Can someone explain to me gently why children of the same parents can be so physically different?

Question

What I'm asking is why aren't children of the same parents exactly the same? Is it that each sperm has a different set of chromosones or each egg...or does it happen later on in the development?

Answer 1

This can be simply explained with the word VARIATION! Every child inherits 50% of all the genetic information from each parents. Therefore, 50% from his/her mother and 50% from his/her father. However, a child does not look 100% like either parents of one of his/her parents because Mutation occurs. this kind of mutation however benefits the child (or offspring).

But before mutation can perform a drastic change on a child, a child's genetic information varies due to the different alleles that code for different traits in a whole 22 pairs of Chromosomes!! If both parents are Homozygous recessive (have the same allele that code for the recessive trait) for curly hair, the child would definately have curly hair. But then, there are times where you get Multiple alleles where there are 3-6 different alleles that code for a certain trait.
e.g: If his mother is heterozygous for green eyes (blue eyed father, green eyed mother but green is dominant over blue) and the father has grey eyes (father has grey eyes and mother had green) the child of these parents might either inherit green eyes (if he inherits both green eyes alleles) or grey eyes (because it is dominant over green or blue).

When it comes to beneficial mutation or Variation. It is when a mistake has occured but the mistake is not so drastic it might change the child completely. During the process of Meiosis, the chromosomes of both parents are lined up in pairs before the spiliting of the cell. The lining up itself can shuffle the chromosomes, hence letting the child inherit traits from both parents. However, this does not end there... there are times when chromosomes get too close and overlaps each other, the funny part is. during the seperation of cells, the chromosome would break off and take genetic information (i know this is somewhat vague, so i've googled you a photo) of the other. Hence the variation.

Answer 2

appearance is due mainly to genes half your genes which are bundled into chromosomes each human has 22 pairs plus the sex chromosomes X X female XY male. A child has 23 from its dad and 23 from its mum. In most cases the body only uses one copy of each pair the copy used is determined randomly so a child will be a mix of mum and dad. Also the copy from the dad/mum in the sperm is not exactly like the dads/mums DNA. when the sperm/egg is created it goes through a process called meiosis which occures only via mutations called chiasmata which ensures that each sperm or egg is a little different than its owner. So each sperm is a modified version thus plus other natural mutation to the DNA mean that the offspring is genetically different to the parents. there are some environmental factors also but to smaller effect. these mutations are essential for the origin of species and evolution. note this is a gross over simplification but the whole detailed answer is not only confusing but time consuming

Answer 3

An individual contains 23 pairs of chromosomes. Two of these are six chromosomes X and Y, but these can be more or less ignored in this explanation.

In the other 22 pairs which are called autosomes, one half of the pair is inherited from the mother and the other from the father. At the same position on each chromosome is a gene which performs the same function e.g. a gene specifying blood group. Each gene has different variants. For blood group there are three possibilities A B or O. As an individual has only 2 chromosomes, then at most it can carry only 2 of these variants, one on each chromosome. These may be the same or different variants.

Every individual therefore carries one or two versions of every gene one which has come from each of its parents.

When the germ cells for the next generation (i.e. eggs and sperm) are formed, pairs of chromosomes bind to each other and some variants are swapped between each pair before they separate and the new 'mixed up' chromosomes are passed on to different germ cells. As there are many genes spread throughout the chromosomes and in theory at least this 'swapping' (technically called recombination) can occur anywhere, it is highly unlikely that any two new chromosomes created in this way will be identical. Therefore, every child inherits a different combination of genetic variants from each parents than its siblings. This is why we all look different from our brothers and sisters.

One simple example. You have two genes 1 & 2. For gene 1 you have variants A and B and for gene 2 variants C and D (You inherited A and C from your mother; B and D from your father). After you could pass on either AC (as mother), AD (new variation), BC (new variation), BD (as father). So for only 2 genes there are 4 possible combinations, so now multiply by 10s of thousands to see why it is highly unlikely that anyone would inherit the same combination of variants from thier parents as their siblings.

The environment also interacts with our genes causing further variation, but it is the mixing of genetic variants is at the heart of the differences between close relatives.

Answer 4

A person carries two versions of each gene, but only one of those genes will have an effect in that person.

When eggs and sperm are made however, all the genes are distributed into them randomly, so it doesn't matter if the gene did or didn't have an effect in the parent.

The next step that introduces variation is which sperm fertilizes which egg, the results being a child that ends up with lots of the genes that were visible in the parents, and therefore looks a lot like them, or a child that gets lots of the genes that didn't have an effect in the parents, and doesn't look much like them at all. (And all variations in between that obviously!)

Hope that's straightforward engouh?!

Answer 5

The issue here is 'traits'. There are dominant traits and recessive ones. Our genetic codes carry many different traits, spanning well back into our ancestries.
Typically, dominant traits will be expressed, which is why most siblings look similar. However, every now and then a recessive one will pop up, sometimes coming from waaay back in the gene pool.

Here's an example:
There was a tribe of people from the cauacasus mountain area of southern Russia who were the origin of the Amazon warrior women myths. These people were eventually pushed eastward out of the region. Through many generations they eneded up in the area of Mongolia, and intermarried with the indigenous people until all caucasoid features had genetically dissapeared.
Every now and then though, a girl will still be born with blonde hair, blue eyes, and distinctly European facial features. She is a throwback to her early Russian ancestry, showing that these traits still exist in the gene pool, even if very recessive.

Answer 6

Grandparents? Well, I suppose they're in the mix too. But sexual reproduction (as opposed to asexual) results in a randomized roll of the dice of millions of genes, a set from each parent. There are so many combinations to choose from that even fraternal twins will have only a passing resemblance to one another. Generally you can look at a family and see an overall resemblance, but occasionally there are striking differences. It's not all that surprising considering all the genetic possibilities in every fertilized egg!

Answer 7

Just to further elaborate- there is also a field known as epigenetics. This explains all the subtle differences between "identical twins"- which are genetically identicle. Small things like heat, gravity, the presence of a twin, etc.. can all make changes. Calico cats get their spots randomly, it is all due to the random inactivation of the second X chromosome- in cells that the X from the mother is active you get one color, in those that the X from the father is active you can get a different color.

Answer 8

A child receives half of its genetic material from each parent and parents can carry a traiit without actually expressing it. This is what is known as dominance. If you carry two different kinds of the same allele, that is called being heterozygous for a trait, and the dominant trait will be what you display. For example you can carry the allele for red hair even if you have brown hair because brown hair is dominant over red hair. If you and your wife are both heterozygous for red hair, and you both pass on the red hair gene (which you will have a 1 in 4 chance of doing) your child will have red hair.

Answer 9

Answer to this question lies in Variation. There are two types of variation: Continuous and Discontinuous.

Discontinuous variation e.g blood group, eye colour etc is due to the genes present. Its not affected by the environment.

Continuous variaton e.g height, weight etc is affected by the environment.
so even if children were to live in the same place as their parents they would still be physically different as the environment is constantly changing............hope this answers your Q...........Using this info you can come up with another question whether children of the same parents would be physically same as their parents under controlled conditions..

Answer 10

My grandmother on my mum's side had beautiful chestnut brown hair and deep brown eyes. My grandfather on my mum's side was blonde haired and blue eyed. Of all the children and grandchildren they had not ONE of them has brown eyes. Most are blue, blue-green or hazel. Go figure.

I think genetic factors play a huge part in physical development whereas nature/nurture plays a part in the psychological development of the person. My brother and I are totally different in attitudes and philosophies, spiritual matters, yet we were raised by the same parents supposedly the same way. My dad used to say how in heck did we raise Archie Bunker/Jane Fonda kids in the same house. Seven years difference in ages, no disability versus disability , boy versus girl and societal expectations.