What is the beginning phase of meiosis? 1. Please have these Items on your desk. Agenda Science Starters Sheet What is the beginning phase of meiosis? What occurs during this phase? Friday January 27, 2017 Day 2

Table Of Contents 1/27 (Blue) Mitosis/Meiosis Station Work pg 15 1/27 (Purple) DNA Notes pg 16-17

1 DNA The illustration is a ‘model’ of the double helix forming part of a DNA molecule (Slide 14)

DNA stands for deoxyribose nucleic acid 2 DNA stands for deoxyribose nucleic acid This chemical substance is present in the nucleus of all cells in all living organisms DNA controls all the chemical changes which take place in cells The kind of cell which is formed and The kind of organism which is produced , (muscle, blood, nerve etc) is controlled by DNA

DNA is a very large molecule made up of a long chain of sub-units DNA molecule 3 DNA is a very large molecule made up of a long chain of sub-units The sub-units are called nucleotides DNA molecule a sugar called deoxyribose a phosphate group -PO4 and an organic base

Deoxyribose is almost the same as sugar but lacks one oxygen atom 4 Deoxyribose is almost the same as sugar but lacks one oxygen atom represented by the symbol

The most common organic bases are The bases 5 The most common organic bases are Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

Combine to form a nucleotide Nucleotides 6 The deoxyribose, the phosphate and one of the bases Combine to form a nucleotide adenine deoxyribose PO4 It is the phosphate group which gives DNA its acidic properties

Joined nucleotides 7 PO4 sugar-phosphate backbone + bases A molecule of DNA is formed by millions of nucleotides joined together in a long chain

DNA Structure In fact, the DNA usually consists of a double 8 DNA Structure In fact, the DNA usually consists of a double strand of nucleotides The sugar-phosphate chains are on the outside and the strands are held together by chemical bonds between the bases

2-stranded DNA 9 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4