DNA Structure & Packaging

Terms that are used to describe DNA packaging (slowly gets more condensed).

Histone

structural proteins

Nucleosome

section of DNA that is wrapped around histones

Chromatin

DNA + structural proteins

Chromatid

when a chromosome duplicates (2 chromatids per chromosome)

Centromere

holds chromatids together (middle attachment part)

Chromosome

highly condensed chromatin

Gene

a segment of DNA that codes for a specific protein

What are nucleotides?

multiple repeating subunits

What are the 3 components of DNA?

1. deoxyribose (sugar)

2. phosphate group

3. nitrogenous base

What are the 4 nitrogenous bases in DNA?

• adenine —> A

• thymine —> T

• cytosine —> C

• guanine —> G

Which nitrogenous base is different in RNA?

Thymine is replaced by uracil

The type of bond that joins a sugar and a phosphate group…

… a phosphodiester linkage (makes up the sugar-phosphate backbone)

The type of bond that joins a nitrogenous base to a sugar…

… a glycosidic/glycosyl bond

How many H-bonds are there between A & T?

2 H-bonds

How many H-bonds are there between G & C?

3 H-bonds

Which bases are purines?

adenine & guanine

What bases are pyrimidines?

thymine, cytosine (and uracil in RNA)

How many rings are purines?

2 ring structure

How many rings are pyrimidines?

1 ring

Chargaff’s Rule

The percentage/amount of one base pair (A & G) will always more or less equal its complementary base pair (T & C).

What does antiparallel mean?

The DNA strands run in opposite directions.

• 5’ end aligns with 3’ end

Structure of DNA

double helix

What is the other strand of DNA if the given strand codes:

5’ - ATGCCGTA - 3’

3’ - TACGGCAT - 5’