Cell Division: DNA PDF

 Cell Division: DNA I can describe the shape of DNA (double helix). Explanation of Concepts DNA (deoxyribonucleic acid) is a molecule found in the nucleus of cells. It is shaped like a double helix, similar to a ladder twisted around...

 Cell Division: DNA I can describe the shape of DNA (double helix). Explanation of Concepts DNA (deoxyribonucleic acid) is a molecule found in the nucleus of cells. It is shaped like a double helix, similar to a ladder twisted around itself. 48 Living World Page 156 2023 I can explain the role of DNA (a molecule bearing the organism's genetic code). Explanation of Concepts DNA is the molecule in living organisms that contains the genetic code. A strand of DNA contains many segments, called genes. Each gene has a specific task; some genes determine eye colour, while others produce proteins used during the digestion of nutrients. Humans have approximately 25 000 genes. Questions Dylan and Lisa are discussing their hair colour. Dylan has blonde hair, while Lisa has black hair. Assuming that they have not altered their original hair colours, how would you explain the different hair colours? Answer: 1. They have different genes. The segment of DNA that codes for hair colour are different for Dylan and Lisa. Living World Page 157 2023  Cell Division: Mitosis and Meiosis I can describe the functions of mitosis (reproduction, growth, regeneration). I can describe the function of meiosis (production of gametes). I can distinguish between mitosis and meiosis based on their functions. Explanation of Concepts The two types of cell division are mitosis and meiosis. Mitosis During mitosis, a cell divides once, resulting in 2 daughter cells. These daughter cells are genetically identical to the original parent cell. Each daughter cell contains the same number of chromosomes as the parent. Meiosis During meiosis, a cell divides twice, resulting in 4 daughter cells called gametes. The gametes are genetically different from each other and from the parent cell. Each daughter cell contains half as many chromosomes as the original parent cell. Living World Page 158 2023  Mitosis Meiosis 49 Comparison of Mitosis and Meiosis Mitosis Meiosis Growth – increasing the number Production of gametes for of cells sexual reproduction Functions Repair – replacing damaged cells Asexual reproduction Number of Two Four daughter cells Number of chromosomes in Same as parent cell Half as many as in parent cell daughter cells Where it occurs Everywhere in the body Ovaries and testes Living World Page 159 2023 Questions Which of the following statements is NOT a function of mitosis? A) Growth B) Tissue repair C) Production of sex cells D) Asexual reproduction Identify the mitotic function that is being illustrated in each example below. a) A strawberry plant will extend its roots to make a second, genetically identical plant. b) An athlete’s broken arm heals. c) Red blood cells are replaced approximately every 3 months. d) In its first 6 months, a baby will increase in size from 1 cm - 2.5 cm every month. The process of meiosis is important for sexual reproduction. Explain. Identify whether the following are examples of mitosis or meiosis. Explain your answers. a) A baby’s first tooth is coming in. b) Spermatozoa are produced in the testicles. c) A woman’s ovaries produce an ovum every month. d) After several days, a student’s paper cut is healed. Living World Page 160 2023  A parent cell is shown below: Which of the choices below correctly shows the result of mitosis and meiosis for this parent cell? 50 Answer: 1. C 2. a) Asexual reproduction b) Repair c) Tissue regeneration d) Growth 3. Meiosis will create gametes. These are sex cells (ova and spermatozoa). Without sex cells, sexual reproduction would not be possible. 4. a) Mitosis: this is an example of growth, which is a function of mitosis. b) and c) are examples of meiosis. The function of meiosis is gamete production (spermatozoa and ova). d) Mitosis: this is an example of tissue regeneration, which is a function of mitosis 5. D Living World Page 161 2023  Cell Division: Genetic Diversity I can indicate the advantages of sexual development. I can associate genetic diversity with sexual reproduction. Explanation of Concepts Genetic diversity is all the possible genetic combinations of a species. Sexual reproduction helps to increase genetic diversity. When sexual reproduction occurs, the resulting offspring is a unique combination of genes from the mother and father. During fertilization, gametes will fuse together to form one cell. This cell will now contain half the genetic material from the mother (23 chromosomes) and half the genetic material from the father (23 chromosomes), making it a diploid cell (23 pairs of chromosomes). Since the combination of genes is random, each offspring is different and therefore genetic diversity can increase. Living World Page 162 2023 Questions Which of the following statements is true about genetic diversity? A) Sexual reproduction decreases genetic diversity. B) Sexual reproduction has no effect on genetic diversity. C) Genetic diversity describes all the genetic recombinations passed on in a family. D) Genetic diversity includes all the genetic variation that occurs in a species. Anna, Andrea and Anita are triplets. Anna and Andrea are identical, but Anita is not. How can this be possible? A population of birds has developed over several years on an isolated island. Ecologists in the region have noticed that many of these birds have a shortened life span because the population has a higher occurrence of a defective gene. These ecologists would like to save the population from disappearing. One option they are considering is to bring in the same species of birds, from a different community, which does not show this defective gene. What effect would introducing this new population of birds have on the genetic diversity of the existing bird community? Explain your answer. Answer: 1. D 2. Anna and Andrea came from the same set of gametes. This set of gametes split after fertilization to create identical twins. Anita came from a different set of gametes that was fertilized at the same time as Anna and Andrea. This set of gametes contained different genetic material; therefore she is not identical to Anna and Andrea. 3. Introducing a new population of birds of the same species may allow for an increase in genetic diversity. Sexual reproduction between the existing population and the new population will increase the number of possible genetic combinations. This will increase genetic diversity. NOTE: This would be a short term solution. Sexual reproduction over several generations in an isolated population will eventually decrease genetic diversity. Living World Page 163 2023