Cell Cycle, Cell Death and Tissue Homeostasis Flashcards
What is the predominant cell type in the epidermis?
Keratinocytes
What is the primary function of keratinocytes?
- formation of a barrier against environmental damage
What are the keratinocyte cells called after they have completed differentiation?
Corneocytes
What are the keratinocyte differentiation stages regulated by?
Ca
Where do epidermal stem cells reside?
In the lower part of the epidermis (stratum basale) and are attached to the basement membrane through hemodesmosomes
What are dendritic cels?
Antigen-presenting cells
What is the main function of a dendritic cell?
To process antigen material and present it on the cell surface to the T cells
- act as messengers between innate and adaptive immune system
What is tissue homeostasis?
Maintenance of normal tissue morphology and function under physiological or pathological conditions
Regulation of which processes contributes to tissue homeostasis?
- balance of cell proliferation, differentiation and death
What are the 2 key tasks of a cell cycle?
- DNA Duplication
2. Accurate DNA segregation
What are the 4 phases of the eukaryotic cell cycle and what happens in each stage?
G1/0: G0- cell cycle arrest/ exit G1 - growth and preparation for DNA synthesis S: DNA replication - duplication of hereditary material and a copy of each chromosome is formed G2: Preparation for mitosis - cell checks that DNA replications is completed - make microtubules M: Mitosis occurs - cell divides into 2 daughter cells
What is the life cycle of the DNA during the cell cycle?
- DNA replication occurs in the S phase
- genetic material is duplicated
- DNA in chromatin form
- 2 identical sister chromatids are formed, held together by a centromere - During Prophase in mitosis, each DNA condenses and supercoils (becomes shorter and thicker)
- During Anaphase the sister chromatids are pulled apart of separate poles of the cell
How is DNA compacted into chromosomes?
- starts with a short region of DNA double helix
- Wrap DNA around the addition of histone proteins
- The combined loop of DNA and protein is called a nucleosome
- Next the nucleosomes are packaged into a thread, forming chromatin
- “beads on a string” - The chromatin fiber is coiled into a structure called a “solenoid”
What are the 5 stages of Mitosis?
Prophase, Prometaphase, Metaphase, Anaphase, Telophase
What happens during Prophase?
- sister chromatids pairs disentangle and condense in the nucleus
- duplicated centrosomes move apart
- mitotic spindle assembly
What happens during Prometaphase?
- breakdown of the nuclear envelope
- chromosomes attach to spindle microtubules and move
What happens during Metaphase?
- chromosomes are aligned at the spindle equator
What is the kinetochore?
The protein structure on the chromatids where the spindle fibers attach during cell division to pull sister chromatids apart.
What happens during Anaphase?
- sister chromatids synchronously separate
- daughter chromosomes move apart towards the spindle poles
What happens during Telophase?
- two sets of daughter chromosomes arrive at the spindle poles and decondense
- new nuclear envelopes assembly
- contraction of the contractile ring
What happens at the end of mitosis?
- contractile cytokinesis
- completed nuclear envelope surrounds decondensing ring
- contractile ring creating cleavage furrow
How can you study cell-cycle progression?
- look at cell morphology/ appearance
- DNA labelling (e.g. DNA-binding dyes)
- Antibodies recognising microtubules
- Incorporate artificial thymidine analog BrdU is incorporated into newly synthesised DNA
- analysis of DNA content with a flow cytometer (FACS)
