Autosomal recessive nonsyndromic deafness 109 is a genetic condition that causes hearing loss without other health problems. Most people with this condition have congenital or early-childhood hearing loss that does not worsen quickly. Hearing can range from mild to profound, and both ears are usually affected. It is lifelong, and people of any sex or background can be affected if they inherit two altered copies of the gene. Treatment focuses on hearing support like hearing aids, cochlear implants, and speech and language therapy, and many people do well with timely care.
Overview
Autosomal recessive nonsyndromic deafness 109Symptoms
Autosomal recessive nonsyndromic deafness 109 typically presents with permanent sensorineural hearing loss from birth or early childhood, usually affecting both ears. Features are limited to hearing, so families may notice poor response to sound and delayed speech.
Outlook and prognosis
Many people with autosomal recessive nonsyndromic deafness 109 have stable, lifelong hearing loss that doesn’t affect other body systems. With early identification, hearing technology, and communication support, most develop strong language and lead full, independent lives. Genetic counseling can guide family planning and expectations.
Causes and risk factors
Autosomal recessive nonsyndromic deafness 109 is caused by inheriting two nonworking copies of a hearing-related gene.
Risk is higher when both parents carry the variant, including consanguineous or founder groups; environment rarely alters severity.
Genetic influences
Genetics is central to Autosomal recessive nonsyndromic deafness 109; inherited variants in both copies of a gene cause it. Parents are usually carriers without hearing loss. Family history and genetic testing help confirm diagnosis, guide counseling, and support reproductive planning.
Diagnosis
The genetic diagnosis of Autosomal recessive nonsyndromic deafness 109 starts with clinical features of sensorineural hearing loss found on newborn or audiology screening. Genetic tests confirm the cause and inheritance. Imaging may help exclude other ear conditions.
Treatment and drugs
Treatment for autosomal recessive nonsyndromic deafness 109 focuses on hearing support and communication. Many benefit from hearing aids, cochlear implants, and timely speech-language therapy; newborn and early-childhood screening guide choices. Ongoing follow-up fine-tunes devices, supports learning, and addresses family needs.
Symptoms
You may first notice that a baby doesn’t startle to loud sounds or turn toward a voice, while otherwise growing and looking healthy. Early features of Autosomal recessive nonsyndromic deafness 109 often include not passing the newborn hearing screen and missing softer sounds in both ears. Features vary from person to person and can change over time. This hearing difference affects hearing only and is usually present from birth or early childhood.
Hearing is reduced in both ears, often to a similar degree. Soft speech, whispers, and distant or high-pitched sounds can be hardest to catch. It may stay steady or change slowly over time.
Many babies do not pass the newborn hearing screen in one or both ears. Follow-up hearing tests confirm inner-ear hearing loss. Early referral helps families get support quickly.
Without early support, babies may babble less and toddlers may talk later or have unclear words. With timely hearing devices and therapy, language can develop well. Social communication improves as access to sound increases.
The outer ear and ear canal look typical on exam. There is typically no ear pain or fluid causing the hearing change. The difference comes from how the inner ear or hearing nerve processes sound.
How people usually first notice Autosomal recessive nonsyndromic deafness 109?
People often first notice autosomal recessive nonsyndromic deafness 109 in a baby who doesn’t startle to loud sounds, doesn’t turn toward voices, or misses early speech milestones like babbling and first words; newborn hearing screening is usually the first clue, sometimes within the first days of life. Because this condition affects hearing without other physical differences, families may only see the first signs of autosomal recessive nonsyndromic deafness 109 during those early checks or when a child seems unresponsive to sound at home or in childcare. Doctors typically confirm it with repeat hearing tests and, in some cases, genetic testing when hearing loss is suspected early in infancy.
Types of Autosomal recessive nonsyndromic deafness 109
Autosomal recessive nonsyndromic deafness 109 is a genetic form of hearing loss with recognized clinical variants tied to changes in the PAX3 gene; these variants can shift how early hearing loss starts and whether inner-ear shape is affected on imaging. People may notice different sets of symptoms depending on their situation. When discussing types of Autosomal recessive nonsyndromic deafness 109, clinicians usually refer to genotype-based variants that align with specific PAX3 mutations, which can influence severity and onset. Not everyone will experience every type.
Congenital-onset type
Hearing loss is present from birth and typically affects both ears. Many have stable, severe-to-profound sensorineural loss that is identified on newborn screening.
Early-childhood onset
Hearing starts near normal but declines in the first years of life. Families may notice delayed speech or turning up the TV as the first signs.
Adolescent-onset type
Hearing is near typical in early childhood, with measurable decline during school years or adolescence. Some report trouble following conversations in noisy classrooms before everyday quiet settings become hard.
Imaging-associated variant
Some variants show subtle inner-ear structural differences on MRI or CT, even without other body features. This can correlate with more severe or earlier sensorineural loss.
Genotype-severity variant
Certain PAX3 changes are linked with more severe loss, while others relate to milder or later-onset loss. Discussing specific variants of Autosomal recessive nonsyndromic deafness 109 with a genetics team can help clarify expected severity.
What genetics can tell you about symptoms
Some people with autosomal recessive nonsyndromic deafness 109 have changes in the TMC1 gene, which disrupts inner ear hair cells that convert sound vibrations into nerve signals. This usually causes congenital or early-childhood, bilateral sensorineural hearing loss that ranges from moderate to profound.
Causes and risk factors
Autosomal recessive nonsyndromic deafness 109 is caused by inherited changes in a single gene from both parents. Genetic risk of autosomal recessive nonsyndromic deafness 109 is higher when both parents are carriers or are related by blood, such as cousins. If both carry the same change, each pregnancy has a 25% chance of being affected.
Loud noise, repeated ear infections, head injury, and some antibiotics or chemotherapy do not cause this condition, but they can reduce any remaining hearing. Some risks are modifiable (things you can change), others are non-modifiable (things you can’t).
Environmental and biological risk factors
Environmental and biological risk factors for Autosomal recessive nonsyndromic deafness 109 are limited and specific. This hearing difference is set before birth, so outside exposures generally don’t change whether it occurs. Doctors often group risks into internal (biological) and external (environmental). For this condition, the internal side is primary, and no clear external trigger has been confirmed.
This condition is present from birth and reflects a fixed internal cause set at conception. It is not known to be linked to pregnancy complications or childhood illnesses.
No specific toxins, infections, medications, or pollutants are known to raise the chance of Autosomal recessive nonsyndromic deafness 109. When exposures affect hearing, they usually cause other types of hearing loss rather than this condition.
Research has not shown a consistent connection between older maternal or paternal age and risk. Most cases arise regardless of parent age.
Prematurity, low birth weight, or delivery complications can be tied to acquired hearing issues, but they are not established risks for Autosomal recessive nonsyndromic deafness 109. This condition is determined before birth.
Genetic risk factors
In this form of hearing loss, the cause is genetic: it happens when a child inherits a nonworking copy of the same hearing gene from each parent. Understanding the genetic risk factors for autosomal recessive nonsyndromic deafness 109 can help families plan testing and care. Some risk factors are inherited through our genes.
Recessive inheritance: The condition appears when both copies of the same hearing gene carry harmful changes, one from each parent. When both parents are carriers, each pregnancy has a 25% chance of autosomal recessive nonsyndromic deafness 109.
Carrier parents: Carriers usually have normal hearing but can pass the nonworking gene to their children. A couple in which both partners are carriers has the highest genetic risk for autosomal recessive nonsyndromic deafness 109.
Two different changes: Many affected children inherit two different changes, one on each copy of the gene. This still disrupts the same gene and leads to hearing loss.
Variant type matters: Changes that stop the protein early can cause stronger effects than some single-letter changes. The type of change may influence the degree of hearing loss or whether it stays stable or progresses.
Shared ancestry: Partners with the same regional or community background are more likely to carry the same rare gene change that started generations ago. This raises the chance that a child inherits two nonworking copies.
Related parents: Parents who are related by blood have a higher chance of sharing the same rare change. This increases the likelihood of autosomal recessive nonsyndromic deafness 109 in their children.
Family history: Having siblings or close relatives with early, non-syndromic hearing loss points to a higher genetic likelihood. This can guide targeted testing for the known family changes.
Other genes: Certain genes can modify when hearing loss begins or how fast it changes. These modifiers help explain why severity can differ even within one family.
Single-gene cause: Autosomal recessive nonsyndromic deafness 109 is linked to changes in a single hearing-related gene at a defined spot in DNA. Finding the exact changes confirms the diagnosis and clarifies carrier status.
Lifestyle risk factors
This condition is inherited; daily habits do not cause it, but they can influence symptom burden, communication success, and risk of additional hearing decline. Focusing on how lifestyle affects Autosomal recessive nonsyndromic deafness 109 can help preserve residual hearing, reduce listening fatigue, and improve safety. The points below link common lifestyle choices to concrete effects on hearing and day-to-day function.
Listening to headphones or earbuds at high volume can accelerate loss of any remaining hearing and worsen tinnitus. Keeping volume moderate and limiting duration helps protect cochlear hair cells you still rely on.
Regular use and proper maintenance of hearing aids or cochlear implants improve speech understanding and reduce listening fatigue. Inconsistent use can slow auditory brain adaptation and make conversations more exhausting.
Using earplugs during concerts, clubs, or power-tool use prevents additional noise-induced damage to residual hearing. Skipping protection can make speech-in-noise hearing even harder.
Tobacco smoke reduces inner-ear blood flow and is linked to faster hearing decline. Quitting lowers oxidative stress on cochlear structures you depend on.
Risk prevention
For autosomal recessive nonsyndromic deafness 109, the condition itself can’t be prevented once inherited, but you can lower the chance of extra hearing loss and support healthy language development. Prevention is about lowering risk, not eliminating it completely. Early identification, careful sound protection, up-to-date vaccines, and regular hearing checks help protect any remaining hearing. If you’re planning a family, reproductive options can reduce the chance of this condition in future children.
A genetics professional can explain the autosomal recessive pattern and your chances of having a child with this condition. Carrier testing for you and your partner helps guide family planning.
If both partners are carriers, options like IVF with embryo testing or prenatal testing can lower the chance of having a child with autosomal recessive nonsyndromic deafness 109. A counselor can review benefits, limits, and timing.
Make sure your baby completes newborn hearing screening and any needed follow-up quickly. Early confirmation of hearing loss allows timely support and helps prevent language delays.
Hearing aids or a cochlear implant, when appropriate, can maximize access to sound. Early use supports speech, learning, and social development.
Transmission
Autosomal recessive nonsyndromic deafness 109 is inherited, not contagious; it can’t be caught from others or spread through daily contact. It follows an autosomal recessive pattern, meaning a child is affected only when they receive two nonworking copies of the same gene—one from each parent, who typically have normal hearing but carry a single altered copy. When both parents are carriers, each pregnancy has a 25% (1 in 4) chance of an affected child, a 50% (1 in 2) chance of a carrier child, and a 25% chance of a child who is neither affected nor a carrier. New genetic changes can appear for the first time in a child, but most cases happen when two carriers have a child. A genetic counselor can explain how Autosomal recessive nonsyndromic deafness 109 is inherited and discuss the genetic transmission of Autosomal recessive nonsyndromic deafness 109 in your family.
When to test your genes
Consider genetic testing if you have early-onset hearing loss without other health issues, a family history of childhood deafness, or relatives known to carry GJB2/GJB6 or related variants. Testing helps confirm diagnosis, clarify inheritance, and guide hearing care choices, including cochlear implant planning and newborn screening. Couples with a family history or from high‑carrier communities may test before pregnancy to understand risks.
Diagnosis
For many families, the first clues are missed newborn hearing screens or noticing that a baby doesn’t startle to sound or turn toward voices. Diagnosis of Autosomal recessive nonsyndromic deafness 109 often starts with hearing tests and a medical review to make sure there are no features pointing to a broader syndrome. Genetic testing may be offered to clarify risk or guide treatment. Putting these results together helps confirm the cause and supports care planning for the child and family.
Hospitals typically use quick, painless tests to check hearing within the first days of life. If a baby does not pass, a repeat screen or full evaluation is arranged. Early follow-up helps prevent delays in speech and language.
An audiologist measures how the inner ear and hearing nerve respond using tests like otoacoustic emissions and auditory brainstem response. These tests define the degree and type of hearing loss. Results guide next steps and timing of interventions.
A clinician looks for features that might suggest a broader syndrome, such as differences in the eyes, skin, kidneys, or thyroid. Finding no extra features supports a nonsyndromic cause. This exam also guides which tests are most useful.
A detailed family and health history can help reveal a pattern that fits autosomal recessive inheritance. Doctors ask about relatives with hearing loss, age at onset, and any related conditions. Even a seemingly negative history is useful information.
Stages of Autosomal recessive nonsyndromic deafness 109
Autosomal recessive nonsyndromic deafness 109 does not have defined progression stages. Hearing patterns vary between people and families—some have hearing loss from birth or early childhood that stays fairly steady, while others notice slow changes over time—so doctors do not use a step-by-step stage system. Diagnosis and monitoring rely on hearing tests (like an audiogram or newborn screening), sometimes an auditory brainstem response (ABR), and genetic testing to confirm this specific inherited type. Different tests may be suggested to help map your hearing levels and rule out other causes, and discussing early symptoms of autosomal recessive nonsyndromic deafness 109—such as missing soft sounds or delayed speech—can guide next steps.
Outlook and prognosis
Looking at the long-term picture can be helpful. For most people with Autosomal recessive nonsyndromic deafness 109, the condition affects hearing but not overall health or life span. There’s no known increase in mortality tied directly to this type of genetic hearing loss, and many children grow into healthy adults who learn, work, and socialize fully. Early care can make a real difference, especially when newborn screening, timely hearing aids or cochlear implants, and speech-language support are in place.
The outlook is not the same for everyone, but many living with Autosomal recessive nonsyndromic deafness 109 have hearing loss present from birth that stays fairly stable over time. Some may notice gradual changes in hearing across years, while others find their levels stay about the same. Because the inner ear is the main issue and other organs aren’t typically involved, day-to-day health outside of hearing is generally typical. If you’re wondering about early symptoms of Autosomal recessive nonsyndromic deafness 109, families often first notice missed startle responses to loud sounds or delayed babbling in infancy.
With ongoing care, many people maintain strong communication, education, and employment outcomes. Modern hearing technology, therapy, and accessible environments support language development and social connection, which shape long-term quality of life more than the gene change itself. Talk with your doctor about what your personal outlook might look like, including whether your hearing is expected to remain stable and which supports are the best fit now and as you age.
Long-term effects
Autosomal recessive nonsyndromic deafness 109 typically presents with permanent inner‑ear hearing loss without other medical findings. Parents may first notice early signs of Autosomal recessive nonsyndromic deafness 109 in infancy, or it may become clearer in early childhood. Long-term effects vary widely, but most involve communication and learning environments rather than overall health. Life expectancy is expected to be typical.
Hearing loss is usually present from birth or early childhood and tends to be stable to severe over time. In some families, the degree can shift slowly, with changes noticed across years.
Reduced sound input can delay spoken language milestones compared with hearing peers. Communication strengths often reflect the language pathways available in early years.
Cognition is typically average, and many pursue mainstream schooling. Early communication barriers can influence reading fluency and classroom participation later on.
Conversations in noisy places can remain tiring and may limit spontaneous interaction. Over time, this can raise the risk of loneliness, anxiety, or low mood.
How is it to live with Autosomal recessive nonsyndromic deafness 109?
Life with autosomal recessive nonsyndromic deafness 109 often centers on communication, connection, and access rather than on medical complications. Many people build rich daily routines using sign language, visual alerts, captions, and hearing technology when helpful, and they navigate school, work, and social life well when environments are designed with accessibility in mind. Family members, friends, and coworkers may need to learn new communication habits—like maintaining eye contact, reducing background noise, and using clear visual cues—which can deepen patience and closeness over time. With early identification, culturally respectful support, and consistent accommodations, most can participate fully in their communities and pursue their goals without their hearing status defining their potential.
Treatment and drugs
Treatment for Autosomal recessive nonsyndromic deafness 109 focuses on improving hearing and communication, since the condition itself affects hearing without other medical features. Options often include hearing aids to amplify sound, bone-anchored devices in some cases, and cochlear implants when hearing loss is severe; a doctor may adjust your device settings over time to balance clarity and comfort. Beyond devices, speech and language therapy, auditory training, and educational support can help with day-to-day communication at school, work, and home. Genetic counseling can explain the inherited pattern, discuss family planning, and help you understand what testing means for relatives. Alongside medical treatment, lifestyle choices play a role, like learning communication strategies, using captioning and assistive apps, and ensuring regular follow-up with an audiologist to keep technology working at its best.
Non-drug treatment
Living with hearing loss affects conversations at home, school, and work, so practical, non-drug supports matter day to day. For autosomal recessive nonsyndromic deafness 109, options focus on improving access to sound and communication while building strong language skills. Non-drug treatments often lay the foundation for progress at any age. Early identification leads to more choices and smoother adjustments for families.
Newborn and infant hearing checks help flag issues quickly. This can guide timely steps when early symptoms of autosomal recessive nonsyndromic deafness 109 are suspected.
Modern digital devices amplify speech and tailor sound to your hearing profile. They can be fitted from infancy and adjusted as hearing needs change.
For severe to profound loss, these devices bypass the inner ear and directly stimulate the hearing nerve. They require surgery and ongoing programming and therapy to maximize benefit.
A small mic worn by a speaker sends clearer sound to hearing aids or implants. This reduces background noise in classrooms, meetings, and busy homes.
Your genes may have an impact on how drugs work for you
Even with the same diagnosis, people can process hearing-related medications differently because common gene variants affect drug absorption, activation, and side effects. Pharmacogenetic testing can sometimes guide safer dosing or drug choice, though clinical decisions still rely on your hearing goals and overall health.
Pharmacological treatments
There’s no medication that can restore hearing in Autosomal recessive nonsyndromic deafness 109; care focuses on hearing devices, communication strategies, and protecting any remaining hearing. Medicines are sometimes used for specific situations like a sudden drop in hearing, ear infections, chemotherapy-related hearing risk, or distress from tinnitus or poor sleep. Not everyone responds to the same medication in the same way. Acting early—such as when early symptoms of Autosomal recessive nonsyndromic deafness 109 are first noticed—can help you get timely evaluation and the right non-drug supports.
Prednisone or dexamethasone may be used if a sudden sensorineural hearing drop is suspected. They don’t reverse stable genetic hearing loss and are usually tried only for a brief window early on.
Amoxicillin or amoxicillin‑clavulanate can treat bacterial middle‑ear infections that temporarily worsen hearing. They target the infection itself, not the underlying genetic hearing changes.
Sodium thiosulfate can help reduce cisplatin‑related hearing damage in some children receiving chemotherapy. It does not improve baseline hearing in this condition but may preserve what’s left during treatment.
Nortriptyline or clonazepam may be considered off‑label for severe tinnitus‑related anxiety or sleep disruption. Benefits vary and side effects like drowsiness or dry mouth need monitoring.
Genetic influences
In Autosomal recessive nonsyndromic deafness 109, hearing loss usually happens when a child inherits two changes in the same hearing‑related gene—one from each parent. A “carrier” means you hold the gene change but may not show symptoms. Parents with typical hearing are often carriers, and with each pregnancy there is a 25% chance the child will have the condition, a 50% chance the child will be a carrier, and a 25% chance the child will inherit neither change. Because it is nonsyndromic, the gene change affects hearing without other medical features; the timing and degree of hearing loss can vary from birth to early childhood and from mild to severe. Families may first notice early symptoms of Autosomal recessive nonsyndromic deafness 109 such as a limited response to loud sounds or delayed speech, which often leads to hearing checks. Genetic testing can confirm the specific gene change, clarify carrier status in relatives, and guide family planning and support.
Is Autosomal recessive nonsyndromic deafness 109 genetic?
Genetics is central to Autosomal recessive nonsyndromic deafness 109; inherited variants in both copies of a gene cause it. Parents are usually carriers without hearing loss. Family history and genetic testing help confirm diagnosis, guide counseling, and support reproductive planning.
Pharmacogenetics—how genetics influence drug effects
Most treatments for Autosomal recessive nonsyndromic deafness 109 focus on hearing support, like hearing aids or cochlear implants, rather than medicines. Alongside medical history and hearing tests, genetic testing can sometimes identify how your body might react to certain drugs, especially those that can damage hearing. For example, some people carry changes in mitochondrial genes that make aminoglycoside antibiotics (such as gentamicin) far more likely to cause rapid, permanent hearing loss, so clinicians try to avoid them or use alternatives and close monitoring when antibiotics are needed.
For people with Autosomal recessive nonsyndromic deafness 109, the condition itself doesn’t usually change how the liver and gut handle everyday medicines, so most drugs are dosed in the usual way unless other health issues are present. Other medicines, like certain chemotherapy drugs, may also harm hearing; genetic markers that predict this are being studied, but they aren’t routinely used to guide treatment yet. Your care team will weigh your genetics together with age, kidney function, other medicines, infections, and noise exposure to choose the safest options for you.
Interactions with other conditions
Living with Autosomal recessive nonsyndromic deafness 109 usually means hearing differences without problems in other organs, but everyday health issues can still matter. Doctors call it a “comorbidity” when two conditions occur together, and common ear problems like recurrent ear infections or fluid behind the eardrum can temporarily make hearing worse and complicate testing or hearing-aid fitting. Medicines that are tough on the inner ear—such as certain antibiotics (aminoglycosides), chemotherapy drugs (like cisplatin), and some water tablets (loop diuretics)—along with loud noise exposure, may add to hearing loss, so care teams often try to avoid or closely monitor these when possible. If a cochlear implant is part of care, preventing meningitis with recommended vaccines and treating middle-ear infections promptly becomes especially important. When learning or attention differences are also present, it can be harder to sort out what’s due to hearing versus another condition, and supports may need to be adjusted over time. Talking with your care team about how Autosomal recessive nonsyndromic deafness 109 interacts with other conditions can help tailor safe medications, hearing technology, and follow-up so you get the most from communication and education at every age.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
History
Throughout history, people have described children born with normal health who did not develop hearing like their peers, especially in families where more than one child was affected. Families and communities once noticed patterns—cousins who signed fluently, siblings who did not respond to soft speech, grandparents recalling similar stories from earlier generations.
From early theories to modern research, the story of Autosomal recessive nonsyndromic deafness 109 has moved from observation to precise genetic understanding. Early medical notes grouped many kinds of hearing loss together, often mixing those linked with other health issues and those limited to hearing. Over time, descriptions became more careful, separating “nonsyndromic” hearing loss—where hearing is the main concern—from forms that also affect vision, balance, or other organs.
In the late 20th and early 21st centuries, advances in genetics helped explain why some families had multiple children with hearing loss despite parents hearing normally. Researchers learned that when both parents quietly carry the same gene change, a child can inherit both copies and be born with hearing loss, which is why it’s called autosomal recessive. As gene mapping improved, specific locations in our DNA were linked to different nonsyndromic types, each labeled with a number; Autosomal recessive nonsyndromic deafness 109 refers to one of these defined genetic types.
Initially understood only through symptoms, later work identified the exact gene changes behind this form. That shift mattered clinically. It clarified that the hearing loss in this condition typically occurs without other medical features, guided testing toward targeted gene panels, and informed counseling for parents about recurrence risk in future pregnancies. It also helped separate this condition from look‑alike causes, such as infections or medication effects, that require different approaches.
Screening programs changed the day‑to‑day experience, too. As newborn hearing screening became routine in many countries, early symptoms of Autosomal recessive nonsyndromic deafness 109—like not startling to sudden sounds or not turning toward a parent’s voice—were detected sooner. Earlier confirmation opened doors to timely support with hearing technology, sign language exposure, and family-centered therapy, which can shape communication outcomes in childhood.
Despite evolving definitions, the core thread has remained: careful family stories paired with objective testing move the field forward. Today, genetic testing can sometimes pinpoint the exact change responsible for Autosomal recessive nonsyndromic deafness 109. That knowledge supports more personalized planning while honoring what communities long observed—hearing differences often run in families, even when they are not visible in every generation.