5- Mitotic Cell Cycle Flashcards
stages of mitosis
Gene
Length of DNA coding for a SPECIFIC polypeptide
DNA
- Made up of a series of genes
- one DNA found in each chromatid
- linear in eukaryotic cells and circular in prokaryoyic cells
Allele
Different versions of the same gene
chromatins
- DNA + histone proteins
- exists in two forms:
* Eurochromatin: loosely coiled, mostly at interpahse, not densely stained, contains the active genes
* Heterochromatin: tightly coiled, mostly at metaphase, densely stained, genes are mostly inactive. - when its tightly packed (hetero), its easier to separate infos into two new cells.
- its the material of which chromosomes are made, consisting DNA, proteins & small amounts of RNA (visible as patches)
chromatids
one of two identical parts of chromosomes held together by centromere, containing DNA with identical genes
chromosomes
- appearance:
* one thick strand before s phase
* two sister chromatids with 2 identical DNA molecules joined together by centromere after s phase - tightly coiled chromatin
centromere
- Structure: REPEATING non-coding DNA sequence with no active genes present
- Function: Holds 2 sister chromatids together
how do genes become proteins?
Gene1>transcription > mRNA>ribosomes>translation
>protein
define mitosis
a nuclear division producing two genetically identical daughter nuclei, each containing the same number of chromosomes as the parent nucleus.
what are the importance of mitosis? state some examples.
- Growth: producing genetically identical cells (clones), allowing growth of multicellular organisms form unicellular zygotes
- Replacement of cells and repair of tissues: by mitosis, followed by cell divisions. Cell replacement in humans is rapid in skin and in the lining of the gut. Some animals can regenerate whole body parts, such as starfish.
- A sexual reproduction. unicellular organisms’ cell division results in reproduction
- immune response. Cloning of B and T lymphocytes during the immune response
why are the cells produced during mitosis genetically identical?
(6 marks)
- sister chromatids separate during anaphase
- semi conservative replication occurs
- Complementary base pairing (A,T,C,G)
- each strand of a DNA acts as a template
- the two double heliced produced are identical
- cells have same alleles and chromosomes
cell cycle
sequence of events that takes place form one cell division until the next; its made up of interphase, mitosis & cytokinesis
stages of interphase
- Growth 1 (G1)
- S phase (DNA synthesis)
- Growth 2 (G2)
what happens in G1?
- increase in: vol of cytoplasm, protein synthesis, transcription + translation, metabolically active> increasing respiration> increasing ATP, number of organelles
- produces enzymes required for DNA replication
- prepares the cell for s phase by producing protiens, RNA and enzymes
- accumulating of enough energy reserves to complete the task of “chromosome replication”
what happens if growth factors are insufficient or if the cell has reached its maximum?
cell will not divide & will remain in “G zero”
what happens in s phase?
- DNA synthesis occurs
- chromosomes replicate along DNA, so histone protiens also replicate
- centrioles also replicate
- centrosomes divide
what happens in G2?
- DNA is checked
- cell continues to grow
- organelles increase in number
- sharp increase in tubulin synthesis to make microtubules to make to form mitotic spindles
- nuclear envelope is present
- mitochondria divides
whats the G0 phase?
- its when cells are in an “inactive stage”; theyre not actively preparing to divide.
- some cells enter this phase temporarily until an external signal triggers the start of G1
- other cells that never/rarely divide remain in G0 permanently
what are the 4 stages of mitosis?
- prophase
- metaphase
- anaphase
- telophase
