2.6 Cell Division And Diversity Flashcards
What happens in interphase?
G1 - growth of cells/organelles, increased number of organelles/protein synthesis
Synthesis - DNA replication
G2 - growth of cell/organelles/protein synthesis
What happens at G0 checkpoint
Cell leaves the cycle temporarily or permanently if:
- the cell is fully differentiated
- The DNA is damaged (cells will repair DNA)
G1 checkpoint
Ensure requirements (e.g. chemicals needed) for DNA replication are met
G2 checkpoint
Check for mutations in DNA (daughter cells might not receive identical genetic information, proteins might not function)
Metaphase checkpoint
Ensure chromosomes have attached to spindles correctly
What is the role of mitosis?
Asexual reproduction
Repair of damaged cells/tissues
Growth of an organism
Describe prophase
Nuclear envelope breaks down, chromosomes condense, spindle fibres form
Describe metaphase
Chromosomes line up along equator of the cell, spindle fibres attach to the centromere of chromosomes
Describe anaphase
Chromatids are pulled to opposite poles of the cell as spindle fibres contract breaking centromere
Describe telophase
Nuclear envelope begins to reform, chromosomes uncoil, cell surface membrane undergoes cytokinesis, spindle fibres break down
Describe cytokinesis
Davidson of the cytoplasm
Describe mitosis and meiosis
Mitosis: production of two genetically identical diploid daughter cells
Meiosis: production of four genetically different haploid daughter cells (gametes)
Define stem cells
Undifferentiated cells that can differentiate into specialised cells by dividing by mitosis
Describe totipotent, pluripotent, multipotent and unipotent stem cells
Totipotent - differentiate into any type of cell including extraembryonic and placental cells
Pluripotent - can differentiate into any type of cell apart from extraembryonic and placental cells
Multipotent - can form more than one cell type of a particular lineage e.g. haematopoetic stem cells
Unipotent - give rise to one cell
The role of meiosis
Genetic variation by crossing over and independent assortment
Independent assortment; in meiosis 1 and 2 the order in which chromosomes line up along the equator in metaphase is random
Crossing over (at chiasma); in prophase 1 homologous chromosomes form bivalents and maternal and maternal chromosomes exchange genetic material
Describe how neutrophils are adapted
Defend the body against disease
- Flexible shape allows them to engulf foreign particles or pathogens
- Many lysosomes in their cytoplasm contain digestive enzymes to break down the engulfed particles
- Multilobed nucleus
- Attracted to and travel towards infection sites by chemotaxis
Describe how erythrocytes are adapted to their function
Carry oxygen in the blood
Biconcave disc shape provides a large surface area for gas exchange
- No nucleus, mitochondria, endoplasmic reticulum and very little cytoplasm so more room for haemoglobin (protein that carries oxygen)
- Very small so large SA:V ratio
- Flexible because of their well developed cytoskeleton helping them to travel through narrow capillaries
- Cover the surfaces of organs
- Cells joined by interlinking cell membranes and a membrane at their base
- Ciliated epithelia have cilia that beat to waft particles away
- Squamous epithelia are very thin to allow efficient diffusion of gases
Describe how sperm cells are specialised for their function
- Flagellum so they can swim to the egg
- Lots of mitochondria to provide energy to swim
- Acrosome (at the head of the sperm) contains digestive enzymes to enable the sperm to penetrate the surface of the egg
- Small but long and thin so they can move easily
Where can stem cells be found in humans?
- Early embryos (can develop into any type of cell)
- In a few places in adults (can develop into a limited range of cells)
- Stem cells in umbilical-cord blood
- Induced pluripotent stem cells (iPs cells) developed in laboratories by reprogramming differentiated cells to switch on certain key genes and become undifferentiated
Uses of stem cells
Replace damaged cells
- Treat neurological disorders e.g. Parkinson’s and Alzheimer’s
- Developmental biology e.g. how organisms grow and develop, help us understand about cancer and developmental disorders
- Bone marrow transplants
- Drug research
Define tissue, organ, organ system
Tissue - group of specialised cells working together to carry out a function
Organ - group of tissues working together to carry out a function
Organ system - a number of organs working together to perform an overall life function
