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cousin marriang
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cousin marriang

My first cousin which is 30 is dating my daughter which is 24.  How close is the bloodline there.


This discussion is related to Marrying my second cousin.
Tags: cousins
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1227139_tn?1367231533
I have posted something very similar to your question about a week ago, and I hope that my message will give you some clarity.  On the surface the immediate and short answer is there should not be any problem in terms of bloodlines, since that would make their relation second cousins.  However, if there are any known genetic issues, there would be a small percentage of both having the same genetic issue and therefore if they were to have children, it would be passed on.

Read my post here and see if any of this relates to you:

Here is a fact sheet (Centre for Genetics Education) I have used often to educate others who have the same questions as you do regarding blood relatives:

Important points

    * Consanguinity describes a relationship between two people who share a common ancestor: a 'shared blood' relationship
    * The most common form of a consanguineous relationship or marriage is between first cousins and in some societies, can account for a large proportion of relationships
    * Traditionally, some cultures have practised and continue to practise marriage between relatives such as cousins as a means of strengthening family ties and retaining property within the family
    * We all carry several harmful faulty gene copies on our chromosomes but have a working copy on the other partner chromosome to provide the information for our bodies
    * Usually two unrelated people will not carry the same faulty gene copy
          o Children of unrelated parents are at low risk of inheriting from each of their parents a copy of the same faulty gene that could result in a genetic condition
          o They have a risk of between 2% and 3% (2 to 3 out of every 100 births) of having a child with a birth defect or disability, many of which will be genetic
    * People who are blood relatives share a greater proportion of the same genes than unrelated people do because they have a common ancestor such as a grandparent from whom they inherited their genes through their parents
    * The closer the biological relationship is between relatives, the more likely that they will have the same faulty gene in common
    * Children of parents who are blood relatives generally have a small increased risk over that of unrelated parents of inheriting from each of their parents a copy of the same faulty gene that could result in a genetic condition
          o For example, if parents are first cousins, the risk is a little higher (about twice) ie. 5% to 6% (5 to 6 out of every 100 births). Looked at another way, where parents are first cousins, there is about a 95 chance out of 100 (95%) that they will have a baby unaffected by a condition due to the parents' faulty genes
          o The chances of having a baby with a problem would be higher, and parents more likely to share the same faulty gene copy, if their parents and/or grandparents are also close blood relatives
    * In most families where the parents are close blood relatives, there will be no history of a specific condition and there are no tests that can usefully be carried out to see if the baby is at risk for being affected by a particular genetic condition
    * Where there is a family history, or where the parents' ancestry suggests their risk for having a faulty gene for a condition is increased eg. thalassaemia, genetic testing may be possible to determine if the parents are carriers of the same faulty gene
    * It is important for couples who are close blood relatives and thinking about becoming parents, to seek genetic counselling to obtain current information and explore their reproductive options (see Genetics Fact Sheet 3)

'Consanguinity' comes from two Latin words: con meaning shared and sanguis that means blood. Consanguinity describes a relationship between two people who share a common ancestor: a 'shared blood' relationship; for example, a relationship between two cousins.

The most common form of a consanguineous relationship or marriage is between first cousins and in some societies, can account for a large proportion of relationships.

Traditionally, some cultures have practised and continue to practise marriage between relatives such as cousins as a means of strengthening family ties and retaining property within the family.

Genes and families

The cells of the body contain the genes or set of instructions for the cell to make all the necessary proteins (chemicals) for our bodies to grow and work normally.

If a gene is changed so that it does not work properly, the gene is described as being faulty (i.e. there is a gene mutation present). The result is that either a protein is produced that is faulty, produced in limited quantity or is not produced at all.

Genes come in pairs: one copy of each gene inherited from the mother and one copy from the father. Since there are two copies of the genes in the cells, a change in one of the gene copies that could be potentially harmful will generally have no direct effect on an individual's health: the working gene copy will usually override the faulty copy of the gene. These changes are called 'recessive' (or hidden) to the working copy and the individual is said to carry the faulty gene.

Carrying a single faulty gene copy does not usually cause a problem. But if an individual has two copies of the same faulty gene containing a recessive mutation, the cell will not receive the right instructions to enable normal function and may result in the individual having a genetic condition.

Importantly, everyone carries several faulty gene copies without having any impact on their health or development.

There are thousands of possibly harmful faulty gene copies but usually two unrelated people will not carry the same faulty gene copy.

* Children of unrelated parents are at low risk of inheriting from each of their parents a copy of the same faulty gene that could result in a genetic condition
    * They have a risk of between 2% and 3% (2 to 3 out of every 100 births) of having a child with a birth defect or disability, some of which will be genetic

While everyone usually has the same number and type of genes, there are small differences in the genetic information between individuals that make us unique. Since our genetic information is passed down to us from our parents and grandparents and so on, family members will have more similarities in their genetic information than differences.
Continued in next comment below....
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1227139_tn?1367231533
Continued from comment above....


    * People who are blood relatives share a greater proportion of the same genes than unrelated people do because they have a common ancestor such as a grandparent from whom they inherited their genes through their parents
    * Children of parents who are blood relatives generally have a small increased risk over that of unrelated parents of inheriting from each of their parents a copy of the same faulty gene that could result in a genetic condition
    * For example, if parents are first cousins, the risk is a little higher (about twice) ie. 5% to 6% (5 to 6 out of every 100 births). Looked at another way, where parents are first cousins, there is about a 95 chance out of 100 (95%) that they will have a baby unaffected by a condition due to the parents' faulty genes

For:  First cousins, half-uncles and aunts and half-nephews and nieces
The degree of relationship is: Third degree relatives (30)
Proportion of genes they have in common:  Eighth (1/8, 12.5%)
What is the risk for having children with a problem when parents are close blood relatives?

It is not true that those having a child with a blood relative have a very high chance that their children will have birth defects or a disabling condition.

Where the parents have no family history of a specific condition and their parents and perhaps grandparents are not blood relatives:

    * If parents are unrelated, their risk for having a child with a birth defect or disability is between 2% and 3% (2 to 3 out of every 100 births)
    * If parents are first cousins, the risk is a little higher (about twice) ie. 5% to 6% (5 to 6 out of every 100 births). Looked at another way, where parents are first cousins, there is about a 95 chance out of 100 (95%) that they will have a baby unaffected by a condition due to the parents' faulty genes

In general, parents being close relatives has no effect on the number of babies born with genetic conditions that are due to a faulty gene on the X chromosome or a faulty gene that is 'dominant' to the working copy of the gene.

It seems likely, however, that when parents are close relatives there will be some increased risk for a child inheriting conditions that are due to a number of different genes acting together (polygenic) or where there is an interaction between genes and the environment such as spina bifida and some forms of congenital heart disease.

Unfortunately, what this increased risk actually is for parents in their individual situation is difficult to calculate.

A cautionary note

In societies with a tradition of first cousin marriage, many couples are often more closely related than first cousins are and consequently their risk may be significantly higher.

    * The risk is much higher than 5% to 6% when both the parents of the first cousin couple - and their grandparents - are also blood relatives
    * The actual risk that parents in this situation have needs to be worked out for each family during genetic counselling

I know this is a lot of information, but I hope that it helps.  You can apply whatever relates to you.
In addition to anything I have mentioned, please keep in mind, that while I or others may have extensive knowledge in many areas, you should always seek professional medical advice from your own physician, as it pertains to medical conditions or concerns.

Good luck, and if you have any other questions that I can help you with, please feel free to message me directly.

Sincerely,
Sandi (Dragon1973)
MedHelp Genetics Community Leader;
Children - Special Needs Community Leader;
Down syndrome Community Leader & Ds Group Forum Founder/Moderator
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