II. ReplicationII. Replication

- The process of DNA making - The process of DNA making a copy of itselfa copy of itself

Steps for ReplicationSteps for Replication

1. 1. DNA helicaseDNA helicase (enzyme) – breaks hydrogen (enzyme) – breaks hydrogen bonds between bases separating the 2 strandsbonds between bases separating the 2 strands

2. The complimentary bases are brought to the 2. The complimentary bases are brought to the single strandsingle strand

3. 3. DNA polymeraseDNA polymerase connects the new DNA connects the new DNA strand with the old and rezips the moleculestrand with the old and rezips the molecule

DNA ReplicationDNA Replication

T --T -- A – T -- A A – T -- A

A --A -- T – A -- T T – A -- T

G --G -- C – G -- C C – G -- C

A --A -- T – A -- T T – A -- T

G --G -- C – G -- C C – G -- C

C --C -- G – C -- G G – C -- G

T -- A – T -- AT -- A – T -- A

T --T -- A – T -- A A – T -- A

DNA helicase

new old oldnew

DNA polymerase

DNA polymerase

ReviewReview

1.The making of more DNA is called ?1.The making of more DNA is called ?

2. Which enzyme is used first in the making of more DNA – DNA 2. Which enzyme is used first in the making of more DNA – DNA polymerase or DNA helicase ?polymerase or DNA helicase ?

3. This enzyme is like a glue – putting the base pairs back together.3. This enzyme is like a glue – putting the base pairs back together.

4. Replicate this strand of DNA4. Replicate this strand of DNA G – CG – C

A – TA – T

C – GC – G

T – AT – A

T – AT – A

5. How would you describe the shape of DNA ?5. How would you describe the shape of DNA ?

III. RNAIII. RNA - - ribonucleic acidribonucleic acid

- function : makes proteins- function : makes proteinsA.A. Differences between DNA and RNADifferences between DNA and RNA DNADNA RNARNA 2 strands2 strands 1 strand1 strand deoxyribose sugardeoxyribose sugar ribose sugarribose sugar

thymine basethymine base uracil baseuracil baseB. 3 types of RNAB. 3 types of RNA 1. 1. messenger RNA (mRNA)messenger RNA (mRNA)

- straight strand- straight strand- takes information from DNA in nucleus to the ribosome to make - takes information from DNA in nucleus to the ribosome to make proteinsproteins

2. 2. transfer RNA (tRNA)transfer RNA (tRNA) - folded strand- folded strand

- 20 different kinds- 20 different kinds- brings amino acid to ribosome to make proteins- brings amino acid to ribosome to make proteins

3. 3. ribosomal RNA (rRNA)ribosomal RNA (rRNA) - round- round - makes ribosomes- makes ribosomes

C. C. Transcription –making of RNA from DNA

• Done in the nucleus then travels to ribosomes inDone in the nucleus then travels to ribosomes in

cytoplasmcytoplasm

• Uses Uses RNA polymeraseRNA polymerase (enzyme) to break bonds (enzyme) to break bonds betweenbetween

bases separating the 2 strands of DNAbases separating the 2 strands of DNA

DNA strand

C – G

T – A

A – T

T – A

T – A

G – C

A - T

mRNA

C

U

A

U

U

G

A

G

A

U

A

A

C

U

mRNA

ReviewReview

1. What are the 3 types of RNA. 1. What are the 3 types of RNA.

2. Give 3 differences between RNA and DNA.2. Give 3 differences between RNA and DNA.

3. The process of making more DNA is called ________ while 3. The process of making more DNA is called ________ while the making of RNA is __________.the making of RNA is __________.

4. How does a cell know it is making RNA from DNA instead of 4. How does a cell know it is making RNA from DNA instead of making more DNA from DNA ?making more DNA from DNA ?

5. Change the following DNA strand into mRNA5. Change the following DNA strand into mRNA

T-T-A-A-G-C-G-A-T-CT-T-A-A-G-C-G-A-T-C

6. RNA is used in the making of ___________.6. RNA is used in the making of ___________.

7. There are 20 different kinds of this type of RNA.7. There are 20 different kinds of this type of RNA.

III. Protein SynthesisIII. Protein Synthesis the making of proteins using information coded from DNA and the making of proteins using information coded from DNA and carried out by RNA.carried out by RNA.

• A. Amino AcidsA. Amino Acids

- basic building blocks of proteins- basic building blocks of proteins

- 20 different ones- 20 different ones

- joined together by peptide bonds- joined together by peptide bonds

- carried by tRNA- carried by tRNA

• B. B. CodonCodon – 3 bases in a row within a mRNA strand – 3 bases in a row within a mRNA strand

that call for a specific anticodon thatthat call for a specific anticodon that

codes for a specific amino acid.codes for a specific amino acid.

*** *** AUGAUG is the universal start codon for all is the universal start codon for all

organisms.organisms.

C.C. Translation Translation – process of making proteins – process of making proteins by using mRNAby using mRNA

A U G G C G U U G G C U

U A C C G C A A C C G A

tRNA

Start alanine leucine alanine amino acids

mRNA

occurs in ribosomes

codon

anticodon

ReviewReview

1.1. Change the following DNA strand into mRNA. Change the following DNA strand into mRNA. A-T-C-G-C-G-T-T-A-G-C-T A-T-C-G-C-G-T-T-A-G-C-T

2.2. Assemble the protein from the mRNAAssemble the protein from the mRNA

sequence from your answer to #1.sequence from your answer to #1.

**errors do occur but rarely – about 1 **errors do occur but rarely – about 1 per billion nucleotidesper billion nucleotides

• Factors that damage DNAFactors that damage DNA

a. excessive body heat (fever)a. excessive body heat (fever)

b. radiation (UV & X-rays)b. radiation (UV & X-rays)

c. chemicals (carcinogens)c. chemicals (carcinogens)

-- DNA has proofreading enzymes -- DNA has proofreading enzymes that constantly try and repair that constantly try and repair mistakes in base pairing.mistakes in base pairing.

• Human Genome ProjectHuman Genome Project

- project with scientist all over the - project with scientist all over the world to map out the sequence and world to map out the sequence and location of all traits (genes) on all location of all traits (genes) on all human chromosomes. Humans have human chromosomes. Humans have 3.5 billion base pairs per sex cell.3.5 billion base pairs per sex cell.