1. Genes are pieces of DNA that contain instructions for traits and are made up of different arrangements of bases including adenine, thymine, cytosine, and guanine. 2. DNA carries hereditary information in the form of genes on structures called chromosomes in cell nuclei. It directs the synthesis of proteins through a process involving transcription of DNA into mRNA and translation of mRNA into proteins. 3. Mutations, or changes in genes, over time due to errors in DNA replication or exposure to mutagens can lead to evolution as mutations result in hereditary changes and variations between organisms that natural selection can act upon.

1. HEREDITY AND EVOLUTION
HEREDITY AND HEREDITARY CHANGES

2. CAN YOU RECALL?
• Which component of the cellular nucleus of living organism carries hereditary
characters?
Ans. Chromosome
• What do we call the process of transfer of physical and mental characters from
parents to the progeny?
Ans. Heredity
• Which are the components of DNA molecule?
Ans. Phosphate, a pentose sugar- deoxyribose, purines-adenine and guanine,
pyrimidines-cytosine and thymine

3. WHAT ARE GENES?
• Genes are pieces of DNA that make up a trait.
• Different genes consist of different arrangements of the adenine,
thymine, cytosine, guanine bases.
• These bases can be arranged to form different proteins (chemical
messages)
• These messages control different traits (some determine how we
look, some determine how we feel and function).
• There are many millions of possible combinations of these 4 bases –
this accounts for the differences, and similarities, between life forms
on earth.

4. JOHANN GREGOR MENDEL Is
pioneer of the modern
genetics. Around the period
of 1886, it took a long time
for him to understand the
condition of research about
heredity.

5. IN 1901, The reasons behind the
sudden changes were understood
due to mutational theory of HUGO
DE VRIES.

6. Meanwhile in 1902, Walter Sutton observed the pair chromosomes
in the cells of grasshopper.

7. Ostwald Avery, Mclyn Mccarthy and Colin Macleod
proved that except viruses, all living organisms have
DNA as genetic material.

8. In 1961, proposed a model for process of protein synthesis with the help
of DNA in bacterial cells. It help to uncover the genetic code hidden in
DNA. Thereby, the technique of recombinant DNA technology emerged
which has vast scope in the field of genetic engineering.

9. RECOMBINANT DNA TECHNOLOGY
• Recombinant DNA technology, joining together
of DNA molecules from two different species that are
inserted into a host organism to produce new genetic
combinations that are of value to science, medicine,
agriculture, and industry.

10. USES OF GENETICS
• Diagnosis, treatment and prevention of hereditary disorders
• Production of hybrid varieties of animals and plants
• In industrial processes in which microbes are used.

11. H.W.
• What are genes?
• What are chromosomes?
• What is DNA?
• Explain the structure of DNA.
• State the various types of RNA and explain their function.
• Write the names of some genetic disorders.

12. H.W.
• What are genes?
• Ans. Genes are the working subunits of DNA. Each gene contains a
particular set of instructions, usually coding for a particular protein or
for a particular function.
• What are chromosomes?
• Ans. They are thread-like structures present in the nucleus of cell
which contain genetic information.
• What is DNA?
• Ans. DNA is the genetic material which carries all hereditary
information.

14. • DNA contains information about protein synthesis. It synthesizes proteins as per requirement for a
body. Thus proteins are synthesized through RNA by DNA. Only one of the two strands of DNA is used in
this process. According to the sequence of nucleotides present on DNA, m RNA is produced. Sequence of
nucleotides in m RNA which is produced is complementary to DNA strand used for synthesis.
• i.e. Adenine binds with uracil and cytosine binds with guanine. This process is called as transcription. It
occurs in nucleus. RNA polymerase binds to DNA molecule at initiation site and unwinds it. The template
strand of DNA is used for coding m RNA. Sequence of nucleotides complementary to DNA is produced on
m RNA.

15. • Dr Hargobind Khorana has made an important contribution in discovery of triplet codon for 20 amino acids.
For this work, he has been awarded with the nobel prize in 1968 along with other two scientists- Marshall
W. Nirenberg and Robert W. Holley.
•

17. TRANSLATION
The m RNA formed in nucleus comes in cytoplasm through nuclear pore.
It brings the coded message from DNA.
The message contains the code for amino acids.
The code for each amino acid consists of 3 nucleotides. It is called as triplet codon.
Each m RNA is made up of thousands of triplet codons.
As per the message on m RNA, amino acids are supplied by the t RNA. t RNA has anticodon having
complementary sequence to the codon on m RNA. This is called as translation.

18. • Amino acids produced by t RNA are bonded together by peptide bonds with the help of RNA. During this
process, the ribosome keeps on moving from one end of m RNA to the other end by the distance of one
triplet codon. This is called as translocation. Such many things come together to form complex proteins.
This proteins control various functions in the body of living organisms and their appearance too.

19. Living organisms can produce new individuals like themselves due
to genes only and some of those genes are transmitted to the next
generation without any changes. Due to this, some of the
characters of parents are transmitted to their offsprings. However,
some time changes occur in those genes. Sometimes, any
nucleotide of the gene changes its position that causes a minor
change which is nothing but the mutation. Some mutations may
be minor but some may be considerable. Example mutation may
cause the genetic disorders like Sickle Cell anaemia. This is an
everlasting process and it is one of the proof for Darwin's theory of
natural selection.