Course_ Genetics

Lec. no_ One

2nd/ Grade – Fall Semester 2021-2022

Date_ 27/10/2021

shatha.saadi@tiu.edu.iq

Dr. Shataha S. Jumaah/Lecturer

وديكتي

What is a eukaryotic in a cell?

Eukaryotes are organisms whose cells contain

a nucleus and other membrane-bound

organelles. There is a wide range of eukaryotic

organisms, including all animals, plants, fungi,

and protists, as well as most algae. Eukaryotes

may be either single-celled or multicellular.

The Nucleus & Its Structures• The nucleus means the cell’s DNA is surrounded by a membrane.

• Nuclear envelope is a double-membrane structure that constitutes the

outermost portion of the nucleus.

• Inner and outer membranes of the nuclear envelope are phospholipid

bilayers.

• The nuclear envelope is punctuated with pores that control the passage of

ions, molecules, and RNA between the nucleoplasm and cytoplasm.

• The nucleoplasm is the semi-solid fluid inside the nucleus where we find

the chromatin and the nucleolus.

• Chromosomes are structures within the nucleus that are made up of DNA,

the genetic material.

• In prokaryotes, DNA is organized into a single circular chromosome. In

eukaryotes, chromosomes are linear structures.

Chromatin•Chromatin: a complex of DNA, RNA, and proteins within the cell nucleus out of which chromosomes

condense during cell division.

•Chromosomes(DNA+ Proteins) that forms chromosomes within the nucleus of eukaryotic cells.

•DNA wrapped around nuclear proteins (histone) forming a structure resembling beads on a string, in

order to fit inside the nucleus. These protein-chromosome complexes are called chromatin in the

nucleoplasm.

•Chromatin exists in two forms. 1stform, called euchromatin, is less condensed and can be

transcribed. The 2ndform, called heterochromatin, is highly condensed and is typically not

transcribed.

•Histones are water-soluble proteins that are rich in the basic amino acids lysine and arginine and are

complexed with DNA in the nucleosomes.

•A nucleosome is a section of DNA that is wrapped around a core of proteins. Inside the nucleus,

What Is DNA?

• Deoxyribonucleic acid is a complex molecule that contains all of

the information necessary to build and maintain an organism.

• All living things have DNA within their cells.

• Serves as the primary unit of heredity in organisms of all types.

• So Basically we have 2 types of genetic materials

1. DNA 2. RNA

1

2

3DNA has

three main

components

Phosphate

Deoxyribose(a pentose

sugar) Base (there

are four different

ones)

Genetic MaterialsDNA Structure

1. Two polynucleotide chain are spirally or helically twisted

which appears like a “Twisted ladder”.

2. Both the polynucleotide strands of DNA are having an

opposite polarity.

3. Diameter of ds-DNA helix is 20Å.

4. Distance between the two nucleotides is 3.4Å.

5. The length of DNA helix is 34Å after a full turn and consist

of 10 base pairs (bp) per turn.

6. The DNA is twisted in “Right-handed direction”, or we can

say in a “Clockwise direction”.

•Nucleotides are formed by the condensation of a pentose sugar, phosphate and

one of the 4 bases

• The following illustration represents one nucleotide

DNA Double Helix and Hydrogen Bonding

Made of two strands of nucleotides that are joined together by hydrogen bonding, hydrogen bonding occurs as a result of complimentary base pairing

Each pair is connected through hydrogen

bonding Hydrogen bonding always occurs between and

•because they form H bonds with each other

•because they form hydrogen bonds with each other

When phosphodiester links are formed . . .

When the covalent bonds are

formed between nucleotides the

attach in the direction of 5’→3’

The 5’ end of one nucleotide

attaches to the 3’ end of the previous

nucleotide

How is DNA packaged inside cells?

• The human have 100 trillion cells & each cell has its own DNA .

• DNA packaging:-is the phenomenon of fitting DNA into dense compact forms

• During DNA packaging, long pieces of double-stranded DNA are tightly looped, coiled, and

folded so that they fit easily within the cell.

• Eukaryotes wrapping their DNA around special proteins called histones, thereby

compacting it enough to fit inside the nucleus

1. Diagnosis of Genetic Diseases .

2. DNA Typing (DNA Fingerprinting) .

3. Gene Therapy .

4. Recombinant DNA Technology in the Synthesis of Human Insulin.

5. Hepatitis B Vaccine .