Malalay Institute Of Higher

Education

Madical Faculty

Author and computerized by: Noor

Sadat daughter of M. Essa

Semester: PCB 2

DNA DNA structure

- Neoclutide

DNA replication

DNA structureNucleotide

- Nucleotides are organic molecules that serve as the monomers, or subunits, of nucleic acids like DNA and RNA. The building blocks of nucleic acids, nucleotides are composed of a nitrogenous base, a five-carbon sugar (ribose or .deoxyribose), and at least one phosphate group

OSugar

ONitrogen's bases

OPhosphate group

Sugar

C5H10O4

Deoxyribose, or more precisely 2-

deoxyribose, is a monosaccharide with

idealized formula H-(C=O)-(CH2)-

(CHOH)3-H.

Its name indicates that it is a deoxy

sugar, meaning that it is derived from

the sugar ribose by loss of an

oxygen atom.

2-Deoxy-D-ribose

2-Deoxy-D-erythro-

pentose

Thyminose

IUPAC names

Properties

Molecular formula C5H10O4

Molar mass 134.13 g·mol−1

Appearance White solid

Melting point 91 °C (196 °F; 364 K)

Solubility in water Very soluble

Nitrogenous Bases

A nitrogenous base is simply a nitrogen

containing molecule that has the same

chemical properties as a base. They are

particularly important since they make

up the building blocks of DNA and RNA:

adenine, guanine, cytosine, thymine and

uracil.

ONucleotide Base Definition: A nucleotide

base is a heterocyclic base

containing nitrogen that forms the base part

of nucleotide molecules.

OAlso Known As: nuclei base, nitrogenous

base

OExamples: Cytosine, guanine, and

adenine are all nucleotide bases.

Adenine

OAdenine, abbreviated 'A', has a two-ring

structure, so that makes it a purine. When

it's in DNA, it pairs up with Thymine. When

it's in RNA, it pairs up with Uracil. Adenine

also has other jobs in the cell - it makes up

part of the energy molecule ATP and

electron carriers FAD and NAD, which are

used in cellular respiration.

Thymine

OThymine is a pyrimidine (one

ring), and it's only present in DNA,

where it pairs with Adenine. Its

cousin Uracil does the same job

in RNA.

Guanine

OGuanine is part of both DNA and

RNA, where it bonds with

Cytosine. Guanine is a purine

(having two rings). Fun fact: it was

first discovered in bird feces,

known as guano ... hence the

name

Cytosine

OCytosine is part of DNA and RNA,

and bonds with Guanine. It has

one ring, so it's a pyrimidine.

Note

ONote :that adenine only bonds with thymine,

and cytosine only bonds with guanine.

The nitrogen bases are held together by

hydrogen bonds: adenine and

thymine form two hydrogen bonds; cytosine

and guanine form three hydrogen bonds.

A

C

T

G

C

A

T

C

To crack the genetic code found in DNA

we need to look at the sequence of bases.

The bases are arranged in triplets called

codons.

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

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

Phosphate group

Definition and Structure

OSurround a phosphorus atom with four

oxygen atoms and you get a phosphate.

Attach that cluster to one of the many carbon-

containing molecules in our bodies (or, really,

in any living thing) and we call that group of

phosphorus and oxygen atoms a phosphate

group.

PO43-

Role in Nucleic Acids

O Nucleic acids, like DNA, are made of nucleotides.

Where do phosphates come in? Well, nucleotides

include a base, a sugar, and one or more

phosphates.

O When the nucleotide is off by itself, it may have three

phosphates. When it gets joined to the growing

strand of DNA (or RNA), two of its phosphates are

lost, and the remaining one attaches to another

nucleotide's sugar. This makes a sugar-phosphate

backbone with those important bases (like adenine,

thymine, and so on) hanging off

DNA replication

Replication = DNA copies itself

exactly

(Occurs within the nucleus)

A. Basic Facts of DNA Replication

1. Complementary base pairing

makes replication possible

C – G

A - T

2. One side of

DNA

molecule is a

template for

making the

other side

(strand)

B. Process of DNA Replication

1. Uncoil & unzip

DNA molecule

2. Enzyme (-ase)

break

3. weak Hydrogen

Bond between

bases

Replication

C. Semi-conservative replication

1. Each new DNA

molecule

contains

one old strand

&

one new strand

Thanks from your attention