In: Biology
1)A black guinea pig crossed with an albino guinea pig produced twelve black offspring. When the albino was crossed with a second black guinea pig, six blacks and six albinos were obtained. What is the best explanation for this genetic situation?
A)Albino is recessive; and the second black guinea pig was homozygous dominant
B)Albino is co-dominant; and the second black guinea pig was heterozygous
C)Albino is recessive; and the second black guinea pig was heterozygous
D)Albino and black are codominant.
2)Which of the following processes would best help explain independent assortment?
A)the fact that any pair of chromatids in a tetrad can cross over
B)the random arrangement of chromosomes at metaphase I
c)the separation of chromatids at anaphase II
D)the random arrangement of gene loci on a chromosome
E)the random arrangement of chromosomes at metaphase II
1) let the alleles be B- black b- albino
the first black guinea pig is BB and albino is bb
BB * bb
Bb
all progenies are black
the second guinea pig is Bb
Bb * bb
B | b | |
b | Bb ( black) | bb ( white) |
both black and white guinea pigs are possible in the ratio
black: white=1:1
so the answer is C)Albino is recessive, and the second black guinea pig was heterozygous
2) Independent assortment of the homologous chromosomes is any one of the chromosomes from the homologous pair can move to the daughter cell, during prophase I the homologous chromosomes pair up and exchange genetic material between non-sister chromatids, and during metaphase I these homologous chromosomes align at the metaphase plate such that anyone the chromosome from the homologous pair can move to the daughter cell, so the arrangement of paired homologous chromosomes at the metaphase I is responsible for the independent assortment of chromosomes.
B) the random arrangement of chromosomes at metaphase I.