lecture 22 large-scale chromosome changes ii
DESCRIPTION
LECTURE 22 LARGE-SCALE CHROMOSOME CHANGES II. chapter 15 overview chromosome number chromosome structure problems. CHANGES IN CHROMOSOME NUMBER. what are the genotypic & phenotypic probabilities in the progeny of a P cross A/A/A/a A/A/A/a ? - PowerPoint PPT PresentationTRANSCRIPT
LECTURE 22 LARGE-SCALE CHROMOSOME CHANGES II
chapter 15 overview chromosome number chromosome structure problems
CHANGES IN CHROMOSOME NUMBER
what are the genotypic & phenotypic probabilities in the progeny of a P cross A/A/A/a A/A/A/a? P gametes: P(A/A) = P(A/a) = ½, P(a/a) = 0 F1 genotypes: P(A/A/A/A) = (½)2 = ¼
P(A/A/A/a) = 2(½)2 = ½
P(A/A/a/a) = (½)2 = ¼
F1 phenotypes: all A A/A/a/a? A/a/a/a?
} work out these ones for next class
autopolyploids
3 classes of chromosome change
OVERVIEW
2 general questions to consider... is the genome complete?
is the genome balanced?
OVERVIEW
CHANGES IN CHROMOSOME STRUCTURE
implications chromosome structure mutations phenotypes
1. abnormal gene # segmental aneuploids 2. abnormal gene
environment position effect
3. break points disrupt gene function
CHANGES IN CHROMOSOME STRUCTURE
things to keep in mind each chromatid is has a single DNA molecule need either...
2+ double strand breaks crossing over between repetative sequences
chromosome breakage ends highly reactive (normal telomeres not)
double strand breaks are lethal unless repaired repaired by joining broken ends
CHANGES IN CHROMOSOME STRUCTURE
more things to keep in mind repair can restore original sequence or generate rearrangement acentric products are lost & inviable dicentric products are broken & inviable rearrangements can be
spontaneous induced by radiation... X- or -rays
mainly studied in heterozygotes
CHANGES IN CHROMOSOME STRUCTURE
2 types of rearrangements1. unbalanced change gene dosage
deletions uncover deleterious alleles usually lethal
duplications extra material evolutionary divergence
CHANGES IN CHROMOSOME STRUCTURE
2 types of rearrangements2. balanced change gene dosage
inversions reduced fertility reduced recombination in inverted region
translocations reorganizes linkage 50% sterility fertility novel linkage of genes on translocated
chromosomes
CHANGES IN CHROMOSOME STRUCTURE
origins of rearrangements by 2 processes1. break / rejoining
spontaneous radiation
CHANGES IN CHROMOSOME STRUCTURE
origins of rearrangements by 2 processes1. break / rejoining
spontaneous radiation
2. crossing over illegitimate
CHANGES IN CHROMOSOME STRUCTURE
visualization in heterozygotes strong pairing affinity during meiotic prophase I abnormal patterns seen in rearrangement
heterozygotes (–/+)
CHANGES IN CHROMOSOME STRUCTURE
biological importance research tools
new combinations of genes mapping recombination suppression mutant rescue
applied research medicine & agriculture evolutionary significance genome reshuffling
CHANGES IN CHROMOSOME STRUCTURE
deletions 1 chromosome break terminal 2 chromosome break interstitial
CHANGES IN CHROMOSOME STRUCTURE
deletions intragenic within 1 gene
do not revert ( point mutations) can be viable if gene not vital
multigenic > 1 gene do not revert usually homozygous lethal sometimes heterozygous lethal
CHANGES IN CHROMOSOME STRUCTURE
deletions multigenic > 1 gene
uncovers recessive alleles on homologue pseudodominance deletion mapping
CHANGES IN CHROMOSOME STRUCTURE
deletions multigenic > 1 gene
uncovers recessive alleles on homologue pseudodominance deletion mapping
CHANGES IN CHROMOSOME STRUCTURE
deletions multigenic > 1 gene
deletion mapping ~ linkage maps
CHANGES IN CHROMOSOME STRUCTURE
deletions multigenic > 1 gene
deletion mapping ~ human disease, e.g.: cri du chat syndrome
CHANGES IN CHROMOSOME STRUCTURE
duplications (2 chromosome breaks) adjacent, same order tandem adjacent, reverse order reverse
CHANGES IN CHROMOSOME STRUCTURE
duplications intragenic within 1 gene
do not revert ( point mutations, see below) can be viable if genetic balance not critical
multigenic > 1 gene do not revert (see below) homozygous lethal if genetic balance critical can be heterozygous lethal if balance critical
CHANGES IN CHROMOSOME STRUCTURE
duplications illegitimate recombination possible, e.g.: Bar
CHANGES IN CHROMOSOME STRUCTURE
duplications important for gene evolution, e.g.: human
hemoglobin genes
CHANGES IN CHROMOSOME STRUCTURE
duplications important for gene evolution, e.g.: human
hemoglobin genes
CHANGES IN CHROMOSOME STRUCTURE
inversions does not include centromere paracentric does include centromere pericentric
CHANGES IN CHROMOSOME STRUCTURE
inversions does not include centromere paracentric
A B C D E F G H
CHANGES IN CHROMOSOME STRUCTURE
inversions does not include centromere paracentric
A B C D E F G H
CHANGES IN CHROMOSOME STRUCTURE
inversions does not include centromere paracentric
A C B D E F G H
CHANGES IN CHROMOSOME STRUCTURE
inversions does include centromere pericentric
A B C D E F G H
CHANGES IN CHROMOSOME STRUCTURE
inversions does include centromere pericentric
A B C D E F G H
CHANGES IN CHROMOSOME STRUCTURE
inversions does include centromere pericentric
A B F E D C G H
CHANGES IN CHROMOSOME STRUCTURE
inversions no change in total genetic material breakpoints can (but not always) disrupt genes
no disruption viable homozygotes disruption heterozygotes only (majority)
do not revert recombination in inversion segm. aneuploidy
recombinant gametes lethal , fertility recombination suppression
CHANGES IN CHROMOSOME STRUCTURE
inversions breakpoints between genes
CHANGES IN CHROMOSOME STRUCTURE
inversions breakpoints between genes... disruption of 1
breakpoints within genes... gene fusion
CHANGES IN CHROMOSOME STRUCTURE
inversions loops
CHANGES IN CHROMOSOME STRUCTURE
inversions loops
CHANGES IN CHROMOSOME STRUCTURE
inversions loops
CHANGES IN CHROMOSOME STRUCTURE
inversions crossing over in a
paracentric inversion heterozygote
CHANGES IN CHROMOSOME STRUCTURE
inversions crossing over in a
paracentric inversion heterozygote 1 normal viable 1 inversion viable 1 acentric lost 1 dicentric 2 lethal
deletion products
CHANGES IN CHROMOSOME STRUCTURE
inversions crossing over in a
pericentric inversion heterozygote
CHANGES IN CHROMOSOME STRUCTURE
inversions crossing over in a
pericentric inversion heterozygote 1 normal viable 1 duplication
lethal 1 deletion lethal 1 inversion viable
CHANGES IN CHROMOSOME STRUCTURE
translocations (reciprocal or Robertsonian) no change in total genetic material do not revert meiosis segmental aneuploidy
lethality semi-sterility
rearrangement of linkage groups can restructure genomes
CHANGES IN CHROMOSOME STRUCTURE
translocations heterozygotes
adjacent-1 4 lethal
adjacent-2 rare, 4 lethal
alternate 2 normal + 2 carrier
CHANGES IN CHROMOSOME STRUCTURE
translocations pseudolinkage observed from test cross of
translocation heterozygote: a/; a+b+/b a/a; b/b
CHANGES IN CHROMOSOME STRUCTURE
translocations position-effect variegation
PROBLEMS
#1-55 on pp. 512-520 consider (read & think about)
all of the questions at the very least you should do
#s 22, 23, 26, 40, 49