What Are Chromosomes? - Definition, Function, Types & Structure

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  • 0:00 What Are Chromosomes?
  • 0:45 Reading Karyotypes
  • 2:19 Chromosomal Replication
  • 2:42 Lesson Summary
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Lesson Transcript
Instructor: Dominic Corsini
In this lesson, you'll find out why primates look so human while learning about the different types of chromosomes and how they work. You'll also get a chance to see what a chromosome looks like and discover how many genes are found in the human body.

What Are Chromosomes?

When was the last time you visited the zoo? Most visitors have their favorite animals, even the adults. Some of the most fascinating to observe are the primates. When you watch chimpanzees, orangutans, or gorillas, it's incredible how human-like they appear. As you may have heard, primates are related to humans, but what makes them appear so human?

The answer to this question lies in the primates' DNA, which stands for deoxyribonucleic acid. For example, chimpanzees have roughly 98% of the same DNA as humans. This DNA is found on chromosomes, which are tightly coiled segments of DNA. Humans have 46 total chromosomes or 23 pairs.

Reading Karyotypes

Human karyotype
Human Karyotype

Karyotypes are pictures of chromosomes. A karyotype, like this karyotype of a human, can teach us several things about chromosomes. For starters, notice that there are two copies of each chromosome. That's because humans contain pairs of each chromosome: one copy came from your biological mother, the other from your biological father.

In the bottom right corner of the karyotype, you'll find a unique set of chromosomes. Depending on your gender, you'll have either an XX combination for female or an XY combination for male.

The chromosomes in this karyotype also contain black and white bands. These represent the different genes people have. Genes are sections of a chromosome that contain the genetic information for making a specific characteristic, such as dark hair. Humans have around 23,000 genes. Thus, most karyotypes are simplified for easy viewing.

When people search for karyotypes or chromosomes, they may discover a different type of image.

Human karyotype after replication
Human Karyotype 2

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