A man who is achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X- linked recessive. What proportion of their sons would be color-blind and of normal height ?
4. One out of four
On the basis of information given in the pedigree, if II 3 marries a hemophilic man, what is the probability that her first child will be normal ?
If a chiasma forms between the loci of genes A and B in 20 % of the tetrads of an individual of genotype AB/ab, the percentage of gametes expected to be Ab is :
An individual with c d genes was crossed with the wild type ++. On test crossing F1, the progeny were +c 105, +d 115, c d 880 and ++900. Distance between c d genes is :
1. 11 map units
2. 5.5 map units
3. 44 map units
4. 22 map untis
Based on the genic balance theory, you would predict that a human with XXY sex chromosomes and a normal number of autosomes would be :
A mechanism that can cause a gene to move from one linkage group to another is :
3. Crossing over
Phenylketonuria can be easily treated with :
1. Gene therapy
2. Hormone replacement therapy
3. Enzyme replacement therapy
4. Dietary restrictions
Which of the following statements regarding X inactivation in mammals is FALSE ?
1. The process is entirely random
2. X inactivation may ocassionally occur in males
3. This process ensures a homogenous phenotype in heterozygotes
4. X inactivation occurs early in embryonic development
The pedigree in figure shows the transmission of trait in a particular family. Based on this pattern of transmission, the trait is most likely :
2. autosomal recessive
3. sex-linked dominant
4. sex-linked recessive
Abnormal chromosomes are frequent in malignant tumors. Errors such as translocations may place in gene in close proximity to different control regions. Which of the following might then occur to make the cancer worse ?
1. An increase in non-disjunction
2. Expression of inappropriate gene products
3. A decrease in mitotic frequency
4. Death of the cancer cells in the tumor
Males are more often affected by sex-linked traits than females because
1. males are hemizygous for X chromosome
2. male hormones such as testosterone often alter the effects of mutations on X chromosome
3. female hormones such as estrogen often compensate for the effects of mutations on the X chromosome.
4. X chromosomes in males generally have more mutations than X chromosome in females
In an animal with XO method of sex determination, which of the following could be the normal number of chromosomes in its somatic cells ?
1. 26 in males
2. 17 in females
3. 33 in females
4. 13 in males
For loci carried on the X chromosome, the reciprocal crosses will :
1. always give the same phenotypic ratio among the offspring in the and generations
2. sometimes give the same phenotypic ratio among the offspring in the and generations
3. always give different phenotypic ratios among the offspring in the and generations
4. wil sometimes give different phenotypic ratio among the offspring in the and generations
A woman receives her X chromosomes from :
1. her mother only
2. her father only
3. both her mother and her father
4. extranuclear DNA in her mother's egg
A dihybrid test cross shows a frequency of recombination of 50 %. The best explanation will be :
1. The two genes are likely to be located on different chromosomes
2. All of the offspring have combinations of traits that match one of the two parents
3. The genes are located on sex chromosomes
4. Abnormal meiosis has occured
The frequency of Down syndrome in human population is most closely correlated with which of the following ?
1. Frequency of new meiosis
2. Average of the ages of mother and father
3. Age of mother
4. Age of father
The recombination frequency between genes A and B is 9 percent ; between A and C is 17 percent ; and between B and C is 26 percent. What is the sequence of genes on the chromosome ?
4. Can't be determined from the given information
If a pair of homologous chromosomes fails to separate during anaphase of meiosis I, what will be the chromosome number of the four resulting gametes with respect to the normal haploid number (n) ?
1. n+1 ; n+1 ; n-1; n-1
2. n+1 ; n-1 ; n; n
3. n+1; n-1 ; n-1 ; n-1
4. n+1 ; n+1; n; n
The frequency of crossing over between any two linked genes will be :
1. Higher if they are recessive
2. Dependent on how many alleles there are
3. Determined by their relative dominance
4. Proportional to the distance between
A man who has achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. How many of their daughters might be expected to be color-blind dwarfs ?
4. One out of four