Biology Week 5: DNA and Traits

Day 1-2 | Day 3 | Day 4 | Day 5Day 6 | Lab1 | Lab2 | Key termsWeekly Quiz| Quizstar

  1. Deoxyribonucleic acid
  2. Polymer
  3. Nucleotide
  4. Double helix
  5. Deoxyribose sugar
  6. Ribose sugar
  7. Nitrogen bases
  8. Purines
  9. Adenine
  10. Guanine
  11. Pyrimidines
  12. Thymine
  13. Cytosine
  14. Uracil
  15. Phosphate
  16. Base-pairing
  17. Replication
  18. Chromosome
  19. Gene
  20. Allele
  1. Chromatid
  2. Homologous
  3. Diploid
  4. Haploid
  5. Ribonucleic acid
  6. Messenger RNA
  7. Transfer RNA
  8. Ribosomal RNA
  9. Transcription
  10. Protein synthesis
  11. Translation
  12. Gene pool
  13. Hybrid
  14. Gregor Mendel
  15. Genotype
  16. Phenotype
  17. Homozygous
  18. Heterozygous
  19. Monohybrid
  20. Dihybrid
  1. F1 generation
  2. F2 generation
  3. Probability
  4. Punnett Square
  5. Heredity
  6. Karyotype
  7. Polygenic trait
  8. Multiple-allele
  9. Sex-linked
  10. X-linked
  11. Y-linked
  12. Genetic engineering
  13. Clone
  14. Plasmid
  15. Recombinant DNA
  16. Gene therapy
  17. Population sampling
  18. Pedigree
  19. Eugenics

DeoxyriboNucleic AcidThe double helix shape of a DNA molecule

click to find the answer to today's question How many chromosomes are found in a normal human body cell?


"To get a good understanding of DNA" Watch this online video on DNA structure and replication and complete the quiz at the end.

  DNAlink to an Internet Website is a complex molecule found in all living things. The primary function of DNA in organisms is to store and transmit the genetic information that tells cells which proteins to make and when to make them.

DNA and RNA are polymers, complex molecules composed of repeating subunits. The repeating subunits in DNA and RNA are called nucleotides. link to a local picture

the key points to useful information on this page
In 1953, James Watson and Francis Crick proposed a model for the DNA molecule that consisted of two nucleotide chains that wrap around each other to form a double spiral. This shape is called a double helix. The picture at the top of this page represents a double helix.

Each nucleotide is composed of:link to an Internet Website

  1. A Sugar:
  2. One of these four nitrogen bases: link to a local picture
    1. Purines - have a double ring of carbon and nitrogen atoms.
      • Adenine
      • Guanine
    2. Pyrimidines - have a single ring of carbon and nitrogen atoms.
      • Thymine
        • Thymine is replaced by uracil in RNA.
      • Cytosine
  3. A phosphate group - PO4

Base-pairing rules: these rules describe the behavior of the bases.
  1. Cytosine always bonds with guanine by forming three hydrogen bonds.
  2. Adenine always bonds with thymine by forming two hydrogen bonds.

A pair of bases that always bond together is known as a complementary base pair.

Replicationlink to an Internet Website the process of duplicating the DNA molecule. View these animations on DNA Replication link to an Internet Website link to an Internet Website link to an Internet Website

An idea about size:
  • An average cell nucleus is about 6 micrometers in diameter.
  • The total length of the DNA in the human genome is 1.8 meters.
  • For DNA to fit in a nucleus, there must be several levels of coiling and supercoiling.

Chromosome:link to an Internet Website
a coiled, double rod-shaped form of condensed DNA that forms during cell division.

the formation of a chromosome prior to cell division
DNA is normally found in long strands in the cell nucleus. The coiled structures we call chromosomeslink to a local picture are found in cells only during cell division. DNA is duplicated prior to cell division. When the chromosomes form, one side of each chromosome consists of the original cell DNA while the other side consists of the duplicated DNA. One half of each chromosome goes to both cells during cell division. This insures that the new cell will have exactly the same genetic make-up as the original cell.

Every species has a distinct numberlink to an Internet Website of chromosomes.

Humans have 46 chromosomes (23 pairs).

Other important terms:

click for a career
RiboNucleic Acid

RNA is responsible for the movement of genetic information from the DNA in the cell nucleus to the site of protein synthesis in the cytoplasm. RNA's sugar molecule is ribose instead of the deoxyribos sugar in DNA.

Types of RNA:
  1. Messenger RNA - mRNA - a single uncoiled strand that transmits information from DNA to the ribosomes during protein synthesis.
  2. Transfer RNA - tRNA - a single folded strand that bonds with a specific amino acid.
  3. Ribosomal RNA - rRNA - a globular form that is the major constituent of the ribosomes.

Protein synthesislink to an Internet Website the formation of proteins using information coded on DNA and carried out by RNA.

Transcription - the process of forming a mRNA strand from a DNA strand.

Translationlink to an Internet Website the assembling of protein molecules from information encoded in mRNA.

The central points on this page are:
  • DNA duplicates itself in replication.
  • DNA produces RNA in transcription.
  • RNA produces proteins in translation.
the central dogma of nucleic acids


"To review protein synthesis " Watch this online video on transcription and translation.


Day 1-2 Assignment - DNA and Traits
This assignment must be turned in by the end of class tomorrow to receive credit.
Scoring criterialink to a local webpage

Honors biology: complete number 1 below and the Honors biology section, "What will your DNA do today?"

  1. Use this time-linelink to an Internet Website to answer the following questions:

    1. What was the intended purpose of the U.S. Immigration Act of 1924?

    2. How many U.S. states had compulsory sterilization laws in 1931?

    3. The first recombinant DNA molecule was produced in 1972 by what person?

    4. What event happened in 1978 that can be considered the dawn of biotechnology?

    5. How did the U.S. Army begin using biotechnology in 1992?

    6. In what year did scientists first successfully transfer DNA from one life form into another?

DNA Replication


  1. What is the primary function of DNA?

  2. The nitrogen bases of DNA always combine in specific pairs. Which bases always bond together? This is called the base paring rule.

  3. How are purines and pyrimidines related to the base paring rule?

  4. Who discovered the base paring rule?

  5. Remember the S phase in the cell cycle? What is taking place in this phase? The following is how it happens: Use this DNA workshop  link to an Internet Website site to complete the replication process and copy the sequence of the replicated DNA here.

  6. Describe in your own words how DNA replicates itself?

Protein Synthesis

  1. Use these animationslink to an Internet Website to answer the following questions:

 Transcription animation

  1. Where does protein synthesis begin?

  2. Where is the information stored that is used to make proteins?

  3. What does the animation say happens during transcription?

  4. What does the promoter do?

  5. What is the coding region?

  6. What signals the end of the gene?

  7. What does RNA polymerase do?

Translation animation

   h. What does mRNA do with the encoded information after transcription?

   i. What molecule reads the mRNA?

   j. What is a codon?

   k. What is the start codon?

   l. What does a tRNA look like? What is its function?

  m. How do codons and anticodons work together?

  n. As the strand moves what is being produced?

  o. What finally ends the strand?

  p. What has been made from this process?

  q. Can this be done in multiple sets?

  r. What have you just watched in these animations? 


  1. Why are the base pairing rules a little different between DNA replication and RNA transcription.

  2. Using information from number 1: How are the nitrogen bases in RNA different from the nitrogen bases in DNA?

  3. What are the three different types of RNA?

  4. Describe the function of each type of RNA?

  5. Explain how ribosomes are involved in translation.

  6. Use your own words to describe what happens in each of the following processes (protein synthesis):

  7. Explain why proteins are important in your body?

Honors Biology : What will your DNA do today?

      1. To help you answer this question visit this web site link to an Internet Website and complete this hand out. Word to a local webpage
      2. Once at the web page use the lower left arrow to navigate to different scenes.
      3. Follow the directions on the hand out.



      Research Links:










      A normal human body cell has 46 chromosomes.