الرحيم الرحمن الله بسم

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اء� و�األ� م� الس�([164]البقرة آية: )

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([7]السجدة آية: )

Cellular composition

DNA is contained in nucleus of cell

Where is DNA located in the Cell?

46

GenesWhat are the genes?They are parts of DNA present on the chromosomes and control the individual hereditary traits

•Every living thing has DNA. That means that you have something in common with a zebra, a tree, a mushroom and a beetle!!!!.•Dna is like a fingerprint because everyone’s is a little different!•It contains information equal to some 600,000 printed pages of 500 words each!!!

(a library of about 1,000 books)

A HISTORY OF DNA• Discovery of the DNA double helix

A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928)

B. Rosalind Franklin - X-ray photo of DNA.(1952)

C. Watson and Crick - described the DNA molecule from Franklin’s X-ray.(1953)

composition of DNA

• DNA molecule is composed of two stands coiled around each other like the spiral ladder called the double helix

• The sides of ladder consisted of :-sugar molecules-phosphate groups

DNA (DeoxyriboNucleic Acid)

• Backbone is made of sugar-phosphate

• Base pairs bind the backbone together

DNA molecule 1-the gene is the building block of nucleic acid (DNA)2-the gene consists of more smaller blocks called Nucleotideseach nucleotide consists of three components :1- phosphate group2-deoxyribose sugar3-nitrogenous base (4 types)

•In 1953 Watson and Crick determined the structure of DNA:-•DNA and its BuildingNucleotides: Guanine (G) Adenine (A) Cytosine (C) Thymine (T).•Base inside, sugar outside

:There are four types of nitrogenous base

A ) ) 1-AdenineT))2-ThymineC))3-cytosine

G))4-guanine • Adenine always

pairs with Thymine• Guanine binds with

Cytosine

DNA forms double helix with two complimentary strands holding together by hydrogen bonds

between A-T (2 bonds) and G-C (3 bonds)

G

G

A

T

T

A

A

C

T

G

C

A

T

C

• Genetic information is carried in the linear sequence of nucleotides in DNA• Genetic information contains

instructions to synthesize proteins

Function of DNA

How do you inherit your genes ?1-By MEIOSIS DIVISION reproductive cells produce:o Male gametes(sperms) containing half number of

chromosomes(N)o Female gametes(ova) containing half number of

chromosomes (N)2-After fertilization, a zygote (contain 2N of

chromosomes ) 3-The cell group together forming tissues which

form organs until all the body of the fetus is formed

• How do the genes perform their function ?

Produce

Responsible of occurrence of forms showing

They control body growth , features , function

Every gene

A specific enzyme

Chemical reaction

A specific protein

A special hereditary

trait

DNA to ProteinGenome: the complete set of information in an organism’s DNA

Total length of DNA about 2 meters long in a human cell, encoding about 30000 proteins

• Example : • The inheritance of trait of eyes :If you inherit one gene from one of your parents and

it is responsible for the brown coloured eyes trait (the dominant trait )

• It is working on the formation of an enzyme which is responsible for the occurrence of a chemical reaction producing a protein that makes the trait of the brown eye appears on you

Mutations• What is meant by mutations ? It is change in the natural of the hereditary

factors that control the traits of a living organism which results in change in the living organism traits

• How does the mutation occur?Changing the chemical composition of one or

more genes leads to changing the hereditary trait resulting from this gene . So a new trait that never appeared in the parents

What Causes Mutations?

• There are two ways in which DNA can become mutated:– Mutations can be inherited. • Parent to child

– Mutations can be acquired. • Environmental damage• Mistakes when DNA is copied

Results due mutations :• The appearance of undesirable trait

like :1)Birth deformation in the human and

the animal 2)Sterilization in plant • The appearance of desirable changes

(rare)

Kinds of mutations 1-the site of occurrence :• Genetic mutations • Chromosomal mutations 2-The inheritance :• Somatic mutations • Gamete mutation 3-The origin :• Spontaneous mutations • Induced mutations

Genetic mutation

• What is meant by?It is changing the chemical composition of one gene

or more • How the genetic mutation occurs ?The genetic mutation occurs when a change occurs in

the Nitrogenous bases of the gene For example :If (A)base is replaced with (C) base

Gene Mutations

• Point Mutations – changes in one or a few nucleotides– Substitution

• THE FAT CAT ATE THE RAT• THE FAT HAT ATE THE RAT

– Insertion• THE FAT CAT ATE THE RAT• THE FAT CAT XLW ATE THE RAT

– Deletion• THE FAT CAT ATE THE RAT• THE FAT ATE THE RAT

• Example The grey mice have MELANIN PIGMENT but the white

mice don't have this pigment due to a change in the gene composition responsible for this trait

The origin of the mutation1-The spontaneous mutation

2-The induced mutation

1-The spontaneous mutationit is a mutation occurs due to the influence from the surrounding environment• It is occurs without the interference of the human

being • Its percentage is very low

Reasons of its occurrence • Radiation • Chemical substance • High or very low temperatureIts importance It cause NATURAL VARIATION between the genera

and special of the animals and various plants , where the new traits that are produced from the occurrence of mutations are inherited across the successive generations

The induced mutation• What is meant by ?It is a mutation which is controller by human being to

obtain desirable traits • Its important It is obtain desirable traits in specific living organisms

especially in the plants

ل�ق! الل�ه� • ذ�ا خ� ه�ل�ق� اذ�ا خ� ون�ي م� ر!

أ� ف�ال�ذ�ين� م�ن د!ون�ه� ب�ل�

الظ�ال�م!ون� ف�ي ب�ين3 ) (11ض�الل3 م�([11]لقمان آية: )

و السالم عليكم ورحمته الله و

بركاته