DNA Continued (Deoxyribonucleic Acid). DNA is wrapped tightly around histones and coiled tightly to...

DNA Continued(Deoxyribonucleic Acid)

DNA is wrapped tightly around histones and coiled tightly to form

chromosomes

See p. 332

Genetic material of cells…Genetic material of cells…

• GENES – units of genetic material that CODES FOR A SPECIFIC TRAIT

• Like for eye color or hair color.

• Genes located on chromosomes

• DNA is made up of repeating molecules called NUCLEOTIDES

The Code of Life…The Code of Life…• The “code” of the chromosome is the SPECIFIC

ORDER that bases in the nucleotides occur.

A T C G T A T G C G G…A T C G T A T G C G G…

Genetic Diversity…Genetic Diversity…

• Different arrangements of NUCLEOTIDES

in a nucleic acid (DNA) provides the key

to DIVERSITY among living organisms.

DNA Replication• During Interphase

• DNA must be copied

• The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing:

A-T, G-CA-T, G-C

DNA ReplicationDNA Replication

• Each strand of the original DNA serves as a template for the new strand

• See page 334

DNA ReplicationDNA Replication

The two strands of the parental molecule separate, and each functions as a template for the making of a new complementary strand.

.

Parental DNA

DNA Template

New DNA

Steps in Replication1. An enzyme called DNA Helicase unwinds and unzips the DNA molecule

Steps in Replication2. An enzyme called DNA Polymerase attaches to the parent DNA molecule in several different spots. It inserts the complementary bases, making two copies of the DNA molecule

Speed of Replication

Prokaryotes have a single circular strand of DNA to replicate. This takes about 40 minutes.

Speed of Replication

Eukaryotes if their DNA was done by one polymerase molecule per chromosome would take about a month for the DNA to replicate.

Multiple polymerase latch on the replicating DNA simultaneously and as a result replication in humans takes about an hour.

1. Why is replication necessary?

2. When does replication occur?

3. Describe how replication works.

4. Use the complementary rule to create the complementary strand:

A---?G---?C---?T---?A---?G---?A---?G---?C---?A---?G---?T---?

Replication Quiz

1. Why is replication necessary?So both new cells will have the correct DNA

2. When does replication occur?During interphase (S phase).

3. Describe how replication works.Enzymes unzip DNA and complementary

nucleotides join each original strand.4. Use the complementary rule to

create the complementary strand:

A---TG---CC---GT---AA---TG---CA---TG---CC---GA---TG---CT---A

Replication Quiz

What is the purpose of DNA? • DNA controls cell function by serving as a

template (blueprint) for PROTEIN structure. (Remember Proteins made of amino acids.)

What do proteins do? • Proteins are found everywhere .... every

nook and corner in the cell .. most things are made from proteins as well

The processes to make proteins

We need RNA

• Single stranded nucleic acid

• Sugar in the nucleotide is RIBOSE not deoxyribose

• Uracil replaces Thymine in the base pairs.

Types of RNA

Messenger RNACarries code from DNA to ribosomes to make proteins

Ribosomal RNAMakes up the ribosome

Transfer RNA“grabs” the amino acids from the cytoplasm to make proteins

mRNA

rRNA

tRNA

TranscriptionTranscription

• DNA can “unzip” itself and RNA nucleotides match up to the DNA strand.

mRNA is produced by a process known as :

Transcription

Making proteins

Codon: (Three nucleotides on mRNA)

Anticodon: three complementary nucleotides on tRNA

How are Proteins made? • By reading the codon (3 nucleotides in a row) on

the mRNA by the ribosome RNA.

• Then matching the codon with the anticondon (3 opposite nucleotides) on the tRNA

• The tRNA is carrying an amino acid which then links together with other amino acids.

• Called Translation

TranslationTranslation

• The cell uses information from “messenger” RNA to produce proteins

Transcription/Translation Quiz1. Why is transcription necessary?

2. Describe transcription.

3. Why is translation necessary?

4. Describe translation.

5. What are the main differences between DNA and RNA.

6. Using the chart on page 338, identify the amino acids coded for by these codons: UGGCAGUGC

1. Why is transcription necessary?Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm.

2. Describe transcription.

RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble MRNA.

3. Why is translation necessary?

Translation assures that the right amino acids are joined together by peptides to form the correct protein.

4. Describe translation.The cell uses information from MRNA to produce proteins.

5. What are the main differences between DNA and RNA.DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil.

6. Using the chart on page 303, identify the amino acids coded for by these codons: UGGCAGUGCtryptophan-glutamine-cysteine

AMAZING DNA FACTS…AMAZING DNA FACTS…

• DNA from a single human cell extends in a single thread for almost 2 meters long!!!

• It contains information equal to some 600,000 printed pages of 500 words each!!!

(a library of about 1,000 books)