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Chromosomal Mutations When Good Meiosis Goes Bad When Good Meiosis Goes Bad

Chromosomal Mutations When Good Meiosis Goes Bad

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Page 1: Chromosomal Mutations When Good Meiosis Goes Bad

Chromosomal Mutations

When Good Meiosis Goes BadWhen Good Meiosis Goes Bad

Page 2: Chromosomal Mutations When Good Meiosis Goes Bad

MUTATION REVIEW• Mutation is any change to a cell’s DNAMutation is any change to a cell’s DNA

- most mutations are bad - most mutations are bad

– – some can be beneficialsome can be beneficial

- mutation is required for evolution to - mutation is required for evolution to occuroccur

• Mutations can occur randomly 1 in 100,000 Mutations can occur randomly 1 in 100,000 replicationsreplications

• Mutations can be caused by mutagens Mutations can be caused by mutagens

Page 3: Chromosomal Mutations When Good Meiosis Goes Bad

GENE MUTATION

• Mutations can occur in genesMutations can occur in genes

- - point mutation point mutation – one nucleotide substituted for another– one nucleotide substituted for another

the fat cathe fat catt ate the rat the fat ca ate the rat the fat carr ate the rat ate the rat

- - frameshift mutation frameshift mutation – a nucleotide is either– a nucleotide is either

inserted or deleted from a geneinserted or deleted from a gene

- all of the DNA triplets from the point of mutation - all of the DNA triplets from the point of mutation

onward are altered.onward are altered.

deletion:deletion: the fthe faat cat ate the rat the ftc ata tet her att cat ate the rat the ftc ata tet her at

insertioninsertion:: the fat cat ate the rat the fa the fat cat ate the rat the fann tca tat eth era t tca tat eth era t

Page 4: Chromosomal Mutations When Good Meiosis Goes Bad

CHROMOSOME MUTATIONCHROMOSOME MUTATION

• Chromosome mutations occur when there Chromosome mutations occur when there

is an error in meiosisis an error in meiosis

• chromosomes hold many genes – chromosomes hold many genes –

mutation has huge impactmutation has huge impact

• can result in extra copies of entire can result in extra copies of entire

chromosomeschromosomes

• can be changes to parts of chromosomescan be changes to parts of chromosomes

Page 5: Chromosomal Mutations When Good Meiosis Goes Bad

DIAGNOSISDIAGNOSIS

• A A karyotypekaryotype is produced to examine an individual’s is produced to examine an individual’s chromosomeschromosomes

- a karyotype is a picture - a karyotype is a picture

of a person’s chromosomes of a person’s chromosomes

as homologous pairsas homologous pairs

- allows many - allows many

chromosomal chromosomal

mutations to be seenmutations to be seen

Page 6: Chromosomal Mutations When Good Meiosis Goes Bad

PRODUCING A KARYOTYPE• Fluid is taken from the womb by Fluid is taken from the womb by amniocentesisamniocentesis

-the fluid contains cells from the embryo-the fluid contains cells from the embryo

-the cells are grown in a tissue culture and induced to -the cells are grown in a tissue culture and induced to undergo mitosis.undergo mitosis.

- they are treated making them easier to see and - they are treated making them easier to see and photographed in metaphase.photographed in metaphase.

-pictures of homologous chromosomes are matched up -pictures of homologous chromosomes are matched up and examined for mutationsand examined for mutations

Page 7: Chromosomal Mutations When Good Meiosis Goes Bad
Page 8: Chromosomal Mutations When Good Meiosis Goes Bad

NONDISJUNCTION• Occurs when a tetrad fails to split in meiosis IOccurs when a tetrad fails to split in meiosis I

or chromatids fail to split in meiosis IIor chromatids fail to split in meiosis II

Page 9: Chromosomal Mutations When Good Meiosis Goes Bad

MORE NONDISJUNCTION • Nondisjunction causes some gametes to receive Nondisjunction causes some gametes to receive

an extra copy of a chromosome an extra copy of a chromosome

– – called called trisomy trisomy – the zygote produced from – the zygote produced from this gamete will have 3 copies of the this gamete will have 3 copies of the chromosome after fertilizationchromosome after fertilization

- trisomy 21 causes Down Syndrome- trisomy 21 causes Down Syndrome

• Nondisjunction causes other gametes to receiveNondisjunction causes other gametes to receive

no copies of a chromosomeno copies of a chromosome

- called - called monosomy monosomy –the zygote produced from –the zygote produced from this gamete will have only one copy of the this gamete will have only one copy of the chromosome after fertilizationchromosome after fertilization

-monosomy is usually lethal-monosomy is usually lethal

Page 10: Chromosomal Mutations When Good Meiosis Goes Bad

DELETIONDELETION

• A portion of a A portion of a

chromosome is lost.chromosome is lost.

• Deletions are responsible Deletions are responsible

for many syndromes:for many syndromes:

Cri du Chat, Wolf-Cri du Chat, Wolf-

Hirschhorn syndrome Hirschhorn syndrome

etc…etc…

Page 11: Chromosomal Mutations When Good Meiosis Goes Bad

INVERSIONINVERSION

• A segment of a A segment of a

chromosome will chromosome will

reverse end to end.reverse end to end.

• Most common on Most common on

chromosome 9 – not chromosome 9 – not

harmfulharmful

Page 12: Chromosomal Mutations When Good Meiosis Goes Bad

DUPLICATIONDUPLICATION

a segment of a a segment of a chromosome is duplicated chromosome is duplicated producing extra copies of producing extra copies of genes-on a chromosome.genes-on a chromosome.

can have harmful effects – can have harmful effects – Pallister-Killian SyndromePallister-Killian Syndrome

can lead to new genetic can lead to new genetic

combinations -combinations - potential potential force for evolutionforce for evolution

Page 13: Chromosomal Mutations When Good Meiosis Goes Bad

TRANSLOCATIONTRANSLOCATION

• a part of a chromosome a part of a chromosome joins another non-joins another non-homologous chromosomehomologous chromosome

• non- Robertsonian non- Robertsonian (balanced) – 2 non (balanced) – 2 non homologous homologous chromosomes exchange chromosomes exchange parts – not harmfulparts – not harmful

• Robertsonian Robertsonian (unbalanced) – one (unbalanced) – one chromosome gives up a chromosome gives up a part to a non-homologous part to a non-homologous chromosome – Down chromosome – Down SyndromeSyndrome

Page 14: Chromosomal Mutations When Good Meiosis Goes Bad

NORMAL KARYOTYPES

Page 15: Chromosomal Mutations When Good Meiosis Goes Bad

g

Page 16: Chromosomal Mutations When Good Meiosis Goes Bad