1. the greater degree of phenotypic variation observed in human females compared
ID: 67219 • Letter: 1
Question
1. the greater degree of phenotypic variation observed in human females compared to males is explained by
a. genomic imprininting
b. mosaicism
c. chromosomal nondisjunction
d. genetic epistasis
e. incomplete dominance
2. What is the most likely mode of inheritance for the trait illustrated in the pedigree above ?
a) autosomal recessive
b)autosomal dominant
c) X-linked recessive
d)X-linked dominant
e)Y-linked
3. During the S phase of the cell cycle ,DNA is replicated . The number of chromosomes in a dividing cell is ------------------ during the S phase , and the number of chromatids is -----------------
a.increased; decreased
b.decreased;increased
c.increased; unchanged
d.unchanged;increased
e.unchanged;decreased
4. Which of the following gametic genotypes cannot be generated by a diploid individual with the genotype AabbCcDD?
a.abCD
b.ABCD
c.abcD
d.Abcd
e.All of the above genotypes could be present in a gamete from this individual .
5. The genes encoding sex -influenced and sex -limited traits are located on ................
a. the X chromosome
b. the Y chromosome
c. the X and Y chromosomes
d.autosomes
e. some on autosomes and some on X or Y chromosomes.
6. In a test cross , an individual with a ................... phenotype and an unknown genotype is crossed to an individual has a ...................phenotype and a ..................genotype.
a.recessive;dominant;homozygous dominant
b.dominant;dominant ; homozygous dominant
c.recessive;recessive homozygous recessive
ad.dominant ;recessive homozygous recessive
e.dominant ; recessive;heterozygous
7.what are the expected phenotypic proportions in the progeny of the following cross assuming that both genes are independent?
GgTt x ggtt ( gene G encodes trait 1; gene T encodes trait 2)
a. 3 dominant for both trait 1 and 2 :1recessive for both traits 1 and 2 ;
b.9 recessive for both traits : 3 dominant for trait 1 and recessive for trait 2 : 3 recessive for trait 1 and dominant for trait 2:1 dominant for both traits 1and 2;
c.1 dominant for both traits:1dominant for traits 1 and recessive for trait 2:1 recessive for trait 1 and dominant for trait 2:1recessivefor both trait 1and 2:
d. 9 dominant for both traits : 3 dominant for trait 1 and recessive for trait 2 : 3 recessive for trait 1 and dominant for trait 2:1 recessive for both traits 1and 2;
Explanation / Answer
3. d. unchanged; increased
The number of chromosomes in a dividing cell is ------unchanged----------- during the S phase , and the number of chromatids is ------increased-------.
The cell cycle contains four different stages, which include G1 (gap phase1), G2 (gap phase 2), S (synthesis phase) and M (mitotic phase). During the “S” (synthesis) phase of the interphase of the cell cycle, the single chromatids replicate into two (identical sister chromatids). The chromosome number remains unchanged.
4. b.ABCD
The gametes with genotypes ABCD cannot be generated by a diploid individual with the genotype AabbCcDD because there is no dominant B allele.
5. c. the X and Y chromosomes
Among these 23 pairs of chromosomes, 22 pairs are autosomes and remaining one pair are sex chromosomes. These sex chromosomes determine the sex (male or female) of an individual. In each pair, one chromosome is from mother and another is from father.
In humans, females contain 22 pairs of autosomes (non-sex chromosomes) and one pair of homologues “X” chromosomes. But in males, each cell contains 22 pairs of homologues autosomes and another of one “X” chromosome paired with one “Y” chromosome.
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