Bio exam 2- Chapter 11

What is the DNA structure

Two strands are held together by hydrogen bonds between pyrimidines and purines. The sugar-phosphate backbone faces the exterior, and the nitrogenous base pairs face the interior.

What is the secondary structure of DNA?

Two DNA strands line up in opposite directions to each other in antiparallel fashion. The antiparallel strands twist to form a double helix

What is the tertiary structure?

DNA forms more compact three-dimensional structures in cells

What are the 4 stages of DNA replication?

1. Unwinding

2. Priming the leading strand

3. Building the leading strand

4. Priming and building the lagging strand

How are nucleic acids directional?

One end has an unlinked 5’ phosphate group, and the other end has an unlinked 3’ hydroxyl group

Where does replication start?

A replication bubble forms when DNA is being synthesized

What proteins are responsible for opening and stabilizing the double helix?

DNA Helicase, Single-strand DNA-binding proteins, The helicase + topoisomerase

What does DNA helicase do

breaks hydorgen bonds between the two DNA strands to separate them

What do single-strand DNA-binding proteins (SSBPs) do

attach to the separated strands to prevent them from closing

What do the helicase + topoisomerase do

Unzip the double-stranded DNA for replication, making a forked structure called replication fork

What does RNA primase do

generates short strands of RNA that bind to the single-stranded DNA to initiate DNA synthesis by the DNA polymerase

What bonds connect sugar and phosphate components along a DNA strand?

Phosphodiester bonds