Unit 1 DNA

1. What are the three requirements of DNA as hereditary material?

DNA must be able to replicate, store information, and change.

2. What is DNA made of?

DNA is a molecule composed of atoms and built from repeating units called deoxyribonucleotides.

3. What are the three parts of a deoxyribonucleotide?

A phosphate group, a deoxyribose sugar, and a nitrogenous base.

4. What are the four nitrogenous bases in DNA?

Adenine, thymine, cytosine, guanine

5. Which DNA bases are pyrimidines?

Thymine and cytosine; they have one ring.

6. Which DNA bases are purines?

Adenine and guanine; they have two rings.

7. What bond connects deoxyribonucleotides in a DNA strand?

Phosphodiester bonds, which are covalent bonds.

8. What is the sugar-phosphate backbone?

The alternating chain of sugars and phosphate groups forming the outside of a DNA strand.

9. What does it mean that DNA has directionality?

The two ends of a DNA strand are different: the 5′ end and the 3′ end.

10. What is the 5′ end of DNA?

The end associated with a phosphate group.

11. What is the 3′ end of DNA?

The end associated with an OH group.

12. What does bp stand for?

Base pairs; DNA length is often measured in base pairs.

13. What does it mean that DNA is double-stranded?

DNA usually consists of two strands held together by hydrogen bonds between bases.

14. What does complementary mean in DNA?

Each base on one strand pairs with a specific base on the other strand.

15. What does antiparallel mean?

The two DNA strands run in opposite directions, one 5′→3′ and the other 3′→5′.

16. What are the DNA base-pairing rules?

A pairs with T, and G pairs with C.

17. How many hydrogen bonds form between A and T?

Two hydrogen bonds.

18. How many hydrogen bonds form between G and C?

Three hydrogen bonds.

19. Why do purines pair with pyrimidines?

This pairing maintains a consistent width of the DNA double helix.

20. How does DNA structure allow faithful replication?

Each original strand acts as a template for making a complementary new strand.

21. What is the shape of DNA?

A double helix.

22. What are the major and minor grooves?

Grooves of different depths that form along the DNA double helix because of base-pair arrangement.

23. What are two key elements of DNA and RNA function?

Complementary base pairing and recognition of specific sequences by proteins.

24. Why is complementary base pairing important?

It allows accurate copying of genetic information and helps molecules recognize matching sequences.

25. What is the difference between a covalent bond and a hydrogen bond in DNA?

Covalent phosphodiester bonds connect nucleotides within a strand; hydrogen bonds connect paired bases between strands.

26. What happens during DNA replication according to the notes?

The two original strands serve as templates to make two DNA molecules.