DNA Structure AS Biology Gnetic control of protein

DNA Structure AS Biology. Gnetic control of protein structure and function

Molecular Genetics u u u the human body is organized into levels organ system organ tissue cells are basic units of life DNA (deoxyribonucleic acid) is the blueprint that tells a cell how to perform cellular processes. AS Biology. Gnetic control of protein structure and function

u What is DNA? u https: //www. youtube. com/watch? v= zwibg. NGe 4 a. Y AS Biology. Gnetic control of protein structure and function

DNA Structure DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix. “twisted ladder” A molecule of DNA is made up of millions of tiny subunits called Nucleotides. AS Biology. Gnetic control of protein structure and function

Structure of a nucleotide A nucleotide is made of 3 components: u 1. A Pentose sugar u This is a 5 carbon sugar u The sugar in DNA is deoxyribose. AS Biology. Gnetic control of protein structure and function

Structure of a nucleotide 2. A Phosphate group u Phosphate groups link the sugar on one nucleotide onto the phosphate of the next nucleotide to make a polynucleotide. u AS Biology. Gnetic control of protein structure and function

Structure of a nucleotide u 3. A Nitogenous base u In DNA the four bases are: – – Thymine Adenine Cytosine Guanine AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

Nitrogenous bases – Two types Pyramidines Purines Thymine - T Cytosine - C Adenine - A Guanine - G AS Biology. Gnetic control of protein structure and function

Purines have a nine-membered double ring and pyrimidines have a six-membered single ring AS Biology. Gnetic control of protein structure and function

Adenine AS Biology. Gnetic control of protein structure and function

Guanine AS Biology. Gnetic control of protein structure and function

Cytosine AS Biology. Gnetic control of protein structure and function

Thymine AS Biology. Gnetic control of protein structure and function

Sugar phosphate bonds (backbone of DNA) u Nucleotides are connected to each other via the phosphate on one nucleotide and the sugar on the next nucleotide AS Biology. Gnetic control of protein structure and function

Base pairing u The Nitrogenous Bases pair up with other bases. For example the bases of one strand of DNA base pair with the bases on the opposite strand of the DNA. AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

Base pairs are held together by Hydrogen bonds u. A T (2 Hydrogen Bonds) u. G C (3 Hydrogen Bonds) u AS Biology. Gnetic control of protein structure and function

The Rule: u Adenine always base pairs with Thymine (2 hydrogen bonds) u Cytosine always base pairs with Guanine. (3 hydrogen bonds) u This is because there is exactly enough room for one purine and one pyrimidine base between the two polynucleotide strands of DNA. AS Biology. Gnetic control of protein structure and function

Complementary base pairing Purines Pyrimidines Adenine Thymine Guanine Cytosine AS Biology. Gnetic control of protein structure and function

Nature of the Genetic Material u 1 - it must contain, in a stable form, information encoding the organism’s structure, function, development and reproduction u 2 - it must replicate accurately so progeny cells have the same genetic makeup u 3 - it must be capable of some variation (mutation) to permit evolution AS Biology. Gnetic control of protein structure and function

Replication of DNA and Chromosomes u Speed of DNA replication: 3, 000 nucleotides/min in human 30, 000 nucleotides/min in E. coli u Accuracy of DNA replication: Very precise (1 error/1, 000, 000 nt) AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

Taylor and co-workers (1957) 3 H-labelled after chromosomes AS Biology. Gnetic control of one further replication protein structure and function in unlabelled media

Meselson and Stahl (1958) AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

A replicating Drosophila chromosome AS Biology. Gnetic control of protein structure and function

Origins initiate replication at different times. AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function

AS Biology. Gnetic control of protein structure and function