Chapter 5 (part 2) - fuse after done memorizing

What is one way that gene expression is regulated?

through the use of the chromatin remodeling complex

What is the chromatin remodeling complex?

A protein that hydrolyzes ATP in order to rotate the DNA wrapped around in the nucleosome, allowing for some of the DNA sequence to either be exposed or buried

• Promoting the binding of proteins to the DNA or preventing the binding of proteins to the DNA

What do the 4 different histones make up?

they make up the core of a histone

What is unqiue about each of the 4 kinds of histone?

Each of them have their own N terminal region that sicks out of the histone called histone tails that provides gene expression regulation

What does each histone have?

Multiple positions in their amino acids that can be modified through chromatin modification that adds either an acetyl group, methyl group, or phosphate group to the position

What are euchromatin?

Chromosome regions that are less densely packaged with there being two kinds: active euchromatin and quiescent euchromatin

What are heterochromatin?

Chromatin that are more densely packaged

What is Active euchromatin

A type of euchromatin that contains genes that are expressed

What is quiescent euchromatin?

A type of euchromatin that contains genes that remain silenced until they are needed, which causes the euchromatin to become a facultative heterochromatin that expresses the gene and returns to its inactive state once done

What are constitutive heterochromatin?

These are regions in a chromosome that remain in a heterochromatin state and are permanently condensed

• With an example of these being centromeres and telomeres

How do heterochromatin specific histone modifications help form heterochromatin and allow them to spread?

The modified histone recruits a “reader-writer” protein complex that contains a histone-modifying enzyme, allowing for the modified histone to be identified by the reader and spread onto neighboring nucleosome by the writer while recruiting heterochromatin specific proteins in the process until it reaches a barrier DNA sequence, preventing the spread from continuing and reaching euchromatin regions

What does females having 2 X chromosomes potentially lead to?

It can potentially lead to higher expression levels of all the genes on each X chromosome, which can result in problems occurring

What is determined at the early developmental stages of embryonic development?

One of the female X chromosomes are randomly turned into a barr body and remain condensed, with each cell division having that same chromosome remain condensed in every descendant of the original cell

What is the barr body?

the inactivated X chromosome of a female that is completely condensed and not expressed

What can occurs if a mom or dad has any mutations on their X chromosome that can lead to diseases?

50% of the cell will be able to carry out enough function in order to survive but is not always guaranteed

What is an example of X-inactivation?

Tortoiseshell cats as they are always females with one of their X chromosomes being inactive and carrying the orange fur gene while the other X chromosome is active and carries the black fur gene

How is heterochromatin inherited?

During DNA replication, the histone modification of the parent is passed done to the daughter strands and once replication is complete, the reader-writer complex begins to spread the modification to neighboring nucleosomes along with heterochromatin specific proteins binding to the modified histones, reassembling the same chromatin structure found in the parent in order to retain the identity of the parent cell