From DNA to Proteins Replication Chapter 8 From DNA to Proteins Replication

The Components and Structure of DNA DNA is a long molecule made up of nucleotides. Each nucleotide has three parts. 5-carbon sugar called deoxyribose a phosphate group one of four nitrogenous bases

Two of the nitrogenous bases are adenine and guanine and they belong to the purine group. They have 2 rings in their structure. The other two nitrogenous bases are thymine and cytosine. They belong to the pyrimidine group and have only one ring in its structure.

The backbone of the DNA chain is formed by sugar and phosphates of each nucleotide. The nitrogenous bases stick out sideways but facing inward and any sequence of bases is possible.

Chargaff’s Rules – An American biochemist, Erwin Chargaff, discovered the percentages of guanine and cytosine to be almost equal and the same was true for adenine and thymine.

Adenine pairs with thymine and guanine pairs with cytosine. He concluded that A=T, and C=G. From that he was given credit for Chargaff’s Rules. Adenine pairs with thymine and guanine pairs with cytosine.

The double helix is made up of a chain of nucleotides The double helix is made up of a chain of nucleotides. The two strands are held together by hydrogen bonds between adenine and thymine and between guanine and cytosine. Scientists realized that this principal is base pairing explained by Chargaff’s rules.

What happens during DNA replication? Prokaryotic (ex. bacteria) cells lack a nucleus (and many other organelles) Their DNA molecules are located in the cytoplasm (not in the nucleus-like eukaryotic cells) Most have single, circular DNA (located in ONE chromosome)

Eukaryotic cells have DNA that is more complicated More than 1000X more DNA than prokaryotes DNA Is found in nucleus (not in cytoplasm-like prokaryotic cells) Number of chromosomes differs from one species to the next # of chromosomes Humans—46, Fruit flies—8, Giant sequoia tree—22

DNA Replication DNA molecules contain everything they need (within themselves) to replicate The parent (original) strand is used to make the new (replicated) strand Strands are made by base pairing (AT, CG)

DNA Replication

Base pairing: Ex: A T C C A G G T G DNA copy:

Duplicating DNA strands Replication - the duplication/copying of DNA During DNA replication, the DNA molecule separates into two strands It then produces two new complementary strands (following the rules of base pairing) Each strand of DNA serves as a template (model) for the new strand

DNA replication results in two DNA molecules Each DNA molecule has: One new strand One original strand

What do you know??? Name the parts of a nucleotide List the bases in DNA What does DNA stand for? When does replication take place? What enzymes are involved in replication? What direction are the strands copied? What is the result of replication?