Vocabulary Key Terms

• DNA• DNA replication• Codon• Intron• Exon• Translation• Central Dogma• Transcription• RNA

• mRNA• tRNA• Anticodon• Genes• Nucleotide• Nitrogen base• Amino Acids (AA)

Where in the cell are we looking at?

5a. Know the general structures and functions of DNA, RNA &

protein.

12—1 The Components and Structure of DNA

• What is the overall structure of the DNA molecule?

• The Components and Structure of DNA• DNA is made up of ______________________. • A nucleotide is a monomer of nucleic acids made

up of a five-carbon sugar called ________________, a phosphate group, and a nitrogenous base.

The Components and Structure of DNA

• There are ______ kinds of bases in in DNA:

• adenine• guanine • cytosine• thymine

The Components and Structure of DNA

• The backbone of a DNA chain is formed by ______________ and _______________ groups of each nucleotide.

• The nucleotides can be joined together in any order.

The Components and Structure of DNA

• Chargaff's Rules– Erwin Chargaff discovered that:

• The percentages of _________________ [G] and _____________________ [C] bases are almost equal in any sample of DNA.

• The percentages of ________________ [A] and __________________ [T] bases are almost equal in any sample of DNA.

The Components and Structure of DNA

– X-Ray Evidence • ______________________

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

• She aimed an X-ray beam at concentrated DNA samples and recorded the scattering pattern of the X-rays on film.

The Components and Structure of DNA

• The Double Helix 

– Using clues from Franklin’s pattern, James Watson and Francis Crick built a model that explained how DNA carried information and could be copied.

– Watson and Crick's model of DNA was a ___________ _____________ in which _____ strands were wound around each other.

Who Discovered the DNA molecule?

• Discovery of DNA:– ___________:

Proposed that DNA is made of 2 chains of nucleotides joined together by the nitrogen bases

– Double Helix: DNA composed of 2 strands twisted together

James Watson & Francis Crick

The Components and Structure of DNA• DNA Double Helix

The Components and Structure of DNA

• Watson and Crick discovered that ____________________ bonds can form only between certain base pairs—adenine and thymine, and guanine and cytosine.

• This principle is called ________________.

From DNA to Protein

• Why is DNA Important?– All of the characteristics that you have are

affected by the _____________ that you have in your cells.

– Controls the color of your eyes, hair, or if you can digest milk.

– ______________ the order of the amino acids Δ’s the kind protein made.

From DNA to Protein• RNA: _____________________ Acid

– a nucleic acid – single stranded– Sugar in RNA is ribose– Instead of Thyamine, Uracil (U) – (A)

H

Three Types of RNA

• Help to build proteins– Messenger RNA (___________): brings info from

the DNA in the nucleus to the cell’s factory floor, the cytoplasm.

– Ribosomal RNA (_________): clamp onto the mRNA and use its info to assemble the amino acids in the correct order

– Transfer RNA (___________): transports amino acids to the ribosome to be assembled into protein

RNA Facts

• RNA exists in many structural forms – mRNA: serves as a __________ during

protein synthesis– tRNA– rRNA

DNA vs. RNA

• Deoxyribose sugar• Adenine• Guanine• Cytosine• ______________• 2 strands

• Ribose sugar• Adenine• Guanine• Cytosine• ___________• One Strand

Proteins

• Proteins are ________________ composed of amino acid ______________.

• Different types of proteins function as enzymes and transport molecules, hormones, structural components of cells, & antibodies that fight infection.

1d. Know the central dogma of molecular biology outlines the

flow of information from transcription of ribonucleic acid

(RNA) in the nucleus to translation of proteins on

ribosomes in the cytoplasm.

12-2 Chromosomes and DNA Replication

• 12–2 Chromosomes and DNA Replication

DNA and Chromosomes

• DNA and Chromosomes– In prokaryotic cells, DNA is located in the

__________________.– Most __________________ have a single

DNA molecule containing nearly all of the cell’s genetic information.

DNA and Chromosomes

Chromosome

E. Coli Bacterium

Bases on the Chromosomes

DNA and Chromosomes

• Many eukaryotes have ________ times the amount of DNA as prokaryotes.

• Eukaryotic DNA is located in the cell ______________ inside chromosomes.

• The number of chromosomes varies widely from one species to the next.

DNA and Chromosomes

– Chromosome Structure• Eukaryotic chromosomes contain DNA and

protein, tightly packed together to form _______________.

• Chromatin consists of DNA tightly coiled around proteins called ______________________.

• DNA and histone molecules form nucleosomes. • Nucleosomes pack together, forming a thick fiber.

DNA and Chromosomes– Eukaryotic Chromosome Structure

Chromosome

Supercoils

Nucleosome

DNA double helix

Histones

Coils

DNA Replication

• What happens during DNA replication?– DNA Replication

• Each strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing.

• In most prokaryotes, DNA replication begins at a single point and continues in two directions.

DNA Replication

• In eukaryotic chromosomes, DNA replication occurs at hundreds of places. Replication proceeds in both directions until each chromosome is completely copied.

• The sites where separation and replication occur are called ____________________.

DNA Replication

• Duplicating DNA – Before a cell divides, it duplicates its DNA in a

process called ____________________. – Replication ensures that each resulting cell will have a

complete set of DNA.

• During DNA replication, the DNA molecule separates into ______ strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template for the new strand.

DNA Replication

Nitrogen Bases

Replication Fork

DNA Polymerase

Replication Fork

Original strandNew Strand

Growth

Growth

DNA Replication

• How Replication Occurs– DNA replication is carried out by enzymes that “unzip”

a molecule of DNA.– Hydrogen bonds between base pairs are broken and

the two strands of DNA unwind.

• The principal enzyme involved in DNA replication is _______________________.

• DNA polymerase joins individual nucleotides to produce a DNA molecule and then “proofreads” each new DNA strand.

DNA Replication

1. __________________ breaks up the hydrogen(H+) bonds between the nitrogen bases that holds the 2 strands together—unzips the DNA molecule

2. Free floating _______________ bond to the single strands by base pairing

3. Another _______________ bonds these new nucleotides into a chain

DNA Replication4. This process continues until the entire

molecule has been unzipped and replicated.

5. Each new strand formed is a _________________ of the original, or parent, strands.

6. The result is the formation of two DNA molecules, each of which is __________________ to the original DNA molecule.

12-3 RNA and Protein Synthesis

• 12–3 RNA and Protein Synthesis

12–3 RNA and Protein Synthesis

• _______________ are coded DNA instructions that control the production of proteins.

• Genetic messages can be decoded by copying part of the nucleotide sequence from DNA into RNA.

• _______________ contains coded information for making proteins.

The Structure of RNA

• The Structure of RNA• RNA consists of a long chain of nucleotides.• Each nucleotide is made up of a ___-carbon sugar,

a phosphate group, and a nitrogenous base.

• There are three main differences between RNA and DNA:

• The sugar in RNA is ribose instead of deoxyribose. • RNA is generally single-stranded.• RNA contains ______________ in place of

thymine.

Types of RNA

• What are the three main types of RNA?

• Types of RNA

– There are three main types of RNA:• _________________ RNA

• ribosomal RNA

• _______________ RNA

Types of RNA

• Messenger RNA (mRNA) carries ______________ of instructions for assembling amino acids into proteins.

Types of RNA

• Ribosomes are made up of proteins and ribosomal RNA (rRNA).

Ribosome

Ribosomal RNA

Types of RNA

• During protein construction, transfer RNA (tRNA) transfers each amino acid to the _________________.

Amino acid

Transfer RNA

Transcription

• What is transcription?– Transcription

• RNA molecules are produced by copying part of a nucleotide sequence of DNA into a complementary sequence in RNA. This process is called ______________________.

• Transcription requires the enzyme ___________________________.

Transcription

– During transcription, RNA polymerase binds to DNA and separates the DNA strands.

• RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA.

• RNA polymerase binds only to regions of DNA known as ______________________.

• Promoters are signals in DNA that indicate to the enzyme where to bind to make RNA.

Transcription Steps1. __________________ unzip the molecule of

DNA2. Free RNA nucleotides pair with complementary

DNA nucleotides on one of the DNA strands• AGC TAA CCG ______ strand• UCG AUU GGC _____ strand

3. When the base pairing is completed, the mRNA molecule breaks away as the DNA strands rejoin.

4. The ______________ leaves the nucleus and enters the cytoplasm

Transcription

RNA

RNA polymerase

DNA

RNA Editing

• RNA Editing• The DNA of eukaryotic genes contains sequences

of nucleotides, called __________________, that are not involved in coding for proteins.

• The DNA sequences that code for proteins are called _________________.

• When RNA molecules are formed, introns and exons are copied from DNA.

RNA Editing

• The ____________ are cut out of RNA molecules.

• The _____________ are the spliced together to form mRNA.

Exon IntronDNA

Pre-mRNA

mRNA

Cap Tail