Biology: DNA Structure and Replication

DNA

is a biological molecule that carries the genetic instructions for all cells, located in the nucleus, structure: a double helix

Nucleotide

A compound made up of a phosphate group, a 5-carbon sugar group, and a nitrogenous base

Adenine always pairs with

thymine and has 2 weak hydrogen bonds

Guanine always pairs with

cytosine and has 3 weak hydrogen bonds

Cytosine always pairs with

guanine and has 3 weak hydrogen bonds

Thymine always pairs with

adenine and has 2 weak hydrogen bonds

hydrogen bonds

Bonds between the bases

Chargaff's Rule

AT (apple in the tree) and CG (car in the garage)

DNA Backbone

sugar-phosphate backbone (phosphodiester)

antiparallel

The 2 strands of DNA run in opposite directions, one strand runs from 5' to 3', while the other runs from 3' to 5'

deoxyribose

The sugar group in the nucleotide

ribose

Sugar in RNA

RNA

Single strand, ribose is the sugar, bases: A, U, G, C

Uracil

A base of RNA, instead of thymine

DNA replication

When a cell is ready to divide, it must first copy its DNA. The process of making an identical copy of DNA ensures that each new cell will have the same DNA as the original cell.

Helicase

The start of the DNA replication "unzips" the two strands of DNA, and opens the origin of replication.

DNA polymerase

Adds/builds complementary nucleotides to the growing strands. Adds nucleotides to RNA primer After all nucleotides are added to the complement strand RNA primer is removed. Proofreads the strand before the backbone is finished. Goes from 5' to 3' direction

Primase

Puts primer to help assist the DNA polymerase know where to build

Ligase

Fills in the gaps made from the Okazaki fragments on the lagging strand

Semi Conservative

Two identical DNA molecules are formed, each with an "old" strand and a "new" strand

Watson

the double helix structure of DNA

Crick

identification of the structure of DNA

Franklin

double helix structure of deoxyribonucleic acid + photo 51 (photo to show the structure of DNA)

Explain the principal function of DNA

Contains genetic information, passed onto offspring, and controls the cell's activities

Describe the basic structure of DNA (backbone, rungs, parts of nucleotides, etc.)

Double helix (2 strands), antiparallel, has base pairs, is a long molecule

Compare the structure of DNA with that of RNA.

RNA is usually single-stranded, uracil base instead of thymine, it is shorter than DNA, and broken down quickly

Explain how the DNA molecule maintains a consistent diameter.

It is maintained by the two rings called purine that pair with one ring called pyrimidine, to give equal-length rings on the DNA ladder.