Chapter 2.1 Flashcards
What is the G0 phase of interphase
- cell is simply living and serving its function
- >no preparation for division
What do individual chromosomes look like in interphase
- they are not very visible
- > they are in a less condensed form known as chromatin
- > they must be available to RNA polymerase so that genes can be transcribed
- > cannot be tightly coiled like in mitosis as that wouldn’t allow RNA polymerase in
What is the G1 phase referred to as? What happens during this phase
- it is the presynthetic gap
- cells create organelles for energy and protein production
- > eg; mitochondria, ribosomes and ER
- cells also increase their size
What is the S stage referred to as? What happens during this phase
- it is referred to as the synthesis of DNA
- during this stage:
- > cell replicates its genetic material(results in two sister chromatids)
- > chromatids are bound at the centrosome
- during this stage, 92 chromatids are present
- > 46 chromosomes are still present
- > cells entering G2 phase have twice as much DNA as cells in G1
What is the G2 phase referred to as? What happens during this phase?
- postsynthetic gap
- DNA has been duplicated
- > cell checks if there are enough organelles and cytoplasm to divide between two daughter cells
- cell also checks if replication proceeded correctly from the S phase
What is the point of the G1/S checkpoint? What does it check for? Note this point is referred to as the restriction point.
- cell determines if DNA is in good enough condition for synthesis
- > if there is damage to the DNA
- > cell undergoes arrest until the DNA has been repaired
- > main protein in control of this is p53
What is the point of the G2/M checkpoint? What is it concerned with? Does p53 play a role here too?
- cell is mainly concerned with ensuring that adequate size has been achieved
- also that organelles have been properly replicated to support two daughter cells
-p53 does play a role in the G2/M checkpoint
What is the role of the CDK/cyclin in relation to transcription factors?
- these complexes activate transcription factors through phosphorylation
- > transcription factors then promote transcription of genes required for the next stage of the cell cycle
What is usually one of the most common mutations found in cancer cell
- it is the mutation of the gene that produces p53
- > this is called TP53
- > when this gene is mutated, the cell cycle is not stopped to repair damaged DNA
- mutations accumulate
- > result in cancerous cells that keep dividing continuously
- > can create tumours
What are the characteristic of prophase?
- first phase of mitosis
- condensation of chromatin into chromosomes
- centrioles move towards opposite sides of the cell
- > form spindle fibers(microtubules)
- nuclear membrane dissolves during mitosis
- nucleoli become less distinct
- Kinetochores appear at the centromere
What is the use of kinetochores
- they appear at the centromeres
- >serve as attachment points for specific fibers of the spindle apparatus(kinetochore fibers)
What are the characteristics of metaphase
- the centrioles are at the opposite side of the cell
- the chromosomes have lined up at the equatorial plate
What are the characteristics of anaphase
- centromeres split
- > so that each chromatid has its own distinct centromere
- > essentially the sister chromatids seperate
- > the kinetochrore fibers shorten and let go
What are the characteristics of telophase
- chromosomes uncoil
- >resuming their interphase form
