Heredity: Who will baby be like?<

Genetic baggage, hereditary lottery

It all starts when the egg and the sperm meet.Each of the two sex cells arrives with its luggage of 23 chromosomes.Their merger will give a complete being, provided with 46 chromosomes.Each of them looks a bit like a necklace (in fact a long DNA molecule), made up of hundreds of "pearls": the genes.They are the ones who code our physical characteristics: blue or brown eyes, thick or fine mouth, small or medium size.They are responsible for inheritance but impossible to predict which genes the baby will inherit! To make an egg, the mother gave half of her genetic capital (23 chromosomes out of the 46 she owns) and abandoned theother .Same thing for daddy.In this confusion, which can say where the gene of curly hair and that of blue eyes will be found?Are they part of the "lot" received by the baby or have they passed by the hatch?Mystery.Especially since this first wheel of the heredity lottery will soon be followed by a second!Because, then, the parents' genes intersect, which will determine the color of the eyes, the nature of the hair or the shape of the nose of their child.For each of these characteristics, the latter has, in fact, received two genes - scientists speak of "alleles" - one transmitted by his father, the other by his mother.Both can carry the same information ("blue" allele for eye color, "steep" for the nature of the hair, "busy" for the shape of the nose) or two different information ("blue" and "brown"For the eyes," steep "and" curly "for the hair," busy "and" right "for the nose).If the two alleles are similar, no problem: the child carrying two "blue" alleles will necessarily have blue eyes.On the other hand, if the two alleles are different ("blue" and "brown"), it is ... the strongest that will prevail!

Dominant genes, recessive genes

You should know that certain alleles dominate and that they have the power to intimate others to be silent when it comes to inheritance.We then speak of dominant genes for those who express themselves and become visible, and recessive genes for those who are silent and remain hidden.A little abusively since it would be more correct to talk about alleles.These dominant genes (let's call them for more simplicity), we know them.In general, these are those who code the darkest colors and the most typical features.They have the power to silence the genes that code light colors and neutral features.Faced with a brown father with a busy nose and a blonde mother with a straight nose, we will therefore be able to bet, without too much likely to be mistaken, that their baby will rather look like his dad.But nothing has been played because the reality is more complex and makes a pleasure to thwart the forecasts.Too bad for forecasts, and so much the better for diversity!Because it is in this multiplicity of possibilities that your baby will be absolutely unique and will not look like any other.The magic of inheritance!

My husband has blue eyes and I brown, will my daughter have clear eyes?

You should know that the "blue eyes" gene is recessive.In other words, there must be double copy (one transmitted by the mother, the other by the dad) to be able to express himself.So you can only have a little girl with blue eyes if you yourself transmit a "blue eyes" gene.But do you have one?Impossible to know it and predict heredity.At home, it is the dominant "brown eyes" gene that has expressed.He can hide a second brown gene, as he can hide a blue.Your husband, on the other hand, is necessarily carrying two blue genes since he has blue eyes.First hypothesis: you are carrying two brown genes.It's played in advance: your "brown" will prevail over the "blue" of your husband.Second hypothesis: you are carrying a hidden "blue eyes" gene.There is then one in four chance so that you have a blue girl girl.

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We are a family of girls.Will I have one in turn?

Theoretically, it's right or facing each time: 50 % chance of having a boy, 50 % of having a girl.It is however to note that there are families of girls and families of boys.Series of series?Physiological explanations?Heredity magic?The only scientific certainty is that the sperm determines the sex of the child.Either the egg eggs a sperm that brings a sex chromosome X, and it is a girl.Either he crosses a sperm that transmits a sex chromosome y, and it is a boy.However, some studies show that the sex of the child depends on the day you make love in relation to the date of your ovulation.We know indeed that sperm carrying a chromosome are faster but less resistant in time than sperm carrying an X chromosome.Consequence: if you have a sexual intercourse close to ovulation, you will be more likely to have a boy.If it takes place three or four days before or after ovulation, you will therefore have more likely to have a girl.

We are both musicians.Will our child be gifted for music?

Difficult to decide in the old debate of the innate and the acquired.Are we born a musician or do we become because we bathe in music?Question of inheritance?We have been able to show that, in the brain of musicians, the hearing cortex (the area of the brain which treats sounds) was greater than in the average population.But that does not solve the problem.Is it because we inherit a auditory cortex developed at birth that we become a musician?Or is it because we like music that our hearing cortex develops?This is the story of the egg and the hen!Today, we do not know how to answer this question.But it is obvious that everything is not genetic and that the environment in which we live has an influence on our brain.In positive or negative.Because evolving in the middle of a family of musicians, it can bring you closer to music ... that you disgust!

I am very small, my husband is tall.Will our child be medium in size?

Certainly, genetics influence the size since we know that a small father and mother will have a small child and that two large parents will have a tall child.But when a "big" meets a "small", they can make a large child as well as small or medium -sized.Impossible to predict how heredity will take place!In addition, the environment also plays an important role.As we know: new generations tend to grow more.The phenomenon is linked to food changes.Thus, today, almost all children exceed their parents.

Can we know in advance the blood group of our baby?

In terms of blood group and inheritance, it is difficult to establish forecasts.Only two configurations allow certainties: two AB parents will not be able to have a child o.And two parents where will have a child o.For the rest, impossible to predict.Because for that, we should be able to know the blood groups transmitted by the grandparents.We know on the other hand the "power relations" between the blood groups: o is recessive compared to A and B.But A and B are of equal weight, they say that they codominate.They will express themselves together: this is how we meet blood groups AB.

My husband has a twin brother.Will I also have twins?

It is not the fathers who are decisive in the case, it is a story of women.There are two types of twinness: the mother makes two eggs the same month, and then the couple will wait for false twins.Either his egg is divided, and then they will be real twins.We have every reason to think that this division is genetically programmed.A woman who has real twins in her family is much more likely than the average to have twins too.And if she herself has a twin sister, the chances are even higher!

Can our child have fine lips when we both have a luscious mouth?

Yes, if you are both carriers of the recessive gene "fine lips" and these two genes meet.They will associate to express this physical character who has remained masked in your home.

One of my cousins is Down's syndrome.Is the gene present in the family?

Down's syndrome is not a genetic disease but an anomaly of the 21st pair of chromosomes.It results from an "course accident", it is not a question of inheritance.The ovum (in 90 % of cases) or the sperm (10 % of cases) contains two chromosomes 21 instead of one.The child therefore receives three chromosomes 21 instead of two.The older the mother, the higher the risk of transmitting this extra chromosome: 1 in 2,000 risk around 20 years, 1 in 100 years around 40 years.Nevertheless, there is little risk that you give birth to a child with Down's syndrome without knowing it.Today we have examinations which make it possible to detect the presence of trisomy before the end of the first trimester of pregnancy (anatomical landmarks during ultrasounds, dosage of certain hormones called "serum markers", supplemented if necessary by an amniocentesis).Then it's up to you to decide whether you want to continue your pregnancy or not.It is a choice that only concerns you and your companion.

My sister has a child with cystic fibrosis.Do I have to worry or not?

When the cystic fibrosis gene exists in his family and we know, we can ask for a genetic consultation to determine the probabilities of transmitting the disease to his child.But, more often than not, cystic fibrosis appears by surprise.Neither the mother of the mother nor the father's family counts of anyone affected and heredity is not in question.You should know, in fact, that cystic fibrosis is a recessive hereditary disease.In other words, one can be the bearer of the gene without knowing it and without suffering from it.This is called being "healthy carrier".Unfortunately, if each of the two parents transmits his "bad" genes to the child, he will be suffering from cystic fibrosis.Two healthy carriers have one in four risk to have a sick child, two out of four risks to have a healthy carrier child (like them) and ... one in four chance to have a healthy child.Be aware that if only one of the two families carries the gene, the risk of transmission is very low.A healthy carrier father and a healthy mother (or vice versa) can only have a healthy or healthy child.It is when the gene exists in both families that the risks should no longer be overlooked.

I'm fat.Does my baby risk also having weight problems?

If your build comes from a food balance problem, your baby will not inherit.Unless you send him your bad habits!On the other hand, if it is of metabolic origin, therefore genetic, there are, in fact, risks that your child also experiences weight problems.Nothing is played for all that.The corpulence of the dad will be taken into account.Then ... everything will depend on the heredity lottery!

We are a mixed couple.What color will our baby's skin be?

Everything is possible.The color of the skin is not coded by a single gene but by several.This results in subtle combinations and a multitude of possibilities.The whole color palette can exist, from the clearest to the darkest.Most of the time, however, heredity means that the child inherits a pretty coffee with milk, mixture of the dark skin of his dad and the clear complexion of his mom (or vice versa).It all also depends on genealogy.If the dad has been African for several generations, for example, it is likely that the child will be more "coffee" than "milk".On the other hand, if the dad is mixed, he will undoubtedly have clearer skin.But one thing is certain: even with the latter, it will bronze better than the others!

In my family, there are several daltonians.Is it transmitted?

Daltonism is a genetic anomaly carried by the X chromosome.Contrary to what we are used to saying, the Daltonians do not confuse green and orange, but perceive these two colors as a gray.There are many more daltonian boys (8 %) than girls (0.5 %).Normal: girls have two X chromosomes.Assuming that one of the two parents carries daltonism, there remains a "healthy" to compensate (the healthy X is dominant on the X carrier of the anomaly).In boys on the other hand (carrying an X chromosome and a Y chromosome), no second X to compensate for the anomaly!Anyway, no need to worry: we live very well by wearing a red sweater and orange pants without knowing it!

What is genetic council?

This medical consultation is mainly aimed at couples who have already given birth to a malformed child or suffering from a serious hereditary disease (myopathy, cystic fibrosis).And people from families where there is a member (or more) carrying a serious hereditary disease.The goal ?Inform future parents, before design, on the statistical risks of transmission of the disease to their child.Then it is up to them to decide whether or not they take the risk of pregnancy.If they choose to design a baby, they will be able to benefit from an antenatal diagnosis.It allows, around the fourth month of pregnancy, to assert the presence or absence of the sought -after disease.In the event that the embryo proves to be reached, the couple will have the choice to continue or interrupt pregnancy.To find out the genetic consultation closest to you, call rare diseases Info Services on 0 810 63 19 20 (price of a local call).