Chromosomal Rearrangements: Deletions

Hi this video we're going to talk about chromosome rearrangements but specifically focused on deletions. So deletions are a type of chromosomal rearrangement and this results in a loss of a part of a chromosome. And so deletions typically require um double stranded breaks. So two breaks to cut out that segment of the chromosome. And the deleted chromosome segment usually contains no centrum ear and it's lost after cell division. So once the deletion is um made it's just sort of floating around and because it doesn't have a central mirror that those micro tubules creating those daughter cells will not attach onto it. And so it'll just be degraded and lost during cell division. Now there are many types of deletions including entra genic deletions deletions within a gene which is going to completely like obliterate that gene. Right? Usually not gonna work. You have multi genic deletions which is multiple genes. So it gets rid of a ton of genes. More than one you have terminal deletions. This gets rid of an end of a chromosome and inter calorie deletions. And this gets rid of an interior of a chromosome. And you can imagine that these are fairly severe mutations. So relations calls a couple of important phenotype sis the first and probably most important is called pseudo dominance. And this is if a let's see let's redraw this here. So if we have these two chromosomes right? And we'll say that we had dominant alleles on one and recessive alleles on the other. Now let's say that this region here gets deleted. So this is no longer here. So normally before this was deleted. The genotype of this gene would be dominant and recessive. Which means that it would have a dominant phenotype. Right? But when this gets deleted the genotype of this or this organism is this? So you have this one recessive allele because you only have one because you have this recessive and there's no dominant allow. This recessive shows its phenotype and that's called pseudo dominance. So there's no dominant allele there it's been deleted. So that recessive allele a single recessive allele shows whatever phenotype it's supposed to show. Now in order to create the deletion there is a structure that forms called a deletion loop. And this is created between the normal home a. Log and the partner containing that's supposed to say containing. I don't know what auto corrected their the missing segment. And this allows for proper segregation during mitosis. So here's an example of deletion loop. So here you have A. And B. C. And D. And here's your loop. So this deletion will be cut out. And at the end you're going to get a. You're going to get the centrum here and you're going to get d. Let me actually back up so you can see this that solution that's what it's gonna look like. Except it will probably be much shorter. It'll be like a D. Teresa oops I'm sorry I'm making this worse. There we go. And so an example of a deletion in humans is this syndrome called cried Cat syndrome. And it's actually a deletion in chromosome five. And it has this interesting phenotype where the babies who get it um, sound like cats meowing when they cry. So that's how it gets the same cry. Do cats crying cat um syndrome. And so when they have babies cry, it sounds like a cat's meow, which is it's very odd. Um, But it's due to inhalation on chromosome five. So that's a relevant example in the real world for all your future doctors. So with that let's not move on.

An intragenic deletion is a deletion found where?

• A. In a centromere
• B. In a gene
• C. In multiple chromosomes
• D. In multiple genes

Deletions can cause what type of phenotype?

• A. Leaky allele
• B. Psudodominance
• C. Intercalary
• D. Faulty

Which of the following genetic diseases is an example of a chromosomal deletion?

• A. Down syndrome
• B. Familial down syndrome
• C. Cri du Chat syndrome
• D. Klinefelter's Disease