3. With modern molecular methods it is now possibleto examine variants in DNA sequence from a verysmall amount of tissue like a hair follicle or even asingle sperm. (See the Fast Forward Box Mappingthe Crossovers that Generate the Chromosomes ofIndividual Human Sperm.) You can consider thesevariants to be alleles of a particular site on a chromosome (a locus; loci in plural). For example,AAAAAAA, AAACAAA, AAAGAAA, andAAATAAA at the same location (call it B) on homologous autosomes in different sperm might becalled alleles 1, 2, 3, and 4 of locus B (B1, B2, etc.).John’s genotype for two loci B and D is B1B3andD1D3. John’s father was B1B2and D1D4, while hismother was B3B3and D2D3.a. What is (are) the genotype(s) of the parental typesperm John could produce?b. What is (are) the genotype(s) of the recombinanttype sperm John could produce?c. In a sample of 100 sperm, 51 of John’s sperm werefound to be B1and D1, while the remaining 49 spermwere B3D3. Can you conclude whether the B and Dloci are linked, or whether they instead assortindependently?
3. With modern molecular methods it is now possible
to examine variants in DNA sequence from a very
small amount of tissue like a hair follicle or even a
single sperm. (See the Fast Forward Box Mapping
the Crossovers that Generate the Chromosomes of
Individual Human Sperm.) You can consider these
variants to be alleles of a particular site on a chromosome (a locus; loci in plural). For example,
AAAAAAA, AAACAAA, AAAGAAA, and
AAATAAA at the same location (call it B) on homologous autosomes in different sperm might be
called alleles 1, 2, 3, and 4 of locus B (B1
, B2
, etc.).
John’s genotype for two loci B and D is B1
B3
and
D1
D3
. John’s father was B1
B2
and D1
D4
, while his
mother was B3
B3
and D2
D3
.
a. What is (are) the genotype(s) of the parental type
sperm John could produce?
b. What is (are) the genotype(s) of the recombinant
type sperm John could produce?
c. In a sample of 100 sperm, 51 of John’s sperm were
found to be B1
and D1
, while the remaining 49 sperm
were B3
D3
. Can you conclude whether the B and D
loci are linked, or whether they instead assort
independently?
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