Nucleic Acids and Genetics

Chapter 5

A. P. BiologyMr. Knowles

Liberty Senior High School

Is Genetics Important to Me?

Genetics• Basic unit of heredity- Gene- a linear sequence of

nucleotides of DNA.• Genotype- genetic make-up of organism; its

potential characteristics.• Phenotype- the observable physical traits of an

organism.• The Phenotype is the organism’s physical

expression of its Genotype.

Eukaryotes are Diploid• Locus - is a gene’s location on the chromosome.• Allele- an alternative form of a gene at a

specific locus.• Eukaryotes have pairs of identical

chromosomes- diploid. May have two alleles of a gene.

• Prokaryotes are not diploid.

When good DNA goes Bad!• A permanent change in the

sequence of nucleotides -mutation. Mutations change the information of that gene.

• DNA- function is to store and transfer information.

Mistakes in DNA -->Mutations

How is DNA Accurately Transferred?

• DNA serves as a template for its own replication; an exact pattern.

• How, you ask?

• By base pairing.

What is a Nucleotide? • Subunits of DNA/RNA are

Nucleotides = nitrogenous base + deoxy- or ribose sugar (5 carbons) + PO4

• Purines: Adenine and Guanine• Pyrimidines: Cytosine, Thymine,

Uracil

Monosaccharides of Nucleic Acids

Adenosine Monophosphate• Base = adenine

• In DNA, sugar = deoxyribose (In RNA, sugar = ribose)

• A phosphate group, PO4

• The Nucleotide = AMP

Adenosine Monophosphate

Adenosine Triphosphate (ATP)

Guanosine Monophosphate

Thymine Monophosphate

Cytosine Monophosphate

Uracil Monophosphate (in RNA)

Base Pairing Rules

• In DNA,

A = T

C G

• In RNA,

A = U

C G

H-Bonding Between Bases

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Characteristics of DNA• Chains of nucleotides linked together by

phosphodiester bonds.

• Carbon 5 of deoxyribose is attached to PO4.

• Carbon 3 of deoxyribose is a OH- free to attach to the next nucleotide.

• Double helix is held together by H-bonding.

Double Helix• DNA is antiparallel:

5’PO4 -------------------------3’OH

3’OH -------------------------5’PO4

The 3-D Structure of DNA

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DNA Replication• Begins at a specific location on the

circular bacterial chromosome-origin (OriC).

• Occurs in two directions at the same time-two moving replication forks- points where the two strands separate to allow replication of DNA.

Bring on DNA

Replication!

Replication, must I see!

Replication Fork

Show methe

Replication!

DNA Replication

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DNA ReplicationProkaryotes

• single, circular chromosome.

• one single origin on the chromosome.

• rate of over 1,000 nt/second.

Eukaryotes

• multiple, linear chromosomes.

• several origins on each chromosome.

• rate of about 50-100 nt/second