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The parents will both have a specific gene defect. If they do there is then a 1 in 4 chance of them having a child with cf. so if you are considering having children you should have a blood test to find out if you are a carrier of the gene causing cf. hope that helps.

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15y ago
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14y ago

the two 'healthy' parents are carriers. they have one 'good' gene and one 'bad (cf gene'

two normal ones come together = the child isn't even a carrier.

1 good + 1 bad come together = carrier (like the parents)

2 bad come together = a cf child

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13y ago

"Cystic fibrosis (CF) is an autosomal recessive disease. That means that if both parents have cystic fibrosis, so will any children that they have. If one parent has cystic fibrosis and the other does not, then the chance drops dramatically (almost to zero)."

Not wholly correct. CF is a recessive disease which means that you must posses two copies of the faulty gene (1 from your mother and 1 from your father) in order to present with the condition. If one parent has CF then the chances of them presenting with the disease are as follows.

If the other parent also has CF, then 100% as you stated

If the other parent is a carrier (has one Normal gene and one faulty gene) then there is a 50% (not almost 0%) chance that the child will have CF, and if not, they will be a carrier.

If the other parent doesn't have CF and doesn't carry the faulty gene. Then the child will not have CF but will be a carrier.

The original question was how can two parents who do not have CF produce a child that has CF. In this instance, both parents have to carry the recessive gene, but it doesn't present in them because the gene is recessive, it is overruled by the dominant, normal gene. Using a genetic cross diagram known as punnett square, we can work out that there will be a 25% chance of the child between the two parents who carry the faulty gene, inheriting CF, a 50% chance they will be a carrier, and a further 25% chance that they will neither have the disease or be a carrier.

Furthermore, CF also effects the reproductive system (predominantly in males i believe), so many sufferers are unable to have children.

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13y ago

both parents would have to be ''carrier's'' (they have one cf gene and one normal gene each)

the child has a one in four chance of having CF, it could eaither inherit:

-one good from the mother, one good from the father = healthy, non CF, non ''carrier'' child

-one good from the mother, one bad from the father = healthy, ''carrier'' child

-one good from the father, one bad from the mother = healthy, ''carrier'' child

-one bad from the mother, one bad from the father = CF child

(DingoBot flagged this please do not delete because this is a legit answer. Thanks Short fry)

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14y ago

a child with cf has parents which 'carry' the cf gene therefore they do not have it

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13y ago

it is genetically inherited if both parents have the faulty gene

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9y ago

You will start with the child first and build up backwards. You will then be able to figure out the parents and perhaps even further up.

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11y ago

bad guy

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Q: How can a child with cystic fibrosis have two parents that do not have cystic fibrosis?
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What are is the percentages of a child not having cystic fibrosis with parents who both have the trait?

If both parents are just carriers of the gene that causes CF then there is a 75% chance that the child will not have CF. To break it down farther... 25% chance that they will have CF. 50% that they will be a carrier. 25% that they will have two normal genes.


What are the chances of passing on the CF gene?

If the spouse he or she has the gene needed to pass on cystic fibrosis, then yes it will have children with cystic fibrosis. If the spouse does not have that gene then the child will not have cystic fbrosis but will be a gene carrier of cystic fibrosis.


What is cystic fibrosis gene disorder?

The genes on each chromosome control specific functions of the human body. The gene on chromosome 7 produces a protein called cystic fibrosis transmembrane regulator. Mutation in the DNA level of chromosome 7 leads to the absence of this protein which leads to cystic fibrosis. Cystic fibrosis is a recessive disease. It means that both copies of the gene must be defective. An affected person will have abnormal cystic fibrosis transmembrane regulator gene on each chromosome 7. Therefore both biological parents must have an abnormal gene. One abnormal copy is inherited from each parent. A person with one normal gene and one abnormal gene is called a cystic fibrosis carrier. Cystic fibrosis carriers do not show any symptoms but they may pass the abnormal gene to their children. Therefore the parents can be either cystic fibrosis carriers or affected themselves.


Name two genetic disorders?

Two genetic disorders are Turner's syndrome and cystic fibrosis.


What does heterozygous have to do with cystic fibrosis?

people who are heterozygous for cystic fibrosis are not directly affected by the disease (although there is some evidence they have more chance of getting Asama) however they do still carry the gene for CF (they are carriers) this means if they have kids with another carrier they have a 25% chance of having a CF positive child (out of four one non effected, two carriers, and one diseased)

Related questions

What would a genetic counselor tell parents who had cystic fibrosis or were carries of the cystic fibrosis about the chances of their children having cystic fibrosis?

If both parents are carriers then the child has a 25% chance of having cystic fibrosis. If one parent has CF and the other the other was just a carrier then the child has a 50% chance of having CF. If one parent has CF and the other has two normal genes then there is no chance of the child having CF. If one parent is a carrier and the other has two normal genes then there is no chance of the child having CF. If both parents have CF then there is a 100% chance that the child will also have CF.


What is the probability of two healthy people where one is a carrier being parents to a child born with cystic fibrosis?

If only one person is a carrier of cystic fibrosis than there is no chance of having a child with it. Both parents have to be carriers and even then there is only a 25% chance. If only one carries than there is a 50% chance that their children will carry but will not have cystic fibrosis.


A family pedigree of two unaffected parents with a child who suffers from cystic fibrosis?

You will start with the child first and build up backwards. You will then be able to figure out the parents and perhaps even further up.


How can one child be born healthly and second one have cystic fibrosis?

To have a child with cystic fibrosis both parents must be a carrier or a sufferer. A carrier is a person who has one healthy gene, and one diseased gene, so they dont have cystic fibrosis but they can pass it on to their children. Children inherit one gene from each parent. To get cystic fibrosis a child must get two copies of the 'disease' gene - one from each parent. If two carriers have children, each child has a 25% chance not getting a Cystic fibrosis disease gene, 50% of being a carrier and 25% of being a sufferer. This is not affected by if the child is male or female. So essentially the answer is bad luck.


How can you get cystic fibrosis?

For a baby to be born with Cystic Fibrosis, both parents must be carriers of the faulty CF gene. Where both parents carry the faulty gene, each child has a one in four chance of having CF, a two in four chance of being a carrier and a one in four chance of not having any CF genes.


Do you need one or two parents to inherit cystic fibrosis?

you need two parents to get it but one parent to become a carrier. You need two parents with one of the alleles to inherit it but if you have one parent with the allele you might be a carrier. If you have two parents with the allele it does not mean that you will definitely have it. This is because the allele for cystic fibrosis is recessive.


How is a child born with cystic fibrosis?

Cystic fibrosis is genetic and is not contagious A person gets it when he/she inherits two mutated genes off each parent. A healthy couple can have a child with Cystic fibrosis because the parents would be carriers of the disease (even though they are unaffected by it themselves). 25% of children are at risk of the disease as it can be passed down from previous generations.


What is the genotype of two normal parents who have a child with cystic fibrosis?

The genotype would have to be homozygous recessive if the child was completely effected by the disease. The "normal" paretns would have to have heterozygous recessive genotypes. This makes sense since the allele that causes sickle cell shows incomplete dominance when present with a normal allele in a pair. The "normal" parents actually would have a mixture of sickle cell shaped red blood cells combined with normal shaped ones. The carrier parents does not display symptoms of the disease since the regular red blood cells alone can fill the body's need for oxygen under normal circumstances. The only time the cArrier would notice would be under times of extreme oxygen demand, such as a sprint.


A couple who are both carriers of the gene for cystic fibrosis have two children who have cystic fibrosis What is the probability that their next child will be phenotypically normal?

If both parents are carriers on cystic fibrosis, just because two children may have the disease it doesn't mean that say,a further 3 children in future will be "normal". Inheriting genes is like a lottery. I can say though that because cystic fibrosis is recessive, every offspring born under carriers will always have a 75% chance of being phenotypically normal.


To be a cystic fibrosis carrier do your parents have to have a cystics fibrosis gene?

Yes, since the disease is a recessive inherted trait BOTH parents must carry the gene but will not have the disease itself. Approximately 30,000 people in the United States have cystic fibrosis. An additional ten million more-or about one in every 31 Americans-are carriers of the defective CF gene, but do not have the disease. The disease is most common in Caucasians, but it can affect all races.


Can you get Cystic fibrosis?

Cystic fibrosis is a genetic disease and can only be inherited through genes. It all depends on your parents alleles. Let's say that the allele for cystic fibrosis is c. If your Mum has the allele Cc it means she is hetrozygous. If you Dad has the same allele he is also hetrozygous. When they had children, the two small c's could come together to make a child with the alleles cc. (This means that the child has cystic fibrosis and has homozygous reccessive alleles.) When they had children their alleles could also come together to make CC (homozygous dominant- this means that person doesn't carry an allele for cystic firbrosis and will never get it. This means that if that person had children with another person who has the alleles CC, their child wouldn't get it), or it could make a child with Cc alleles. The child with Cc alleles wouldn't get cystic fibrosis because the allele big C (dominant allele) over powers the allele small c (reccessive- the cystic fibrosis allele). Although this person doesn't have cystic fibrosis their children might because they carry the allele for cystic fibrosis, which is c.


Is cystic fibrosis common?

Cystic fibrosis is the most common life threatening disease in the UKOne in 25 people have the cystic fibrosis gene in them (but may not have the disease). Most people aren't even aware that they carry the gene. If two people who have the gene reproduce, the odds that they have a child with cystic fibrosis is 1 in 4. The chance that they will have a child who carries the gene but doesn't have the disease is 2 in 4 (half). The chance that they have a child who does not have the disease or carry the gene is 1 in 4.