Biology Blueprint Of Life section 4

• A sugar
• A phosphate
• A nitrogen base

An organised structure of DNA and protein

A unique triplet code

The production of 2 identical double stranded molecules of DNA from an original double helix molecule

• DNA double helix unwinds 
• Enzyme called helicase causes the DNA to progressively unwind

• DNA unzips (2 strands separate)
• -Weak hydrogen bonds between complementary bases break     

-Exposure of nucleotide bases

Nucleotides are added to each single stand

• Enzyme called DNA polymerase picks up nucleotides and slots them to
• complementary base partner

• o   Replication ensures that the
• genetic code of a cell is passed to each new daughter cell that arises from it

• o   An exact replica/copy is needed
• so that the new cells have the same, distinctive message that the original cell
• had

o   Genetic material is transmitted

-From one cell to another during mitosis: growth, repair, maintenance

-From one generation to another in meiosis: sexual reproduction

• Nucleic acid
• single stranded
• has uracil(U) instead of Thymine(T)

(Messenger RNA)

A type of RNA

Single stranded not twisted into helix

• Function – intermediate molecule that carries information from DNA to
• ribosome in cytoplasm

• (Transfer RNA)
• A type of RNA
• Occurs in cytoplasm

• A type of RNA
• Forms a structural part of the ribosome

When the code on a DNA strand is written across onto a strand of mRNA

Part of the DNA in the nucleus unzips as it would if it were about to duplicate

RNA nucleotides pair up with the nitrogen bases on the exposed strands of DNA

• Base pairing in transcription
• U-A
• A-T
• G-C
• C-G

mRNA carries the coded message from DNA into the cytoplasm. The message then has to be changed into another 'language' or translated, to be able to make polypeptide chains.

• mRNA attaches to a ribosome
• mRNA codons match with tRNA anticodons
• tRNA brings an amino acid to a ribosome
• A polypeptide is built as amino acids join together at the ribosome

A large complex macromolecule made up of one or more long chains called polypeptides

• The overall structure of protein
• Arrangement of amino acids determines configuration of protein

• A change in genetic material- change in the sequence of nucleotides in DNA
• Most are harmful
• 2 types: Large scale mutations & point mutations

Also known as chromosomal mutations

-These mutations involve changes to parts,whole or set of chromosomes

e.g. Down syndrome

• These mutations are chemical changes in one or a few base pairs so that the allele of a gene changes 
• Can lead to production of an abnormal protein

Chemicals or radiation that increase the likelihood of a mutation occuring

The rate of mutation is directly proportional to the dose received and length of exposure

Chemical mutagens: ingested chemicals (smoking), irritants/poisons

Biological mutagens: viruses

Mutagenic radiation: ionising radiation, ultra-violet (sunlight, tanning salon)

• Examples:
• Marie Curie- exposed to large amounts of radiation due to research-developed many illnesses and died to leukimea

Survivors of Hiroshima suffer physical mutations

Theory of punctuate equilibrium proposes that evolution occurs in short bursts of rapid change, followed by long periods of stability within population

-Put forward by Stephen Jay Gould and Niles Eldridge based on fossil evidence

-Differs from Darwins theory of gradualism

• -Suggested that if evolution was gradual, there would be fossil remains to
• show these ongoing changes