Bio 12 DNA Structure EXAM

DNA (Deoxyribonucleic Acid)

Contains the genetic material of an organism, directs and controls cellular functions, and is the only molecule capable of making an exact copy of itself through DNA replication.

DNA Replication

The process by which DNA makes an exact copy of itself.

Histones

Proteins that DNA wraps around to help package DNA inside the nucleus.

Nucleosomes

DNA wrapped twice around a set of 8 histone proteins. They help compact DNA so it fits inside the nucleus.

Chromatin

Coiled fibers made of packed nucleosomes. This condenses into chromosomes during cell division.

Chromosomes

Highly condensed chromatin formed during cell division.

DNA Structure

DNA consists of two strands of nucleotides twisted into a double helix.

Double Helix

The twisted ladder shape of DNA.

DNA Backbone

The sides of DNA are made of alternating deoxyribose sugars and phosphate groups.

Nitrogen Bases

The four bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G).

Adenine (A)

A purine nitrogen base that always pairs with thymine.

Thymine (T)

A pyrimidine nitrogen base that always pairs with adenine.

Cytosine (C)

A pyrimidine nitrogen base that always pairs with guanine.

Guanine (G)

A purine nitrogen base that always pairs with cytosine.

Complementary Base Pairing

Adenine pairs with thymine, and cytosine pairs with guanine through hydrogen bonds.

Purines

Nitrogen bases with two nitrogen rings. Adenine and Guanine.

Pyrimidines

Nitrogen bases with one nitrogen ring. Cytosine and thymine.

Hydrogen Bonds

Weak bonds between complementary nitrogen bases that hold the two DNA strands together. Billions of these bonds make DNA strong and stable.

Phosphodiester Bonds

Strong covalent bonds that join the phosphate group of one nucleotide to the deoxyribose sugar of the next nucleotide, forming the DNA backbone.

Glycosyl Bonds

Covalent bonds that connect the deoxyribose sugar to a nitrogen base.

Nucleotide

The basic building block of DNA consisting of a phosphate group, deoxyribose sugar, and a nitrogen base.

Polymer

A large molecule made of repeating units. DNA is an example of this because it is made of repeating nucleotides.

5′ End

The end of a DNA strand with a phosphate group attached.

3′ End

The end of a DNA strand with a hydroxyl (-OH) group

Antiparallel

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

Chargaff's Rule

In double-stranded DNA, the amount of adenine equals thymine, and the amount of cytosine equals guanine.