Course_ Genetics
Lec. no_ One
2nd/ Grade – Fall Semester 2021-2022
Date_ 27/10/2021
Dr. Shataha S. Jumaah/Lecturer
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 .