Topic 2: Eukaryotic Chromosomes

How are eukaryotic chromosomes different from bacterial?

There are multiple chromosomes that are linear

What is the origin of replication?

the initiation site for proteins that do DNA replication

What is the telomere?

highly repetitive sequences on the ends of DNA that prevent important DNA from being lost

What is the centromere?

highly repetitive sequences in the middle of the chromosomes that provide attachment of kinetochore

What is the kinetochore?

protein complex bound to centromere thru mitosis/meiosis

What are histones?

proteins that are made of Lys and Arg to bind the negatively-charged DNA

What are nucleosomes?

condensation units of DNA wrapped around histone proteins

What is the structure of histone?

octamer protein with 2 sets of 4 identical subunits and H1, the linker protein

Name the four subunits of histones.

H2A, H2B, H3, H4

What is chromatin?

DNA-protein complex in eukaryotes that condense into chromosomes

What is the next level of condensation after the 30 nm fiber?

radial loop domains

What proteins promote the formation of radial loop domains? What are their functions?

SMC proteins that form a ring for the 20 nm fiber to be pushed through, the CTCF protein that attaches to the 30 nm fiber and pushes it through the SMC protein

What are the structural and function differences between heterochromatin and euchromatin?

Heterochromatin are highly repetitive areas that are condensed, euchromatin are not repetitive and are not condensed

What chromosomal regions are mainly composed of heterochromatin?

telomeres and centromeres

What is the difference between facultative and constitutive heterochromatin?

facultative can decondense when needed, constitutive cannot

How does the level on condensation change when the cell is in interphase vs mitosis/meiosis? Why?

condensation turns into the metaphase chromosomes for easier manipulation during cell division

What is a chromosome territory?

location inside of the nucleus where the chromosomes are

What is a metaphase chromosome?

highest form of condensation

What is the function of Condensin II?

forms DNA into large loops

What is the function of Condensin I?

forms smaller loops on top of the big DNA loops

What is the function of Cohesin?

promotes binding between sister chromatids