Summary Grade 12 Biology

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Discovery of DNA + RNA Molucles :




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Structure was discovered by Watson + Crick in 1953
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They won the Nobel Prize for their work ☐::•IggG⑨tz@
In 1953 Rosalind Frank helped didn't get Prize




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discover , but died and a nobel



structure of DNA :
Contains ---o←
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instructions for making proteins from 20 different amino acids

Appears as chromatin when the cell is not dividing
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Makes up chromosomes in the nucleus
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Subunits DNA called nucleotides
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of
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Nucleotides contains a
phosphate a
Deoxyribose sugar , 1 nitrogen base CAT Cor G)


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Deoxyribonucleic Acid ( DNA)




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sugar .




base pairs phosphate
backbone
s carbon sugar - d "" "" "
p ••
A : ::::: T •

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Nucleotide •••• T : ::::: A
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Base Pairing Purine bonds to
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C
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a Pyrimidine
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Base pair
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Example A : - - T
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and C - - -


G
single nucleotide
•• G : : : : : :c
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BEGGAR S
Nucleotide
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structure DNA :




Steps Containing bases held together by weak hydrogen bonds
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or
rungs
of DNA made of 4 Nitrogen -




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Purines (double carbon -


nitrogen rings) include adenine (A) and guanine (G)
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Pyrimidines (single carbon -

nitrogen rings) includes thymine G) and cytosine (c)




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Weak H bond

, DNA Replication :
Occurs two of original DNA if
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during Interphase -
makes exact copies the .
not ,
a mutation occurs


1. The double helix unwinds and flattens out

2. An enzyme .
DNA helicase unzips the strand ,
at the weak hydrogen bond this exposes the
Nitrogen bases

3. Free nucleotides in the nucleus bond to the expose bases ,
following the base
pair ruling
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G -



C and A T Another enzyme DNA
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.
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polymerase will be responsible
for recapping the strands


4. The base pairing continues until the entire strand has their complement Whfrf IS DNA FOUND 8
5. Now there are two identical strand of DNA
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Found in nucleus + cytoplasm
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sugar
Contains the Nitrogen base uracil (v)
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Base pairings are A- U and C G

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to
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↳ Synthesis
Thyptnine
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Adenine Guanine
cytosine uracil •
DNA is too
large to
get out of the

nucleus RNA to it's
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Protein synthesis
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Phosphate OH OH
2-
Deoxyribose Ribose



3. Life at Molecular ,
Cellular and tissue level → DNA .
the code to life Two nucleic Acids are :




1. Deoxy ribonucleic Acid ( DNA)
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2nudeiAidRNA
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Molecules
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W of life
Nucleic acids called or Most extraordinary molecules on Earth

Control
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Cellular Activity

Development
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of organisms
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↳
Done by Controlling the synthesis of Proteins


first step making Proteins
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"
"
W Proteins make up structures , ENZYMES
much are proteins

Controlling Chemical Processes
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inside cell

↳ Thus , control structure + Functioning of all Living organisms




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Proteins
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Controlling synthesis of


Enzymes
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control
making up chemical
structure of processes inside
body cells

to stores info that controls cellular activity t development of
entire
organisms
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functioning
of
living organisms
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Genetic replication

DNA Replication Base Pairing : A = T
C =
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If 2 strands separate
B-•
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as

BBB * LG HB HB B. • mg
a template for a
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Thymine
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MMB
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Cytosine
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, complementary new chain
Guanine
Replicate)
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B- GB (ie each strand could
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Francis Crick
Sydney Brenner
1-


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Triplet code was used in reading genetic material in DNA 1- transferring info from Nucleus
to RNA to
cytoplasm via where Proteins are made


•
In DNA ,
form is function : Double -

stranded molecule could both Produce exact copies of itself

( replicate) 1- Carry genetic instructions
ie
Sequence bases form info be stored and
.
of in DNA a code
by which genetic can


transmitted


where is DNA found ?
•

mainly in the Nucleus of the cell


•
Forms Part of the Chromosomes that make up the
chromatine network


-
Chromatin =
Chromosomal material made up of DNA tRNA
1- histone Proteins found cell
as in a non
dividing
-




•
DNA molecule is coiled so that these long structures
can fit inside the nucleus


•
I 2
metres DNA in a cell