DNADNA

Deoxyribonucleic acidDeoxyribonucleic acidEncodes instructions for Encodes instructions for making many other making many other molecules necessary for molecules necessary for lifelife

I. Structure of DNA

• Long molecule made up of repeating units called Nucleotides.

NucleotideNucleotide 3 parts3 parts

> 5 carbon sugar > 5 carbon sugar (deoxyribose or pentose)(deoxyribose or pentose)

> Phosphate group> Phosphate group

> Nitrogeneous base> Nitrogeneous base

Nitrogen Bases

Purines

Adenine (A)

Guanine (G)

Pyrimidines

Cytosine (C)

Thymine (T)

Chargaff’s Rule

• The amount of purines equals the amount of pyrimidines.

• Adenine pairs with Thymine

• Cytosine pairs with Guanine

• This is known as base pairing. The bases are held together by hydrogen bonds

DNA research

• Rosalind Franklin

- used x-ray diffraction to get information about the structure of DNA

- x-shaped and twisted

Watson and CrickWatson and Crick

- figured out the DNA - figured out the DNA molecule was a double helix molecule was a double helix (twisted ladder)(twisted ladder)

- sides were held together by - sides were held together by hydrogen bondshydrogen bonds

II. Compare DNA to RNA

DNA Sugar is deoxyribose (pentose) Nitrogen bases are Adenine, Cytosine,

Guanine, & Thymine 2 strands Instructions that control the cell’s

activities (architect)

RNA

Sugar is ribose Has uracil instead of thymine 1 strand Takes the instructions from DNA and

makes proteins

DNA Replication

Process by which DNA makes copies of itself

STEPS:1. Double helix unwinds2. DNA polymerase moves along the

separated parent strand, matching the bases on each parent strand to a new complementary strand.

Practice

Transcription• Manufacture of mRNA.

• Process of transferring information from a strand of DNA to a strand of RNA

• Messenger ribonucleic acid (mRNA) is a molecule of RNA encoding a chemical "blueprint" for a protein product. mRNA is transcribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes.

• In mRNA as in DNA, genetic information is encoded in the sequence of four nucleotides arranged into codons of three bases each. Each codon encodes for a specific amino acid, except the stop codons that terminate protein synthesis.

Practice

Translation

• Takes place on ribosomes

• Ribosomes synthesize (make) proteins

• Variations of the nitrogen bases determines the composition and manufacture of proteins --- this is called protein synthesis

Practice p. 303

3 types of RNA are involved in carrying out the instructions for protein synthsis

• Messenger RNA (mRNA) carries the coded instructions for protein

synthesis from the DNA in the nucleus to the ribosomes

• Transfer RNA (tRNA) brings the amino acids to the ribosome in the

correct order so that they can be built into the new protein

• Ribosomal RNA (rRNA) along with several proteins, this makes up the

structure of a ribosome

Relate changes in DNA instructions to cause mutations

• A change in the sequence of nucleotides is called a gene mutation (point mutation)

• Mutations produces a variation that improves the function of an organism

• These variations can contribute to the adaptation of a species to its environment or could be lethal

• Mutagens- factors in the environment that cause mutations to occur.

Types of mutationsDeletion

G ----- C

C -----

T ----- A

T ----- A

A ----- U

Or G C T T A

C A A U

Addition

G --- C

C --- G

T --- A

A --- U

G--- C

--- T or

G C T A G

C G A U C T

• Substitution

G --- C

C --- G

T --- C

T --- A

A --- U

G --- C

Inversion

• (think of math and inverting fractions--- flipping them)

G C T T A G A C C (mRNA) A G C A U C U G GOr A C T T C G (DNA) T C A T C G

DNA Sentences• Choose a card• Write the “sentence” on your paper• Replicate the “sentence” (A matches with T and

C matches with G)• Transcribe the new “sentence” (A matches with

U, T matches with A, G and C match)• Break into codons (3 bases)• Walk around the room and find the correct

codon• Flip the card up and write the anticodon down. • You should have created a sentence with a start

and stop codon.