education

3. PRESENTER
Kulsoom pirjan

4. TOPIC OF PRESENTATION
mutation

5. Sub topics
1..mutation 7..Base alteration
2..DNA, molecular basis of
mutaion
8..Genetics variation
3..Types of mutation 9..Mechanisms of change
4..The causes of mutation
5..Morphological mutation
6..Lethal mutation

6. Mutation
• A mutation is a permanent change in the sequence of
DNA. In order for an observable effect, mutations must
occur in gene exons or regulatory elements.
• In biology, a mutation is a permanent change of the
nucleotide sequence of the genome of an organism, virus,
or extrachromosomal DNA or other genetic elements. .

7. Mutation cont..
• Mutations can involve the duplication of large sections of
DNA, usually through genetic recombination.
• These duplications are a major source of raw material for
evolving new genes, with tens to hundreds of genes
duplicated in animal genomes every million years.

8. Due to small change in in DNA sequences
resultant , mutation occur

11. DNA, The molecular basis of mutations
• Since mutations are simply changes in DNA, in order to
understand how mutations work, you need to understand
how DNA does its job.
• Your DNA contains a set of instructions for "building" a
human. These instructions are inscribed in the structure of
the DNA molecule through a genetic code.

12. DNA, The molecular basis of mutations
cont…
• DNA is made of a long sequence of smaller units strung
together. There are four basic types of units.
• example,.. A, T, G, and C. These letters represents the
type of base each unit carries. adenine, thymine, guanine,
and cytosine.

13. DNA, The molecular basis of mutations
cont…
• The sequence of these bases encodes instructions. Some
parts of your DNA are control centers for turning genes on
and off, some parts have no function, and some parts
have a function that we don't understand yet.
• Other parts of your DNA are genes that carry the
instructions for making proteins — which are long chains
of amino acids. These proteins help build an organism.

14. DNA, The molecular basis of mutations
cont…
• Protein-coding DNA can be divided into codons — sets of
three bases that specify an amino acid or signal the end
of the protein.

15. DNA, The molecular basis of mutations
cont…
• Codons are identified by the bases that make them up in
the example at right, GCA, for guanine, cytosine, and
adenine.
• The cellular machinery uses these instructions to
assemble a string of corresponding amino acids (one
amino acid for each three bases) that form a protein.

16. DNA, The molecular basis of mutations
cont…
• The amino acid that corresponds to "GCA" is called
alanine; there are twenty different amino acids
synthesized this way in humans. "Stop" codons signify the
end of the newly built protein.
• After the protein is built based on the sequence of bases
in the gene, the completed protein is released to do its job
in the cell.

17. DNA Structure

18. Types of mutations
• There are many different ways that DNA can be changed,
resulting in different types of mutation.
1. Substitution
2. Insertion
3. Deletion
4. Frameshift

19. Substitution
• A substitution is a mutation that exchanges one base for
another(i.e., a change in a single "chemical letter" such
as switching an A to a G).
• 1. change a codon to one that encodes a different
amino acid and cause a small change in the protein
produced. For example, sickle cell anemia is caused by a
substitution in the beta-hemoglobin gene, which alters a
single amino acid in the protein produced.

20. Substitution
• 2.change a codon to one that encodes the same amino
acid and causes no change in the protein produced.
These are called silent mutations.
• 3. change an amino-acid-coding codon to a single
"stop" codon and cause an incomplete protein. This can
have serious effects since the incomplete protein probably
won't function.

22. Insertion
• Insertions are mutations in which extra base pairs are
inserted into a new place in the DNA.

23. Deletion
• Deletions are mutations in which a section of DNA is lost,
or deleted

24. Frameshift
• protein-coding DNA is divided into codons three bases
long, insertions and deletions can alter a gene so that its
message is no longer correctly passed. These changes
are called frameshifts.
• For example, consider the sentence, "The fat cat sat."
Each word represents a codon. If we delete the first letter
and parse the sentence in the same way, it doesn't make
sense.

25. Frameshift

27. The causes of mutations
Mutations happen for several reasons.
• 1. DNA fails to copy accurately
• Most of the mutations that we think matter to evolution are
"naturally-occurring." For example, when a cell divides, it
makes a copy of its DNA — and sometimes the copy is
not quite perfect. That small difference from the original
DNA sequence is a mutation.

29. 2.External influences can create
mutations
• Mutations can also be caused by exposure to specific
chemicals or radiation. These agents cause the DNA to
break down. This is not necessarily unnatural — even in
the most isolated and pristine environments, DNA breaks
down. Nevertheless, when the cell repairs the DNA, it
might not do a perfect job of the repair. So the cell would
end up with DNA slightly different than the original DNA
and hence, a mutation.

32. Other types of mutation
Morphological mutations
Morph means “form.” Morphological mutations affect the
outwardly visible properties of an organism, such as shape,
color, or size.
i,e…curly wings in Drosophila, and dwarf peas are all
morphological mutations etc.

34. Lethal mutations
• A mutant trait that leads to a phenotype incapable of
effective reproduction. lethal gene n. A gene whose
expression results in the death of the organism.
• In another words a lethal mutation refers to any and all
mutations that prevent an organism from reproducing in
any way. Lethal mutations do not have to kill the organism
to classify as lethal. An example of a lethal mutation in
humans is Turner Syndrome

36. • Mutations to control genes can transform one body part
into another. Scientists have studied flies carrying Hox
mutations that sprout legs on their foreheads instead of
antennae!

39. Base alteration
• Some mutagens are not incorporated into the DNA but
instead alter a base, causing specific mispairing.
• Certain alkylating agents, such as ethyl methanesulfonate
(EMS) and the widely used nitrosoguanidine (NG),
operate by this pathway.

40. Base alteration cont..
• Although such agents add alkyl groups to many positions
on all four bases, mutagenicity is best correlated with an
addition to the oxygen at the 6 position of guanine to
create an O-6-alkylguanine.
• This alkylation leads to direct mispairing with thymine..

43. Genetics variation:
• Without genetic variation, some of the basic mechanisms
of evolutionary change cannot operate.
• There are three primary sources of genetic variation,
which we will learn more about.
A. Mutation
B. Gene flow
C. sex

44. Genetics variation cont..
• 1. Mutations are changes in the DNA. A single mutation
can have a large effect, but in many cases, evolutionary
change is based on the accumulation of many mutations.
• 2. Gene flow is any movement of genes from one
population to another and is an important source of
genetic variation.
• 3. Sex can introduce new gene combinations into a
population. This genetic shuffling is another important
source of genetic variation.

45. Genetic shuffling is a source of variation.

46. Mechanisms of change:
• Mutation
• A mutation could cause parents with genes for bright
green coloration to have offspring with a gene for brown
coloration. That would make genes for brown coloration
more frequent in the population than they were before the
mutation.

47. mutation

48. Migration and gene flow
• In population genetics, Gene Flow (also known as gene
migration) refers to the transfer of genes from the gene
pool of one population to another.
• Gene flow may change the frequency and/or the range of
alleles in the populations due to the migration of
individuals or gametes that can reproduce in a different
population.

49. Migration and gene flow cont..
• Plant populations can experience gene flow by spreading
their pollen long distances away to other populations by
means of wind or through birds or insects (bees, for
example) and once there, this pollen is able to fertilize the
plants where it ended up. Pollen is a fine to coarse
powder containing the microgametophytes of seed plants,
which produce the male gametes (comparable to sperm
cells).

50. Migration and gene flow cont..
• Human migrations have occurred throughout the history
of mankind and are defined as the movement of people
from one place to another. this movement needs to be
associated with the introduction of new alleles into a
population through successful mating of individuals from
different populations

52. Genetic drift
• Imagine that in one generation, two brown beetles
happened to have four offspring survive to reproduce.
Several green beetles were killed when someone stepped
on them and had no offspring. The next generation would
have a few more brown beetles than the previous
generation — but just by chance. These chance changes
from generation to generation are known as genetic drift

54. Natural selection
• Imagine that green beetles are easier for birds to spot
(and hence, eat). Brown beetles are a little more likely to
survive to produce offspring. They pass their genes for
brown coloration on to their offspring. So in the next
generation, brown beetles are more common than in the
previous generation.

55. Natural selection
• All of these mechanisms can cause changes in the
frequencies of genes in populations, and so all of them
are mechanisms of evolutionary change. However, natural
selection and genetic drift cannot operate unless there is
genetic variation .