2.1.6 cell division

• A cell with a single set of unpaired chromosomes is referred to as a haploid cell.
• A cell with two complete sets of chromosomes is referred to as a diploid cell.
• A sex cell, such as a sperm or pollen, is formed when two gametes fuse together.
• Mutations occur during DNA replication.
• Infinite replication increases the chances of mutation or accumulation of mutations.
• Change in sequence of bases is a mutation.
• Primary structure of a protein is the sequence of amino acids.
• Mutations lead to changes in amino acid sequence.
• A change in an organism’s DNA is referred to as a mutation.
• Cytokinesis is the physical division of the cell.
• DNA has been checked for errors.
• The function of a protein is dependent on its tertiary structure.
• 3° structure (3D shape) of a protein is dependent on its primary structure.
• Mitosis is the process of replicating and dividing the genome.
• There is an increased chance of harmful mutation.
• Cell division that produces identical daughter cells is referred to as mitosis.
• Cell division that results in 4 haploid daughter cells is referred to as meiosis.
• The cell cycle includes the processes taking place during interphase (G1, S and G2), mitosis and cytokinesis, leading to genetically identical cells.
• The cell cycle is regulated by the use of checkpoints to control the cycle.
• During the cell cycle, genetic information is copied and passed to daughter cells.
• In multicellular organisms, stem cells are modified to produce many different types of specialised cell.
• To understand how a whole organism functions, it is essential to appreciate the importance of cooperation between cells, tissues, organs and organ systems.
• Cells reproduce by duplicating their contents and then splitting into two daughter cells.
• Prokaryotes do this through a simple process called binary fission.
• All eukaryotic, multicellular organisms develop from a single original cell, the fertilised egg (zygote).
• Repeated divisions of the zygote, by a process of cell division called mitosis, give rise to all the cells that make up multicellular organisms.
• Mitosis divides repeatedly by mitosis fertilised egg to initially produce a ball of genetically identical cells – the early embryo.
• The function of mitosis is to produce new cells, each of which receives a set of chromosomes identical to those of the original cell that gave rise to them.
• Mistakes during copying, or unequal division of the genetic material between cells, can lead to cells that are unhealthy or dysfunctional, which may lead to diseases such as cancer.
• G1 is a stage in the cell cycle where the cell size, nutrients, growth factors, and DNA damage are checked, and if satisfied, the cell is triggered to begin DNA replication.
• G2 is a stage in the cell cycle where the DNA has replicated without error, and the cell will signal the start of mitosis.
• Genetically identical cells are the result of mitosis.
• DNA isn’t replicated all the way to the end, so every time DNA replication occurs, the telomeres shorten, limiting the number of times a cell can replicate, known as the Hayflick limit.
• Cancerous cells have uncontrolled cell division and hence have a modified cell cycle that repeats too quickly.
• Carcinogens can alter DNA to form oncogenes, such as UV, cigarette smoke, and x-rays.
• When a normal body cell mutates, it may divide to produce a clone of cells that form a tumour.
• Malignant tumours may spread from their site of origin, develop their own blood and lymph supply, and transport malignant cells to other body sites.
• Protooncogenes are genes involved in normal cell growth which if mutated, may become an oncogene.
• Telomeres are repetitive sequences of DNA at the end of chromosomes that protect the genes at the end of chromosomes and stop chromosomes from fusing.
• A cell might enter G0 due to senescence, which is when normal cells can only divide a limited number of times, about 50, known as the Hayflick limit.