DNA Replication &

Protein Synthesis

Designed by Mr. Gaccione

DNA is located in the nucleus in the form of chromosomes.

If the DNA of one cell is stretched out, it makes a 7 ft. long string.

There are 5 trillion cells in the human body.

If you connected all the DNA together, it would be long enough that it would take light over 10 hours10 hours to travel its length.

• Chromosomes contain a single, long piece of DNA

• A chromosome is about 0.004 mm long • The DNA is about 4 cm long

• This is 10,000x longer than the chromosome • Thus DNA must be wrapped tightly to fit into cells

• Imagine fitting 900 yards (300m) of rope into a backpack.

• The DNA molecule looks like a ladder that has been twisted.

• The DNA molecule is • made from two strands, • twisted together in a • double helix.

• Watson & Crick – • created the double • helix model for DNA.

The Structure of DNADNA is a long molecule made up of repeating units called nucleotides.

Each nucleotide is made up of three parts:

1. phosphate group2. carbon sugar (deoxyribose)3. nitrogen base

Repeating Nucleotides

• The sides of the DNA ladder(backbone) is formed by phosphate and sugar groups.

• The nitrogenous bases are • the rungs of the DNA ladder.

• DNA is 250 million nitrogen bases long.

• RNA is 3000 nitrogen bases long.

• There are four kinds of nitrogenous bases.

• They are divided into two classes:

purines and pyrmidines

•Purines (bigger) – Adenine and Guanine

•Pyrmidines (smaller) – Cytosine and Thymine

Nitrogenous Bases

Chargaff’s Rules• Chargaff discovered how the

nitrogenous bases bond together.

•Adenine always bonds with Thymine Cytosine always bonds with Guanine

DNA

Hydrogen bonding

•The particular order of the nitrogen bases is called the DNA sequence.

•This sequence makes each individual unique.

•An elm tree, eel & an elephant has the same DNA, but what makes them different is the order of the bases.

DNA Sequence

• Each chromosome carries 2,000 genes.

• 23 chromosomes = 30,000 to 40,000 genes

This is known as “The Human Genome”

• Genes are locations on chromosomes that give us our traits.

• Many of these are common to all human beings.

• So, 99.9% of your DNA is identical to everyone else's.

DNA & Genes

• The remaining 0.01% influences the differences between us.– height, hair color and – susceptibility to a particular disease

• Environmental factors, such as lifestyle (smoking and nutrition) also influence the way we look and our susceptibility to disease.

DNA & Genes

• Mutations are caused by mutatgens.Examples of mutagens:

UV rays, smoking & radiation

• Mutations are mistakes in the nitrogen bases or in the DNA sequence.

Mutations

Point Mutation

C

Thymine mutation

• Caused by exposure to UV light.

• 2 adjacent thymine residues become covalently linked.

Mutations• RNA polymerase adds ribonucleotides not

deoxynucleotides

• RNA polymerase does not have the ability to proofread what they transcribe

• RNA will have an error 1 in every 10,000 nucleotides

• DNA will have an error 1 in ten million nucleotides)

DNA Replication DNA replication makes an exact copy of the strand,

complete with 1 old and 1 new strand.

Step 1 DNA unwinds & unzips with the help of DNA polymerase Step 2 Each strand of the parent DNA is used as a

template to make the new daughter strand. Step 3 Free floating nucleotides are added by DNA polymerase.

DNA Replication

C T A C C G G

G A T G G C C T A T

• ･ DNA acts as a “manager” in the process of making proteins.

• ･ DNA is the template or starting sequence that is copied into RNA that is then used to make a protein.

DNA to mRNA to Protein

RNA differs from DNA

1. Ribose is the sugar rather than deoxyribose.

2. Uracil instead of ThymineAdenine, Guanine Cytosine stay the same.

3. Single stranded

Three Different RNAs1. messenger RNA (mRNA) – takes a message

or 3 letter code(codon) from DNA

GUA---UUC---GUU---AGU---UGA

2. ribosomal RNA (rRNA) – meeting place for three RNAs

3. transfer RNA (tRNA) – brings anti-codon & amino acid

Ribosome

Protein Synthesis -2 StepsTranscription & translation

Transcription:First step in protein synthesis

mRNA transcribes a message (code) from DNA

Occurs in the nucleus

Protein Synthesis Transcription

DNA

Cytoplasm

Nucleus

RNA

Transcription

ExportG AAAAAA

Protein Synthesis -Transcription

Step 1 DNA unwinds & unzips with the help of RNA

polymerase

Step 2 Only one strand of the parent DNA is used as a

template to make mRNA.

Step 3Free floating nucleotides are added by RNA

polymerase, making mRNA.

Protein Synthesis-Transcription

Protein Synthesis Transcription

Protein Synthesis -Transcription

aking mR from D template

C U A C C G G A U A

Protein Synthesis -Translation

Translation Goal: to make a protein

Second step in protein synthesis

All three RNAs meet(mRNA, rRNA & tRNA)

Occurs in the cytoplasm

Amino acid

UAC--UUC--GUU--AUG--

--AUG--Amino acid

Anti-codon

tRNA brings anti-codon & amino acid

Protein Synthesis - Translation

Draw and label the boxes, tRNA, mRNA & rRNA

tRNA

mRNA

rRNA

Ribosome

- AUG--UUC--GUU--AGU--UGA 5’

Amino Acid?

Amino Acid?

Amino Acid?

Amino Acid?

Amino Acid?

rRNA & mRNA are in the cytoplasm. Where is tRNA???

Translation

Met Phe Val Ser Stop!

ANTI-CODON?UAC ANTI-

CODON?

ANTI-CODON?

ANTI-CODON?

ANTI-CODON?

AAG CAA UCA ACU

Protein Synthesis -Translation Review

??

?

??

? ?

?

?

? ?

rRNA

mRNA

rRNA

rRNA

tRNAmRNA

mRNA

mRNA

tRNA

tRNA

Amino acid

Protein Synthesis -Translation Review

• Translation is the meeting of all three RNAs (mRNA, rRNA & tRNA).

• It takes place in the cytoplasm. • • The goal is to string together amino acids to

form a protein.

• Proteins make up our skin, blood, muscles, heart, enzymes, stomach lining & intestinal linings.

Protein Synthesis - Key Words

TranscriptionDNA

Double Helix3’-5’ strand 5’-3’ strand

Phosphate GroupDeoxyribose

SugarsRibose sugars

Hydrogen Bonds

RNA polymeraseNucleus

Nuclear poreER

Complementary base pairs

rRNAmRNAtRNA