Chromosome - Science PDF

Chromosome members: Antonette, Anika, Roy, Raevic, Ysay, Majid, Anghel, Elysse, and Akilah Roy: Greetings everyone! Let us introduce ourselves first. I am Sir Christian (---and I am Sir Raevic), we will be acting as Ms. Alyssa's substitutes for this discussion, representing group 4. Raevic: Good m...

Chromosome members: Antonette, Anika, Roy, Raevic, Ysay, Majid, Anghel, Elysse, and Akilah Roy: Greetings everyone! Let us introduce ourselves first. I am Sir Christian (---and I am Sir Raevic), we will be acting as Ms. Alyssa's substitutes for this discussion, representing group 4. Raevic: Good morning Grade 9! [...] Raevic: Bago tayo magstart, let's have a bit of fun, shall we? Roy: We have prepared a short, yet fun game for you all. Not only to test your understanding but to also get a brief overview of what the lesson is about. Let's begin! [insert game] Roy: Well done everyone! Thank you for participating. Let’s officially begin the discussion- Raevic: Apapap- stop the car! May announcement kami: at the end of the lesson, may SA kayong sasagutan. Pero may catch, there’s a cash prize! [further elaborate if needed] So listen closely and keep in mind any important details worth remembering. Let’s actually begin now! Roy: As we start, let’s have a short recap, what is a chromosome based on the previous lesson earlier? Roy: Yes, Antonette? Antonette: A chromosome is defined as a structure found inside the nucleus of a cell. A chromosome is composed of DNA organized into genes, the determiners of hereditary characteristics. Roy: Correct! Now that we know what chromosomes are, let us move on to homologous chromosomes. Raevic: Homologous chromosomes are two chromosomes in a pair. This pair of chromosomes are found in diploid organisms. Moreover, they have an identical structure and carry genes for the same traits. Typically, one of the chromosomes contained in the pair is inherited from the father and the other one from the mother. Roy: As mentioned earlier, for two chromosomes to be recognized as homologous chromosomes, they have to have the same structure. Raevic: The basic parts of a homologous chromosome include the kinetochore or centromere, the p arms, and the q arms. Roy: The position of the centromere and the length of the arms play a vital role in determining if two chromosomes are homologous. They must have the centromere in the same location and must have the arms in the same length. Furthermore, they need to contain the same set of genes, exactly in the same order. Raevic: However, take into account that homologous are not exact copies, unlike the sister chromatids. Why do you think so? What about you, Anika? Anika: This is because homologous chromosomes consist of one paternal chromosome and one maternal chromosome. Raevic: Great answer! These paternal and maternal chromosomes pair up during meiosis. They are similar only in terms of their structure and because they have the same order of genes. Roy: Fun fact! Did you know that gorillas have 48 chromosomes, or that dogs have 78, while a mosquito has 6? Each organism has different numbers of chromosomes, there are two types: diploid and haploid numbers. The number of chromosomes present in somatic cells or body cells are called the diploid number (2n). A diploid organism has two sets of chromosomes, one from each parent. As mentioned before, dogs have 78 chromosomes, while humans have 46. These chromosomes exist as homologous pairs, thus 23 pairs overall in humans. Raevic: On the other hand, gametes, also known as the egg cell and sperm cell, contain the haploid number (n). The haploid gametes combine during fertilization or as said earlier, during meiosis. Therefore, the total of 46 chromosomes in humans is a result of the combination of the chromosomes of both parents. Roy: Any increase or decrease in the number of chromosomes of any organism can lead to genetic mutation, which can result in death. This abnormality is called “polyploidy.” Hence why, the number of chromosomes in each species is crucial to their survival. Polyploidy has different types, such as triploidy, which includes 3 sets of chromosomes; tetraploidy, four sets of chromosomes; hexaploidy, and so on. Raevic: Let's delve into the chromosomes in humans. As previously stated, humans have 46 chromosomes, 23 pairs. Elysse: But how do people study the chromosomes found in cells? Raevic: Excellent question, Elysse. Chromosomes can be physically studied through a karyotype! A karyotype is an actual representation of the chromosomes, which are laboratory-produced, stained, and magnified and is a picture usually taken during the cell's metaphase stage. Additionally, a karyotype may be used to look for abnormalities in the chromosome number or structure of organisms. Meanwhile, the study of karyotypes or of chromosomes is called cytogenetics. Within a karyotype, the 46 human chromosomes are arranged in 23 pairs. 22 of these pairs are known as autosomes. These are numbered roughly in relation to their sizes, from groups A to G. Roy: The 23rd pair is called gonosomes, the sex chromosomes that differ between males and females, unlike autosomes. Females have two X chromosomes, referred to as homogametic sex chromosomes. On the other hand, males only have one x chromosome, as the other one is the y chromosome, this is called heterogametic sex chromosomes. As a result, gonosomes are responsible for determining the sex or gender of organisms. Raevic: We have reached the end of our lesson! Ano pakiramdam guys? Roy: Wag muna kayo magrelax, kasi time na upang mag SA… Ready na ba? Remember the prize money everyone! [Commence the battle] Roy: We're all done. Once again, I am Sir Christian, (---and I am Sir Raevic), class is dismissed. Good bye Grade 9! [All group 4 members stand up] All: This is Group 4 signing off, thank you for listening!