Question

true or false, please give explaination

TRUE/FALSE. Explain why the answer is true or false. 3) True or False: Assume that a species has a diploid chromosome number of 24. The term applied to an individual with 25 chromosomes would be triploid. 4) True or False: Inversions suppress crossing over by providing a chemical imbalance because of breakpoints within certain genes. e or False: Individuals with familial Down syndrome are trisomic and have 47 chromosomes. 6) True or False: An autotriploid may arise when three sperm cells are involved in fertilization of a single egg

Answer 1

3. False.

because triploid means 3 sets of chromosomes. it means there required 72 chromosomes for triploid formation.

4. False

An inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. An inversion occurs when a single chromosome undergoes breakage and rearrangement within itself. Inversions are of two types: paracentric and pericentric.

Paracentric inversions do not include the centromere and both breaks occur in one arm of the chromosome. Pericentric inversions include the centromere and there is a break point in each arm.

Crossover suppression if occur within the gene causes the disruption of gene and if it is essential one then it could be lethal. But in most cases the effect of suppression is seen during crossing over processes in meiosis leads to non-functional chromosomes.

When a crossover event occurs in inverted region of Para centric chromosome, then one chromatid centromere will lost and chromatid gets two centromeres. In such case of asymmetrical arrangement of centromere, a bridge is formed causing the chromatid break at random, thereby suppressing the crossover product and the bridge is termed as crossover suspension bridge.

5. False

Down syndrome also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21.

6. False

An autotriploid could occur if a normal gamete (n) unites with a gamete that has not undergone a reduction and is thus 2n. The zygote would be 3n. Triploids could also be produced by mating a diploid (gametes = n) with a tetraploid (gametes = 2n) to produce an individual that is 3n. The difficulty arises when autotriploids try to mate because unbalanced gametes are produced because of pairing problems with the additional chromosome set.

In humans triploidy may be the result of either digyny (the extra haploid set is from the mother) or diandry (the extra haploid set is from the father). Diandry is mostly caused by reduplication of the paternal haploid set from a single sperm, but may also be the consequence of dispermic (two sperm) fertilization of the egg.