Chapter 3 Learning Objectives Flashcards
(30 cards)
What is a nucleotide?
A building block of DNA/RNA made of a sugar, a phosphate group, and a nitrogen base.
What are the three parts of a nucleotide?
- Sugar (ribose or deoxyribose)
- Phosphate group
- Nitrogenous base
What is a nucleoside?
A sugar plus nitrogenous base (no phosphate).
Which two bases are purines?
Pure as Gold
- Adenine (A)
- Guanine (G)
Pure as Gold
Which three bases are pyrimidines?
Creepy Tombs Under Pyramids
- Cytosine (C)
- Thymine (T)
- Uracil (U)
Creepy Tombs Under Pyramid
Which bases does DNA have?
- A
- G
- C
- T
Which bases does RNA have?
- A
- G
- C
- U
What bond links sugars and phosphates in a strand?
A phosphodiester bond.
What holds two DNA strands together?
Hydrogen bonds between paired bases.
What is the 5’ end of a chain?
The end with a free phosphate on the sugar’s 5′ carbon.
What is the 3’ end of a chain?
The end with a free –OH on the sugar’s 3′ carbon.
In which direction does DNA/RNA grow?
From the 5’ end toward the 3’ end.
Which bases always pair together?
At The Car Garage
- A with T (or U in RNA)
- C with G
How many hydrogen bonds hold A–T?
Two hydrogen bonds.
How many hydrogen bonds hold C–G?
Three hydrogen bonds.
Why do strands twist into a helix?
To keep backbones outside and bases inside, held by H-bonds.
What sugar is in DNA?
Deoxyribose (missing one –OH).
What sugar is in RNA?
Ribose (has –OH on 2′ carbon).
Is DNA single or double-stranded?
Double-stranded.
Is RNA single or double-stranded?
Usually single-stranded.
Main function of DNA?
Store genetic information.
Main function of RNA?
Help make proteins (mRNA, tRNA, rRNA).
What does “semi-conservative” mean?
Each new DNA has one old strand and one new strand.
What enzyme unwinds the DNA helix?
Helicase.
