of passing the condition to a son or daughter.

X-Linked Recessive Inheritance

The differences in sex choromosomes between men and women also affect the probability of passing an X-Linked recessive genetic disorder. A man with an X-Linked recessive disorder will not pass it to his sons but his daughters could carry a copy of the mutated gene. Meanwhile, a woman who carries the altered gene has a 50% chance of having a son manifesting the genetic disorder and 50% chance of a daughter being a carrier of the altered gene. Males are more affected by this gene mutation. An example of this type of X-Linked Recessive disorder is hemophilia and color blindness, which are disorders that mostly affect males.

Mitochondrial Inheritance

Mitochondria produce energy for cells and contain some DNA code. Genetic mutations in the mitochondria could affect both males and females. Notably, only females can pass this altered gene in mitochondrial DNA to all sons and daughters because the mitochondria of the offspring comes from the mother. Male children with this mitochondrial genetic mutation can manifest the disease, but he will not pass the genetic condition to his children. Examples of this are Kearns-Sayre Syndrome or Leber’s hereditary optic neuropathy

Mutations are Very Common, But Not Always Dangerous

Talking about genetic mutations could easily instill fear. But bear in mind that genetic mutations are actually more common than you think. Most of these mutations will not immediately manifest as an illness. A scientist from the University of Utah Health says that everyone is a mutant, but some individuals are prone to diverge more than others. In the study, the researcher notes that children have about 70 new mutations compared to their parents. However, 70 is only a very tiny fraction out of billions of DNA base sequences upon fertilization.

Notably, the same study shared that genetic mutations passed to offsprings increase with parental age. The impact of these changes depends on where they land on the DNA and the passage of time. For instance, a child born from a 35-year-old mother will have more genetic mutations than a sibling born from the same mother at 25 years old.

For the majority of people, changes in genetic codes don’t have very harmful effects on human health. However, on some occasions, these changes could result in disease. However, a disease-causing mutation, no matter how small, is always a cause for concern. The goal is to prevent the onset of illness and live a healthy life. Get a DNA test and take preventative measures if a genetic mutation shows up in your DNA test results.

Information on Mutated Carrier Genes can Grant Peace of Mind

Staying proactive with your health allows you to make educated choices. Knowing how a genetic mutation affects your family can help you modify your lifestyle habits and take preventive measures to protect yourself and your loved ones. As an example, many women with a higher genetic risk of breast cancer and strong family history have elected to have prophylactic mastectomies after the child bearing age. Harvard Health noted that 60% of women with inherited harmful genetic mutations in BRCA1 or BRCA2 genes will develop breast cancer. Hence, these women are happy with the decision and recommend the same procedure to other women with a strong family history of the disease.

Taking a CircleDNA test, a DNA test that assesses your genetic health risks, potential hereditary conditions and disease risks, could provide you with more clarity, useful information, and peace of mind. This DNA test can also say if you and your partner are genetic mutation carriers of the same gene that you could pass to your offspring. Being educated about certain genetic mutations is vital for family planning.

Many people are starting to take DNA tests to find out their genetic mutations before they opt to have children. If you have a specific genetic mutation that’s considered a cause for concern, or if both you and your partner have a genetic mutation in the same gene, you may decide to get pregnant a different way. You could do IVF and have the embryo screened by using technology like Preimplantation genetic testing (PGT) to help prevent passing these potentially harmful mutations to your children.

Discussing your family history of diseases or genetic mutations with your partner matters, because you could potentially pass them on to your kids. For instance, if you and your partner have a strong predisposition of passing Huntington’s disease to your future kids, you could elect to have embryo screening and IVF to ensure your future kids don’t suffer from this debilitating illness. Prioritizing preventive health and family planning means you also look out for the well-being of your future children and family.

Genetic mutations are just one of the many steps responsible adults should take when they’re ready to start a family, have children, and want to discuss family planning.

References

1. My Medical Choice. (NY Times Angelina Jolie) https://www.nytimes.com/2013/05/14/opinion/my-medical-choice.html
2. The population genetics of mutations: good, bad and indifferent (Laurence Loewe and William Hill)  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2871823/
3. News Feature: Genetic mutations you want (Sarah Williams) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4791022/
4. Inheritance Patterns (National Library of Medicine) https://www.ncbi.nlm.nih.gov/books/NBK115561/#
5. Some parents pass on more mutations to their children than others (Science News Daily) https://www.sciencedaily.com/releases/2019/09/190924143205.htm