# Haploid and Diploid ## Метаданные - **Канал:** Amoeba Sisters - **YouTube:** https://www.youtube.com/watch?v=iE4KFuzu5WQ ## Содержание ### [0:00](https://www.youtube.com/watch?v=iE4KFuzu5WQ) Segment 1 (00:00 - 05:00) Haploid and diploid. You may have heard that haploid means one set of chromosomes and diploid means two sets of chromosomes. Maybe you memorized that. But what does that really mean? What does it mean when we say “sets” of chromosomes? The inspiration for this video was from a quiz question we posted a while back. You can pause the video right now, read it, and try to answer it. Most of the responses were actually not correct with this question. And the answer revealed… is this one. There are two major reasons we think this question was missed a lot. The first reason (1) Understanding how chromosome numbers change after mitosis and meiosis is challenging for students; we have a video to help understand how generally each human cell would have 23 chromosomes after meiosis I and also II. But the second reason this question was challenging? (2) It’s that these terms “haploid” and “diploid” tend to get misunderstood. Hence this video. When we say diploid cells have two chromosome sets, we mean having two versions of each chromosome type. In most cases, if you saw a display of a person’s chromosomes, you would generally see 46 chromosomes but you would notice there are 23 TYPES of chromosomes. These first 22 TYPES fall into the category of autosomes, which means these are chromosomes that are not sex chromosomes. The last TYPE is reserved for the sex chromosomes. So 23 types of chromosomes. With each TYPE of chromosome, you will see there are two chromosomes. One chromosome from one biological parent. One chromosome from the other. In total, that’s 23 chromosomes total from one biological parent. 23 chromosomes from the other biological parent. That means 23 chromosomes - one SET - comes from one biological parent and the other biological parent. That would be two sets, 46 total chromosomes. When we say a diploid cell has two sets of chromosomes, we mean that it has two versions of every chromosome type — one version from each biological parent. In humans, diploid cells are body cells. Like a stomach cell or a muscle cell. A haploid cell has only one version of each chromosome type, so it has just one chromosome set. It would only have one chromosome of each type. Generally, that’d be 23 total chromosomes. In humans, egg cells and sperm cells, which are known as gametes, are haploid cells. They each only have one set of chromosomes. And that’s important because if an egg cell and sperm cell combine, they make a diploid cell called a zygote. The zygote has two sets of chromosomes: one from the egg cell and one from the sperm cell. And that diploid zygote will divide by mitosis to make more diploid cells. On the topic of mitosis: mitosis in humans starts with a diploid cell. The two daughter cells that result after mitosis are identical and both diploid cells. Mitosis starts and ends diploid. In meiosis, meiosis in humans starts with a diploid cell. The starting cell is different in females and males. This cell does meiosis I and, if you’ve seen our meiosis video, you’ll review that homologous chromosomes are separated in meiosis I. Now the daughter cells won’t have two sets of chromosomes anymore; they’ll only have one set of chromosomes. Therefore, after meiosis I, the daughter cells are both haploid. These daughter cells do meiosis II and the sister chromatids are now separated. The result is still only one set of chromosomes in each cell. The result of meiosis II is four daughter cells that are haploid. Now, a few points to add with the terms haploid and diploid. Point #1, Remember: this is a chromosome. And This one though has two chromatids, it’s replicated. But having another chromatid doesn’t change the number of chromosome SETS so the number of chromatids doesn’t make something haploid or diploid. Point #2, You’ll often see this 2n or n thing. In this notation, “n” is the number of chromosomes in a set. Because diploid means two sets, it is represented as 2n and because haploid means one set, it is represented as just n. Point #3, In most cases, humans have 46 chromosomes. So the diploid number of chromosomes (2n) is 46. The haploid number of chromosomes (n) would then be 23. But that’s in most cases for humans. Let’s take an axolotl. If I told you its diploid number of chromosomes is 28, what would its haploid number be? Well that’s 28/2, that’d be 14. That means the gametes of the axolotl, the haploid sperm cells and ### [5:00](https://www.youtube.com/watch?v=iE4KFuzu5WQ&t=300s) Segment 2 (05:00 - 06:00) haploid egg cells of the axolotl, each have 14 chromosomes. How about a type of fruit fly with a diploid number of 8 chromosomes? That means their haploid number would be 4 chromosomes. And last point to mention: So you may be curious: if there are the words haploid for one set of chromosomes and diploid for two sets of chromosomes —can you ever have more sets of chromosomes than that? Yes! For example, triploid means three chromosome sets; learn more in our description about how that can occur. AND, there can be more than three sets. It's actually pretty common in plants. Just remember - as we mentioned in point #1 - it doesn’t matter whether the chromosomes are unreplicated (which you see on the bottom) or replicated top). It’s the number of sets - not the number of chromatids - that makes something haploid, diploid, or triploid. Well, that’s it for the Amoeba Sisters, and we remind you to stay curious. --- *Источник: https://ekstraktznaniy.ru/video/33397*