CLASS 12 BIOLOGY GENETICS NOTES

1. MOLECULAR BASIS OF
INHERITANCE
PREPARED BY
MRS. S RATH
PGT BIOLOGY
www.cbse123.co.cc

2. DNA (Polynucleotide)
DNA
NITROGENOUS
BASE
A DEOXYRIBOSE
PENTOSE
SUGAR
A PHOSPHATE
GROUP
PURINE PYRIMIDINE
CYTOSINE
THYMINE
ADENINE
GUANINE

3. DNA
 Nitrogenous base is linked to pentose sugar through a n-
glycosidic linkage to form a nucleoside.
 Phosphate group attached to5’-OH of a nucleoside through
phospho-ester linkage, and a nucleotide is formed.
 Two nucleotides are linked through 3’-5’ phosphodiester linkage
to form a dinucleotide, and in this manner many nucleotides are
linked forming polynucleotide.
 A polynucleotide has a free sugar at its5’ end and a free
phosphate at its 3’ end.

4. Double helix model of DNA
( Watson and Crick model)
 DNA is made of 2 polynucleotides.
 Backbone is formed by sugar and phosphate.
 Nitrogen bases project inside.
 Hydrogen bonds between nitrogen bases hold the chain together.
 Adenine pairs with thymine through 2 hydrogen bonds and
guanine with cytosine with 3 bonds.
 Two chains have antiparallel polarity.
 Two chains are coiled in a right handed fashion. And pitch of
each helix is3.4nm, and 10 base pairs in each turn.

5. A NUCLEOSOME

6. Griffith’s experiment on transformation

7. DNA is the genetic material

8. Characteristics of genetic material
 Able to generate its replica.
 Chemically and structurally stable.
 Provide the scope for mutation necessary for
evolution.
 Able to express itself in the form of Mendalian
character.

9. RNA (Polynucleotide)
RNA
NITROGENOUS
BASE
A
PENTOSE
SUGAR
A PHOSPHATE
GROUP
PURINE PYRIMIDINE
CYTOSINE
URACIL
ADENINE
GUANINE

10. TYPES OF RNA
RNA
MESSENGER
mRNA
TRANSFER/
SOLUBLE
tRNA
RIBOSOMAL
rRNA

11. A tRNA MOLECULE

12. Semiconservative replication of DNA

13. Meselson- Stahl experiment
(semiconservative replication)

14. Replication of DNA
(schematic representation)

15. A TRANSCRIPTION UNIT
 A promoter
 Structural genes
 A terminator

16. Transcription
A TRANSCRIPTION UNIT

17. TRANSCRIPTION IN
PROKARYOTES

18. GENETIC CODE
 Codons are triplets
 61 codons code for 20 amino acids.
 Unambigous – each coden codes for only one/ particular amino
acid.
 Degenerate – some amino acids are coded by more than one codon.
 Commaless –codons are read in continuous manner in a 5’ to 3’
direction without punctuation
 Universal –codes for same amino acid in any organism.
 AUG- initiation codon and codes for methionine.
 UAA, UAG and UGA are stop codons..

19. MUTATION
MUATION
POINT FRAME SHIFT SILENT

20. TRANSLATION

21. TRANSLATION

22. TRANSLATION

23. COMPONENTS OF OPERON
 Structural gene
 Promoter gene
 Operator
 Regulator gene
 Inducer

24. LAC OPERON IN E.COLI

25. LAC OPERON IN E.COLI

26. GOALS OF HUMAN GENOME
PROJECT (HGP)
 Identification of all genes
 Determination of the sequence of the 3 billion base pairs in human
DNA.
 To store the information in data base.
 Improvement of the tools for data analysis
 Transfer of the technology to other sectors (industries)
 To address the ethical, legal and social issues (ELSI) that may arise
from this project.

27. METHODOLOGIES OF HGP
 Expressed sequence tags (ESTs)- identifying all genes that
expressed as RNA.
 Sequence annotation- sequence the whole sequence of
genome, that included all coding and noncoding sequences
and later assigning function to different regions in the
sequence.

28. SALIENT FEATURES OF
HUMAN GENOME
 Contains3164.7 million nucleotides.
 Size of genes varies, average size contains 3000 bases, the largest gene
dystrophin contains 2.4 million bases.
 Total no. genes about 30000 and99.9 % of the nucleotides are same in
all humans.
 Function of 50% genes are not known.
 2% of the genome codes for protein.
 Repetitive sequence make up large portion of genome which throw
light on structure, dynamics and evolution though they do not have
coding function.
 In 1.4 million locations DNA differs in single base.

29. USES OF HGP
 To diagnose, treat and prevent a number of disease or
disorder that affects human beings.
 Provides clues to the understanding of human biology.

30. THE PROCESS OF DNA FINGER PRINTING

31. STEPS OF DNA FINGERPRINTING
 Extraction
 Amplification
 Restriction digestion
 Separation of DNA sequence/ restriction fragments
 Southern blotting
 Hybridisation
 Autoradiography

32. USES OF DNA FINGERPRINTING
 To identify criminals
 To determine the true biological mother or father in case
of disputes
 To verify an immigrant, really a close relative of a
resident
 To identify racial groups to rewrite the biological
evolution.

33. WWW.CBSE123.CO.CC
"I find that the harder I work, the
more luck I seem to have."
- Thomas Jefferson