mutation note

8/22/2019 Mutation Note

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http://matriculation-biology.blogspot.com

MUTATION(4 hour)

Retold by:

Amran Md Said,Matriculation College of Pahang.

Objective. At the end of this topic, students should be able to:

Explain mutation Classify mutation state types of mutation define mutagen state types of mutagen explain gene/point mutation classify gene mutation describe base substitution as point mutation eng. Sickle cell anemia explain frameshift mutation describe base insertion as a frameshift mutation describe base deletion as a frameshif mutation explain chromosomal mutation

classify chromosomal mutation explain chromosomal aberration (structural changes) state and describe type of chromosomal aberration explain alteration of chromosome number state the types of the alteration explain aneuploidy describe the cause and the affect aneuploidy explain autosomal abnormalities and their effects explain sex chromosomal abnormalities explain euploidy explain polyploidy

What is mutation?

A mutation is a change in the amount, arrangement or structure of the DNA of an organism.

Mutations produce sudden and distinct differences between individuals cause alternation ofchromosome.

Alteration of chromosome number or structure cause some genetic disorders such as Sickle CellAnemia and Down Syndrome

Mutation can occurring in gamete cells or somatic cells.

i) gamete cellsare inherited, It passed to subsequent generations as part of the hereditary endowment of thegames derived from that cell.

ii) somatic cells

can only be inherited by daughter cells produced by mitosis.


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A mutant is an individual or new genetic character arising or resulting from an instance of mutation theblue lobsteris an example of a mutant.

Type of mutationi) spontaneous mutation

- Mistakes happen spontaneously during DNA replication, repair and recombination- eg. nondisjunction

ii) induced mutation- Organism exposed to mutagen

What is mutagen ?

a mutagen (Latin, literally origin of change) is a physical or chemical agent that changes the geneticmaterial

Operate either by causing changes in the DNA of the genes or by causing chromosome damage type of mutagen

i) Physical agentUltraviolet rayIonizing radiation (X-ray, gamma ray, alpha particles, neutron and electron)

ii) Chemical agenteg. Colchicine (usually to treat rheumatic complaints, especially gout)Ethidium bromide (is an intercalating agent commonly used as a fluorescent tag in laboratories for

techniques such as agarose gel electrophoresis)

CLASSIFICATION OF MUTATION:

Classify of mutationi) gene / point mutationii) chromosomal mutation

GENE MUTATION (POINT MUTATION)GENE MUTATION (POINT MUTATION)

Producing alterations in the sequence of DNA nucleotide. involve only one or a few base pair in the coding sequence. Arise due to spontaneous pairing errors that occur during DNA replication, Arise due to mutagens like radiation or chemicals cause damage to the DNA. As a result :

- Change the amino acid sequence and thus, changes the protein- Different protein produced as the effect of mutation may not function as normal

Classify gene mutationi) Base substitutionii) Base insertioniii) Base deletioniv) Base inversion

mutation of base deletion and insertion make cause frame shift mutation Alteration of gene mutation cause some genetic disorders such as Sickle Cell Anemia

Classification of GeneClassification of Gene mutation:mutation:

Base substitution :

One or a few base pairs in the nucleotide sequences in genes is substitute Changes in base sequence results in changes of codon (UAU/UGU) 3 base/ nucleic acid = 1 codon (coding for 1 amino acid) Changes in codon:-

a) amino acid changes(missense mutation)

b) changes a codon to stop codon (nonsense mutation)


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Missense mutations are those that still code for an amino acid but change the indicated amino acid eg.Sickle Cell Anemia.

Nonsense mutations cNonsense mutations change an amino acid codon into a stop codon, nearly always leading to anonfunctional protein.

Sickle cell AnemiaSickle cell Anemia

mutant Hbs cause defective red blood cell. The cells are shaped like a crescent or sickle occurs more commonly in people regions where malaria is or was common. there is a survival value in

carrying only a single sickle-cell gene Those with only one of the two alleles of the sickle-cell disease aremore resistant to malaria, since the infestation of the malaria plasmodium is halted by the sickling of thecells which it infests.

sickle shape body produces abnormally shaped red blood cells.

Hbs stiff & tend to accumulate in small capillary, Hb is not efficient of transporting oxygen

polypeptide chain encode by different gen, cause differ one base only

Normal Mutantnucleotide T base is replaced by A base

DNA chain C T T C A T

transcript

mRNA G A A G U A

translation

code of amino acid glutamic valine

type of protein HB normal HB S

A change in a single nucleotide from T to A in the DNA template leads to an abnormal protein. Amino acid valine replaces glutamic acid at a single position in the protein

Base insertions

Addition of 1 or a few base pairs in the nucleotide sequences in genes mutation of base insertion make cause frame shift mutation


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Normal Mutantadditional nucleotide insertion with base G

DNA chain AGA GTC TTC AGA GGT CTT

transcript

mRNA UCU CAG AAG UCU CCA GAA

translation

code of amino acid Ser Gln Lys Ser Pro Glu

frame-shift happen

Base deletions

Loss of 1 or a few base pairs in the nucleotide sequences in genes mutation of base deletion make cause frame shift mutation

Normal Mutantlost of T base during replication of DNA

DNA chain AGA GTC TTC AGA GCT TCG

transcript

mRNA UCU CAG AAG UCU CGA AGC

translation

code of amino acid Ser Gln Lys Ser Arg Ser

frame-shift happen

Base inversion

2 base pairs or more are inverted in nucleotide sequence

Normal Mutant

inverted in nucleotide sequenceDNA chain AGA GTC TTC AGA TGC TTC

transcript

mRNA UCU CAG AAG UCU ACG AAG

translation

code of amino acid Ser Gln Lys Ser Thr Lys

Frame-shift MutationsFrame-shift Mutations

Involve insertion/deletion of a base pair or more into the nucleotides sequence of DNA Many of these deletions/insertion start in the middle of a codon Shifting the reading frame by one or two bases Frame shift mutations cause the gene to be read in the wrong three base groups (codon) From the mutation point, It abrupt the coding sequence of amino acid. Changes in codons results in changes in amino acids Different polypeptide is produced Effect ~ usually harmful to human E.g.: Major Thalasemia (mutant homozygote alleles)


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CHROMOSOMAL MUTATION

Definition: Abnormalities ~ in chromosomal structure (chromosome aberration) & changes inchromosome number (aneuploidy / euploidy)

Chromosomal mutations take place when the number of chromosomes changes or when structuralchanges occur in the chromosomes

Classification chromosomal mutationi) Chromosomal aberration (structural of chromosomal change)ii) Chromosomal number alteration

- Aneuploidy- Euploidy (polyploidy)

Chromosomes aberration

Changes in the chromosomes structure, are most frequently formed during mitosis or meiosis

Rearrangement a certain segment @ parts of chromosome 4 types of chromosomal aberration

i) Translocationii) Deletion (segmental deletion)iii) Inversioniv) Duplication

Analogy of frame-shift mutation

one sentencesCAN YOU BUY CAT FOR HER SON

after insertion only one alphabet , A at CAT in the sentence,CAN YOU BUY ACA TFO RHE RSO N

we can't read that sentence

after delete only one word, C at CAT in the sentenceCAN YOU BUY ATF ORH ERS ON

we can't read that sentence*peringatan analogi ini untuk kefahaman sahaja ianya tidak boleh digunakan dalam peperiksaan


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Translocation

Translocation : involves a region of a chromosome breaking off and rejoining either the other end of the samechromosome or another non-homologous chromosome

e.g. Robertsonian translocation Robertsonian translocation involves breaks at the extremes ends of the short arms of two

nonhomologous chromosomes (13, 14, 15, 21 and 22) Named after the American insect geneticist W.B.Robertson Also called whole-arm translocation or centric-fusion translocation

Deletion

Deletion: the lost of 1 segment containing 1 or more genes

When the chromosome breaks at two places and lead to the loss of the middle segment The segment lost may contain one or more genes The remaining end of chromosome will join again and become shorten Genetic disease: Cri du chat syndrome (usually mentally retarded and cries like a cat mewing) Loss of a small part of the short arm of chromosome 5 Cri du chat is a rare syndrome (1 in 50,000 live births) caused by a deletion on the short arm of

chromosome 5. The name of this syndrome is French for "cry of the cat," referring to the distinctive cry of children with

this disorder. The cry is caused by abnormal larynx development, which becomes normal within a few weeks of birth. Infants with cri du chat have low birth weight and may have respiratory problems. Some people with this disorder have a shortened lifespan, but most have a normal life expectancy. Where does the abnormal chromosome 5 come from? In 80 percent of the cases, the chromosome

carrying the deletion comes from the father's sperm.


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Inversion

Inversion: a region of a chromosome breaks off and rotates through 180 before rejoining thechromosome

Duplication

Duplication: a region of a chromosome becomes duplicated; an additional set of genes exists

When a single locus or a large piece of a chromosome is present more than once in the genome


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Alteration of chromosomes number

Type of the alteration of chromosomal numberi. aneuploidyii. euploidy / polyploidy

Human somatic cells containing a number of chromosomes which is not a multiple of 23 are called

aneuploids

Aneuploidy

Aneuploidy is a condition in which the number of chromosomes is abnormal due to extra or missingchromosomes, in other words, it is a chromosomal state where the number of chromosomes is not amultiple of the haploid set.

Normal diploid species have 2n chromosomes, where n is the number in the haploid set. Aneuploid individuals would have 2n-1 chromosomes (monosomy), 2n+1 chromosomes (trisomy), or

some other such arrangement. A change in the number of chromosomes can lead to a chromosomal disorder. Aneuploidy is common in

cancerous cells. Aneuploidy occurs during cell division when the chromosomes do not separate properly between the two

cells

Type of aneuploidy Genome situation

Monosomy 2n - 1

Trisomy 2n + 1

Tetrasomy 2n + 2

Disjunction: chromosomes separated to the opposite poles during meiosis

Non disjunction: failure of pair of chromosome to separate and to move to the opposite poles

both sets of chromosomes pass to the same pole of the cell

Cause of aneuploidy

Nondisjunction in Anaphase I & II


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Nondisjunctionin Anaphase I and II (meiosis)

Half the daughter cells produced have an extra chromosomes (n+1) whilst the other half have achromosome missing (n-1)

Fusion gametes between chromosome (n+1) and normal gamete (n), produced embryo with

chromosome (2n+1) : Trisomy; eg. Downs syndrome Fusion gametes between chromosome (n-1) and normal gamete (n), produced embryo with

chromosome (2n-1) : Monosomy; eg. Turner Syndrome

Autosomal abnormalities

Monosomy 21Trisomy 21 (down syndrome)

Monosomy


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Monosomy is the presence of only one chromosome from a pair in a cell's nucleus. Monosomy in human very rare, the majority embryos don't be survive, For live infant reported in human,

the only of monosomy 12

Monosomy 21

The syndrome is generally lethal and only several cases of living newborn infants have been reported,most of whom die between 3 weeks and 20 months of life but some survive into childhood.

Symptoms:- Short distance between eyes- Large ears- Contracted muscle- Large nose with a broad base- cleft lip and/or palate- Short neck- Short thorax- Small hands and feet, overlapping and/or flexed fingers and toes,- hyperactive reflexes (nervous system)

Trisomy

Trisomy is a presence genetic abnormality in which there are three copies, instead of the normal two,chromosomes of a particular numbered type in an organism

A trisomy is a type ofaneuploidy (an abnormal number of chromosomes) Human trisomy can occur with any chromosome. Most trisomies, like most other abnormalities in

chromosome number, result in distinctive and serious birth defects. Most trisomies result in spontaneousabortion; the most common types that survive to birth in humans are:- Trisomy 21 (Down syndrome)- Trisomy 18 (Edwards syndrome)

- Trisomy 13 (Patau syndrome)- Trisomy 9- Trisomy 8 (Warkany syndrome 2)- Trisomy 16 is the most common trisomy in humans, occurring in more than 1% of pregnancies. Thiscondition, however, usually results in spontaneous miscarriage in the first trimester


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A trisomy is theThus the presence of an extra chromosome 21 is called trisomy 21

Symptoms Down syndrome / trisomy 21

Short stature. A child often grows slowly and, as an adult, is shorter than average. Weak muscles (hypotonia) throughout the body. A child may seem to have less strength than other

children of the same age. A short, wide neck with excess fat and skin. Usually, this trait is less obvious as the child gets older. Short, stocky arms and legs. Some children also have a wide space between the big toe and second

toe. Respiratory problems

Where does the extra chromosome come from?

In 90% of Trisomy 21 cases, the additional chromosome comes from the mother's egg. This karyotype is an example ofDown Syndrome (trisomy 21), the most common numerical

abnormality found in newborns. It is characterized by an extra chromosome 21 and the karyotype is

written as: 47,XY,+21. The key to the karyotype description is as follows: 47: the total number of chromosomes (46 is normal). XY: the sex chromosomes (male). +21: designates the extra chromosome as a 21.

Sex chromosomal abnormalities

Aneuploidy, abnormalities in the sex chromosome number Non disjunction during spermatogenesis dan oogenesis e.g. Klinefelter syndrome (47,XXY) and Turner syndrome (45,XO)


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Non disjunction during spermatogenesis

If non disjunction during anaphase I & II sperm will have the abnormal sex chromosome : XY, XX @ YY Abnormal sperm x ovum (X) Klinefelter syndrome (XXY) Super male syndrome (XYY) 3X female (metafemale, XXX)

Non disjunction during Oogenesis

If non disjunction happened Some ovum might not carry any chromosome X & some others might carry 2 chromosome X Abnormal ovum (O) x sperm Turner syndrome (XO) YO : dead Abnormal ovum (XX) x sperm Klinefelter syndrome (XXY) 3X female

Klinefelter syndrome (47,XXY)

Klinefelter's Syndrome is a genetic disorder that happens in 1 in every 500 to 1000 male births. Instead of the normal XY chromosomes, these individuals have and extra X chromosome making them

XXY. Males with Klinefelter's syndrome have two X chromosomes (47-XXY), The X-chromosomes carry

genes in terms of development of testicles, sex hormone production and physical sex development ingeneral as well as to a certain extent also height growth.

It is named after Dr. Harry Klinefelter, a medical researcher at Massachusetts General Hospital, Boston,

Massachusetts, who first described this condition in 1942. Symptoms

delayed speech sensory integration difficulties, including sensitivity to noise hypotonia or low muscle tone auditory processing problems language-based learning disabilities, including reading difficulties anxiety depression gynecomastia or swelling of breast tissue during puberty


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Feminised male (soft voice Sterile male (small testis), failed to produce sperm long hand and leg

Turner syndrome (45,XO)

Turner syndrome results from a chromosomal abnormality in which a female infant is born with only oneX chromosome (instead of the usual two) or is missing part of one X chromosome.

Symptoms short stature "webbing" of the skin of the neck (extra folds of skin extending from the tops of the shoulders to the

sides of the neck) a low hairline at the back of the head low-set ears abnormal eye features, including drooping of the eyelids abnormal bone development, especially the bones of the hands and elbows a lack of breast development at the expected age (usually by age 13) an absence of menstruation (amenorrhea) a larger than usual number of moles on the skin

Abnormal Phenotype

Klinefelter Syndrome (XXY) : 2n+1 (Trisomy)

Sterile male (small testis), failed to produce sperm Feminised male (soft voice) & big breast, long hand and leg Non disjunction during oogenesis

Turner Syndrome (XO) : 2n-1 (Monosomy)

Sterile female (failed to ovulate) Small breast & undeveloped ovary

dwarf, deaf, abnormal heart & low IQ

Euploidy / Polyploidy

cell of organism that has an exact multiple of the haploid number (n) of chromosomes in a nucleus. Gametes fusion will produce cell which have more than 2 set of chromosome, for example: diploid (2n),

triploid (3n), and tetraploid (4n) nuclei or cell are euploid Occurred when a set of chromosome did not separate during gametogenesis Common in plants than in animals, cause gamete not occur in animal, while in plant can produce

vegetative propagate. Triploid (3n) occurs when

i) a gamete (2n) occur non disjunction fused with a normal gamete (n)

Gamete A x AA (non disjunction gamete)

individual of triploid AAAii) chromosomes disable to segregate during meiosis to produce diploid gameteiii) gamete from tetraploid organism (4n) fused with diploid organism gamete (2n).

e.g. plant triploid is a banana, lemon, rose, watermelon (seedless) and crysanthemum Tetraploid plants can be produced by :


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1) Somatic duplication of chromosome number

duplication of chromosome at callus (tip)

origin plant : AA (2n)

(Duplicate)

tetraploid plant AAAA (4n)

2) Fusion of two diploid gametes

P : AA (2n) AA (2n)

G : AA AA

FI: AAAA

2 types of polyploidy- Autopolyploidy- Allopolyploidy

Autopolyploidy:

Is an individual that has more than two chromosome sets, all derived from a single species The chromosomes set are homologous with the parent cell Importance in economic value which autopolyploid plants produce flowers and fruits bigger than normal

diploid plants Involve parent cell from one species mean homologous chromosome

P : AA (2n) AA (2n)

G : AA x AA

FI: AAAA

Allopolyploidy

A polyploid resulting from 2 different species (hybridization) interbreeding and combining theirchromosomes

The chromosome sets are different to parental cell mean non homologous chromosome sets involve F1 hybrids produced from different species are usually sterile (haploid set of chromosome from one

species cannot pair during meiosis with the haploid set from the other species) Chromosome number in a sterile hybrid becomes doubled and produces fertile hybrids (synapsis and

segregation can occur and viable gametes can be produced)


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Importance in producing new species e.g. plant (wheat)

Triticum diccoccum (2n = 4x = 28) x Aegilops squarrosa (2n = 2x = 14)Tetraploid plant

Triticum vulgare (2n = 6x = 42)

Hexaploid plant

P : AA BB

Gamete A x B

Hybrid ( sterile ) AB

duplication

AABB

Gamete, 2n = 2x ( fertile ) AB


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Spartina anglica is a spesies of cordgrass, It is an allopolyploid spesies derived from the hybrid Spartinax townsendii

P Spartina maritima (small cordgrass) x Spartina alterniflora (smooth cordgrass)

Hybrid Spartina x townsendii

dublication

Spartina anglica

Retold by

Amran Md SaidMatriculation College of Pahang.

The end.

mutation note

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