Basic DNA Structure

Question 1

What is Heterochromatin?

Answer 1

Densely packed chromatin that doesn’t allow machinery for replication or transcription to access DNA.

Stains darkly.

Question 2

What is Euchromatin?

Answer 2

Loosely packed chromatin which allows transcription and replication machinery to access DNA.

Stains lighter than heterochromatin.

Question 3

What is a nucleosome?

Answer 3

DNA coiled around a Histone (protein)

Question 4

Why is DNA packing important?

Answer 4

Allows a large amount of DNA to fit in each of our cells.

Determines which genes are expressed.

Question 5

How is DNA packaged into chromosomes?

Answer 5

Nucleosomes (form beads on string)
Coiled into Solenoid
Super Coiled into Chromosome

Question 6

What is a Genome?

Answer 6

A persons entire DNA sequence.

Question 7

What’s the difference between a Nucleotide and a Nucleoside?

Answer 7

Nucleosides lack a phosphate group.

Question 8

What’s the difference between Ribose and Deoxyribose?

Answer 8

Deoxyribose lacks the hydroxyl (OH) group on carbon 2.

Question 9

What are Purines and Pyrimidines?

Answer 9

Purine has 2 rings (A and G)

Pyrimidines have 1 ring (T and C)

Question 10

How are bases complementary to each other?

Answer 10

Bases have dipoles/ are polar molecules and can form hydrogen bonds in certain positions.

Question 11

How is a DNA strand polar?

Answer 11

DNA goes 5’ to 3’

5’ is a negatively charged phosphate group attached to the 5th carbon on the pentose sugar.

3’ is the hydroxyl group on the pentose sugar.