The mechanism of chromosome, gene mutation. The theory of mutation of Hugo De Vries

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2. The mechanism of chromosome, gene mutation. The theory of mutation of Hugo De Vries.

3. learning Objectives

•to explain the mechanism of
chromosome, gene mutation
•study the theory of mutation of Hugo
De Vries and causes mutagenesis

4. Success criteria

1.Know and understand the essence of
chromosome and gene mutations.
2.Can explain emergence mechanism of
chromosome and gene mutations.
3.Learners should describe correctly four types of
mutation out of five.
4.Explain the theory of mutation of Hugo De Vries
and causes mutagenesis.

5. Terminology

• Mutation, gene mutation, chromosomal mutation, point
mutation, deletion, addition, translocation, aneuploidy,
non-disjunction, polyploidy, mutagenesis, mutation
causes, genotype mutation, inheritance, mutation
variability, error, jump, death, new features, biochemical,
physiological, morphological, sex and somatic mutation.

6. What is a Mutation?

• Mutation is a change in the nucleotide sequence of a gene or
a chromosome.
• In biology, a mutation is the permanent alteration of the
nucleotide sequence of the genome of an organism, virus, or
extra-chromosomal DNA or other genetic elements.
• Mutations result from errors during DNA replication or other
types of damage to DNA (such as may be caused by exposure
to radiation or carcinogens).

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8. Hugo De Veirs

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10. The theory of mutation of Hugo De Vries.

• 1. Mutations or discontinuous variations are the raw material of evolution.
• 2. Mutations appear all of a sudden. They become operational immediately.
• 3. Unlike Darwin’s continuous variations or fluctuations, mutations do not
revolve around the mean or normal character of the species.
• 4. The same type of mutations can appear in a number of individuals of a
species.
• 5. All mutations are inheritable.
• 6. Mutations appear in all conceivable directions.
• 7. Useful mutations are selected by nature. Lethal mutations are eliminated.
However, useless and less harmful ones can persist in the progeny.
• 8. Accumulation of variations produce new species. Sometimes a new species is
produced from a single mutation.
• 9. Evolution is a jerky and discontinuous process.

11. Points in Favour of the Mutation Theory

(1) Mutations are actually the source of all variations and hence
fountain head of evolution.
(2) Mutation theory can explain both progressive and retrogressive
evolution.
(3) As the ratio of mutations is not the same in all individuals and their
parts, mutation theory can explain the occurrence of both changed and
unchanged forms.
(4) A number of mutations have appeared in the past.

12. Causes of mutagenesis

• Spontaneous: random changes to base
sequences of gene (UV-light).
•Induced: cause by factors – radiation,
mutagenic chemicals, high temperature.
• Mutagens: X-ray, radioactive isotopes, cosmic
rays, UV-light and etc.

13. Types of mutation

Mutation
Gene
Small-scale
Chromosomal
Large-scale

14. Gene mutation

• Change in the structure of a DNA molecule,
producing a different allele of a gene, is a gene
mutation.
• The DNA sequence of a gene can be altered in a
number of ways. Gene mutations have varying
effects on health, depending on where they
occur and whether they alter the function of
essential proteins.

15. The types of mutations include:

1. Gene mutation:
• Point: Transition, Transversion, Mispairing
• Frame – shift: Deletion, Insertion
• Missense mutation
• Nonsense mutation

16. Point mutation (DNA)

• Cause by base
substitution

17. Frame – shift mutation (DNA)

• caused by indels (insertions or deletions) of a number
of nucleotides in a DNA sequence that is not
divisible by three.
• can change the reading frame (the grouping of the
codons), resulting in a completely different translation from the
original.
• the reading of the codons after the mutation to code for different
amino acids.

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20. Types of gene mutations.

21. Protein change mutation

•Missense mutation
•Nonsense mutation

22. Missense mutation

• This type of mutation is
a change in one DNA
base pair that results
in the substitution of
one amino acid for
another in the protein
made by a gene.

23. Nonsense mutation

• A nonsense mutation is also a
change in one DNA base pair.
Instead of substituting one amino
acid for another, however, the
altered DNA sequence
prematurely signals the cell to
stop building a protein. This type
of mutation results in a shortened
protein that may function
improperly or not at all.

24. Insertion

• An insertion changes
the number of DNA
bases in a gene by
adding a piece of DNA.
As a result, the
protein made by the
gene may not
function properly.

25. Deletion

• A deletion changes the
number of DNA bases by
removing a piece of DNA.
Small deletions may remove
one or a few base pairs within
a gene, while larger deletions
can remove an entire gene or
several neighboring genes.
The deleted DNA may alter
the function of the resulting
protein(s).

26. Duplication

• A duplication consists
of a piece of DNA that
is abnormally copied
one or more times.
This type of mutation
may alter the function
of the resulting
protein.

27. Frameshift mutation

• This type of mutation occurs when the
addition or loss of DNA bases changes
a gene's reading frame. A reading
frame consists of groups of 3 bases
that each code for one amino acid. A
frameshift mutation shifts the
grouping of these bases and changes
the code for amino acids. The
resulting protein is usually
nonfunctional. Insertions, deletions,
and duplications can all be frameshift
mutations.

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29. Structural Chromosomal Mutations

• This happens when homologous chromosomes paired
• up, genes in chromosomes broke apart, genes inserted in the wrong
chromosome, or genes or set of genes are completely lost in the
chromosome.
• Basically, structural chromosomal mutations are classified
into four:
1. deletion,
2. duplication,
3. inversion,
4. translocation (or shift places).

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31. Deletion

• This type of mutation occurs
when a part of the DNA is
not duplicated or is lost
during DNA replication. The
size of this region can either
be a mere nucleotide or can
be large as an entire
chromosome.

32. Duplication

• This type of mutation occurs
when an extra copy of a region
(or regions) in the DNA is
produced. This duplicated region
can either be located in its
normal location in the
chromosome or sometimes be
located in other parts of the
chromosomes or even in
another chromosome.

33. Inversion

• During inversion, a
portion in the
chromosome is reversed
and gets inserted back
into the chromosome.
• Basically, two types of
inversion exist:
pericentric and
paracentric.

34. Translocation

• Translocation happens when
a fragmented chromosome
tends to join with a nonhomologous chromosome.
This newly-formed segment
then detaches from the
chromosome and moves to a
new position on another
chromosome.

35. Chromosomal Number Mutations

1. Aneuploidy:
2. Polyploidy
Aneuploidy is a type of mutation
in the chromosome number
wherein the ploidy (chromosome
number) of the new individual is
different from its wild type. This is
typically a result of the
nondisjunction of chromosomes
during mitosis or meiosis, hence
producing offspring with either
extra or lost chromosomes.
• Monosomic
• Trisomic
Polyploidy is a type of mutation
that occurs when an individual
bears more than one haploid set
of chromosomes. If the individual
with polyploidy bear three sets of
haploid chromosomes, the
condition is said to be triploidy
whereas if it has four haploid sets,
the condition is said to be
tetraploidy.

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• Interestingly, polyploidy is a common phenomenon among plants as
well as certain groups of fish, salamanders, frogs, and leeches.

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39. Success criteria

1.Know and understand the essence of
chromosome and gene mutations.
2.Can explain emergence mechanism of
chromosome and gene mutations.
3.Learners should describe correctly four types of
mutation out of five.
4.Explain the theory of mutation of Hugo De Vries
and causes mutagenesis.