cartoon-guide

Books such as these, give visual images that are necessary to make learning stick. It is fair to say that I do not remember anything much about cell biology nor anything related to DNA. It was way back in my high school that I had crammed something, held it in my working memory for a few years in order to write exams. Some bits would have percolated to my long term memory, but since I have never retrieved them, they lie somewhere in some inaccessible part of my brain.

In the past two months, I have been exposed to a lot of terminology that is specific to cell biology and genetics. My dad was diagnosed with advanced stage colon cancer and I had consulted three of the best oncologists in the city. Each meeting with the doctor lasted about 30-45 minutes. Some of the meetings were overwhelming. One of the doctors, who is known to be the best in the city, threw a lot of jargon at me, explained various types of scenarios for cancer treatment. Needless to say I was clueless. Here I was, lucky enough, to get a time slot with a leading oncologist and I was completely lost. The only thing I could think of doing is to jot down rapidly the list of words and phrases he was uttering in the conversation. Subsequently I came back home and read up on each term and understood various treatment options. Despite spending time understanding the terms, my knowledge about the treatment options was cursory at best. In any case, there were people around me who were far more intelligent and knowledgeable than me, that choosing the right doctor and the treatment schedule became an easy decision.

Amidst the hectic schedule in making my dad go through various chemo cycles, I have read through a few books on cancer. However as a primer to understanding those books on cancer, I read a few genetics/biology 101 books. This book is amongst the preliminary set of books that I have read in the past month. To begin with, this book has given me a basic collection of visuals that I can use as anchors, while reading general literature. Why do we need visuals ? Can’t one just read the stuff and understand. Well, may be yes. But most likely at least for me, it is a NO. My mind needs visuals to understand stuff better. For example, if one were to read the steps involved in creating protein(a chain of amino acids) from a DNA. it goes something like this :

  1. Enzymes in the nucleus create short sequences of mRNA based on DNA
  2. rRNA attaches itself to mRNA
  3. An appropriate tRNA attaches to rRNA based on mRNA
  4. Each tRNA gives rise to an amino acid
  5. Each amino acid so formed, attaches to the previously formed amino acid.
  6. At the end of every DNA encoding protein, there is a specific stop code that makes rRNA detach from the amino acid production line.
  7. A sequence of amino acids thus attached from the previous steps is nothing but one of the many proteins in the cell.

If one has to follow the above sequence of steps, merely reading them might not be sufficient to understand what’s going on. Some sort of pictures would be helpful and the book exactly fills in that void. The authors do a fantastic job of illustrating the above steps so that the visuals form a very sticky cue for further learning.

Here is a list of terms/concepts/principles covered in the book :

  • Selective breeding
  • Bible story on Jacob’s flock illustrates accurate Genetic observation coupled with total lack of understanding. Science and magic went together
  • Most coherent Greek theory of Heredity(by Hippocrates) : There were fluids inside the bodies of men and women. These fluids battled against each other and the outcome decided whether a particular part of body resembled the mother’s or the father’s
  • Greek Civilization and the Middle Ages had all sorts of crazy ideas about theories of heredity
    • All inheritance came from father
    • Spontaneous generation – Living organisms could arise from non living matter. This was challenged by Francesco Redi
  • Anton Van Leeuwenhoek used microscope and made two important discoveries. First one was to see bacteria and second one was the discovery of sperm cells
  • William Harvey believed that all animals come from the egg
  • Mammals lay very few eggs. Human female produces only a few a month
  • Oscar Hertwig’s observation – Fertilization as the union of sperm and egg
  • Plants – male parts are called anthers (contains pollen) and female part is called the stigma
  • No general laws of inheritance were discovered for a very long time
  • Gregor Mendel – Austrian Monk was to discover the laws of inheritance
  • Mendel’s results
    • Hereditary traits are governed by genes which retain their identity in hybrids
    • One form of gene is dominant over another form of gene. But recessive genes will pop up later
    • Each adult organism has two copies of each gene – one from each parent. When pollen or sperm and eggs are produced, they each get one copy
    • Different alleles are sorted out to sperm mand eff randomly and independently. All combinations of alleles are equally likely
  • All living beings are made of cells – This fact wasn’t appreciated until late 19th century
  • Mitosis and Meiosis – Types of cell replication
  • Mitosis – Extremely accurate process of creating two cells. Number of chromosomes will be same in both the cell
  • Sperm cell and egg cell contain only half a set of chromosomes.
  • In a typical cell, there are 46 chromosomes – 23 pairs
  • Chromosome contains the genetic material
  • Nucleotides – the building blocks for nucleic acids. An individual nucleotide has three components, sugar, phosphate and a base
  • RNA – Nucleotides with ribose
  • DNA – Nucleotides with deoxyribose
  • Proteins – These are chain of amino acids
  • Hemoglobin – One of the most complicated macromolecules. Max Perutz spent 25 years in understanding this protein.
  • Enzymes – These are proteins that take apart or put together other molecules
  • Connection between gene and enzyme – The metabolic role of the genes is to make enzymes, and each gene is responsible for one specific enzyme.
  • RNA – RNA’s are single stranded, much shorter in length (50 to 1000 nucleotides )
  • RNA polymerase – teasing apart a region of DNA and creating a copy. This is also called transcription
  • mRNA – messenger RNA
  • tRNA – transfer RNA
  • rRNA – ribosomal RNA
  • Codon – triplets of bases
  • Amino acid – Each 3 base codon stands for an amino acid
  • 64 codons represent 20 amino acids
  • Each DNA encoding protein has a same codon at the beginning – AUG.
  • The stop codon does not encode any amino acid and they signal rRNA to detach the protein formed
  • anticodon – Loop of tRNA has three unpaired bases
  • amino acid site – At the tail end of tRNA is a site or attaching single amino acid
  • DNA contains sequences encoding for every tRNA, mRNA, rRNA
  • Eucaryotes – Cell with nucleus
  • Procaryotes – Cell with no nucleus
  • Spliceosome – proteins and RNA grabs the mRNA and shears off the loop, discards it, splices the remaining pieces together. This complex is called spliceosome
  • Eucaryotic genes contain Junk DNA
  • Introns – In the middle of perfectly good genes, there may be several meaningless sequences, each hundreds of nucleotides long
  • Protein spools – To help organize all the storage, eucaryotes wrap their DNA around protein spools. Each spool consists of several proteins that are bound together
  • Principle of complementarity – Each base can pair with only one other complementary pair
  • Knowledge about DNA replication in a cell division, is still sketchy
  • Repetitive DNA – Eucaryotic cells harbor lots of so-called repetitive DNA
  • A virus contains only two parts, i.e. a bit of nucleic acid wrapped up in a protein coat. A virus can’t reproduce on its own because it lacks ribosomes and the rest of the living cell’s protein main equipment
  • Retro Virus – RNA virus encoding an enzyme that makes a DNA copy of its RNA and splicies it in to host chromosome
  • Why are some viral infections incurable ? the virus genes can’t be gotten rid of, in your own chromosomes
  • Hypothesis for Junk DNA – Its possible that some of the repetitive and junk DNA in our chromosomes may have come from this ancient virus
  • Repressive Tolerance – Shut the junk DNA down and ignore them
  • Mutation – A mutation in a gene is just a change in the DNA’s sequence of nucleotides. Even a mistake at just one position can have a profound effects
  • Defense against mutation – One amino acid can be encoded by several codons
  • Blood cells illustrate another common fact of life – One kind of a cell can turn in to another kind of cell
  • Alleles – Genes in a plant can be one of two distinct types or Alleles
  • Principle of Independent Assortment – The Alleles of one gene sort out independently of the alleles of another
  • Homologous – Two copies of each cell that resemble each other, having the same shape
  • Phenotype – How an organism looks like ?
  • Genotype – Based on what alleles it has
  • Homozygous – An organism is homozygous with respect to a given gene if its alleles are the same
  • Heterozygous– An organism is heterozygous with respect to a given gene if its alleles are different
  • Haploid – A cell with a single set of chromosomes
  • Diploid – A cell with two sets of chromosomes
  • Operon – Cluster of genes, encoding related enzymes and regulated together is called an operon
  • Promoter region – At the start of Operon, there is a site where RNA polymerase binds to the DNA to begin transcribing the message
  • Attenuation – Shortage of certain types of molecules turns on the gene
  • Jumping Genes – A method of gene regulation
  • Transposons – Movable section of genes
  • Crossover – During Meiosis, chromosomes can exchange genes
  • Gene splicing – Splice two pieces of DNA together
  • Recombinant DNA – The result of splicing two DNA’s together
  • Restriction Enzyme – Gene splicing depends on this enzyme. It creates two pieces of DNA with identical tails
  • Proteins can be produced via Recombinant DNA
  • Gene therapy – Fixing specific defects
  • Genetic engineering

There is a visual for each of the above concept/mechanism. If you are curious to know about the basic ideas of genetics, this book can be a useful starting point. If not anything, it will give visual cues to read and understand the general literature on genetics.

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