1. The document discusses the history and key discoveries in genetics from Mendel's work in 1866 to the sequencing of the human genome in 2001. It includes the discoveries of DNA structure by Watson and Crick in 1953 and the genetic code by Nirenberg in 1966. 2. The structure and composition of DNA, RNA, and nucleotides are described. DNA is made of nucleotides containing deoxyribose, while RNA contains ribose. Both DNA and RNA follow Chargaff's rules about base pairing. 3. Gene structure is explained, including the concepts of exons, introns, and splicing in eukaryotic genes. The location of genes on chromosomes at specific loci is also covered.

1. 1.1. The structure of DNA andThe structure of DNA and
RNARNA
2.2. Gene StructureGene Structure
3.3. Gene TheoryGene Theory
4.4. Biosynthesis of proteinBiosynthesis of protein

2.  1866: Gregor Mendel publishes Experiments in Plant Hybridization,
which lays out the basic theory of genetics. It is widely ignored until
1900.
 1871: Friedrich Miescher isolates “nucleic acid” from pus cells.
 1910: Thomas Hunt Morgan proves that genes are located on the
chromosomes (using Drosophila).
 1953: James Watson and Francis Crick determine the structure of
the DNA molecule, which leads directly to knowledge of how it
replicates
 1966: Marshall Nirenberg solves the genetic code, showing that 3
DNA bases code for one amino acid.
 1972: Stanley Cohen and Herbert Boyer combine DNA from two
different species in vitro, then transform it into bacterial cells: first
DNA cloning.
 2001: Sequence of the entire human genome is announced.

3. The structure of DNA and RNA
 Genetic material of living organisms is either DNA or
RNA.
 DNA – Deoxyribonucleic acid
 RNA – Ribonucleic acid
 Genes are lengths of DNA that code for particular
proteins.

4. DNA and RNA are polynucleotides
 Both DNA and RNA are polynucleotides.
 They are made up of smaller molecules called
nucleotides.
 DNA is made of two polynucleotide strands:
 RNA is made of a single polynucleotide strand:
Nucleotide NucleotideNucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide Nucleotide Nucleotide Nucleotide
NucleotideNucleotide Nucleotide
Nucleotide

5. Structure of a nucleotide
A nucleotide is made of 3
components:
 A Pentose sugar
 This is a 5 carbon sugar
 The sugar in DNA is deoxyribose.
 The sugar in RNA is ribose.

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7.  DNA is a nucleic acid, made of long chains of nucleotides
DNA and RNA are polymers of
nucleotides
Fi
Nucleotide
Phosphate
group
Nitrogenous
base
Sugar
Polynucleotide Sugar-phosphate backbone
DNA nucleotide
Phosphate
group
Nitrogenous base
(A, G, C, or T)
Thymine (T)
Sugar
(deoxyribose)

8. Structure of a nucleotide
 A Nitrogenous base
 In DNA the four bases are:
 Thymine
 Adenine
 Cytosine
 Guanine
 In RNA the four bases are:
 Uracil
 Adenine
 Cytosine
 Guanine

9.  DNA has four kinds of bases, A, T, C, and G
Pyrimidines
Thymine (T) Cytosine (C)
Purines
Adenine (A) Guanine (G)

10. Nitrogenous bases – Two types
Pyramidines
Thymine - T
Cytosine - C
Uracil - U
Purines
Adenine - A
Guanine - G

12. The Rule:
 Adenine always base pairs with Thymine (or
Uracil if RNA)
 Cytosine always base pairs with Guanine.
 This is beacuse there is exactly enough room for
one purine and one pyramide base between the
two polynucleotide strands of DNA.

13. DNA base composition follows Chargaff’s
Rules
 DNA has equal numbers of adenine and thymine
residues (A = T)
 DNA also has equal numbers of guanine and cytosine
residues (G = C)
 Structural basis for Chargaff’s rules lie in the
hydrogen bonds between the bases. G always hydrogen
bonds with C and A always forms base pairs with T.
 Base composition of a specific organism is
characteristic of that organism (independent of tissue
type).
 DNA composition varies among different organisms. It
ranges from 25% to 75% G + C in different species of
bacteria.
 RNA, when forming duplexes, also follows Chargaff’s
rules

14. DNA
 Deoxyribonucleic Acid
 4 Bases
 Purines
 Adenine
 Guanine
 Pyrimidines
 Cytosine
 Thymine*
 Sugar is Deoxyribose
Adenine
OH
P
H
CH2O
H
O
NH2
N
N
N
N
O
O

15. RNA
 Ribonucleic Acid
 4 Nucleotides
 Purine
 Adenine
 Guanine
 Pyrimidines
 Cytocine
 Uracil*
 Sugar is Ribose
OHOH
P
H
CH2O
H
O
NH2
N
N
N
N
O
O
Adenine

16. DNA RNA
Deoxyribonucleic Acid Ribonucleic Acid
Sugar=deoxyribose Sugar= ribose
Contains 1 more H atom
than deoxyribose
Double stranded Single stranded- a single
strand of nucleotides
Nitrogen bases: ATCG Nitrogen bases: AUCG
U=Uracil

17. 2. Gene structure
 Genes are the basic physical and functional units
of heredity. Each gene is located on a particular
region of a chromosome and has a specific
ordered sequence of nucleotides (the building
blocks of DNA).

18. What is a locus?
 A locus describes the
region of a chromosome
where a gene is located.
11p15.5 is the locus for
the human insulin gene. 11
is the chromosome number,
p indicates the short arm
of the chromosome, and
15.5 is the number
assigned to a particular
region on a chromosome.
 When chromosomes are
stained in the lab, light and
dark bands appear, and
each band is numbered.
The higher the number,
the farther away the band
is from the centromere.

19. Exons and Introns
 Eukaryotic genes have introns and exons.
 Exons contain nucleotides that are translated
into amino acids of proteins.
 Exons are separated from one another by
intervening segments of junk DNA called introns.
 Introns do not code for protein. They are
removed when eukaryotic mRNA is processed.
 Exons make up those segments of mRNA that are
spliced back together after the introns are
removed; the intron-free mRNA is used as a
template to make proteins.

20. Splicing
 Exons are sequences of DNA that are expressed
into protein.
 Introns are intervening sequences that are not
translated into protein
DNA
Pre-mRNA
31
1 2 3
1 32
2
Spliced mRNA
3
C
C
C

21. Exons and Coding
Exons often are described as short segments of protein
coding sequence. This is a bit of an oversimplification.
Exons are those segments of sequence that are spliced
together after the introns have been removed from the pre-
mRNA.
The coding sequence is contained in exons, but it is
possible for some exons to contain no coding sequence.
Portions of exons or even entire exons may contain
sequence that is not translated into amino acids.
These are the untranslated regions or UTRs.
UTRs are found upstream and downstream of the protein-
coding sequence.

22. Gene Theory
 The Gene Theory is one of the basic principles
of biology.
 The main concept of this theory is that traits are
passed from parents to offspring through gene
transmission.
 Genes are located on chromosomes and consist
of DNA.
 They are passed from parent to offspring
through reproduction.

23. 4. Biosynthesis of protein
 Messenger RNA= mRNA is a form of RNA that
carries the instructions for making the protein
from a gene and delivers it to the site of
translation.
 Codon= three nucleotide sequence
 Transfer RNA= tRNA single strands of RNA that
temporarily carry a specific amino acid on one end
and has an anticodon
 Anticodon-a 3 nucleotide sequence that is
complementary to an mRNA codon
 Ribosomal RNA= rRNA- a part of the structure
of ribosomes

25. Codon and Anticodon
 Codon-found on mRNA Anticodon-found on tRNA

26.  Transcription= process of making RNA from DNA
 Translation= RNA directions are used to make a
protein from amino acids
• DNA→RNA →Protein
 Transcription Translation
nucleus
Cytoplasm on
ribosome

27. TRANSLATION-
Assembling proteins- in the cytoplasm
 mRNA leaves nucleus and enters cytoplasm
 tRNA molecules with the complementary anticodon
and a specific amino acid arrives at the ribosome
where the mRNA is waiting.
 Peptide bond forms between amino acids
 tRNA molecule leaves and a new one comes with
another amino acid.
 Amino acids continue to attach together until the
stop codon and a protein is formed

29. Explain the steps in protein synthesis.

30.  http://www.youtube.com/watch?
v=NNASRkIU5Fw (RNA: DNA)
 http://www.youtube.com/watch?v=h3b9ArupXZg
(Transcription :Translation)