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Homework Help: Help me understand what a Chromosome and Protein is

  1. Jan 15, 2006 #1
    Hello. Chromosomes and Proteins are 2 things I can't seem to understand.

    1. Chromosome - So is the chromosome, DNA or not!? Where are these chromosomes located? When DNA is mentioned, it's usually a twisting ladder with rungs. The rungs and the sides of the ladder are made with nucleotides and the order of the rungs determine the genetic code.

    So if the whole twisting ladder IS DNA.. then where are the chromosomes? I keep reading that chromosomes carry hereditary info.

    2. Protein - This one is also hard. What on earth is this thing? It's got carbon, hydrogen, oxygen etc... lots of things. It is made up of macro molecules... I'm not sure how to put it. It's like a big mess that has a thousand constituents.
    So somehow oxygen, hydrogen, carbon and all the other molecules will combine to form something called a protein?

    Ok I hope you guys can help me out. These are 2 questions that has been bugging me for a while.

  2. jcsd
  3. Jan 16, 2006 #2


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    You must distinguish between eukaryotic chromosomes (like we carry) an prokaryotic chromosome (like bacteria carry). The single lump of nucleic acid that bacteria carry is often also called a chromosome (singular), even though its structure and organisation differs from that of eukaryotic chromosomes (for e.g. they do not have histones).

    Anyway, I'll focus on eukaryotic chromosomes. These are bodies that can be visualised by high power light microscopy with special stains like Giemsa and easily by electron microscopy. They are discrete quanta of nucleic acid (DNA) coiled up very, very tightly and further complexed with proteins like histone proteins. Think of it as a tangled up telephone wire. The DNA ladder is the basic strand, but it's coiled up many times so that it becomes compact, and thick. The histone proteins aid in the packing of all this nucleic acid;in addition histone protein serves a regulatory (gene switching) function. The material of a chromosome is called "chromatin".

    Chromosomes do not remain static through the cell cycle : in a resting cell, they are often thin and long and difficult to visualise by light microscopy. During the lead up to cell division (mitosis), they become thick and fat as the chromatin becomes even more densely packed. These are called metaphase chromosomes.

    Chromosomes do carry hereditary information in the form of DNA. The human somatic (meaning general body) cell has 23 pairs of chromosomes, giving a total of 46 chromosomes. 22 pairs are known as autosomes, and one member of each pair came from each of your parents (the initial sperm and the egg that fused to make you). The final pair are the sex chromosomes, and they can either be a pair of Xs (making you female) or an X and a Y (making you male). Certain cells in the body which are involved in reproduction (like your testicular cells or ovarian cells) contain only half the genetic complement (meaning 23 single sets, not pairs, of chromosomes).

    There is much more to be said here, but I'll leave it to you to find out.

    Proteins are biological polymers - organic molecules formed from the joining together (chemically) of many small units (monomers). In this case, the small subunits ar known as amino acids, which are organic compounds with an amine group at one end, a carboxyl group at the other and a parent group in the middle. These monomers are joined together by peptide linkages to give a long chain, and this is the protein.
  4. Jan 16, 2006 #3


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    The chromosomes reside within the nucleus of the cell.
  5. Jan 16, 2006 #4
    I'll just write down a little conclusion for you, so you will have a better understanding when finding the rest out by yourself :)

    A chromosome is found within the nucleus of EVERY cell in the human body. The chromosome consists of DNA + structural proteins.
    The DNA (the twisted ladder with nucleotides), which is an extremely long molecule, is coiled millions and millions of times in order to be able to fit inside the nucleus. There are a lot of protein-molecules around the DNA molecule which help it to gain a special structure within its coilings.

    These structural proteins + the DNA are together called a "chromosome".

    The human cell has got 23 pairs of chromosomes. In other words, the entire genome of the human being isn't contained within a single DNA molecule - it's spread out in 23 different DNA-molecules.
    Each DNA-molecule is thus coiled and is surrounded by proteins giving it a special structure and this would form a chromosome. Each of the 23 different chromosomes has a copy of itself next to it, thus the 23 pairs of chromosomes.

    Carbon, hydrogen, nitrogen and oxygen can together form amino acids (molecules characterized by an amine-group and a carboxyl-group).
    10-20 amino acids bound together, form what we call a peptide. If two or more peptides are bound together, they are called polypeptides. If more than a certain amount of peptides (I've forgot the actual amount) are bound together, they are no longer called polypeptides, but instead they are called a PROTEIN.
    Proteins are HUGE molecules relative to most other compounds found in living organisms, and they have thousands of different functions inside the organism.

    One of them are giving structure to the DNA molecule as mentioned above.
  6. Jan 17, 2006 #5
    Thanks Arildno and Ashmanovski.

    Ash, that is a really lucid explanation. I get it now.
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