Name ______________________________ Period ______CELL REPRODUCTIONChromosomes and DNA Replication

CHROMOSOMES1. What is the composition of chromosomes?

______________________________________________________________________________

2. Each chromosome is a _______________________ DNA molecule.

3. Define chromatin:

______________________________________________________________________________

4. What does DNA wrap around during the S phase? __________________________

5. Nucleosomes are ____________________________________ formed by multiple wrapped

histone proteins.

6. Long strings of nucleosomes form thick coils that pack together to make up ________________.

7. During what phase of mitosis are chromosomes visible under a microscope? ________________

8. What shape does DNA take in prokaryotic organisms? __________________________________

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Chromatids and the Centromere9. After replication each chromosome consists of _____________ identical copies called

______________________________ attached to one another at a region called

the___________________________.

Chromosome Numbers10. Do all species have the same number of chromosomes in their cells? ________________

11. How many chromosomes are found in human cells? ____________

12. Chromosomes of the same size and shape with the same genes are called

__________________________________________.

DISCOVER OF DNA STRUCTURE13. What is the genetic material of all life on Earth? ______________

Griffith Searches for the Genetic Material14. What was he searching for?

__________________________________________________________________15. Briefly explain the experiment that led to Griffith’s conclusion and discoveries.

_____________________________________________________________________________________

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_____________________________________________________________________________________

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16. Based on his observations, Griffith deduced that something in the killed S-strain was transferred to the previously harmless R-strain, making the R-strain deadly. What did he call that something? ___________________________

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Avery’s Team Makes a Major Contribution17. Whose experiments did his team replicate? ________________________________________________18. Why did they replicate these experiments?

_____________________________________________________________________________________

_____________________________________________________________________________________

19. What conclusions did Avery come up with?_____________________________________________________________________________________

_____________________________________________________________________________________

Hershey and Chase Seal the Deal20. Briefly explain Hershey & Chase experiment.

_____________________________________________________________________________________

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21. What was their conclusion?_____________________________________________________________________________________

Chargaff Writes the Rules

22. What did Chargaff study? _____________________________________________________________________________________

23. What discovery did Chargaff make?_____________________________________________________________________________________

_____________________________________________________________________________________

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24. What name is giving to his discovery? __________________________________________________________

The Double Helix25. What did Watson & Crick discover? _______________________________________________________

26. In what year was this discovery made? ______________

27. What is the shape of a DNA molecule? __________________________________________

28. What type of bonds hold the nucleotides together? __________________________________________

29. What are the three parts of a nucleotide? __________________________________________________

30. Name the four nitrogenous bases found in DNA.

____________________________________________________________________________________

31. Which nitrogenous bases always pair together?

____________________________________________________________________________________4

DNA REPLICATION32. DNA replication occurs during the _________________ of the eukaryotic cell cycle.33. Steps to DNA replication:

(1) ___________________________________________________________________________

(2) ___________________________________________________________________________

___________________________________________________________________________

(3) ___________________________________________________________________________

___________________________________________________________________________

(4) ___________________________________________________________________________

34. What is the name of the enzyme that opens the DNA molecule? _________________________

35. What is the name of the enzyme that “reads” the DNA molecule? _______________________

DNA Replication is Semi-Conservative• DNA replication of one helix of DNA results in two identical helices

– original DNA helix is called the "parental" DNA

– two resulting helices can be called "daughter" helices

• DNA replication is semi-conservative, meaning that one parent strand is always passed on to the daughter helix of DNA

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