1. In a diploid organism of 2n = 10, assume that you can label all the centromeres derived from its female parent and all the centromeres derived from its male parent. When this organism produces gametes, how many male- and female-labeled centromere combinations are possible in the gametes?
3. Suppose you discover two interesting rare cytological abnormalities in the karyotype of a human male. There is an extra piece (or satellite) on one of the chromosomes of pair 4, and there is an abnormal patter of staining on one of the chromosomes of pair 7. Assuming that all the gametes of this male are equally viable, what proportion of his children will have the same karyotype as his?
4. Suppose that meiosis occurs in the transient diploid stage of the cycle of a haploid organism of chromosome number n. What is the probability that an individual haploid cell resulting from the meiotic division will have a complete parental set of centromeres (that is, a set all from one parent or all from the other parent)?© BrainMass Inc. brainmass.com October 16, 2018, 6:48 pm ad1c9bdddf
Crossing over occurs in 4 strand stage. Out of the four chromatids only two participate in crossing over and the remaining two remains unchanged. Hence, 50 % of the individual will be like parents and rest of the 50 % will be recombinants
Six Genetics Problems on sex linkage, alleles, patterns of inheritance and dosage compensation.
1. G6PD is an enzyme found in human white blood cells. It is made by a gene that has 2
alleles, A and B. In females, cells either make the A type or the B type, but never both.
This is very different from most other enzymes, where all cells in a heterozygote make
both types of enzyme. What is the most reasonable explanation for this unusual
behavior of G6PD?
2. In humans, red-green color blindness is recessive and X-linked, while albinism is
recessive and autosomal. What types of children can be produced as the result of
marriages between two homozygous parents, a normal-visioned albino woman and a
color-blind, normally pigmented man? (Give your answer separately for males and
3. Suppose that a mutation occurred in the SRY gene on the human Y chromosome,
knocking out its ability to produce the testis-determining factor. Predict the
phenotype of an individual who carried this mutation and a normal X chromosome?
4. Sex determination in Gryllus campestris (cricket) is by the XO method. The somatic
cells of a cricket are analyzed and found to contain 29 chromosomes.
A. What sex is this individual?
B. What is the diploid number of the opposite sex?
5. Ichthyosis hystrix gravior (a greatly thickened horny condition of the skin) is a rare
human condition, but in the single extensive pedigree which has been studied it occurs
only in males. All the sons of each affected father have the condition. Females are
not only unaffected, but never transmit the gene for this defect. Can you suggest a
possible explanation for this curious and unusual type of inheritance?
6. Dosage compensation is only found in organisms that have sex chromosomes. What is
dosage compensation? Briefly describe how dosage compensation is achieved in
Drosophila and humans.