HS-LS1-1. Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

DNA, or deoxyribonucleic acid, is the blueprint of life. It carries the genetic instructions that determine the structure and function of all living things. Proteins are essential molecules in our bodies that perform a wide range of functions necessary for life. Understanding how DNA directs the creation of proteins helps us comprehend how cells and organisms work. This review will explain how the structure of DNA leads to the formation of proteins, focusing on the processes of transcription and translation.

Main Concepts

Structure of DNA: DNA is composed of two strands that form a double helix. The strands are made up of nucleotides, which include a sugar, a phosphate group, and one of four nitrogenous bases (adenine, thymine, cytosine, or guanine). The order of these bases encodes genetic information.

Transcription: This is the first step in protein synthesis where the DNA code is copied into messenger RNA (mRNA). The DNA double helix unwinds, and an enzyme called RNA polymerase reads one strand of DNA and creates a complementary strand of mRNA.

Translation: After transcription, the mRNA moves to the ribosome, the cell’s protein-making factory. Here, the mRNA sequence is read in sets of three bases (codons), each specifying a particular amino acid. Transfer RNA (tRNA) brings the appropriate amino acids to the ribosome, where they are linked together to form a protein.

Types of Proteins:

  • Enzymes: Proteins that act as biological catalysts to speed up chemical reactions.
  • Structural Proteins: Provide support and shape to cells and tissues (e.g., collagen).
  • Cell Receptors: Proteins on cell surfaces that receive and transmit signals.
  • Hormones: Chemical messengers that regulate various functions in the body (e.g., insulin).
  • Antibodies: Proteins of the immune system that recognize and neutralize foreign substances.

NGSS Aligned Testing Question

Inflammation has been linked to an increased risk for some cancers. Researchers are examining the role of C-enzymes and their production of prostaglandins, which have been linked to the development of these cancers. Experiments using animal models, such as mice, have tested the effect of a modified version of the C-enzyme gene on the occurrence of some cancers. The modified gene has an extra DNA segment added to one end. Animals with the modified gene had a decreased incidence of intestinal cancers. The diagram below represents the expression of the unmodified and the modified genes

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Construct an explanation, based on the evidence provided, that would account for the decrease in cancer that was observed in the animals with the modified gene.

Acceptable responses include, but are not limited to:
— The change in the gene changes the enzyme and it will not work as well. The production of prostaglandins that cause inflammation and the chance of cancer will be reduced.
— The amino acid sequence will be different. The enzyme may not function properly causing less inflammation and less cancer.
— The shape of the enzyme will be different, and it will not connect correctly with the molecule that causes inflammation. There will be reduced inflammation.
— The extra segment would interfere with the ability of the modified genetic code to attach to the ribosome. The production of enzymes will be reduced, reducing inflammation.

Review Questions and Answers

  1. What is the main role of DNA in living organisms?

    2. DNA carries the genetic instructions for building and maintaining all living organisms.

  2. What does the process of transcription involve?

    3. Transcription involves copying the DNA code into messenger RNA (mRNA) in the nucleus.

  3. Where does translation occur in the cell?

    4. Translation occurs in the ribosome, which is located in the cytoplasm.

  4. What is the role of mRNA in protein synthesis?

    5. mRNA carries the genetic information from the DNA to the ribosome, where proteins are made.

  5. How are amino acids related to proteins?

    6. Amino acids are the building blocks of proteins. They are linked together in a specific order to form a protein.

  6. Why are proteins important for living organisms?

    7. Proteins perform crucial functions such as speeding up reactions (enzymes), providing structure (structural proteins), and regulating body processes (hormones and antibodies).

  7. What is an enzyme and what does it do?

    8. An enzyme is a type of protein that speeds up chemical reactions in the body.

  8. What function do cell receptors serve?

    9. Cell receptors receive and transmit signals from outside the cell to regulate cellular activities.

  9. How do antibodies help the immune system?

    10. Antibodies are proteins that identify and help to neutralize foreign substances like viruses and bacteria.

  10. What is the sequence of steps from DNA to protein synthesis?

    11. The sequence is: Transcription of DNA into mRNA → Translation of mRNA into an amino acid sequence → Folding of amino acids into a functional protein.

*continue your studies by accessing another review sheet below*

HS. Structure and Function: HS-LS1-1 : HS-LS1-2 : HS-LS1-3

HS. Matter and Energy in Organisms and Ecosystems: HS-LS1-5 : HS-LS1-6 : HS-LS1-7 : HS-LS2-3 : HS-LS2-4 : HS-LS2-5

HS. Interdependent Relationships in Ecosystems: HS-LS2-1 : HS-LS2-2 : HS-LS2-6 : HS-LS2-7 : HS-LS2-8

HS. Inheritance and Variation of Traits: HS-LS1-4 : HS-LS3-1 : HS-LS3-2 : HS-LS3-3 : HS-LS1-8

HS. Natural Selection and Evolution: HS-LS4-1 : HS-LS4-2 : HS-LS4-3 : HS-LS4-4 : HS-LS4-5