Download DNA Powerpoint - Year 10 Life Science

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Topics Covered
DNA
and
Inheri
tance
Psych
ology
Fossil
s and
Evolu
tion
Globa
l
Syste
DNA and Inheritance
1.1 DNA the molecule (page 2)
Introduction
DNA
 DNA stands for Deoxyribonucleic acid
 Found in the nucleus of cells.
 It determines the characteristics of living things.
 For example, hair colour, eye colour, bone structure, height.
 They are instructions for making an animal or plant.
 Ladder-like structure called a double helix.
 A molecule of DNA is made up of millions of tiny
subunits called nucleotides
Nucleotides
Each nucleotide consists of:
 Phosphate group
 Pentose sugar
 Nitrogenous base
Nucleotides
Phosphate
Sugar
Nitrogenous
Base
DNA Structure
 The phosphate and sugar form the backbone of the DNA molecule
 The bases form the “rungs”
 There are four types of nitrogenous bases:
 Adenine (A)
 Thymine (T)
 Guanine (G)
 Cytosine (C)
 Each base will only bond with one other specific base (Nitrogenous
base pairing)
 C and G always pair together and
 T and A
Complementary Base Pairing
Original Sequence
 The order of one strand determines the order of
the other.
 This is known as the complementary base pairing.
 The sequence of these nitrogen bases along the
strands of DNA is the basis for all inherited
characteristics.
Complementary Sequence
Each base will only bond with one other specific base.
 Cytosine and Guanine
 Thymine and Adenine
Nitrogenous
base pairing
That means, if there are 50 Cytosine's in a DNA molecule,
there will also be 50 Guanines – as they come as a pair!
Modelling DNA activity
Your task is to construct a DNA molecule
Insure you label All parts of the DNA molecule including:
 Nucleotide
 Hydrogen Bond
 DNA backbone
 Original and Complementary sequence
*hint* there should be 12 labels in total
Answer the following questions
1. State the base pairing rule
2. Compare you model to others in the class. Are they the same?
Describe the similarities and differences
3. Calculate the number of different variations of single DNA
Strands that can be made using only the 10 bases you started
off with
Prac #1 Extracting
DNA from
peas
The following website is an useful resource to help answer the discussion questions
http://learn.genetics.utah.edu/content/labs/extraction/howto/
What is DNA?
The Genetic Code
Each strand of DNA contains thousands
of sequences of bases A, T, G and C
This long sequence of bases is read in
sets of three.
Each set of three is called a codon
 There are 20 amino acids that can be used to make
protein
 The body can only make 11 amino acids. The others are
too slow to synthesis therefore must be obtained
through our diet.
Making
a protein
The sequence of Amino Acids in a protein that
determines its function.
Primary
Structure
The shape of the protein depends on its primary
structure, which then determines the proteins
properties and functions
• Some proteins are enzymes (speed up
reactions) Eg: digestive system
• Act as messengers between cells
Roles of
Proteins
• Make up cellular components such as muscle,
hair and nails
• Act as ‘gatekeepers ‘ which allow substances to
enter and leave cells
• Produce haemoglobin which transports oxygen
to our cells.
• Also involved in producing insulin which
controls our blood sugar levels.
Enzymes of the digestive system
Enzymes:
speed up
chemical
reactions
This diagram
shows a cross
section of four
plasma
membrane
proteins
performing
different
functions as
gate keepers
Haemoglobin:
transports
oxygen to our
cells
Insulin:
controls blood
sugar levels
DNA to
Protein
Step 1: DNA is copied into mRNA
The DNA triplets are COMPLEMENTARY to a group of 3
RNA bases, known as a codon
How to make a
protein?
 Cytosine (C) still pairs with Guanine (G)
 Adenine (A) pairs with Uracil (U).
 Eg. DNA: CAT TAC GTA GAA GTC CCA TAA
mRNA: GUA AUG CAU CUU CAG GGU AUU
Step 2: mRNA is used to read the codon chart.
Three bases in a mRNA sequence is called a codon. Each
codon is associated with an amino acid
How to make a
protein?
 You will use a codon chart to make this match
 Abbreviate each amino acid (use first three letters)
mRNA:
GUA AUG CAU CUU CAG GGU AUU
Amino acid: val
met
his leu
glu gly iso
The
Codon
Chart
A codon chart is used to determine the
amino acid sequence of a protein
There are 64 different codons and form
these 20 different amino acids codes for
1000s if proteins.
The
Codon
Chart