It contains oded information that
are used to create another cell.
this will determine what inherited
characteristics you will have.
Found in the nucleus
chromosomes come in pairs.
DNA is a polymer. it is made up of two strands
coiled together in the shape of a double helix.
Gene codes for a specific protein.
a gene is a small section of
DNA found on a chromosome
Each gene codes for a particular
sequence of amino acids, which are put
together make specific proteins.
Only 20 amino acids are used, but they
make up thousands of different
proteins.
Genes tell cells what order to
put amino acids together
DNA also determines what proteins the cell produces.
that in turn determines the type of cell it will produce.
Every organism has a GENOME
genome means - the entire set of
genetic material in an organism
it allows scientists to identify
genes in the genome that are
linked to types of disease.
Knowing which genes link to
inherited disease could help to
provide and develop effective
treatments.
Scientists can look at the genomes
to trace the migration of certain
populations.
All modern humans came from one ancestor from Africa, but
humans can be found all over the world. The human genome is
mostly identical, but as people migrated away from Africa little
changes appeared. By investigating the genome scientists can
discover when new populations split off in different direction and
find what route they took.
The structure of DNA and protein synthesis.
DNA is made up of Nucleotides
DNA is a polymer made up of lottos
repeating units called nucleotides
Each nucleotide consists of one
sugar molecule, one phosphate
molecule and one base.
The sugar and phosphate molecules form
the 'backbone' to the DNA strands.
the sugar and phosphate molecules alternate
one of four different bases join to each sugar.
A
T
C
G
Each base links to a base
on the opposite side.
A+T C+G
This is called complementary base pairing.
it is the order of bases that
decides the order of amino
acids in a protein.
mRNA carries the code to the ribosomes
to make proteins, ribosomes use the code in the DNA.
this is done using a molecule called mRNA -
which is copying the code form DNA, mRNA
acts as a messenger.
the correct amino acids are bought to the
ribosomes in the correct order by carrier molecules.
Mutations
Are changes in the genetic code
Can be inherited.
Most mutations have little to no
effect on a protein in the genetic
code.
However some mutations can
seriously affect a protein, by
changing their shape.
Different types of mutations
Insertions
Where a new base Is inserted
when it shouldn't be.
An insertions changes the way the
groups of three bases are 'read', which
changes the amino acids they code for.
Can change more than one amino acid
and have a 'knock on' effect on other
bases further on in the sequence.
Deletions
Where a random base is
deleted from the sequence.
Can also have 'knock on' effects
further down the sequence.
Substitutions
Where random bases in the sequence
are changed to a different base
Reproduction.
Sexual
transfer of genetic information from twi
'parents' to produce offspring that are
genetically different to either parent.
Involves male and female
gametes - offspring has a
mixture of parent's genes.
'parents' produce gametes by meiosis.
In humans gametes contain 23
chromosomes - half the number of
chromosomes in a normal cell.
this is why offspring inherits
features from both parents - it's a
mixture of chromosomes.
mixing genetic information
produces variation in offspring.
Advantages over asexual reproduction
Offspring have a mixture of two sets
of chromosomes, producing
variation.
Variation increases the survival of a
species in a changing environment.
They have survival advantages.
Individuals with characteristics that make them
better adapted are more likely to breed
successful and pass their genetics on. This is
called natural selection.
You can use selective breeding to 'speed
up' natural selection. This produces
animals with desirable characteristics.
Asexual
Only one parent, so the offspring
are genetically identical.
This happens by mitosis - an
ordinary cell divides into two.
the new cell has
exactly the same
genetic information -
called a clone.
bacteria, some plants
and some animals
produce this way.
Advantages over sexual reproduction.
There only needs to be one parent
this uses less energy because the
organism doesn't have to find a
mate.
this means asexual reproduction is faster.
Many identical offspring can be
produced in favourable conditions.
Meiosis
gametes only have one copy of each
chromosomes, so that when gamete fusion
happens there is the correct amount.
Only happens in the
reproductive organs.
1. before the cell starts to divide
it duplicates its genetic
information, after they replicate,
the chromosomes go into pairs.
2. The first division in
meiosis the chromosomes
pairs line up in the centre of
the cell.
3. The pairs are the pulled apart, so
each new cell only has one copy of
each chromosomes, some from the
father and some from the mother.
4. Th second division, the
chromosomes line up again,
the arms of the chromosomes
are pulled apart.
Gamete fusion replicates itself.
After two gametes have fused during
fertilisation, the resulting new cell dividing
by mitosis to make a copy of itself.
Mitosis repeats many
tamest produce lots of new
cells in an embryo.
as the embryo develops, these cells
then stat to differentiate into the
types of specialised cells that make
up a whole organism.