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EXERCISE 10: THE GENETIC MATERIAL

BIOL 11 (GENERAL BIOLOGY)

DNA AND RNA

• Two types of nucleic acids• Long molecules made up of units

called nucleotides• Each nucleotide is made up of three

parts: • a 5-carbon sugar (pentose)

• a phosphate group

• a nitrogenous base

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OO=P-O

O

N

CH2

O

C1C4

C3 C2

5

Nitrogenous Bases

1. Adenine (A)

2. Guanine (G)

1. Thymine (T)

2. Cytosine (C)

3. Uracil (U)T or C

A or G

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• DNA stores genetic information in most living organisms.

• In simple terms, DNAcontains the instructions for making proteins within the cell.

• DNA is organized into chromosomes, w/c are found within the nuclei of cells.

• Genes are segments in the chromosomes.

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STRUCTURE OF A DNA

• DNA is a very long polymer.

• The basic shape is like a twisted ladder or zipper.

• This is called a double helix (2 strands twisted together).

ONE STRAND OF DNA

• The backbone of the molecule is alternating phosphate and deoxyribose, a sugar, parts.

• The teeth are nitrogenousbases.

phosphate

deoxyribose

bases

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• DNA has four different bases:

• Cytosine C

• Thymine T

• Adenine A

• Guanine G

CHARGAFF’S RULE

• Adenine must pair with Thymine

• Guanine must pair with Cytosine

• Their amounts in a given DNA molecule will be about the same.

G CT A

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DNA STRUCTURE

Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

G

G

A

T

T

A

A

C

T

G

C

A

T

C

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RNA (RIBONUCLEIC ACID)

• RNA forms the genetic material in viruses.

• Serves as genetic messenger, passing information from the DNA to other parts of the cell.

STRUCTURE OF RNA

• Single-stranded molecule composed of nucleotides.

• Pentose sugar is ribose.

• Nitrogenous bases are:

• Adenine (A)

• Guanine (G)

• Cytosine (C)

• Uracil (U)

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TYPES OF RNA

Three main types

• Messenger RNA (mRNA) – transfers DNA code to ribosomes for translation.

• Transfer RNA (tRNA) – brings amino acids to ribosomes for protein synthesis.

• Ribosomal RNA (rRNA) – Ribosomes are made of rRNA and protein.

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DNA Structure vs. RNA Structure