Problem 9
Question
In mammals, the nose is located on the anterior end and the heart in the center. These positions are the result of activation of: a. Hox genes arranged along a number of chromosomes in the same order as they are expressed along the anteriorposterior axis. b.maternal-effect genes after somites differentiate into muscle. c. Hox genes scattered randomly among different chromosomes. d. a transcription factor called the homeobox. e. homeodomain that binds ribosomes.
Step-by-Step Solution
Verified Answer
The correct response is a. Hox genes arranged along a number of chromosomes in the same order as they are expressed along the anterior-posterior axis.
1Step 1: Understand Hox genes
Hox genes are a group of related genes that control the body plan of an embryo along the anterior-posterior (head-tail) axis. They play a critical role in the positioning of body segments and organs. Therefore, understanding their function is key to understanding the given exercise.
2Step 2: Analyze the options
Looking at option a, Hox genes are indeed arranged along chromosomes in the same order as they're expressed along the anterior-posterior axis. But for other options, like b, maternal-effect genes are important for early development, but do not determine the positioning of organs such as the nose and heart. And for c, it contradicts our understanding since Hox genes aren't scattered randomly among chromosomes. Option d seems unrelated as the homeobox is a DNA sequence found within genes that are involved in the regulation of patterns of anatomical development, but doesn't specifically result in nose and heart positioning. Option e appears unrelated as well, as the homeodomain is a protein domain that binds to DNA, not ribosomes.
3Step 3: Choose the best response
From the given options, option a is the best response. This is because the Hox genes' arrangement along chromosomes, in the same order they're expressed along the anterior-posterior axis, leads to the nose being located at the anterior end and the heart in the center in mammals.
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