DNA, RNA, &Protein Synthesis

Chapter 12

DNA-DEOXYRIBONUCLEIC ACID

STRUCTURE:• DOUBLE HELIX (SPIRAL

LADDER)• MADE OF NUCLEOTIDE

SUBUNITS– PHOSPHATE– SUGAR (DEOXYRIBOSE)– NUCLEOTIDE BASE (A,T,C

OR G)

• THE “HANDRAILS” OF THE LADDER ARE THE SUGAR & PHOSPHATE

• THE “STEPS” ARE THE BASES PAIRED UP

All of the following are subunits of a nucleotide except which?

• A. Phosphate

• B. Sugar

• C. Carbohydrate

• D. Base

Which part of the DNA molecule (“ladder”) contains the sugar and

phosphate?

• A. the “steps” of the ladder

• B. Nucleotide bases

• C. Double strands

• D. the “handrails” of the ladder

BASE PAIRING

• The order of nucleotides creates a code– Different for every

living thing– Even identical twins

have some differences in their codes

BASE PAIRING

• DNA IS LIKE THE RECIPE BOOK IN THE CELL FACTORY

– IT IS LOCATED IN THE NUCLEUS (MAIN OFFICE) OF THE CELL.

– IT HAS SPECIFIC INSTRUCTIONS FOR EVERY CELL IN YOUR BODY.

– ONLY THE “PAGES” OR PARTS OF THE INSTRUCTIONS NEEDED BY A PARTICULAR CELL ARE ACTUALLY USED.

EX: THE DNA IN YOUR SKIN CELL HAS ALL OF THE INSTRUCTIONS BUT THE ONLY PART THAT IS USED IS THE INSTRUCTIONS FOR MAKING SKIN.

What is the role (job) of DNA?

• A. making sugars

• B. breaking down sugars

• C. modifying proteins

• D. giving directions to the cell

If a scientist compared the DNA sequence of a human, a dog, and a

tree, she would find the two most similar sequences would be from

the dog and the human.

• True or False?

DNA ReplicationMaking more DNA

• WHEN NEW CELLS OR “FACTORIES” ARE NEEDED, THE DNA IS THE FIRST THING TO BE COPIED. IT OCCURS IN THE FOLLOWING STEPS:

– THE DNA LADDER “UNZIPS”

– FREE NUCLEOTIDES FLOATING IN THE NUCLEUS PAIR UP WITH THEIR COMPLIMENTS (A-T, C-G)

– THIS CONTINUES IN SEVERAL POINTS ALONG THE LADDER UNTIL THE COPYING IS COMPLETE

What ensures that the DNA code is copied correctly each time?

• A. bases pair up A-T, C-G

• B. subunits align

• C. the “ladder” unzips

• D. phosphates and sugars pair up

DNA ReplicationMaking more DNA

• THE 2 NEW LADDERS EACH CONTAIN ONE OLD STRAND AND ONE NEW STRAND.

RNA - Ribonucleic Acid

RNA STRUCTURE:• NUCLEOTIDE SUBUNITS

– PHOSPHATE GROUP– SUGAR (RIBOSE)– NUCLEOTIDE BASE

(A, U, C or G)

• SINGLE STRAND (ONE SIDE OF A LADDER)

RNA – 3 types

FUNCTIONS:• TO CARRY A SINGLE DIRECTION (RECIPE)

TO THE RIBOSOMES (mRNA)

• TO BRING THE AMINO ACIDS (INGREDIENTS) TO THE RIBOSOME ACCORDING TO THE RECIPE (tRNA)

• TO BIND THE AMINO ACIDS (INGREDIENTS) TOGETHER TO MAKE PROTEIN-OR THE CANDY IN OUR FACTORY. (rRNA)

RNA TRANSCRIPTION:copying the DNA code to mRNA

• DNA “UNZIPS”- ONLY THE PORTION NEEDED

• FREE NUCLEOTIDES PAIR WITH THEIR COMPLEMENTS

• ONLY A PORTION OF ONE SIDE OF THE DNA LADDER IS COPIED

• THE MESSENGER RNA PEELS OFF THE DNA TEMPLATE AND LEAVES THE NUCLEUS TO GO TO THE RIBOSOME

Translation:Using mRNA to Make a Protein

• Ribosome “reads” the recipe from the mRNA codon

• tRNA molecules bring the amino acids in the correct order according to the codon – Every 3 bases codes for a

particular amino acid

– Look up the codon on page 303 of textbook to find amino acid

• Amino acid sequence determines the type of protein

Translation:Using mRNA to Make a Protein

Summary:DNA is found in nucleus

mRNA is made in the nucleus from DNA template

mRNA carries the message to the ribosome

Protein is made using mRNA code like a “recipe” and amino acids as “ingredients”

RNA can be found in 3 places. These include all but which of the

following?

• A. ribosomes

• B. cytoplasm

• C. nucleus

• D. vacuoles

Which of the following is a difference between DNA and RNA?• A. DNA has deoxyribose, RNA has ribose

• B. DNA has thymine, RNA has uracil

• C. DNA is double stranded, RNA is single stranded

• D. All of the above are differences between DNA and RNA

Translation:Using mRNA to Make a Protein

A sequence of DNA contains the code:

AAT TCC TGCWhat would be the amino acid

sequence?

1.transcribe: UUA AGG ACG

2.Look up codons on table3. Leu (leucine) Arg (arginine)

Thr (threonine)

What is the amino acid sequence for the DNA strand:

ATG TTA TAT GAG ?

A. TYR ASN ILE LEU

B. MET LEU TYR GLU

C. MET TYR ASN ILE STOP

D. TYR ASN LEU ILE

Mutations• Sometimes a

mistake happens during replication:– The wrong base pairs

up (substitution)

– An extra base is inserted (insertion)

– A base is deleted (deletion)

Mutations• If the mutation occurs

in a portion of DNA that the cell needs, a genetic defect is caused

• If the mutation occurs in a portion of DNA not needed by the particular cell, no effect.