This first cell has 46 chromosomes, 23 from the mother and 23 from the father. All the instructions for how the child will grow are in the genes on these chromosomes. Each cell of the body will contain exact copies of the 23 pairs of chromosomes that were in the first cell that was formed by the egg and sperm. The chromosomes are kept in a special part of the cell called a nucleus.
If you had a very strong microscope, you could see the chromosomes inside the nucleus of the cell. Genes are the blueprints for your body. They are the instructions for building new cells. They tell what color hair and eyes you will have. They tell what diseases you might be likely to get. Genes tell the body's cells how to make factor. There are tens of thousands of genes arranged along the chromosomes.
All of the genes are the same in each cell and they are all arranged the same way. There are 23 pairs of chromosomes in each cell of the body. One pair of chromosomes is different in men and women. It is called the sex chromosome pair. The sex chromosome pair determines if a child will be a boy or a girl.
An egg or sperm only has half of the parent's sex chromosome pair. An egg will always have an X chromosome, since the woman's sex chromosome pair only has Xs.
Sperm can have either an X chromosome or a Y chromosome. If a sperm with an X chromosome fertilizes the egg, the new cell will have two X chromosomes. One came from the father's sperm and one came from the mother's egg. Since the sex chromosome that is made is XX, the cell will grow into a girl baby.
If a sperm with a Y chromosome fertilizes the egg, the new cell will have an X and a Y chromosome. The X came from the mother's egg and the Y came from the father's sperm. Luckily, cells are pretty smart and have an ingenious way of packaging all that info into space-efficient parcels. Enter: the chromosome. With its name rooted in the Greek words for color chroma and body soma , the chromosome is a cell structure or body that scientists can spot under a microscope by staining it with colored dyes get it?
Each chromosome is made up of protein and — you guessed it — DNA. Every chromosome contains exactly one molecule of DNA, to be exact, and that long string of genetic info is tightly wrapped around the protein called a histone , which acts like a spool, efficiently bundling the lengthy, info-rich molecule into the perfect size and shape to fit inside the nucleus of a cell.
Every human cell has 23 pairs of chromosomes for a total of 46 aside from sperm and egg cells , which each contain only 23 chromosomes. The magic number of 46 23 pairs per cell isn't universal among living things.
First, though, humans also happen to be a "diploid" species, which means that most of our chromosomes come in matched sets called homologous pairs the two members of each pair are called homologues. A lot of animals and plants are diploid, but not all of them have a total number of Mosquitoes, for example have a diploid chromosome number of six, frogs have 26 and shrimp have a whopping chromosomes!
But why do humans have 23 pairs? It happened during evolution. Thus, humans have one fewer pair of chromosomes. This is one of the main differences between the human genome and the genome of our closest relatives. Now let's go back to that sperm and egg issue — these cells only have one homologous chromosome from each pair and are considered "haploid. And if you think about it, that makes perfect sense. It means each parent contributes one homologue to a homologous pair of chromosomes in their child's cells.
Consider blood type as a clear example: People with AB blood type inherited two different gene variations on their two homologous chromosomes — one for A and one for B — that, when combined, produced AB. Now you know the textbook example of a healthy human has 23 pairs of chromosomes in almost every cell of their body, but life isn't always a textbook. What happens if something causes more or less chromosomes to develop? A gain or loss of chromosomes from the standard 46 called aneuploidy occurs either during the formation of reproductive cells sperm and egg , in early fetal development or in any other cell of the body after birth.
One of the more common forms of aneuploidy is "trisomy," which is the presence of an extra chromosome in the cells. One well-known result of trisomy is Down syndrome, which is a condition caused by three copies of chromosome 21 in each cell. This is because our chromosomes exist in matching pairs — with one chromosome of each pair being inherited from each biological parent. Of the 23 pairs, 22 are known as autosomes. Females have a pair of X chromosomes, males have an X and Y chromosome.
An individual chromosome, too small to be seen by the naked eye, is made up of a single molecule of double-stranded DNA deoxyribonucleic acid and protein. As mentioned above, the DNA molecule is formed in the shape of a double helix, similar in shape to a spiralling twisted ladder. These bases help form the double helix when two base pairs link together, with A only linking to T and C only linking to G.
These bases are also important because they code for proteins of the body. Each gene has the coding information for a protein or polypeptide, or a sequence of another type of nucleic acid called RNA ribonucleic acid. Thus, the human genome codes for all the proteins in the body. These proteins can have different functions in the body. For instance, some proteins such as keratin, which is found in hair and nails, are structural.
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