inheritance and how gender is dt.....ermined

about inheritance

1. INHERITANCE INHERITANCE

2. CONTENT
•State that chromosomes are made of DNA, which
contains genetic information in the form of genes

•Define a gene as a length of DNA that codes for a protein
•Define an allele as an alternative form of a gene

•Describe the inheritance of sex in humans with reference
to X and Y chromosomes
•State that the sequence of bases in a gene determines
the sequence of amino acids used to make a specific
protein

3. CONTENT
•State that the sequence of bases in a gene determines the
sequence of amino acids used to make a specific protein

•Explain that different sequences of amino acids give different
shapes to protein molecules
•Explain that DNA controls cell function by controlling the
production of proteins, including enzymes, membrane carriers
and receptors for neurotransmitters
•Explain how a protein is made
•Explain that most body cells in an organism contain the same
genes, but many genes in a particular cell are not expressed
because the cell only makes the specific proteins it needs

4. Inheritance
Inheritance 
is the 
transmission
of genetic information from
generation to generation

5. The nucleus
The nucleus of the cell,
containing all of the
genetic material. This
material is inherited from
the parents.

6. The nucleus contains
chromosomes – in normal
human cells, there are 23
pairs of chromosomes.
Each chromosome is made
up of a very special
molecule called DNA.
The nucleus

7. The nucleus contains
chromosomes – in
normal human cells,
there are 23 pairs of
chromosomes. Each
chromosome is made up
of a very special
molecule called DNA.
DNA stands for deoxyribonucleic
acid,
The nucleus

8. Here is an individual
chromosome
Inside, the double
helix of DNA can be
clearly seen.
The nucleus

9. Chromosomes, genes and DNA
chromosome

10. Chromosomes, genes and DNA
Individual sections of a chromosome are called
genes. Each gene ( a short section of DNA) codes
for a particular protein, which may control
particular characteristics, such as eye colour.
Each chromosome may contain thousands of genes.

11. DNA Structure
DNA consists
of two strands,
wrapped into a
double helix.

12. DNA Structure
DNA consists of
two strands,
wrapped into a
double helix.
The two strands are
linked by pairs of
BASES
There are four
bases
Adenine
Thymine
cytosine
guanine.

13. DNA Structure
DNA consists of
two strands,
wrapped into a
double helix.
The two strands
are linked by
pairs of BASES
There are four
bases – adenine,
thymine,
cytosine and
guanine.
Adenine + Thymine
Cytosine + Guanine

14. DNA Structure
DNA consists of
two strands,
wrapped into a
double helix.
The two strands
are linked by
pairs of BASES
There are four
bases – adenine,
thymine,
cytosine and
guanine.
Adenine + Thymine
Cytosine + Guanine
A
T
C
G

15. DNA Structure
DNA consists of
two strands,
wrapped into a
double helix.
The two strands
are linked by
pairs of BASES
There are four
bases – adenine,
thymine,
cytosine and
guanine.
Adenine + Thymine
Cytosine + Guanine
A
T
C
G
DNA molecules form a complete set of
instructions on how an organism should be
‘constructed’ and how the cells should work.

16. DNA Structure
The bases are ‘read’ in
threes, or triplets.

17. DNA Structure
The bases are ‘read’ in
threes, or triplets.
Each triplet codes for a
particular amino acid.

18. DNA Structure
The bases are ‘read’ in
threes, or triplets.
Each triplet codes for a
particular amino acid.
Don’t forget
that proteins are
made up of amino
acids!

19. DNA Structure
The bases are ‘read’ in
threes, or triplets.
Each triplet codes for a
particular amino acid.
Don’t forget
that
proteins are
made up of
amino acids!

20. DNA Structure

21. DNA Structure
The bases are ‘read’ in
threes, or triplets.
Each triplet codes for a
particular amino acid.
So this triplet of bases is
cytosine – cytosine – thymine
or CCT

22. DNA Structure
The bases are ‘read’ in
threes, or triplets.
Each triplet codes for a
particular amino acid.
So this triplet of bases is
cytosine – cytosine – thymine
or CCT
TATGGATGTGCTACCTCG

23. DNA Structure
TATGGATGTGCTACCTCG
Since there are only about 20
different amino acids that
make up all the protein
chains, the different base
triplet combinations are more
than sufficient

24. PROTEIN SYNTHESIS
The process of protein synthesis has two
stages
Transcription 
(rewriting the base code
of DNA into bases of RNA)
Translation 
(using RNA base
sequence to build amino acids into
sequence in a protein)

25. •Proteins are made by
 
ribosomes
 
with the
sequence of amino acids controlled by
the
 
sequence of bases 
contained within DNA
PROTEIN SYNTHESIS

26. •Proteins are made by
 
ribosomes
 
with the
sequence of amino acids controlled by
the
 
sequence of bases 
contained within DNA
PROTEIN SYNTHESIS
•DNA
 
cannot travel out of the
nucleus
 to the ribosomes
(it
is far too big to pass through
a nuclear pore) so the base
code of each gene is
transcribed onto an RNA
molecule called
 
messenger
RNA
 (mRNA
).

27. PROTEIN SYNTHESIS
•DNA
 
unwinds and an mRNA molecules is produced

28. •mRNA then
 
moves out of the nucleus 
and
attaches to a ribosome
PROTEIN SYNTHESIS

29. PROTEIN SYNTHESIS

30. PROTEIN SYNTHESIS
•The ribosome ‘reads’ the code on the mRNA in groups of
three
•Each triplet of bases
 codes for a specific amino acid

31. PROTEIN SYNTHESIS
•In this way the ribosome
 
translates 
the sequence of bases into
a
 
sequence of amino acids 
that make up a protein
•Once the amino acid chain has been assembled, it is released from
the ribosome so it can fold and form the final structure of the protein

32. PROTEIN SYNTHESIS
•In this way the ribosome
 
translates 
the sequence of bases into
a
 
sequence of amino acids 
that make up a protein
•Once the amino acid chain has been assembled, it is released from
the ribosome so it can fold and form the final structure of the protein

33. PROTEIN SYNTHESIS

34. PROTEIN SYNTHESIS

35. PROTEIN SYNTHESIS

36. PROTEIN SYNTHESIS

37. PROTEIN SYNTHESIS

38. PROTEIN SYNTHESIS
•DNA controls cell function by controlling the
production of proteins
•The proteins may be enzymes, antibodies, or receptors
for neurotransmitters
•Although all body cells in an organism contain the same
genes, many genes in a particular cell are not
expressed because the cell only makes the specific
proteins it needs

39. PROTEIN SYNTHESIS
•the gene coding for the protein remains in the
nucleus
•mRNA molecules are made in the nucleus and
move to the cytoplasm
•the mRNA passes through ribosomes
•the ribosome assembles amino acids into protein
molecules
•the specific sequence of amino acids is
determined by the sequence of bases in the
mRNA

40. Genetic mutations
Every time a cell divides, all
the DNA in the nucleus must
be copied exactly.

41. Genetic mutations
Every time a cell divides, all
the DNA in the nucleus must
be copied exactly.
Occasionally a mistake may
occur, and bases may be put
in the wrong order.

42. Genetic mutations
Every time a cell divides, all
the DNA in the nucleus must
be copied exactly.
Occasionally a mistake may
occur, and bases may be put
in the wrong order.
As a result, there will be a
different sequence of amino
acids, and therefore a
different protein will be
made.

43. Genetic mutations
Every time a cell divides, all
the DNA in the nucleus must
be copied exactly.
Occasionally a mistake may
occur, and bases may be put
in the wrong order.
As a result, there will be a
different sequence of amino
acids, and therefore a
different protein will be
made.
This change in the order
of the bases is called a
MUTATION

44. Genetic mutations
Causes Effects
Mutations occur naturally
but ……
• there is an increased risk
if
• individuals are exposed to
mutagenic agents
• such as ionising radiation
(UV, X-rays)
• radioactive substances and
certain chemicals.
• the greater the dose, the
greater the risk.
Most mutations are harmful
and in …
• Reproductive cells can
cause death or abnormality
• in body cells they may
cause cancer
• some mutations are neutral
and some may increase the
survival chances of an
organism
• and its offspring who
inherit the gene