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Psychology Fossils and Evolution Global Systems DNA and Inheritance Topics Covered Fossils and Evolution Psychology Global Systems

1.1 DNA the molecule (page 2) DNA and Inheritance 1.1 DNA the molecule (page 2)

Introduction

DNA DNA stands for Deoxyribonucleic acid Found in the nucleus of cells. It determines the characteristics of living things. For example, hair colour, eye colour, bone structure, height. They are instructions for making an animal or plant. Ladder-like structure called a double helix. A molecule of DNA is made up of millions of tiny subunits called nucleotides

Nucleotides

Nucleotides Each nucleotide consists of: Sugar Phosphate group Pentose sugar Nitrogenous base Nucleotides Phosphate Sugar Nitrogenous Base

DNA Structure The phosphate and sugar form the backbone of the DNA molecule The bases form the “rungs” There are four types of nitrogenous bases: Adenine (A) Thymine (T) Guanine (G) Cytosine (C) Each base will only bond with one other specific base (Nitrogenous base pairing) C and G always pair together and T and A

Complementary Base Pairing The order of one strand determines the order of the other. This is known as the complementary base pairing. The sequence of these nitrogen bases along the strands of DNA is the basis for all inherited characteristics. Original Sequence Complementary Sequence

Nitrogenous base pairing Each base will only bond with one other specific base. Cytosine and Guanine Thymine and Adenine That means, if there are 50 Cytosine's in a DNA molecule, there will also be 50 Guanines – as they come as a pair! Nitrogenous base pairing

Modelling DNA activity Your task is to construct a DNA molecule Insure you label All parts of the DNA molecule including: Nucleotide Hydrogen Bond DNA backbone Original and Complementary sequence *hint* there should be 12 labels in total Answer the following questions State the base pairing rule Compare you model to others in the class. Are they the same? Describe the similarities and differences Calculate the number of different variations of single DNA Strands that can be made using only the 10 bases you started off with

Prac #1 -Extracting DNA from peas The following website is an useful resource to help answer the discussion questions http://learn.genetics.utah.edu/content/labs/extraction/howto/

What is DNA?

The Genetic Code Each strand of DNA contains thousands of sequences of bases A, T, G and C This long sequence of bases is read in sets of three. Each set of three is called a codon

There are 20 amino acids that can be used to make protein The body can only make 11 amino acids. The others are too slow to synthesis therefore must be obtained through our diet. Making a protein

The sequence of Amino Acids in a protein that determines its function. The shape of the protein depends on its primary structure, which then determines the proteins properties and functions Primary Structure

Roles of Proteins Some proteins are enzymes (speed up reactions) Eg: digestive system Act as messengers between cells Make up cellular components such as muscle, hair and nails Act as ‘gatekeepers ‘ which allow substances to enter and leave cells Produce haemoglobin which transports oxygen to our cells. Also involved in producing insulin which controls our blood sugar levels.

Enzymes: speed up chemical reactions Enzymes of the digestive system Enzymes: speed up chemical reactions

This diagram shows a cross section of four plasma membrane proteins performing different functions as gate keepers

Haemoglobin: transports oxygen to our cells

Insulin: controls blood sugar levels

DNA to Protein

How to make a protein? Step 1: DNA is copied into mRNA The DNA triplets are COMPLEMENTARY to a group of 3 RNA bases, known as a codon Cytosine (C) still pairs with Guanine (G) Adenine (A) pairs with Uracil (U). Eg. DNA: CAT TAC GTA GAA GTC CCA TAA mRNA: GUA AUG CAU CUU CAG GGU AUU

How to make a protein? Step 2: mRNA is used to read the codon chart. Three bases in a mRNA sequence is called a codon. Each codon is associated with an amino acid You will use a codon chart to make this match Abbreviate each amino acid (use first three letters) mRNA: GUA AUG CAU CUU CAG GGU AUU Amino acid: val met his leu glu gly iso How to make a protein?

A codon chart is used to determine the amino acid sequence of a protein There are 64 different codons and form these 20 different amino acids codes for 1000s if proteins. The Codon Chart

The Codon Chart