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Chromosomes

Chromosomes

Chromosomes are long pieces of DNA that are found in the center (nucleus) of plant, animal and human cells. Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA). DNA is the material that holds genes and it is considered to be the building block of the human body.

Top Questions Asked on ChaCha.com for Chromosomes

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  1. Why is it so important that human chromosomes have many origins of replication?

    Having many origins of replication helps to speed the duplica...

  2. How many chromosomes does a mule have?

    Mules have 63 chromosomes. It's a mix of a horse's 64 and a d...

  3. What eukaryotic chromosomes contains both dna and protein tightly packed together to form a substance called?

    Chromatin is the complex combination of DNA and proteins that...

  4. Can you describe the structure of the eukaryotic chromosomes?

    Eukaryotic chromosomes consist of a DNA-protein complex that ...

  5. How do proteins help condense chromosomes?

    DNA-bound proteins, which serve to package the DNA and contro...

  1. Why is it so important that human chromosomes have many origins of replication?

    Having many origins of replication helps to speed the duplica...

  2. What eukaryotic chromosomes contains both dna and protein tightly packed together to form a substance called?

    Chromatin is the complex combination of DNA and proteins that...

  3. What are chromosomes made of?

    Chromosomes are made of 50% proteins (structure, protection, ...

  4. What would result if chromosomes did not replicate during interphase?

    Without two identical sets of chromosomes, cell division can ...

  5. How is the structure of chromosomes in eukaryotes different from the structure of chromosomes in prokaryotes?

    Prokaryotes chromosomes have less sequence-based structure th...

  1. How many chromosomes does a mule have?

    Mules have 63 chromosomes. It's a mix of a horse's 64 and a d...

  2. How many chromosomes does each human daughter cell have at the end of meiosis 1 and meiosis 2?

    At the end of the first phases of meiosis, there are 46 chrom...

  3. Are there twice as many centromeres as there are chromosomes after the replication of a cells chromatids?

    No, the statement "after the replication of a cell’s chromati...

  4. How do the structure and location of a prokaryotic chromosomes differ from that of a eukaryotic chromosome?

    Eukaryotic cells have large linear chromosomes and prokaryoti...

  5. How many chromosomes are in mitosis?

    Mitosis produces two daughter cells that are identical to the...

Top Questions Asked on ChaCha Mobile for Chromosomes

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  1. What are chromosomes made of?

    Chromosomes are made of 50% proteins (structure, protection, ...

  2. Where in the cell are chromosomes located?

    In cell biology, the nucleus, also sometimes referred to as t...

  3. How many chromosomes does meiosis produce with cells?

    In meiosis, haploid cells are created. The number of chromoso...

  4. If during metaphase 1 all 23 maternal chromosomes lined up on one side of the cell would genetic diversity increase?

    Tthere would only be two types of gametes. 1-800-2ChaCha, fre...

  5. What is homologous chromosomes?

    Homologous chromosomes: A pair of matching chromosomes in an ...

  1. What are chromosomes made of?

    Chromosomes are made of 50% proteins (structure, protection, ...

  2. Where in the cell are chromosomes located?

    In cell biology, the nucleus, also sometimes referred to as t...

  3. What is a picture of a cells chromosomes called?

    A karyotype is an actual photograph of the chromosomes from o...

  4. When during the cell cycle are chromosomes visible?

    In the Metaphase - this compact form makes the individual chr...

  5. Why it is chromosomes, not individual genes, that assort independently?

    Possibly because each chromosome is individualy linked to a s...

  1. How many homologous chromosomes are in the cells produced meiosis?

    Homologous chromosomes are inherited from each parent and are...

  2. How many chromosomes does meiosis produce with cells?

    In meiosis, haploid cells are created. The number of chromoso...

  3. How are chromosomes organized?

    Chromosomes are organized according to their pair number. The...

  4. Where in the cell are chromosomes located?

    In cell biology, the nucleus, also sometimes referred to as t...

  5. What is homologous chromosomes?

    Homologous chromosomes: A pair of matching chromosomes in an ...

About Chromosomes

Chromosomes naturally come in pairs. Each cell in the human body has 23 pairs of chromosomes for a total of 46 chromosomes. Half of those come from the mother and the other half come from the father.

Two of the chromosomes (the X and the Y chromosome) determine if you are born a boy or a girl. They are called the sex chromosomes. Females have 2 X chromosomes while males are 1 X chromosome and 1 Y chromosome.

The mother always contributes an X chromosome to the child. But, the father may contribute an X or a Y chromosome. So, it is the father that determines the gender of the child.

The unique structure of chromosomes keeps DNA tightly wrapped around spool like proteins, called histones. Without this packaging, DNA molecules would be too long to fit inside of the cells. If all of the DNA molecules in a single human cell were unwound from their histones and placed end to end, they would stretch 6 feet. For an organism to grow and function properly, its cells must constantly divide to produce new cells to replace old, worn out cells.

During cell division, it is essential that the DNA remains intact and evenly distributed among the cells. Chromosomes are a key part of the process that ensures DNA is accurately copied and distributed in the vast majority of cell divisions. However, mistakes do occur on rare occasions.

Changes in the number or of the structure of chromosomes in new cells may lead to serious problems. For example, in humans, one type of leukemia and some other cancers are caused by defective chromosomes made up of joined pieces of broken chromosomes.

It is also crucial that reproductive cells, such as eggs and sperm, contain the right number of chromosomes and that those chromosomes have the correct structure.

If they do not, the resulting offspring may fail to develop properly. For example, people with Down syndrome have three copies of chromosome 21, instead of the two copies found in other people.

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Chromosomes