Nucleic acids  Links to G.C.S.E  D.N.A, genes, chromosomes  Bonding

State that DNA is a polynucleotide, usually double- stranded, made up of nucleotides containing the bases adenine, thymine, cytosine and guanine. State that DNA is a polynucleotide, usually double- stranded, made up of nucleotides containing the bases adenine, thymine, cytosine and guanine. State that RNA is a polynucleotide, usually single- stranded, made up of nucleotides containing the bases adenine, uracil, cytosine and guanine. State that RNA is a polynucleotide, usually single- stranded, made up of nucleotides containing the bases adenine, uracil, cytosine and guanine. © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

Key definition  Nucleotides are the monomers of all nucleic acids. Each nucleotide is formed by bonding together -a phosphate group, -a sugar molecule (ribose/ deoxyribose) -an organic nitrogenous base (

A single nucleotide © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

Sugar group

Structure diagrams of phosphate, ribose and deoxyribose sugars © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

Three nucleotides joined together © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

Organic/ nitrogenous bases There are 5 possible nitrogenous bases, the 4 in DNA are: Purine (double) Pyrimidines (single) -Adenine-Thymine -Guanine-Cytosine The 4 in RNA are: -Adenine-Uracil (similar to thymine) -Guanine-Cytosine

Purine and pyrimidine molecules © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

Extracting DNA

Uses of DNA extraction  Genetic testing

 Body identification

 Analysis of forensic evidence

 Study genes involved in disease such as cancer

State that DNA is a double-stranded polynucleotide. State that DNA is a double-stranded polynucleotide. Describe how a DNA molecule is formed by hydrogen bonding between complementary base pairs on two antiparallel DNA strands. Describe how a DNA molecule is formed by hydrogen bonding between complementary base pairs on two antiparallel DNA strands. Explain how twisting of the DNA molecule produces the double helix shape. Explain how twisting of the DNA molecule produces the double helix shape. Outline how DNA replicates semi-conservatively, with reference to the role of DNA polymerase. Outline how DNA replicates semi-conservatively, with reference to the role of DNA polymerase. © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

Key definition  DNA is a stable polynucleotide molecule. It acts as an information store because the bases projecting from the backbone act as a coded sequence. Organisms differ in their DNA only because they possess different sequences of bases in the DNA

Part of a DNA part molecule © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

A-T, C-G and number of hydrogen bonds © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

A double helix © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

Replication  Takes place during Interphase of the cell cycle  Chromosomes make copies of themselves  DNA is unwound and hydrogen bonds between nitrogenous bases are separated by ‘helicase’ enzymes (like undoing a zip!)  Free DNA nucleotides are hydrogen bonded onto the exposed bases according to base pairing rules by DNA polymerase enzymes  Covalent bonds are formed from the phosphate of one nucleotide and the sugar of the next to seal the backbone.  This continues along the molecule until 2 new double helices are formed, each an exact replica of the original  This is known as semi conservative since each strand contains one strand from the original and one new strand.

DNA replication © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

Structure and function of DNA  The sequence of bases is an example of information storage in the form of codes for proteins.  Long molecules mean a lot of information can be stored.  Base pairing allows for replication.  The double helix gives great stability.  Hydrogen bonds allow for unzipping during copying.

State that a gene is a sequence of DNA nucleotides that codes for a polypeptide. State that a gene is a sequence of DNA nucleotides that codes for a polypeptide. Outline the roles of DNA and RNA in the cells of living organisms. Outline the roles of DNA and RNA in the cells of living organisms. Describe the processes of TRANSCRIPTION and TRANSLATION Describe the processes of TRANSCRIPTION and TRANSLATION © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

RNA RNA is structurally different to DNA  The sugar molecule that makes up the nucleotides is RIBOSE  The nitrogenous base URACIL (U) is found instead of the organic base THYMINE (T)  The polynucleotide is usually single stranded  3 forms exist

RNA types and functions © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

Key definition  A GENE is a length of DNA (part of a DNA molecule) that codes for one or more polypeptides. Each gene occupies a specific place or LOCUS on a chromosome.  Different versions of the same gene are called ALLELES

Making proteins  The sequence coding for a particular protein is exposed by splitting hydrogen bonds between the base pairs  RNA nucleotides form a complementary strand called mRNA (messenger) a copy of the original DNA (TRANSCRIPTION)  The mRNA peels away and leaves the nucleus through a nuclear pore and attaches to a ribosome  tRNA (transfer) brings amino acids to the ribosome in the correct order according to the base sequence on the mRNA (TRANSLATION)  The amino acids are then joined by peptide bonds to give the primary structure (which then gives rise to the secondary and tertiary structures)

Overview of protein synthesis © Pearson Education Ltd 2008 This document may have been altered from the original Week 17

Key definitions TRANSCRIPTION  The cells machinery copies the gene sequence into mRNA (messenger) TRANSLATION  The mRNA (gene sequence) is read by a ribosome and translated into an amino acid sequence  The ribosome reads 3 at a time, each group or CODON corresponds to an amino acid  Ribosomes know to start at AUG and stop at UAA, UGA and UAG (stop codons)