This might seem a really unthoughtful question to experts in genetics but I was just wondering if there is any knowledge in to how the 44 no-sex chromosomes are selected from each parent to make the zygote and is there any understanding as to why these chromosomes were selected rather than the other 22 from each parent?
I realize that each of these 22 non-sex chromosomes have an identical copy to make the 22 pairs from each parent but was wondering if it makes any difference or if there is a reason why one of the paired chromosomes gets selected over the other in the formation of the zygote?
Selected for what? The selection of chromosomes in which stage of fertilization?
Look up "meiosis" and then "Mendel's Laws of segregation and independent assortment" to get a flavour for how the process works and how genes and ultimately chromosomes might be sorted- it is reasonally well understood. There are some examples where this process goes wrong, such as trisomies (ie, downs syndrome),, however these tend to be heavily selected against, and therefore you do not see them.
Hi Ali,
i was asking how the 22 chromosomes from each parent are 'selected' to become the human genome when egg and sperm cell unite. In particular, is there any reason or scientific evidence for why these particular chromosomes were 'selected' or 'chosen' over their paired identical?
The 23 chromosomes are not selected. During meiosis (i.e. the special cell division process that produces gametes), the two chromosomes (one received from dad, the other from mum) from each of the 23 pairs segregate from each other. Two cells are produced containing each a pool of 23 chromosomes. This is a random process in the sense that, for instance, chr 1 received from dad can have segregated in the same cell as maternal chr 2. The complementary cell contains mum chr1 and dad chr 2. In two other gametes produced in the same individual, dad chr1 and dad chr2 wil have segregated togeteher for one cell and mum chr1 and chr2 in the other cell. This random segregation process of chromosomes plus another reshuffling process called recombination makes each gamete unique. NB: Remember that chromosomes of each pair are not exactly identical (say about 1 DNA base every 1000 bases differ between two chr of the same pair). This polymorphism allows to follow mum and dad chr from one pair and is the reason why each chromosomal reassortment has a unique DNA content.
So essentially all 46 chromosomes from both parents are used in the gene network of a normal functioning healthy person (that is with no mutations)?
Yes Marc, this is correct. All 46 chromosomes are used for producing haploid gametes containing each 23 chromosomes in a fertile individual.
However, I am not sure what you mean about "with no mutations" or about "a normal functioning healthy person". We all carry a bunch of mutations. Most of these mutations involve only one copy of the two copies of each gene that mum and dad have respectively transmitted to us. In turn, we transmit this mutation to our progeny in one every two gametes. Fortunately, one intact copy of a gene is usually sufficient to make the process involving this gene functioning. Bad luck is when the two parents each transmit a mutated version of the same gene, making a sick zygote.
Is it correct to say there are chromosomes that never pair with each other because of the way the 92 chromosomes are divided into four cells after the first division in mitosis? As such, there are there four sets of separate chromosome interactions during these divisions as the zygote grows? Unless, you can say these cells with the different chromosome sets join and divide after the first division, then chromosomes could be found to pair with any other chromosome during cell growth.
With regard to your last comment/question: you do not seem to recognize the fact that 3 of the 4 female products have almost no cytoplasm and cannot led to offspring. With regard to the male products, look up intercellular bridges.during meiosis.
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