Science Chapter 1- DNA and Genetics

  1. What does DNA stand for and what is it?
    DNA stands for 'deoxyribonucleic acid'. It is a molecule that determines the characteristics of all living things.
  2. What is a nucleotide?
    A nucleotide is smaller molecules of DNA
  3. What are the parts of a nucleotide?
    • *Phosphate group
    • *Deoxyribose sugar
    • *A nitrogenous base
  4. What do nucleotides form in DNA?
    Its double helix structure
  5. What are the four nitrogen bases that make up DNA?
    • *Adenine
    • *Thymine
    • *Guanine
    • *Cytosine
  6. What is complementary base pairing? Mention the complementary base pairs of nucleotides.
    • Complementary base pairing is a characteristic that causes nulceotides to pair up in one way. The complementary base pairs are:
    • *Adenine with Thymine
    • *Guanine with Cytosine
  7. What are chromosomes and what are they made of?
    Chromosomes are structures that hold genes and are found in the nuclei of all cells. They are made up of DNA and protein.
  8. How many chromosome does each cell in our body have?
    • All cells in our body have 46 chromosomes except for:
    • *Gametes which contain only 23 chromosomes
    • *Red blood cells since they have no nucleus
  9. What are genes?
    Genes is a section of DNA that determines our traits.
  10. What makes each gene different?
    • *The order of bases along the DNA
    • *Each gene codes for a specific protein
  11. What types of proteins can genes code for?
    • *Structural proteins such as collagen and keratin
    • *Growth hormones and insulin for regulation
    • *Enzymes such as amylase
  12. Why is it possible for DNA to be copied?
    Because each cell in our body contains exact copies of the chromosomes that were in the original zygote
  13. Explain the steps of replicating DNA.
    • 1st step:
    • Strands of the double helix begins to separate from each other due to enzymes cutting through

    • 2nd step:
    • The nucleotides pair up with the exposed bases that compliments them

    • 3rd step:
    • The sugar and phosphate molecules bond with the nucleotides thus forming new strands of DNA.
  14. What is a chromatid?
    It is a strand of a chromosome.Two chromosomes joined together is called a chromatid.
  15. What is meiosis?
    It is a cell division that occurs everywhere in the body, it is mainly for growth and repair. Meiosis produces two daughter cells which are identical to the mother cell. Meiosis produces cells with 46 chromosomes, otherwise known as diploid cells.
  16. What is mitosis?
    A cell division that is for the production of gametes. It produces four daughter cells which are different from the mother cell and only give 23 chromosomes otherwise known as haploid cells.
  17. Explain the process of mitosis.
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  18. Explain the process of meiosis.
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  19. What are homologous chromosomes?
    Chromosomes that are the same length, have their centromere in the same position and genes located at the same spot on pairs.Image Upload 3
  20. What is a centromere?
    The point where two chromosomes join.
  21. What is the difference between asexual and sexual reproduction?
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  22. List the female sexual organs and functions.
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  23. List the male sexual organs and functions.
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  24. Why are the four gametes produced all different?
    Because the specific information they all carry are different.
  25. How are all gametes different?
    During meiosis when the chromosomes in a pair separate, the homologous pairs go randomly at either end of the cell, so the four gametes produced would carry different combinations of the information about the specific trait.
  26. What are alleles?
    Variations of genes.
  27. What is a dominant allele? What is it represented by?
    It is the gene observed in the appearance of an individual. It is represented by a capital letter.
  28. What is a recessive allele? What is it represented by?
    Is the hidden gene. It is represented by a lowercase letter
  29. What is phenotype?
    The appearance of an individual.
  30. What is genotype?
    The genetics of an individual.
  31. What are homozygous alleles?
    Same type of allele (meaning two upper case letters or two lower case letters)
  32. What are heterozygous alleles?
    Different type of allele (meaning one upper case and one lower case)
  33. What is pure breeding?
    When both alleles are same.
  34. What do the squares in between a punnet square represent?
    Possible genotype of offspring
  35. Which chromosome do female eggs carry?
    X chromosome.
  36. Which chromosomes do male sperm carry?
    X and Y chromosomes
  37. Which chromosomes form females?
    • XX chromosomes
    • First X from egg
    • Second X is from sperm
  38. Which chromosomes form males?
    • XY chromosomes
    • First X from egg
    • Second Y from sperm
  39. What are sex linked genes?
    Genes that are found on the sex chromosomes.
  40. Why is the X chromosomes longer than they Y chromosome?
    It carries more genes
  41. Why are males more prone to diseases such as colour-blindness?
    In females there are two homologous sex chromosomes. If something is wrong with one chromosome, the other pair can cover it up. However in males, the sex chromosomes are heterozygous so if something is wrong with X chromosome, the Y chromosome can't fix it up since its too small.
  42. How are chromosomal abnormality caused? Provide an example.
    They are caused when mistakes occur in meiosis and the information on the sex cells are changed. For example. down syndrome is a chromosomal abnormality which occurs when chromatids fail to separate during meiosis, leading to an extra chromosome.
  43. How are mutations caused?
    When mistakes are made during DNA replication, causing a base to be changed leading to mistakes in the manufacture of proteins.
  44. What can cause mutations?
    UV radiation, nuclear radiation and chemicals such as nicotine.
  45. Can mutations be passed on?
    Yes, because they can occur in egg or sperm which can be passed onto offspring.
  46. What are the four types of mutations?
    Silence, Missense, Nonsense and Frameshift.
  47. What is Silent Mutation?
    When a single base pair is changed but doesn't affect the protein made.
  48. What is Missense Mutation?
    Changes that don't stop the gene from making a protein but the protein produced is different. This protein may not function well and cause disease
  49. What is Nonsense Mutation?
    Causes cells to stop reading the information of the gene before its end, therefore the protein created is incomplete and can not function. Causes cystic fibrosis
  50. What is Frameshift Mutation?
    This is when a single base is inserted or deleted which causes the information to be jumbled, thus it can not be read to make a protein. Leads to severe genetic diseases.
  51. Explain how mutations can be positive?
    Mutations can be good as they add to the diversity of organisms. Farmers rely on this diversity to improve crops and increase productivity.
  52. What is genetic modification? Why is it used?
    This is when the genetic information of an organism is changed by inserting new genes. It is used to provide organisms with more desirable traits
  53. Explain the significance of GM Canola.
    Genetically modified (GM) canola is resistant to herbicides (weed killers) so that farmers can spray herbicide on the crop to kill weeds while leaving the canola unaffected. This helps reduce production costs however people are concerned as the resistance gene could slowly move into weeds, making them harder to kill in the future.
  54. Explain the significance of Rice.
    Golden Rice 2 is GM using genes from daffodils, corn and bacteria. It contains a chemical called ‘beta-carotene’ which the body converts into vitamin A. It was developed to help people in developing countries where vitamin A deficiency was causing blindness
  55. What is Gene Splicing?
    Bacteria have separate rings of DNA called plasmids. Scientists cut open these plasmids with enzymes and insert (splice) desirable genes into the plasmid.
  56. What is Recombinant DNA technology?
    Combining DNA from different genes. Recombinant DNA technology is used to splice human gene that codes for insulin production and is placed into bacteria to grow, this is then placed into a human.
  57. What is a genome?
    Genome is the genetic information carried by a haploid set of chromosomes
  58. What is the Human Genome Project?
    The Human Genome Project aimed to identify all 25000 genes in the human genome and determine the sequence of the 3 billion base pairs that make up human chromosomes
  59. If humans share 99.9% of their DNA, what causes differences between them?
    Single nucleotide polymorphisms is the difference of only one base in humans. This is what causes variations in humans.
  60. What is Gene testing? Why is it useful?
    When genes are tested to detect any defects in it.It is useful because people can tell if they or fetuses are carrying a particular disease.
  61. Explain how gene testing can be used to diagnose genetic disorders in fetuses through examining whole chromosomes.
    • Down Syndrome—Caused by an extra chromosome (extra chromosome 21)
    • Turner Syndrome– Caused when female only has only one X chromosome
    • Fragile X Syndrome– Causes mental retardation due to unreadable information which is need to make proteins essential for brain development
  62. What are other uses of genetic testing?
    • Identification of a suspect in a criminal investigation
    • Identifying biological parents
    • Analysis of DNA for transplantation to avoid rejection from recipient
  63. What are drawbacks of genetic testing?
    Having knowledge of genes that have the potential to cause disease may affect a persons ability to get life insurance cover so if someone has disease-causing genes then other members of the family may carry the same genes. They must decide what to do with the information once they get it.
  64. What is gene therapy?
    When a defective gene is replaced with a normal gene
  65. How can gene therapy cure cystic fibrosis?
    Cystic Fibrosis is homozygous for a recessive allele of a gene called CFTR. Since 1989 scientists have researched ways of transferring normal CFTR genes into human lungs, this has been unsuccessful
  66. How can cancer be treated?
    Cancerous tumours are fed by uncontrolled growth of abnormal blood vessels. Medical Researchers discovered a gene which can be switched off, reversing growth of blood vessels inside tumours, making the blood vessels more normal in size
  67. How are vaccines made and how do they work?
    It is made by taking a small amount of poison by the bacterium and making it inactive. Our body responds by making antibodies. It works by causing the body to react as it had been infected by a pathogen.
  68. How do we produce antibodies for bacteria?
    Bacteria have certain proteins on their surface that causes the body to produce antibodies when infected by the bacterium
  69. Explain the process of making vaccines with the genome of bacteria.
    Scientists must complete the genome of the bacterium to identify the genetic code that cause surface proteins to be produced, the ones most likely to cause antibodies are selected. The genes for the proteins is spliced into the plasmid of Escherichia coli (E.coli). The E.coli produces the proteins coded for by the spliced genes. These proteins are then tested on mice to see if antibodies are produced. Proteins that cause the most antibody production are tested further. In the end two or three proteins go through human trials before it is released for general use.
  70. What are embryonic stem cells?
    When an embryo is a few days old, it contains cells that are pluripotent, meaning cells that are capable of becoming any of the 220 different cell types in our body aka embryonic stem cells
  71. What are the embryonic stem cell types?
    Cell types include skin, nerve, heart, cartilage, tendon, blood and bone cells
  72. Why are scientists trying to resort to adult stem cells?
    Collecting embryonic stem cell destroys the embryo.For this reason, scientists began experimenting with bone marrow and discovered adult stem cells
  73. Why are stem cells (adult) so important?
    These stem cells allow regeneration and repair of tissue
  74. Why are adult stem cells found?
    Deep with organs that need a constant supply of new cells
  75. What can adult stem cells make?
    • Bone marrow– bone cells, cartilage, tendon, muscle, fat cells, blood cells
    • Brain– brain cells, nerve cells, blood cells
    • Muscle– muscle cells, blood cells, bone, cartilage and fat
  76. Where are adult stem cells found?
    They are found in skin, lining of gut and brain. Scientists believe stem cells have the potential to treat and cure cancer, diabetes and heart disease and spinal cord injuries
  77. What are Induced Pluripotent Cells (IPCS) and why do scientists like it so much?
    This is when matured cells are returned back to their pluripotent state.Scientists believe that these cells have the potential to replace parts of cells or organs damaged by disease.There would by no problems of rejection since the cells are from the patient
  78. What is In-Vitro Fertilisation?
    Process of fertilising eggs outside human body then producing the developing embryo into the women's uterus. It is used to help infertile people
  79. How is infertility caused?
    • Blocked oviducts and sperm ducts
    • Damage to oviduct
    • Abnormal or insufficient sperm
    Stimulation of ovaries
    • One egg matures in ovaries each month, the more collected for IVF the greater the chances
    • To stimulate more eggs to mature women are given a Follicle Stimulating Hormone (FSH)
    Collection of eggs
    Eggs are collected by a needle which is passed through the wall of the vagina into the ovary. Each mature follicle is pierced and the egg is sucked into the tube. They are then placed in a sterile Petri dish in an incubator
    Sperm collection and fertilisation
    Semen is washed to concentrate sperm which is added to the eggs for fertilisation
    Embryo Transfer
    • Embryo’s develop for 2-7days. It is then transferred to the women's uterus
    • When a lot of embryos are produced, they can be frozen and used later
  84. What donor eggs and sperm?
    • Sometimes donor eggs and sperm are used, the baby conceived will only have the genetic information of one parent
    • When donor embryos are used, the baby has no genetic link to either parent
    • Donors may be used to prevent genetic diseases from being passed on
  85. What is embryo testing?
    Embryos are tested in IVF procedures, only embryos shown to be free of sex linked diseases are used. The couple can be sure the baby wont have the disease but the child may be a carrier
  86. Why do scientists use animals for testing?
    it helps scientists to decide which experimental drugs should be abandoned and which should be put forward for human trials
  87. What are the guidelines for working with animals?
    • Reduction– Use less animals, improve data analysis to reduce number of experiments and share information to avoid repetition of experiments
    • Refinement– refine experimental method to reduce harm to animal and improve medical care and living conditions of test animals
    • Replacement- Where possible try experimenting on cells, computer modelling and studies using human volunteers
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Science Chapter 1- DNA and Genetics
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