12. Each strand
consists of:
1) A Sugar Phosphate Backbone
2) Four Base Chemicals
(Attached in pairs)
Adenine pairs with Thymine
Guanine pairs with Cytosine
13. Basic structure of DNA is a sugar-phosphate backbone
with 4 variable nitrogenous bases. This structure is called
a nucleotide.
P
sugar Nitrogen
base
Phosphate
molecule:
HYDROPHILIC
5-carbon
sugar:
DEOXYRIBOSE
Nitrogen
base:
HYDROPHOBIC
BACKBONE BASE
21. Adenine and Guanine are PURINES
Adenine and guanine each have two
rings of carbon and nitrogen atoms.
C
C
C
C
N
N
N
Adenine N
N
C
C
C
C
C
N
N
O
N
Guanine
N
N
C
23. Thymine and Cytosine are PYRIMIDINES
Thymine and cytosine each have one ring of
carbon and nitrogen atoms.
C
C
C
C
N
N
O
N
cytosine
C
C
C
C
N
N
O
O
thymine
C
25. Base Pair Rule
Adenine can bond only
with Thymine
A-T or T-A (2 H bonds)
Cytosine can bond only
with Guanine
C-G or G-C (3 H bonds)
26. Base Pair Rule
Adenine can bond only
with Thymine
A-T or T-A (2 H bonds)
Cytosine can bond only
with Guanine
C-G or G-C (3 H bonds)
27. Importance of base pairing
Genetic information storage
Stability of the double helix
Protein synthesis
Fundamental for the accurate
transmission and expression
of genetic information in
both dna and rna
29. RNA
•Ribonucleic Acid
•Consists only of one
strand of nucleotides
•Has ribose (a 5C
sugar) NOT
deoxyribose
•Has uracil (U) as a
nitrogenous base NOT
thymine
32. DNA by the Numbers
• Each cell has about 3 meters of
DNA.
• The average human has 300
trillion cells.
• The average human has
enough DNA to go from the
earth to the sun more than 400
times.
• DNA has a diameter of only
0.000000002 meters.
The earth is 150 billion meters
or 93 million miles from
the sun.
41. 1. Enzymes called
“Helicase”“unzip”
the DNA molecule
exposing both strands nitrogenous bases.
The DNA is separated into two
strands. A replication fork is created
with 2 single-stranded DNA templates.
42. 2. RNA primer binds to the exposed strand,
to start replication with the help of Primase.
A starting point for DNA
synthesis is provided for DNA polymerase.
43. 3. DNA polymerase III pairs the bases A-T
and G-C. DNA Polymerase checks work and
corrects mistakes
Nucleotides are paired
44. The leading strand is synthesized
continuously in the direction of the
replication fork.
The lagging strand is synthesized
discontinuously in short fragments called
Okazaki fragments
45. 4. “exonuclease” removes the RNA primers and replaces them with DNA nucleotides.
Removal of DNA Primers
46. 5. DNA ligase (enzyme) follows behind and bonds the nucleotides together.
Two strands of DNA are created.
49. The result is two exact
copies of the original DNA
Each new double helix is
composed of one original
DNA strand and one new
strand.
•Semi-conservative
50. The process is fast and accurate
An error occurs in only about one of a
billion nucleotides.
56. QUIZ
1. DNA is a ________ helix.
2. DNA is the __________ of life.
3. Adenine pairs with ________.
4. Guanine pairs with ________.
5. RNA stands for ___________.
Editor's Notes
#2:The biological definition of heredity may also pertain to the association of a particular trait with the genetic constitution of an individual organism, rather than with environmental conditions.
#3:The genes make up the sequences of DNA (genotypes). The genotypes, together with the other factors (e.g. environmental factors), determine the phenotypic trait of an organism.
How do genes influence who you are and what you do?
#6:the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA.
#7:DNA in a cellis primarily located within the nucleus, where it forms chromosomes. However, small amounts can also be found in mitochondria.
#8:and is thus responsible for the biochemistry of an organism.
Carries genetic information for the development, functioning, growth, and reproduction of all known organisms and many viruses.
#13:Hydrophilic- substances that have an affinity with water. They can easily interact with and dissolve in water. They often contain polar groups or charged ions that allow them to form hydrogen bonds with water molecules.
Deoxyribose- 5 carbon sugar. It forms the backbone of the dns molecule linking together the nucleotide units. The prefix “deoxy” indicates that it lacks one oxygen atom compared to ribose.
Hydrophobic- those that repel water and tend not to dissolve it.. These substances typically consist of nonpolar molecules or regions. Meaning they do not readily interact with water molecules
#14:Deoxyribose- 5 carbon sugar. It forms the backbone of the dna molecule linking together the nucleotide units. The prefix “deoxy” indicates that it lacks one oxygen atom compared to ribose.
#20:Purine- characterized by a double ring structure. These bases are essential for the genetic code and play crucial roles in the functioning of the cells, particularly in the process of DNA replication, transcription and translation.
Pyrimidine- consist of a single-ring structure..
#21:Purines consist of a six-membered and a five-membered nitrogen-containing ring, fused together
#23:Pyridmidines have only a six-membered nitrogen-containing ring.
#25:In a DNA double helix, each type of nucleobase on one strand normally interacts with just one type of nucleobase on the other strand. This is called complementary base pairing
Purines form hydrogen bonds to pyrimidines, with A bonding only to T, and C bonding only to G.
#26:Purines bond with pyrimidine to form complementary base pairs that stabilize the double helix structure of DNA and facilitate RNA synthesis and protein synthesis.
#27:Allows complementary nucleotides to bond with each other. Ensures accurate replication and transmission of genetic information during cell division and dna replication
Stabilizes the double helix structure. Preventing the dna strands from separating too easily
Ensures accurate translation of the genetic code into proteins during protein synthesis.
#28:Carries genetic information from the dna in the nucleus to the ribosomes in the cytoplasm
Helps translate the genetic code in mRNA into amino acids
Along with proteins, forms the ribosomes, which are the cellular organelles where protein synthesis occurs.
#32:If you unravel all the DNA in the chromosomes of one of your cells, it would stretch out 2 meters. If you did this to the DNA in all your cells, it would stretch from here to sun more than 400 hundred times!
