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Structure of Chromosomes
Next Generation: HS.LS3.1 HS.LS3.1

Structure of Chromosomes

Description:

This lesson will examine the structure and function of a chromosome.

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Tutorial

What's Covered

This lesson will discuss the structure of chromosomes by looking at:

  1. Chromosomes
  2. DNA

1. Chromosomes

When a cell is getting ready to divide, genetic information in the form of DNA will condense into structures called a chromosomes. This is how genetic information is passed from parent to offspring. Homologous chromosomes are chromosomes that contain the same set of genes and are the same length and shape. One is from the mother of the other is from the father.

Terms to Know

    • Chromosome
    • A condensed DNA structure.
    • Homologous Chromosomes
    • Chromosomes that are paired together that are the same length and shape and contain the same sets of genes. Typically, one of the homologous pair is contributed by each parent.

There are two types of chromosomes within our body:

  • Sex chromosomes-associated with sex and gender
  • Autosomes-all the chromosomes in our body except for the sex chromosomes

Terms to Know

    • Autosomes
    • All of the chromosomes in the body except for sex chromosomes.
    • Sex Chromosomes
    • Chromosomes associated with sex and gender.

The chromosome number is the number of chromosomes in a species cells. Each species has its own number of chromosomes.

ExampleFor humans, the chromosome number is 46. This means that we have 46 chromosomes, or 23 pairs, in our cells. Of those 46 chromosomes, most of them are autosomes. Only two of those chromosomes are sex chromosomes. A mouse has a total of 40 chromosomes.

Chromosomes are only visible in this form when the cell is preparing to divide. The rest of the time, our genetic information can be found in the form of chromatin, which has a balled-up thread-like form, and is found within the cell's nucleus.


2. DNA

DNA is said to be in the structure of a double helix, or ladder that has been twisted. The outside part of the ladder is made up of a phosphate-sugar backbone, that is phosphate and deoxyribose sugar molecules.

The rungs of the ladder are made up of four nitrogenous bases:

  • adenine
  • thymine
  • cytosine
  • guanine.

These nitrogenous bases compose two base pairs. Adenine always pairs with thymine and cytosine always pairs with guanine.

Summary

Chromosomes the form DNA takes when it is a cells is getting ready to divide, and are only visible during this time. Homologous chromosomes are chromosomes that contain the same set of genes. There are two types of chromosomes within our body: autosomes and sex chromosomes. The chromosome number is the number of chromosomes a species has in it’s cells. DNA, the genetic information that makes up chromosomes, come in the form of a double helix. It is made up of phosphate and deoxyribose sugar molecules as the backbone of the structure with adenine/thymine or cytosine/guanine base pairs in between.

Keep up the learning and have a great day!

Source: SOURCE: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

TERMS TO KNOW
  • Chromosome

    A condensed DNA structure.

  • Autosomes

    All of the chromosomes in the body except for sex chromosomes.

  • Sex Chromosomes

    Chromosomes associated with sex and gender.

  • Homologous Chromosomes

    Chromosomes that are paired together that are the same length and shape and contain the same sets of genes. Typically, one of the homologous pair is contributed by each parent.