Naked Science Forum
Life Sciences => Cells, Microbes & Viruses => Topic started by: Heluvagi on 04/06/2016 17:27:06
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I just want to get one thing straight.
This is the situation as I understand it: In each of cells in my body (let's not worry about my sperm cells for the time being), I have 46 chromosomes. I have 23 chromosomes from my father and 23 chromosomes from my mother. The chromosomes I got from my father are intact and do not get mixed up with my mothers' and vice versa. After one cell has split into two, I have 46 haploid chromosomes. During interphase, those chromosomes duplicate so I now have 46 diploid chromosomes. If we take one set of chromosomes to look at - say, chromosome 17 - I have a diploid chromosome from my father and a diploid chromosome from my mother. I actually have 92 chromosomes, but it's easier to say I have 46 diploid chromosomes as each of the chromosomes that are from one parent are completely identical and joined at the centromere.
Have I understood so far?
I may actually get round to asking a question soon, but I'd like to know I understand the theory so far.
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Are you leading up to Chromosome crossover?
https://en.wikipedia.org/wiki/Chromosomal_crossover
This means that the chromosomes passed on to you children are not exactly the same as chromosomes you received from your father or your mother...
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No. I'm simply looking at somatic chromosomes. I mean once all that has happened and my full genetic make up has been decided after fertilization, have I still got a full set of the chromosomes I received from my father AND a full set of chromosomes that I received from my mother.
I understand that I don't literally have ALL of my father's and mother's chromosomes, but I still keep the full set that I received from them both intact and separate from one another. I want to make sure that I understand this correctly. I used to think that my mother's and father's chromosomes got mixed up together.
Is this the case or not?
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As far as I can see, your understanding is correct (or at least it seems to fit my understanding). Just one thing that should also be kept in mind though is that when chromosomes are duplicated, each homologous pair ('identical pair of chromosomes') is composed of two chromatids not chromosomes - I just wanted to make sure you had the correct terminology.
I hope this helps/confirms your understanding.
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The basic premise of what you are saying is correct. Somatic cells (excepting human red blood cells which are non-nucleated) all have a complete diploid set of chromosomes. This means that each cell has 23 pairs of chromosomes. These comprise two copies of chromosome number 1, two copies of chromosome number two and so on. Why two copies? Because you inherited one copy from your father and one copy from your mother.
These chromosomes are structurally identical to each other in that the locations of genes on the chromosomes are the same, although the actual gene sequences / genetic information will vary between the two owing to polymorphisms - these are differences in the genetic message that account for us all being different. Think of the genes being like recipes in a cookbook: the same gene / recipe can prescribe on teaspoon of salt in one book, but two tablespoons of salt in another. Both recipes bake a cake, but the flavour varies subtley between the two.
The exception to the above rule are the so-called heterosomes or sex chromosomes, X and Y. These are structurally different and contain quite distinct genes.
When a somatic cell divides, the chromosomes each copy themselves, duplicating their genetic cargo. The duplicated chromosomes then align at the equator of the cell and split; by a mechanism we don't understand, one copy of each chromosome goes into each of the two daughter cells, resulting in a normal number of chromosomes (46: 23 pairs) in the daughter cells.
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In each of cells in my body, I have 46 chromosomes.
There are a few other types of cells that bypass the usual rule for humans of "23 pairs of chromosomes per cell", to various degrees.
These cells can have several sets of 46 chromosomes; they include liver, placenta and muscle cells.
See:
https://en.wikipedia.org/wiki/Syncytium#Animals
https://en.wikipedia.org/wiki/Hepatocyte#Histology
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I think I get it now. Thanks everyone for taking the time to comment. Actually, now I know I understand, it's helped answer the other question I had so there's no need to ask it now. I'll post another question if I have anymore queries. ty.