chapter 6 (chromosome mutations)
TRANSCRIPT
Chromosome MutationsVariation in Number and Arrangement
What are chromosome mutations?
These are chromosome mutations!
Variation in Chromosome Number
Variations in Chromosome Number
Aneuploidy› Gain or loss, one or more chromosomes› Monosomy, Trisomy
Euploidy› Complete haploid sets
Polyploidy › More than two sets are present
Variations in Chromosome Number
Monosomy X(Turner’s Syndrome)
Haploinsufficiency A single copy of a recessive gene (due
to monosomy) may be insufficient to provide life-sustaining functions
Trisomy 21 (Down’s Syndrome)
Nondisjunction
Klinefelter Syndrome
Prenatal Diagnoses
Prenatal Diagram
Amniocentesis Fetal cells obtained from amniotic fluid
Chorionic Villus Sampling Fetal cells obtained from the chorion of
the placenta
Noninvasive Prenatal Genetic Diagnosis
Fetal cells and DNA are derived directly from maternal circulation
Human Aneuploidy
Patau Syndrome (Trisomy 13)
Patau Syndrome
Edwards Syndrome (Trisomy 18)
Polyploidy
Polyploidy Originates in two ways: 1. the addition of one or more extra
sets of chromosomes, identical to the normal haploid complement of the same species, resulting in autopolyploidy
2. the combination of chromosome sets from different species occurring as a consequence of hybridization, resulting in allopolyploidy
Autopolyploidy
Autopolyploidy
Allopolyploidy
Allopolyploidy
Autopolyploidy vs. Allopolyploidy
Variation in the Composition and Arrangement of
Chromosomes
Deletions Also called a deficiency A chromosome breaks in one or more
places and a portion is lost
Deletions Terminal deletions
Intercalary deletions
Cri du Chat Syndrome Loss of a small part of the short arm of
chromosome 5
Duplications
A piece of the chromosome is present more than once in the genome
Duplications
Duplications 1. may result from
gene redundancy 2. may produce
phenotypic variation 3. have been an
important source of genetic variability during evolution
rDNA and Gene Amplification
rDNA codes for RNA segments Gene amplification occurs when
multiple copies of gene code for a specific product
The Bar Mutation in Drosophila
Fragile X Syndrome (Martin-Bell Syndrome)
Inversions A segment of the chromosome if
turned around 180 degrees within the same chromosome
Inversions
Chromosome 9 Inversion
Translocations
The movement of a chromosomal segment to a new location in the genome
Translocations
Acute Myeloid Leukemia
Fragile Sites
Fragile Sites Appear as gaps in some karyotypes Appear to be susceptible to breakage
in some situations
Fragile Sites and Cancer Chromosome 16, WWOX gene
› Lung, breast, ovary, prostate, bladder, esophagus, pancreas
Chromosome 3, FHIT gene› Esophagus, breast, cervix, liver, kidney,
pancreas, colon, stomach Increased susceptibility to mutations
and deletions