|Reproduction is the action or process of copying something. It is the production of offspring by a sexual or asexual process.
|The production of new living organisms by combining genetic information from two individuals of different types. In humans, the male produces the sperm which fuses with the the egg produced by the female. Sexual reproduction can be internal or external.
|Asexual reproduction is a mode of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only. It does not involve the fusion of gametes and almost never changes the number of chromosomes.
|Mitosis is cell division that results in 2 new daughter cells. It occurs in all cells except the sex cells (somatic cells). The daughter cells are identical "clones". The cells are diploid (2n) meaning that they have paired chromosomes.
|Meiosis is cell division that results in 4 daughter cells. It is the process of cell division that produces sex cells (gametes). In humans, these gametes are the ovum and the spermatozoa (sperm). It contains half the genetic information from each parent. Meiosis results in haploid cells which contain a single set of chromosomes.
|A thread- like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. It is located inside the nucleus of most plant and animal cells.
|A unit of heredity which is transferred from a parent to offspring and is held to determine some characteristic of the offspring.
|The nucleus is the organelle responsible for the activity and growth of a cell. It contains genetic material.
|23 pairs of chromosomes.
|Chromosomes in the sperm and egg?
|The sperm and egg contain 23 chromosomes each.
|Chromosomes in the human body?
|46 chromosomes or 23 pairs of chromosomes. 23 homologous pairs of chromosomes.
|Deoxyribonucleic acid. A self- replicating material which is present in nearly all living organisms as the main constituent of chromosomes. It carries genetic information.
|Importance of Mitosis?
|Mitosis is important for the growth and repair of cells. It is also important for replicating cells.
|Are gametes haploid or diploid?
|Haploid- 23 chromosomes.
|Phases of Mitosis?
|Interphase is the resting phase between successive mitotic divisions of a cell, or between the first and second divisions of meiosis. During interphase, there are several other phases. G1 phase- The cell matures. S phase- the cell is replicated and DNA is copied. By the end of interphase, 2 chromosomes are joined together by centromere. Centrioles form outside the nucleus.
|Prophase is the 2nd phase of mitosis. During prophase, the nucleolus disappears and the chromatin condenses into chromosomes. The centrosomes separate and mitotic spindle forms.
|This phase should not be included if not asked. This a small phase that occurs before metaphase. During this phase, the nuclear envelope disassembles. Chromosomes form two kinetochores at the centromere. Microtubules attach to the chromosomes.
|Metaphase is the third phase of mitosis that separates duplicated genetic material carried in the nucleus of a parent cell into 2 identical daughter cells. During metaphase, the chromosomes align on the metaphase plate (an imaginary line in the middle of the cell)
|The fourth phase of mitosis. The cell chromosomes move away from one another to opposite poles of the spindle.
|Telophase is the fifth phase of mitosis. A new nuclear envelope forms. The chromosomes unfold back into chromatin. The nuclei reappears and the cell continues to elongate.
|Cytokinesis is the sixth phase of mitosis. It is the cytoplasmic division of a cell.
|Memory methods for phases of Mitosis.
|Metaphase- Meet Middle. Telophase- Telephone. Anaphase- Apart. Cytokinesis- Cytoplasm/ looks like your cleavage. Acronym for phases- IPPMATC.
|Half a chromosome.
|The part of a chromosome that links sister chromatids.
|A complex of macromolecules from cells consisting of DNA, RNA and protein.
|An organelle where cell microtubules get organised.
|Structures that are responsible for movement in eukaryotic cells.
|Any chromosome that is not a sex- determining chromosome. Most chromosomes are autosomes. Autosomes all have 46 chromosomes (diploid). Occurs by mitotic division.
|Half the usual number of chromosomes. Haploid cells have 23 chromosomes.
|A cell or organism that has paired chromosomes, one from each parent. 23 pairs of chromosomes.
|A small set of microtubules arranged in a specific way. These are 9 groups of microtubules.
|An imaginary line that splits the cell in half.
|Two parts of Cell division?
|Division of the nucleus and division of the cytoplasm.
|The role of the Centromere?
|The centromere joins the sister chromatids together. As the spindle appears, the centromere of each chromosome attaches to the spindle fibres at the equator.
|The role of the Spindle?
|A spindle is a network of fibres extending between the two poles of the cell. It segregates chromosomes to two daughter cells during mitosis.
|Mitosis is only part of the cell cycle. What is the rest of the cell cycle called?
|Interphase is the name given to the rest of the cell cycle.
|Types of organisms or cells that undergo mitosis?
|Eukaryotic organisms or cells containing nuclei undergo mitosis. e.g. animals, plants and fungi.
|Difference between a chromatid and a chromosome?
|A chromatid is a chromatid when it is attracted to another one. But if the chromatid is alone, it is called chromosome.
|Gametes are specialised cells that combine in sexual reproduction.
|Germ cells are the cells that give rise to gametes.
|Why is Meiosis called a reduction division?
|Meiosis is called a reduction division. It is called a reduction division because meiosis reduces the number of chromosomes in gametes to half of that in somatic cells.
|Why is meiosis important?
|If meiosis did not occur, the offspring would have double the amount of chromosomes in either parent.
|Genetic Variation in meiosis?
|Genetic variation can occur in two ways during meiosis. Firstly, gametes have only half the genetic information of their parent cell because they only receive a single set of randomly chosen chromosomes. Secondly, when chromosomes pair up during meiosis, genetic information may be exchanged between the members of each pair in a process called crossing over. Sexual reproduction allows genetic flexibility which enables species to survive and reproduce in varies and changing environments.
|Crossing over involves the breaking and rejoining of chromatids. It produces chromosomes with new combinations of genetic information.
|A chiasma is a connection between the chromatids that hold the chromosomes together until it is time for them to separate. A chiasma is the highlight of a crossing over event.
|A zygote is a diploid cell that results from the fusion of two diploid gametes. It is a fertilised ovum.
|Phases of Meiosis
|Asexual reproduction takes place in...?
|Can the offspring of asexual reproduction have a different appearance to their parent?
|Describe why asexual reproduction can be a disadvantage?
|Because all of the offspring have the same genetic make- up, they will all respond to change in the same way. In circumstances where environmental conditions are variable, asexually reproducing organisms may be a disadvantage.
|Somatic cells are all cells that make up the body of an organism that do not take part in sexual reproduction.
|Methods of Asexual Reproduction?
|Fission and Budding, Fragmentation, Spore Formation, vegetative reproduction and parthenogenesis.
|Fission is a method of asexual reproduction. It occurs in unicellular organisms such as bacteria and protozoans. During this process, the nucleus of the parent cell divides through mitosis. These 2 equal parts develop into new organisms.
|Budding is a method of asexual reproduction. This occurs in organisms such as yeast. The division of the cytoplasm is unequal unlike fission. The new individual arises as an outgrowth, or bud, from the parent. This process also occurs in small multicellular organisms such as hydras.
|This method of asexual reproduction is very similar to fission but it occurs in multicellular organisms. The body of the organisms breaks into 2 or more parts. These parts regenerate the missing parts to form a new organism. Examples include flatworms, marine worms and echinoderms. Sometimes, the tail gets so far away from the head that it grows a new head and then splits off to form a new worm.
|Spore formation is asexual reproduction that usually occurs in fungi. In the Penicilium fungus, clouds of green powder is formed. This powder is a type of asexually reproduced spore. Spores are called conidia.It is formed in long chains. However, in some other fungi, a clump of conidia is stored inside a structure called a sporangium. The sporangium wall bursts and spores are released. When it lands on a suitable spot, it forms a new fungus.
|Vegetative reproduction occurs in many plants. A part of the plant separates to form a new individual. These parts can be leaves, rhizomes etc.
|Rhizomes are underground stems which branch and give rise to new shoots and roots.
|Runners are stems arising from a bud near the soil surface. Strawberries spread asexually by runners. Bud produces a runner or stolon. It grows out above the ground and produces a new shoot with stem and roots.
|Tubers are swollen underground stems with buds (eyes) that will easily grow into new plants. These plants reproduce sexually by flowering and setting seed. Potatoes are tubers.
|Parthenogenesis means 'virgin birth'. It is the unusual form of cloning which results in the development of an egg in the absence of fertilisation. The egg contains all the information to begin development. It is a form of asexual reproduction that has arisen from sexual reproduction. e.g. Lizards, birds, insects. The resulting embryo is haploid.