The Molecule of Life

DNA DNA is the molecule of life. All ________

_______ contain DNA. DNA is found in the _________ of cells. DNA contains ________ ______ that

determine ____________ __________.

DNA DNA stands for _______________________. It may

sound gibberish, but the name actually tells us two things:

-  DNA contains ______________ (a ___-carbon sugar) -  DNA is a __________ ________ (molecule made up

of _____________)

Nucleotide !

Nucleotides consist of a sugar molecule attached to a nitrogen base and a phosphate group.

Phosphate

Nitrogen Base

Nucleotides have 3 parts: 1)  ____________ 2)  _________________ 3)  _________________

The Nitrogen Bases

There are 4 possible different nitrogen bases: -__________ -__________ -__________ -__________

These 4 different bases allow for __________

______________

Base-pairing rules

DNA is a __________ ________molecule – the two strands are connected by the nitrogen bases.

_________ can only pair with ________ (and vice versa). _________can only pair with _________ (and vice versa).

C G

T A

Purines vs. Pyrimidines The molecular structure of the 4 bases fall

under two categories: 1)  Purines- _______ _____ structures

- adenine and guanine are _______ 2) Pyrimidines- ________ ______ structures

- thymine and cytosine are ___________

Purines always bond with pyrimidines (as per the base pairing rules).

HINT:&Think OPPOSITES- The BIGGER word is the

smaller molecule; the smaller word is the BIGGER molecule.

Chargaff’s Rule Chargaff's rules states that DNA from any cell should have a _____________________________ _________________(as per the base pairing rules). •  In other words, the amount of _______________

____________ and the amount of____________ ___________________.

Erwin Chargaff developed Chargaff’s rules through careful experimentation. His discoveries ______________ _______________________________________________________.

Chargaff’s Rule Example: If a DNA molecule contains 28% cytosine, we can figure out how much guanine, thymine, and adenine are present in the molecule.

Cytosine

Guanine

Adenine

Thymine

How did we figure out how much guanine is present? ________________________________________________ . How to figure how much adenine and thymine? ____________________________________________________________________________________________________________________________.

Watson and Crick The shape of DNA is very complex.

In ______, James ________and Francis ________ determined the shape of DNA based on ________________.

The Structure of DNA: Discovery

Though Watson and Crick tend to get most of the credit for discovering the structure of DNA, their discovery was more of a __________ completion. •  The work and information of other scientists was

used to determine the structure of DNA, namely __________ __________.

The Structure of DNA: Discovery Rosalind Franklin was a very methodical and esteemed scientist. •  Franklin was offered a position at Kings College in ________

to help _______ ________ perfect ____________________. •  Franklin and Wilkins allegedly did not get along. •  Wilkins showed Watson and Crick Rosalind’s work, namely

her famous “_________”, which _____________________ _________________.

DNA- The Double Helix Watson and Crick discovered that the shape of

DNA was a __________ ________. Double=__________________

Helix= ________ Picture a twisted ladder or staircase.

If DNA is straightened out and flattened, it looks like a ladder. !

The Double Helix

The sides of the ladder are composed of sugar (deoxyribose) molecules and phosphates. This is called the “_________-

_____________________.” The nitrogen bases make

up the rungs (steps) of the ladder.

The two strands of DNA are ____________ to each other at the ________. The bases bond together using __________ ________. Adenine and thymine have ____ hydrogen bonds. Guanine and cytosine have ____ hydrogen bonds.

___________ bonds are the _____________ type of bond.

You might think that DNA

should be strongly held together- but it does need to unzip- and quite often!

DNA comes apart during

_________________.

DNA Replication Recall that DNA is found in the

nucleus of all cells. In order to make more cells (which

you are constantly doing), you must make a copy of your DNA first!

DNA Replication occurs during the

__________ phase of the cell cycle (___________________ ________________).

DNA Replication- Step 1

The first step required in order for DNA to make a copy of itself is to _______ those _________ ____________________.

An __________ called _____ ___________ breaks the hydrogen

bonds and ______ the original _______________ molecule.

DNA Replication- Step 2 Once the DNA strands are

unzipped, the nucleotides are exposed.

The second step involves

another __________ called _____ ______________This enzyme ________________ __________________________________________________________________.

1&

2

1

3

Replication Forks DNA is a very long molecule that must

be tightly coiled and packed into our cells.

If the enzymes had to go from one end

of DNA all the way to the other, it would take too long!

_____________ ________ form at

___________ _______ in the DNA to____________________.

2

Replication fork

3

Two replication forks make replication “__________”.

5’ and 3’ Since DNA is a 3-Dimensional molecule made of linked

nucleotides, it really doesn’t have a “left” or “right”; “up” or “down”.

If we have to refer to DNA’s direction we use ___________ (5 prime and 3 prime).

Recall that deoxyribose is a 5-carbon sugar. These numbers (5,3) are in respect to the ____________________________.

Antiparallel DNA molecules are ________________- meaning the two strands run parallel to one another, but in different directions. (It always looks like one strand is ______________ relative to the other).

During DNA replication,

_________________ READS

the parent molecule in the

________________________.

New _________________

_________________________

(opposite). (How to Remember? When you

READ a book you would read chapters 3 to 5)

Leading and Lagging Daughter Strands

DNA Polymerase moves from 3’ to 5’ One new strand will move continuously _____________ the replication fork- this is known as the ____________________. Because the strands are anti-parallel, the other strand will move _______ from the replication fork- this is the ________________.

Leading and Lagging Daughter Strands

The leading strand has _____________ replication - it goes along _______ the ______________ ________. The lagging strand has __________________ replication- it moves ______________ the replication fork.

Lagging Strand Since the lagging strand is traveling away from the fork, as the fork continues to open up, the lagging strand needs to ________ _____________ to adjust (discontinuous). _______________ _____________ are the short segments of new DNA on the lagging strand.

Replica)on!fork!

Final Product- DNA Replication The _______ ___________of DNA

replication is ______________of DNA (_____________ since each molecule is double stranded).

However, it would not be appropriate

to call the molecules “new”.

DNA Replication is __________________ (semi=_________; conserve= to ________)

Each time DNA is copied, the original DNA molecule is saved. DNA is never destroyed during replication!

Each new molecule ___________________________________________________________________.

!

Self Check Quiz 1.  The letters D.N.A. stand for

___________________________. 2.  DNA is shaped like a _______ _______. 3.  The four nitrogen bases are: adenine, ___________,

_________, ____________. 4.  Adenine always bonds with ____________. 5.  Cytosine always bonds with ____________. 6.  DNA is important because it determines your physical

_______________. 7.  DNA replication is _______- _________________. 8. DNA replicates (circle one) [before | after] cell division. 9. DNA replicates using specific [enzymes |

carbohydrates]. 10. Thymine and cytosine are [purines | pyrimidines]. 11. Nitrogen bases are paired together using [hydrogen |

covalent] bonds.

Why DNA is important: DNA is important because it holds the “recipe”

for making proteins. Your entire body is made out proteins! DNA is your personalized instruction manual

and yours is unique to you (though everyone in this room shares about 99% of the same DNA, that’s what makes us human!)

DNA is very important; it controls the workings of the cell. However, it is _______________________. (Like a mob boss in jail?)

In order to get all of its instructions to the rest of the cell, DNA relies on its trusty sidekick.... !

Ribonucleic Acid

R.N.A. is also a nucleic acid- it is made out of linked nucleotides (like DNA). Recall that nucleotides are made of a sugar, phosphate, and nitrogen base.

DNA vs. RNA

RNA and DNA are very similar, but there are some differences.

First of all, DNA is double stranded, and RNA is __________ ____________. This means that ________ __________________ _________________.

RNA contains 4 nitrogen bases: adenine, guanine, cytosine and __________.

*Thymine is NOT present in RNA.

Uracil is ____________ ___________________________. It essentially takes the place of ____________. !

The last major difference between DNA and RNA is that ________________________ _________________. (Recall DNA contains deoxyribose).

Ribose has one more oxygen atom than deoxyribose.

Ribose Deoxyribose

Recap RNA is single stranded, so it is smaller than

DNA. This means it can leave the nucleus (which DNA cannot).

RNA contains the sugar ribose. RNA has 4 bases: A, T, C, and U. The base

pairing rules are as follows:

C pairs with G pairs with A pairs with U pairs with

NO thymine in RNA

3 Types of RNA

RNA’s job is to help DNA make proteins. DNA must deliver its code to the remainder

of the cell- it relies on 3 molecules: 1)  ________________ (__RNA) 2)  ________________ (__RNA) 3)  _________________(__RNA)

Messenger RNA

mRNA is ________________ to the original strand of ______. mRNA is first created in the _________ and then travels to the ribosomes out in the cytoplasm. mRNA uses the DNA’s _______ (or message) to make ________!

Example) DNA Strand: G G C T T A mRNA strand:

Proteins

Recall that proteins are made up of smaller parts called _________ ______. Another word for protein is “__________”.

Individual DNA codes are called “_________”. The codons correspond to specific amino acids. mRNA also has codons, which are complementary to DNA codons. !

Codons

______________________________________________________________.

Example) DNA codon: cytosine-cytosine-adenine (CCA for short) Each codon codes for one amino acid. This is

where we need RNA’s help.

C&C&

A

DNA Template Strand: A C G T T A G C C mRNA strand: U G C A A U C G G mRNA is always complementary to the

template DNA strand. How many codons are there? What does the other DNA strand look like?

Three DNA codons are transcribed into three mRNA codons. mRNA codons are specific to amino acids.

This is the beginning step of PROTEIN

SYNTHESIS. Protein= well, protein synthesis= to make

DNA Template Strand: A C G T T A G C C mRNA strand: U G C A A U C G G

1)  UGC 2)  AAU 3)  CGG

Which three amino acids do these mRNA codons code for? !

Amino Acids

Though there are only 20 different amino acids, they are sequenced differently and come in different shapes to make for thousands of different proteins.

Protein Synthesis •  A ____ ______ process in which DNA is

_________ into corresponding proteins •  The first process is known as __________ •  The second process is _____________ •  Occurs in the ________and ___________

Transcription Transcription is the first part

of protein synthesis. During transcription, mRNA

is created by __________ the DNA’s code.

Transcription occurs in the

nucleus. (That’s where the DNA is!)

Transcription

During transcription, the ______________________________ temporarily ________ DNA and ____ ___________________ ___________________________ to the growing mRNA strand.

Transcription Recall that mRNA is the messenger. It copies

DNA’s code (or “message”; “instructions”) and it is now responsible for delivering this message to the rest of the cell.

Once the mRNA strand is completed, it leaves

the nucleus (exits via _______________). Transcription is complete. (No protein yet...next stop, the ribosomes!)

Translation Translation is the final step of protein synthesis-

it involves ALL THREE types of RNA (mRNA, tRNA and rRNA).

•  Translation is a process in which the _______

that was ______________ during _________________is _____________

____________________________ (proteins). •  occurs in the cytoplasm, on the

_________________

Ribosomal RNA (rRNA)= a major component of _____________; also ___________________________together to make ________________ (proteins)!

The goal of the 3 types of RNA is to work together to make proteins using the DNA’s instructions!

!!!!

Translation Transfer RNA (tRNA)= helps _________

________ _______ to the corresponding mRNA codons (tRNA is always ____________ to the mRNA strand)

mRNA codons: U G C A A U C G G tRNA anticodons: tRNA bases are referred to as “_______________”

because they are complementary to mRNA codons.

Example) If the ________codon is

______, that would translate to the amino acid _________.

The _______molecule that will deliver leucine to the ribosome has the anticodon ______.

Once the amino acid is delivered, the tRNA releases itself from the ribosome, and leaves to find another amino acid to add to the growing protein chain.!!!!

ANTICODON&

LEUCINE!Translation

tRNA transfers amino acids to the ribosome. The amino acids are attached to the tRNA via a specialized ________ called _____ _______________.

Analogy: tRNA is a librarian; mRNA codons are the book codes; amino acids are the books. tRNA reads the mRNA and fetches the appropriate amino acid.

Label the following: mRNA, tRNA, ribosome, codons,

anti-codons, peptide (protein) chain, amino acid

Puttin’ it all together DNA codes for ___________. Proteins are made during

protein _____________. Transcription occurs in the

__________. The final __________of transcription is an ___________ strand.

Translation occurs on the __________. The final product of translation is a protein.

Codons There are 64 possible codons: 43 = 64 64 codons for 20 amino acids. Can more than one codon specify the same

amino acid?

4 possible bases (A, T, C or G)

3 bases in a codon (triplets)

Start and Stop Signals

Proteins are made up of a very specific sequence of amino acids.

DNA contains “start” and “stop” codons so that the cell knows where to start decoding proteins and where to stop.

The _________ codon= _______ (codes for the amino acid _______________ [MET])

Stop codons=