MODULE 1
UNIT 1: DNA
- nucleus is surrounded by a double nuclear membrane with pores
o pores form the passage between the nucleus and cytoplasm
- nuclear membrane encloses the nucleoplasm, jelly like liquid
- nucleolus, small round body is suspended in the nucleoplasm
- chromatin network, mass of thread-like structures, also in the nucleus
- nucleus regulates the structure and metabolism of the cell
nucleic acids
- organic molecules that control the synthesis of proteins in all living cells by
storing and transferring genetic information
- two types of nucleic acid occur in living cells
o DNA (deoxyribonucleic acid)
o RNA (ribonucleic acid)
DNA
LOCATION OF DNA
- occurs mainly in the nucleus, where it forms part of the chromatin network
– chromosomal DNA
- a small amount of DNA occurs outside the nucleus, in the mitochondria and
chloroplasts in plants (extranuclear DNA)
CHROMOSONES & GENES
- chromosomes are long, thin, thread-like structures composed of DNA
that is wrapped around proteins called histones
DNA histone protein
© 2021 Emma Thorp
, - a short segment of a DNA molecule that codes for a particular protein is
known as a gene
- each gene carries the code for the synthesis of a particular protein
- proteins determine the characteristics of an organism
DISCOVERY OF THE STRUCTURE
- 1865: Gregor Mendel, finds that each characteristic is controlled by a
specific gene
- 1962: Watson, Crick and Wilkins, receive the Nobel Peace Prize for
Physiology/Medicine after their discovery of the structure of DNA
- 1990: The Human Genome Project is established with James Watson as
the first director
STRUCTURE OF DNA
- is a giant molecule, consisting of two strands, twisted to form a double
helix
- when unwound, looks like a ladder
- DNA is a polymer, made up of a large number of similar units (building
blocks), monomers
- monomer of DNA: nucleotides
NUCELOTIDES
- each nucleotide consists of three parts
o sugar molecule – deoxyribose (D)
o phosphate group (P)
o nitrogenous base -four different types:
adenine (A)
guanine (G)
cytosine (C)
thymine (T)
- adenine and guanine, large molecules: purine bases
- cytosine and thymine, smaller molecules: pyrimidine bases
© 2021 Emma Thorp
, FORMATION OF NUCLEOTIDES
- deoxyribose combines with phosphate group
- one nitrogenous base combines with deoxyribose
- four different nitrogenous bases, four different nucleotides in a DNA
molecule
D A T D D G C D
P P P P
FORMATION OF DNA
- deoxyribose of one nucleotide forms a bond with the phosphate group of
another
- two long stands, look like the sides of a ladder are formed
- the sides of the DNA ladder consist of alternating deoxyribose molecules
and phosphate groups
- each rung, of the DNA ladder is formed by the linking of two nitrogenous
bases; a large purine and a small pyrimidine base
- two bases together is known as a base pair
- nitrogenous bases are joined by weak hydrogen bonds, which are easily
broken by enzyme action
- adenine to thymine, guanine to cytosine
- two hydrogen bonds form between adenine and thymine
- three hydrogen bonds form between guanine and cytosine
D A T D
P P
D G C D
P P
D A T D
P P
D G C D
© 2021 Emma Thorp
P P
UNIT 1: DNA
- nucleus is surrounded by a double nuclear membrane with pores
o pores form the passage between the nucleus and cytoplasm
- nuclear membrane encloses the nucleoplasm, jelly like liquid
- nucleolus, small round body is suspended in the nucleoplasm
- chromatin network, mass of thread-like structures, also in the nucleus
- nucleus regulates the structure and metabolism of the cell
nucleic acids
- organic molecules that control the synthesis of proteins in all living cells by
storing and transferring genetic information
- two types of nucleic acid occur in living cells
o DNA (deoxyribonucleic acid)
o RNA (ribonucleic acid)
DNA
LOCATION OF DNA
- occurs mainly in the nucleus, where it forms part of the chromatin network
– chromosomal DNA
- a small amount of DNA occurs outside the nucleus, in the mitochondria and
chloroplasts in plants (extranuclear DNA)
CHROMOSONES & GENES
- chromosomes are long, thin, thread-like structures composed of DNA
that is wrapped around proteins called histones
DNA histone protein
© 2021 Emma Thorp
, - a short segment of a DNA molecule that codes for a particular protein is
known as a gene
- each gene carries the code for the synthesis of a particular protein
- proteins determine the characteristics of an organism
DISCOVERY OF THE STRUCTURE
- 1865: Gregor Mendel, finds that each characteristic is controlled by a
specific gene
- 1962: Watson, Crick and Wilkins, receive the Nobel Peace Prize for
Physiology/Medicine after their discovery of the structure of DNA
- 1990: The Human Genome Project is established with James Watson as
the first director
STRUCTURE OF DNA
- is a giant molecule, consisting of two strands, twisted to form a double
helix
- when unwound, looks like a ladder
- DNA is a polymer, made up of a large number of similar units (building
blocks), monomers
- monomer of DNA: nucleotides
NUCELOTIDES
- each nucleotide consists of three parts
o sugar molecule – deoxyribose (D)
o phosphate group (P)
o nitrogenous base -four different types:
adenine (A)
guanine (G)
cytosine (C)
thymine (T)
- adenine and guanine, large molecules: purine bases
- cytosine and thymine, smaller molecules: pyrimidine bases
© 2021 Emma Thorp
, FORMATION OF NUCLEOTIDES
- deoxyribose combines with phosphate group
- one nitrogenous base combines with deoxyribose
- four different nitrogenous bases, four different nucleotides in a DNA
molecule
D A T D D G C D
P P P P
FORMATION OF DNA
- deoxyribose of one nucleotide forms a bond with the phosphate group of
another
- two long stands, look like the sides of a ladder are formed
- the sides of the DNA ladder consist of alternating deoxyribose molecules
and phosphate groups
- each rung, of the DNA ladder is formed by the linking of two nitrogenous
bases; a large purine and a small pyrimidine base
- two bases together is known as a base pair
- nitrogenous bases are joined by weak hydrogen bonds, which are easily
broken by enzyme action
- adenine to thymine, guanine to cytosine
- two hydrogen bonds form between adenine and thymine
- three hydrogen bonds form between guanine and cytosine
D A T D
P P
D G C D
P P
D A T D
P P
D G C D
© 2021 Emma Thorp
P P
