The Structure and Organization of Genetic Material in
Eukaryotes
Asist Prof. Nüket Bilgen
GENETIC MATERIALS IN MODERN GENETICS DNA (DEOXYRIBONUCLEIC ACID) FORMS THE GENETIC MATERIAL FOR ALMOST ALL
ORGANISMS ON THE PLANET
** THERE IS AN EXCEPTION:
SOME VIRUSES STORES INFORMATION IN RNA
RNA (RIBONUCLEIC ACID) AS THE GENETIC MATERIAL (LEWIN, 1999).
DO YOU RECOGNIZE
THIS FELLOW??
Until the 1940s, the proteins or their building blocks “amino acids” forming chromosomes were thought to be the carrier and storage for genetic information that passes from generation to generation
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Griffith's experiment (1928) – Bacterial Transformation principle"
- There is a hereditary material
Avery, MacLeod and McCarty experiment (1944) -DNA is the hereditary material – The first evidence
Hershey and Chase experiment (1952)
-DNA is the hereditary material – The second evidence
Other evidences:
- Somatic cells contain twice amount of DNA in comparison to gametes
- Mutation Experiments
Griffith 1928 bacterial transformation
Avery, Macleod ve McCarty 1943
Hersey and Chase 1952 radioactive
isotopes.
Genetic Material Must Have Four Characteristics
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1. REPLICATION
2. INFORMATION STORAGE
3. EXPRESSION OF THE STORED İNFORMATİON
4. VARIATION BY MUTATİON
• Replication of the genetic material is a fundamental property of all living organisms- Cell cycle and cell divisions
• Storage of information requires the molecule to act as a repository regardless of whether expressed or not by the cell- most cells contain a complete copy of the organism’s genome
• Mutations- The genetic material is also the source of diversity among organisms, through the process of mutation.
a change in the chemical composition of DNA Changes in transcription
and translation Changes in proteins
Central Dogma
Expression of the stored genetic information is a complex process that is the underlying basis for the concept of information flow within the cell
RNA is synthesized from DNA and protein is synthesized from RNA
Questionare
• Is Central dogma valid?
• -yes
• -no
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Central dogma is not valid in modern genetics
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1. DNA can also be synthesized from RNA - Reverse Transcription
- Reverse transcription is the transfer of information from RNA to DNA
- retroviruses, such as HIV, as well as in eukaryotes, in the case of retrotransposons and telomere synthesis.
2. The final product of DNA is not necessarily have to be protein.
-Functional RNA molecules (tRNA, siRNA) which are transcribed from DNA but not
translated into proteins.
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• Nucleic acids consist of polynucleotide chains.
• Nucleic acids contain four types of bases,
two purines: adenine (A), guanine (G) and two pyrimidines: cytosine (C) and thymine (T). In RNA thymine is replaced by uracil (U).
Nucleobases
The human genome contains approximately 3 billion of these base pairs!
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DNA chains are complementary and antiparallel
Watson-Crick DNA Model, B-DNA
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* The physical structure of DNA was discovered by Watson and Crick in 1953.
1959, Boston, Massachusetts, USA:
James Watson and Francis Crick
Anti-parallel
a double helical structure- the base pairs are nearly perpendicular to the helix axis
the double helix is right-handed
10–10.5 base pairs per turn
2 nm in diameter
DNA contains major groove and minor groove.
Each full turn of the helix is 3.4nm. There are 10 bases in each turn.
The coil has a diameter of 2 nm.
3 helical forms of DNA
Physiological
cond. Rare.
High salt const.
Analytical methods used in DNA Research ;
DNA's ability to absorb UV light,
Precipitation behavior,
Denaturation and renaturation feature,
Electrophoretic properties,
• DNA organization into chromosomes
Eukaryotic chromosomes
Kromatit
Kromozom
Kromatit
SUPERCOIL
Chromosomal DNA associated proteins
Histon proteins
Nonhiston proteins
Nucleosome is the basic unit of chromatin.
DNA organization into chromosomes
Heterochromatin- Euchromatin
• Heterochromatin is dark color
• Euchromatin is
light colored.
Telomere
- heterochromatin Centromere
- heterochromatin
Genes, repetitive sequences, Replication originations
- mostly euchromatin
CENTROMERE
•
Sentromer
Telomeres
Embriyonik hücre kök
Kromozom
Yetişkin
