DNA STRUCTURE Structure Function Replication DNA Deoxyribonucleic Acid

DNA STRUCTURE Structure, Function, Replication

DNA (Deoxyribonucleic Acid) • DNA is an organism's genetic material. • DNA contains the instructions an organism needs to develop, live and reproduce. • DNA is found in (almost) every cell

Add this to your notes • DNA exists in the form of chromatin. • Chromatin condenses into chromosomes just before a cell divides.

When was the DNA molecule “discovered”? • DNA was first observed by a German biochemist named Frederich Miescher in 1869. • But for many years, researchers did not realize the importance of this molecule.

When was DNA STRUCTURE “discovered”? • It was not until 1953 that James Watson, Francis Crick, Maurice Wilkins and Rosalind Franklin figured out the structure of DNA — a double helix — which they realized could carry biological information. • Watson, Crick and Wilkins were awarded the Nobel Prize in Medicine in 1962 "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material. " • Franklin was not included in the award, although her work was integral to the research. Rosalind Franklin: DNA's unsung hero • https: //www. youtube. com/watch? v=BIP 0 l. Yrdir. I

Ameba Sisters: DNA Structure and Function • https: //www. youtube. com/watch? v=_POd. Wsii 7 AI

DNA Structure • DNA exists in two long stands shaped like a twisted ladder (double helix)

DNA Structure • DNA is made up of repeating units called nucleotides.

Nucleotides Each nucleotides are made up of: • phosphate group, • Pentose sugar molecule (5 carbon sugar), • nitrogenous base

There are FOUR types of Nitrogenous Bases • adenine (A), • thymine (T), • guanine (G) and • cytosine (C).

DNA molecule is shaped like a twisted ladder • The sides of the ladder are made of the sugar and phosphate molecules joined to each other. • The rungs of the ladder are made up of pairs of nitrogenous bases, one from each of the strands.

The nitrogenous bases pair up in the middle: • A only pairs with T • C only pairs with G • The base pairs are held together by hydrogen bonds

Chargaff's Rule (Base Pair Rule): • DNA from any cell should have a 1: 1 ratio of pyrimidine (C, T) and purine (A, G) bases • more specifically, that the amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine.

Check your understanding • How does DNA normally exist in the cell? • What is the name of the repeating units that make up a DNA molecule? • Name the 4 parts of these units. • What is Chargaff's Rule? • Why is DNA called the "Blueprint of life"?

How is DNA related to chromosomes? • Chromosomes exist in pairs • Humans have 23 pairs of chromosomes • When an organism reproduces, copies of its chromosomes (DNA) are transferred to the offspring.

What is a gene? • A gene is a short section of the DNA molecule that contains the instructions to make a specific protein.

Genetic code • It is the sequence of bases is our genetic code that determines what protein is made. • A sequence of bases that code for a protein is called a gene. •

What is a gene? • In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases • An organism’s genome is its complete set of genes

Karyotype A Karyotype is the number and visual appearance of the chromosomes in the cell nuclei of an organism.

The Human Genome Project • Mapped three billion base pairs in the human genome • Aim to identify all the genes in the human genome • Completed in 2001 • The project involved scientists from 18 different countries

Why are proteins important? • Proteins determine our characteristics (traits) and are building components of cellular structures

What is the importance of proteins? • Proteins are molecules that all the cells of the body need in order to work properly: • Proteins determine the characteristics of the organism. Eg. Hair and eye colour. • Some proteins carry out cell functions: enzymes, hormones • Other proteins are parts of cell structures: cell membrane. • Humans have as many as 100 000 proteins.

Where are proteins made? • Proteins are made in the cytoplasm of the cell by ribosomes. • Ribosomes are made in the nucleolus and then move to the cytoplasm.

Extra: DNA The book of you • Ted Ed video • https: //ed. ted. com/lessons/dna-the-book-of-you-joehanson

Homework • DNA Structure WS

DNA • DNA is an organism’s genetic material that contains all the instructions for the development and function of living things • Special sequences of DNA that contain instructions to make a protein is called a gene. • DNA is in every single cell that has a nucleus.