Question Video: Describing How Chromosomal Abnormalitites Can Be Caused | Nagwa Question Video: Describing How Chromosomal Abnormalitites Can Be Caused | Nagwa

Question Video: Describing How Chromosomal Abnormalitites Can Be Caused Biology • First Year of Secondary School

The passage provided outlines how chromosomal abnormalities can be caused. Chromosomal abnormalities can be caused by changes in the _ of chromosomes, or a complete loss or _ of entire chromosomes. Which word would be most appropriate to replace the first blank? [A] Appearance [B] Bonding [C] Replication [D] Structure. Which word would be most appropriate to replace the second blank? [A] Fusion [B] Specialization [C] Segmentation [D] Gain

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Video Transcript

The passage provided outlines how chromosomal abnormalities can be caused. Chromosomal abnormalities can be caused by changes in the blank of chromosomes or a complete loss or blank of entire chromosomes. Which word would be most appropriate to replace the first blank? (A) Appearance, (B) bonding, (C) replication, or (D) structure.

This question is asking us about chromosomes and chromosomal abnormalities. So let’s take a moment to review what a chromosome is. Inside most of our cells, we have a nucleus which contains our DNA. This DNA is organized into 46 chromosomes that we could see here. Chromosomes are numbered from one to 22, with chromosome one being the largest and chromosome 22 being the smallest, while chromosomes X and Y are sometimes called our sex chromosomes because they determine our biological sex.

We have two copies of each chromosome. One comes from our biological father and the other comes from our biological mother. So, in total, we have 23 pairs of chromosomes for a total of 46 chromosomes. If we take a closer look at one of these chromosomes, we can see that there are many genes within it. These genes are needed for the cell and for us to properly function. Chromosomal abnormalities exist in some individuals where parts of a chromosome are missing or duplicated. These kinds of structural changes in a chromosome can impact the genetic information on it and cause problems for the cell. Therefore, the word that is most appropriate to replace in the first blank in this passage will be “structure.”

Now, let’s look at the second part of this question.

Which word would be most appropriate to replace the second blank? (A) Fusion, (B) specialization, (C) segmentation, or (D) gain.

Besides structural changes in a chromosome, entire chromosomes can be missing or duplicated. Some syndromes, such as Down syndrome, are caused by an additional copy or a gain of chromosome 21. Because there’s now three copies of this chromosome, there’s now additional copies of the genes that it contains. This additional genetic information can cause problems for the cell that are manifested as Down syndrome. Therefore, the word that’s most appropriate to replace the second blank is “gain.”

Therefore the passage now correctly reads “Chromosomal abnormalities can be caused by changes in the structure of chromosomes or complete loss or gain of entire chromosomes.”

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