Cell Cycle
Purpose of the cell cycle
To duplicate cells to replace dead or damaged cells and to form new cells for growth and to keep the body functioning.
What are the 4 stages of Mitosis
Prophase, metaphase, anaphase, telophase
Difference between mitosis and meiosis
Mitosis makes perfect replicas of cells, meiosis makes cells with haploid nuclei (half of the chromosomes) for reproduction
True or False: mitosis is responsible for making gametes for sexual reproduction in humans
False - Meiosis creates these
Name one form of asexual reproduction
Binary Fission, Multiple fission, Budding, Fragmentation, Stolons/runners, Vegetative Propagation, Plantlets, Parthenogenesis
Two stages of the cell cycle
Interphase and Mitotic Phase
Describe the process of in anaphase Mitosis
Spindle fibers shorten and pull the pairs of chromatids apart at the centromere to form single stranded chromosomes.
Difference between the two cycles of meiosis
Main difference is that the first cycle splits homologous pairs and the second splits sister chromatin
Define homologous chromosomes
This is a pair of chromosomes which have the genes for the same characteristics found in the same locations (locus)
Give an example of an organism that carries out asexual reproduction
Bacteria, Paramecium, starfish, hydra, some sharks
Phases of cell division
Prophase, metaphase, anaphase, telophase
Describe the process of in metaphase Mitosis
Chromosomes line up at the metaphase plate of the cell attached to spindle fibers at their centromeres
Difference between prophase in mitosis and prophase I in meiosis
The difference is that in prophase I in meiosis the chromatids exchange genetic information and in prophase in mitosis this does not occur and the purpose of this is for genetic variation in the offspring
Define the female Gonads and their function
The ovaries, and they produce the eggs and also secrete the hormones estrogen and progesterone
Difference between sexual and asexual reproduction
Sexual reproduction requires two parents and all the offspring have variation in their features, asexual reproduction requires only one parent and produces identical genetic copies of the parent
The process of cytokinesis and its importance
It is important for the division of cells and ensuring that there is equal distribution of genetic material, during cytokinesis contractile fibers form around the cytoplasm and contract dividing the cell into two.
Process of telophase in Mitosis
Chromosomes start to uncoil and become chromatin and the nuclear membranes reform around the new sets of chromosomes.
Difference between diploid and haploid
A diploid nucleus has all the chromosomes found in the body cells (46 in humans) and haploid nucleus contains half the chromosomes found in the body cells (23 in humans)
Similarities between reproduction in animals and plants
Both carry out sexual reproduction meaning that they form male and female gametes which need to meet to become fertilized and form a zygote
Advantages of asexual reproduction
Mates are not required. The process of reproduction is rapid. An enormous number of organisms can be produced in very less time. Positive genetic influences are passed on. Energy efficient.
Process of interphase
G1 - cells increase in size, more ATP is produced and the organelles replicate. S - DNA is replicated. G2 - More ATP is produced, proteins and enzymes needed for mitosis are formed and checks are made to ensure DNA is replicated properly in preparation for cell division
Process of prophase in Mitosis
Chromatin condenses into chromosomes, pairs of centrioles move to opposite sides of the cell, the nuclear membrane and nucleolus disappear, microtubules extend from the centrioles and form spindle fibers between the pairs, chromosomes attach to spindle fibers at the centromere and are moved to the equator of the cell.
Overview of the process of Meiosis II
Prophase occurs causing the formation of spindles around the chromosomes, then for metaphase II the chromosomes align along the equator, then the centromeres divide and chromatids move to opposite poles during anaphase II and lastly during telophase the nuclear membrane reforms around each set of chromosome
Outline formation of a zygote
The sperm and egg meet inside the female parent, the enzymes in the acrosome of the sperm break down the jelly coating of the egg and the two haploid nuclei are allowed to meet. This forms the new diploid nucleus of the zygote.
Disadvantages for asexual reproduction
Lack of diversity, since the offspring are genetically identical to the parent they are more susceptible to the same health problems. There is limited diversity among organisms. They are unable to adapt to changes in environments.