The document summarizes key concepts about DNA structure and function. It describes that DNA is composed of nucleotides containing bases that pair in a double helix structure. It was discovered that DNA contains the genetic material and replicates in a semi-conservative manner according to the Watson-Crick model. Mutations in DNA can result in changes to genes that are inherited.

1. Paran, Lariza Mhay D.
Valente, Marielle Julia F.

2.  Inherited traits are
affected by genes
that are transmitted
from parents to
offspring in
reproduction
 Genes are
composed of the
chemical
deoxyribonucleic
acid = DNA

3.  DNA was discovered by Friedrich
Miescher in 1869
 In 1920s microscopic studies with
special stains showed that DNA is
present in chromosomes
 In 1944 Avery, McLeod and McCarty
provided the first evidence that DNA
is the genetic material

6.  In 1953 Watson and
Crick proposed the
three dimensional
structure of DNA
 Molecular structure of
DNA is a double-
stranded helix
comprised of a linear
sequence of paired
subunits = nucleotides
 Each nucleotide
contains any one of four
bases =
adenine, thymine,
guanine and cytosine
 Pairing between
nucleotides of the
double helix is
complementary:

7.  DNA backbone
forms right-handed
helix
 Each DNA strand
has polarity =
directionality
 The paired strands
are oriented in
opposite directions =
antiparallel

9.  Mutation refers to any heritable
change in a gene
 The change may be: substitution
of one base pair in DNA for a
different base pair; deletion or
addition of base pairs
 Any mutation that causes the
insertion of an incorrect amino

10. MUTATION INACTIVATES
NORMAL, WILD TYPE ENZYME

12. •The genetic complement of a cell
or virus constitutes its genome
•In eukaryotes, this term is
commonly used to refer to one
complete haploid set of
chromosomes, such as that found
in a sperm or egg
•The C-value = the DNA content of
the haploid genome

13.  DNA is a linear polymer of four
deoxyribonucleotides
 Nucleotides composed of 2'- deoxyribose (a
five-carbon sugar), phosphoric acid, and the
four nitrogen-containing bases denoted A, T, G
and C

14.  Two of the bases, A and G, have a double-ring
structure; these are called purines
 The other two bases, T and C, have a single-
ring structure; these are called pyrimidines

16.  The duplex molecule of DNA consists of two
polynucleotide chains twisted around one
another to form a right-handed helix in which
the bases form hydrogen bonds
Adenine pairs with thymine; guanine with
cytosine.
A hydrogen bond is a weak bond . The stacking
of the base pairs on top of one another also
contribute to holding the strands together. The
paired bases are planar, parallel to one
another, and perpendicular to the long axis of
the double helix.

17. • The backbone of
each polynucleotide
strand consists of
deoxyribose sugars
alternating with
phosphate groups
that link 5 ' carbon of
one sugar to the 3'
carbon of the next
sugar in line
• The two
polynucleotide
strands of the double
helix run in opposite

19. DNA Replication
Watson-Crick model of
DNA replication:
Hydrogen bonds
between DNA
bases break to allow
strand separation
Each DNA strand is a
template for the
synthesis of a new
strand
Template (parental)
strand determines the

21.  The linear DNA duplex in a
eukaryotic chromosome also
replicates bidirectionally
 Replication is initiated at many sites
along the DNA
 Multiple initiation is a means of
reducing the total replication time

22.  One strand of the newly made DNA
is synthesized continuously =
leading strand
 The other, lagging strand is made in
small precursor fragments = Okazaki
fragments
 The size of Okazaki fragments is
1000–2000 base pairs in prokaryotic
cells and 100–200 base pairs in

25.  DNA denaturation: Two DNA strands can be
separated by heat without breaking
phosphodiester bonds
 DNA renaturation = hybridization: Two single
strands that are complementary or nearly
complementary in sequence can come
together to form a different double helix
 Single strands of DNA can also hybridize
complementary sequences of RNA