Name _____GRACE KURIAN______
CHAPTER 16: THE MOLECULAR BASIS OF INHERITANCE
1. After Morgan and fellow scientists developed the Chromosomal Theory of Inheritance, the search was on for the chemical mechanism of inheritance. What are the two components of the chromosome? - Chromosomes are made up of proteins(60%) called histones and DNA(40%) the reacae was on to determine which of these organic molecules actually determined or controlled the heritable traits passed from generation to generation. finally concluded to be dna based on the hershey chase blender experiment (though mccarty macleod actually determined it first but the scientific community didn't believe it could be dna). next the race was on to determine the exact structure of dna which was determined by watson and crick in 1953 using a xray diffraction photograph taken by rosalyn franklin.
3. How did Griffiths and Avery’s experiments increase our understanding of the molecular basis of inheritance? -We learned that mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.
4. Define transformation.
-Transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material (exogenous DNA) from its surroundings and taken up through the cell membrane(s).
5. What did the experiments done by Alfred Hershey and Martha Chase show?
The experiments showed that heritable material was contained in the DNA of bacteriophage and not within the protein coat.
6. What are Chargaff’s rules?
They state that the equivalences for any given species between the number of A and T, and C and G bases are approximately equal.
7. If a species has 35% adenine in its DNA, determine the percent of the other three bases.
35% thymine; 15% guanine; 15% cytosine
8. What was the role of Maurice Wilkins and Rosalind Franklin in determining the structure of
DNA?
Maurice Wilkins and Rosalind Franklin were credited with determining the shape of the double helix by using X-ray crystallography.
9. Use the diagram to describe the structure of DNA.
10. What happens at the DNA replication fork?
At the replication fork, the DNA elongates and new strands grow.
11. Make a list of the enzymes involved in replication and their role.
DNA pol 3- elongates DNA in 5’ to 3’ direction.
DNA Ligase- joins the sugar-phosphate backbones of Okazaki fragments.
Primase- Starts a RNA chain from scratch, primes DNA replication
Helicase- untwists DNA at replication forks
12. Why does the DNA have to add nucleotides in the 5’ to 3’ direction?
The 3’ end is free, and so nucleotides can be added to it. Nucleotides can never be added to the 5’ end. 13. Label the diagram of DNA replication. Include the directions and the terms.
14. Describe the “priming of the DNA” before replication.
Primers are short stretches of RNA with 3’ end that initiate replication of DNA. Okazaki fragments must all be primed separately.
15. List some of the steps involved in DNA repair.
DNA polymerases proofread each nucleotide against its template and removes the nucleotide.
Special enzymes can initiate mismatch repair of nucleotide excision repair to already synthesized
DNA strands.
16. What is the problem that occurs at the ends of the chromosome during replication?
The 5’ ends of DNA strands have no way to be completed, and as a result of repeated rounds of replication, the DNA will become shorter and shorter.
17. What is a telomere and its role in cell division.
A telomere is a DNA sequence that does not code for genes. They can repeat hundreds or thousands of times to make sure that an organism’s DNA does not erode after multiple replications.
18. Why was there no selection pressure for prokaryotes to evolve a telomere-like solution on their chromosome?
Prokaryotes have circular DNA without a start or an end.
19. Why is telomerase an active area in cancer research?
Telomerase activity has been found in
