Chapter 11.5: Chromosome Segregation

Question 1

Describe centromeres in yeast

Answer 1

o In yeast, centromeres consist of two highly conserved nucleotide sequences separated by AT-rich DNA

Question 2

Describe centromeres in higher eukaryotic organisms

Answer 2

o The centromeres of higher eukaryotic organisms are contained within blocks of certain repetitive, simple noncoding sequences known as satellite DNAs

Question 3

Define kinetochores

Answer 3

specialized structures composed of DNA and proteins that are the sites at which chromosomes attach to the spindle fibers

Question 4

What are specialized structures composed of DNA and proteins that are the sites at which chromosomes attach to the spindle fibers?

Answer 4

kinetochores

Question 5

Compare kinetochores between yeast and higher eukaryotes

Answer 5

o Each of the simple kinetochores in yeast cells connect only with a single spindle fiber, but the kinetochores in higher eukaryotes attach to many spindle microtubules

Question 6

What is cohesin and what is its function?

Answer 6

o A highly conserved, multisubunit protein complex called cohesin acts as the glue that holds sister chromatids together during mitosis and meiosis until segregation takes place

Question 7

Compare cohesin function between meiosis I and meiosis II

Answer 7

o Cohesin complexes hold chromatids together until the enzyme separase cleaves the cohesion at anaphase. In meiosis I, shugoshin protects cohesin and this keeps sister chromatids together; in meiosis II, shugoshin is removed, so separase can cleave cohesin at anaphase of this division