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Thread: Genes

  1. #1
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    Question Genes

    So we all know that a human has 46 Chromosomes, but wouldn't there be billions, maybe trillions of Chromosomes in the ENTIRE human body? Or does each cell have 46 of the same Chromosomes as there are in the other cells, so we only have 46 DIFFERENT Chromosomes?

    Another question I have is, how many genes would there be in a singular Chromosome? Say for the first Chromosome we have x amount of genes. Does this mean that in another cell the first Chromosome would also have the same x amount of genes which provide the SAME traits/characteristics?

    Another question. Since we have 2 pairs of 23 Chromosomes in a cell, does that mean they've got the exact same genes? What I mean is say for example Chromosome 1 in the first 23 Chromosomes have certain characteristics in it, does that mean Chromosome 1 in the second pair of 23 Chromosomes will have the exact same characteristics?

    One more thing. Does each Chromosome have a particular trait to it? So let's say the 2nd Chromosome only has genes in it which help for sight or something of that sorts, or does each Chromosome have a combination of different genes. If it's the latter, why do we need 46 Chromosomes if there are already the same genes being produced for the other Chromosomes as well?

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    Re: Genes

    1. All cells with the exception of gametes (sex cells), red blood cells and B cells (cells used in the body's immune response to fight off antigens) have the same DNA and therefore the same chromosomes in them. This is because when cells replicate, their DNA also replicates and thus you get cells all with the same chromosomes.

    2. Yes the first chromosome in each cell would have the same genes. How many genes in a chromosome? Chromosome 1 for example has 1,961 genes, chromosome 15 has 561 genes whereas chromosome 22 has 417 genes. It varies greatly.

    3. Alright so a 'locus' is a specific band, strip, area (whatever you want to call it) of a chromosome that contains a gene (DNA sequence). A variation of this gene (though at the same locus) is called an allele. So in the 1st pair of chromosomes (one being paternal, the other maternal), each has a corresponding locus where the gene (for example) for hair colour is located. If the paternal chromosome has the 'B' allele but the maternal chromosome has the 'b' allele then the dominant allele takes over and the offspring will have brown hair. So 'chromosome 1' in each pair will have the same genes (i.e. each codes for hair colour) but different alleles (or the same).

    Chromosome Pairs (one from mother, one from father).gif

    Locus on homologous chromosomes.gif

    4. Each chromosome does NOT have a particular trait to it because there aren't enough chromosomes to fulfil that purpose. Instead each gene corresponds to a trait. One thing that biologists do know is that a particular gene will always be on a specific chromosome (e.g. the 2 most predominant genes used in expressing eye colour in humans are both located on the 15th chromosome). So one chromosome will have genes for different traits on it.

    To answer your other question as to why you need multiple chromosomes with the same genes - well for the body to be productive, it needs multiple cells expressing genes at the same time. For example with eye colour, theres no point in having one cell produce a protein for brown eye colour when you need hundreds of thousands of cells to produce that colour in order to have a visible phenotype (the brown eyes). When cells specialise (i.e. a stem cell becomes a muscle cell) you cant have just one muscle cell in your arm, you need many more. So each cell uses the DNA located in chromosomes to 'express' the gene in order to produce a protein to create a particular effect.

    Hope that answered all your questions!
    Last edited by polskicygan; 1 Aug 2017 at 12:35 AM.
    pikachu975 likes this.

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    Re: Genes

    Quote Originally Posted by polskicygan View Post
    1. All cells with the exception of gametes (sex cells), red blood cells and B cells (cells used in the body's immune response to fight off antigens) have the same DNA and therefore the same chromosomes in them. This is because when cells replicate, their DNA also replicates and thus you get cells all with the same chromosomes.

    2. Yes the first chromosome in each cell would have the same genes. How many genes in a chromosome? Chromosome 1 for example has 1,961 genes, chromosome 15 has 561 genes whereas chromosome 22 has 417 genes. It varies greatly.

    3. Alright so a 'locus' is a specific band, strip, area (whatever you want to call it) of a chromosome that contains a gene (DNA sequence). A variation of this gene (though at the same locus) is called an allele. So in the 1st pair of chromosomes (one being paternal, the other maternal), each has a corresponding locus where the gene (for example) for hair colour is located. If the paternal chromosome has the 'B' allele but the maternal chromosome has the 'b' allele then the dominant allele takes over and the offspring will have brown hair. So 'chromosome 1' in each pair will have the same genes (i.e. each codes for hair colour) but different alleles (or the same).

    Chromosome Pairs (one from mother, one from father).gif

    Locus on homologous chromosomes.gif

    4. Each chromosome does NOT have a particular trait to it because there aren't enough chromosomes to fulfil that purpose. Instead each gene corresponds to a trait. One thing that biologists do know is that a particular gene will always be on a specific chromosome (e.g. the 2 most predominant genes used in expressing eye colour in humans are both located on the 15th chromosome). So one chromosome will have genes for different traits on it.

    To answer your other question as to why you need multiple chromosomes with the same genes - well for the body to be productive, it needs multiple cells expressing genes at the same time. For example with eye colour, theres no point in having one cell produce a protein for brown eye colour when you need hundreds of thousands of cells to produce that colour in order to have a visible phenotype (the brown eyes). When cells specialise (i.e. a stem cell becomes a muscle cell) you cant have just one muscle cell in your arm, you need many more. So each cell uses the DNA located in chromosomes to 'express' the gene in order to produce a protein to create a particular effect.

    Hope that answered all your questions!
    I understand, thank you so much!

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