In Drosophila, loss-of-function Ultrabithorax mutations ...

Question

In Drosophila, loss-of-function Ultrabithorax mutations result in the posterior thoracic segments differentiating into body parts with an identity normally found in the anterior thoracic segments. When the Ultrabithorax gene was cloned, it was shown to encode a transcription factor and to be expressed only in the posterior region of the thorax. Thus, Ultrabithorax acts to specify the identity of the posterior thoracic segments. Similar genes were soon discovered in other animals, including mice and humans. You have found that mice possess two closely related genes, Hoxa7 and Hoxb4, which are orthologs (see Genetic Analysis 14.2 for definition) of Ultrabithorax. You wish to know whether the two mouse genes act to specify the identity of body segments in mice.

How will you determine whether the mouse genes have redundant functions?

Accepted Answer

Hi, everyone. Let's look at our next problem. Ox genes play an important role in development and mutations in these genes can also be responsible for other types of developmental abnormalities. Mutations in the Hawks D 13 genes have been linked to a hearing loss B, sterility, C skeletal disorders or D SIN polydactyly. Well, when we talk about Hawks genes, those genes are active very early on in development, helping to direct the fates of various cells as they develop into the anatomical structures. So, in that case, um skeletal disorders are really common um with Hawks gene mutations. However, we're talking about a very specific gene here, Hawk D 13 and mutations in that particular gene are connected to choice D sin polydactyly which is results in the fusion of digits or presence of extra digits in the hands and feet. So, skeletal disorders are often linked to Hawks mutations. That's choice C but it's not as specific as this question is looking for. We have a more specific choice in choice D when we look at A and B hearing loss and sterility, both can be caused by Hawks gene mutations, um hearing loss because Hawks gene one hacks gene determines the development of those inner ear structures. So if there's problems with that, that can lead to genetic forms of hearing loss and sterility. Because Hawks gene mutations can cause developmental abnormalities in the female reproductive tract that can lead to sterility. But that's not specific to this Hawks D 13 gene. The way sin polydactyly is one interesting thing to note. We know that for example, when we look at the Dr Sophal model, that hawks gene mutations lead to really drastic consequences like antenna on the top of the head and things like that. So you might think that Hawk gene mutations in humans would be lethal or just extremely severe and detrimental. But in vertebrates, there's a lot of redundancy in the hawks genes, there's hawks genes clusters that kind of all work together. And so that causes some of these hawks gene mutations to be less severe phenotypic than one might expect. So, just an interesting little note there. So our answer here, mutations in the hawks D 13 genes specifically is choice D sin polydactyly. See you in the next video.

Key Concepts

Hox Genes

Orthologs

Gene Redundancy

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