Topic 2 - cell division, cell diversity and cell organisation Flashcards
Within multicellular organisms, not all cells retain the ability to (1)
1 - divide
What does mitosis produce
Genetically identical daughter cells
What is mitosis useful for
Growth, repair and asexual reproduction
How many main stages does the eukaryotic cell cycle have
3
What are the main stages of the eukaryotic cell cycle
Interphase consists of two growth phases (G1& G2) and a DNA synthesis stage (S). The cell may exit the cell cycle at G0
What is mitosis
Mitosis is the nuclear division
What is cytokinesis
Cytokinesis is when the cell splits in two, forming two identical daughter cells.
How does cytokinesis occur in animal cells
In animal cells, the plasma membrane folds inwards until the two dents meet to separate the two daughter cells
How does cytokinesis occur in plant cells
In plant cells, cellulose starts to build up at the equator (the end plate). Plasma membrane forms in the middle of the end plate resulting in two fully separated plant cells
Give the description of prophase
DNA condenses & coils, nuclear envelope breaks down, centrioles move to opposite poles
Give the description of Metaphase
Spindle fibres attach to centromeres & chromosomes line at the equator
Give the description of Anaphase
Centromeres divides, chromatids move to opposite poles
Give the description of Telophase
Chromosomes uncoil, nuclear envelope reforms
What is the purpose of cell cycle checkpoints
Cell cycle checkpoints ensure the cell only divide at the appropriate time when ready and helps detect DNA damage.
Give the checkpoint location and function of Restriction Point / G1/S Checkpoint
Between G1 and S
Decides whether cell proceeds to S-phase
Give the checkpoint location and function of G1 Checkpoint
End of G1
Checks cell is ready for S-phase
Give the checkpoint location and function of G2/M Checkpoint
Between G2 and mitosis
Checks and repairs all of the DNA before the cell enters mitosis
Give the checkpoint location and function of Mitosis checkpoint
In the middle of mitosis
Checks cell is ready to proceed in mitosis. Ensures that the cell doesn’t proceed to the next stage before it’s ready
List the 4 cell cycle checkpoints
Restriction point (G1/S checkpoint)
G1 checkpoint
G2/M checkpoint
Mitosis checkpoint
What is produced from meiosis
Meiosis produces 4 haploid daughter cells (gametes) that are genetically different from each other.
Comment on the name of the genetic information in the cell in Meiosis 1 vs Meiosis 2
1 - homologous chromosomes
2 - sister chromatids
What happens in Meiosis 1 vs Meiosis 2
In meiosis 1, homologous chromosomes are separated from each other, with one chromosome from each pair going into one of the two daughter cells. In the second meiotic division, the sister chromatids from each chromosome are separated
Description of Prophase 1
Chromatin condenses & coils, nuclear envelope breaks down, centrioles move to opposite poles. Crossing over occurs between homologous chromosomes
Description of Metaphase 1
Spindle fibres attach to centromeres & chromosomes line at the equator
Description of Anaphase 1
Homologous chromosomes move to opposite poles
Description of Telophase 1 and cytokinesis
Chromosomes uncoil, nuclear envelope reforms. Animal cells divide by cytokinesis
Description of Prophase 2
Chromatin condenses & coils, nuclear envelope breaks down, centrioles move to opposite poles.
Description of Metaphase 2
Spindle fibres attach to the centromeres & chromosomes lines up at the equator
Description of Anaphase 2
The centromeres divide and the chromatids are pulled to opposite poles
Description of Telophase 2 and cytokinesis
Chromosomes uncoil, nuclear envelope reforms. Cells divide to form 4 haploid cells.
How does variation occur in meiosis
Variation results from independent assortment of chromosomes and crossing over during meiosis 1. Also, random fertilisation of the gametes.
what are stem cells
Stem cells are undifferentiated cells that are able to express all of their genes
By which process do stem cells divide
Mitosis
Which process do stem cells undergo by which they become specialised for different functions
Cell differentiation
What process an fully developed stem cells not undergo
Mitosis
Comment on the potent capacity of totipotent stem cells
Can divide and differentiate into any type of cell.
Comment on the potent capacity of pluripotent stem cells
Can self-renew and differentiate into any type of cell except the cells that make up the placenta.
Comment on the potent capacity of multipotent stem cells
Can only differentiate and divide into a limited number of cell types
Comment on the potent capacity of unipotent stem cells
Can only differentiate into a single type of cell e.g. cardiomyoblasts can only differentiate into cardiomyocytes.
Comment on the potent capacity of unipotent stem cells
Can only differentiate into a single type of cell e.g. cardiomyoblasts can only differentiate into cardiomyocytes.
Comment on the presence of totipotent stem cell in mammals and its differentiation
Totipotent stem cells are only present in mammals in the first few cell divisions of an embryo. During development, totipotent cells become specialised by expressing different genes and producing different proteins.
What are induced pluripotent stem cells
Induced pluripotent stem cells are unipotent stem cells that have been reprogrammed to become pluripotent by using protein transcription factors to express genes associated with pluripotency.
What are some of the uses of pluripotent stem cells
Pluripotent stem cells can be used to replace cells and treat human disorders like leukaemia and diabetes
What type of cells can bone marrow stem cells differentiate into
Bone marrow stem cells can differentiate into any type of blood cell
What is the role of meristem cells in plants
Meristem cells in plants are involved in the production of new xylem and phloem tissue
Comment on adaptations of erythrocytes
Erythrocytes have a large SA:V, with their biconcave shape. They lack a nucleus, so more haemoglobin can be stored
Comment on adaptations of neutrophils
Neutrophils have a multilobed nucleus allowing them to move and engulf material more easily
Comment on adaptations of sperm cells
Sperm cells have a tail to allow movement. There is a high density of mitochondria to provide ATP to the tail. Sperm cells have a streamline shape and a specialised lysosome (acrosome) that contains digestive enzymes to enter an egg cell
Comment on adaptations of squamous epithelial cells
Squamous epithelial cells are thin and flat to reduce the diffusion distance for gas exchange.
Comment on adaptations of ciliated epithelial cells
Ciliated epithelial cells in the trachea have cilia to move mucus along the trachea
Comment on adaptations of palisade cells
Palisade cells contain lots of chloroplasts, are long and cylindrical allowing close packing. The chloroplast can be moved by the cytoskeleton to maximise light absorption
Comment on adaptations of guard cells
Guard cells control the opening and closing of the stomata. ATP is used to pump K^+ ions into the cell, making water move in by osmosis in order to open the stomata for gas exchange
Comment on adaptations of root hair cells
Root hair cells have protrusion to increase their surface area for water absorption. They also have protein pumps and lots of mitochondria to transport minerals into the cell in order to lower the cells water potential.
