Question

What are the different kinds of chromosomal duplication, and how do they differ from each other? What human disorder results from deletion of a region on chromosome 5 producing newborns that cry like a cat? If Dr. Obama wishes to reveal regions of the chromosomes that are rich in A-T base pairs in a karyotype preparation, she should use ___ to stain G bands on the chromosomes. A typical human karyotype has a total of ___ chromosomes and includes ___ pair(s) of autosomes and ___ pair(s) of sex chromosomes. If a karyotype has no copy of chromosome 5, we describe the loss of both members of this homologous pair as a ___ for chromosome 5. Gain of two homologous chromosomes (2n + 2) is referred to as ___. What kinds of alterations very often lead to an imbalance in the amount of specific gene products? What other kinds of alterations can sometimes lead to imbalances? A single recessive mutant allele in the absence of a wild type allele that is lost due to deletion expresses as a dominant mutant phenotype. This is the definition of which of the following genetic terms? A ___ inversion includes the centromere, but a ___ inversion does not. What is the end result of a single crossover occurring within either a paracentric inversion loop or a pericentric inversion loop during Prophase I? A strain of barley has a diploid genome that is 2n = 14. This strain is crossed with a wild grass strain having a genome that is 2n = 14. The resulting hybrid strain has a genome that is ____ n = ___. If chromosomal nondisjunction then occurs in this hybrid strain, a polyploid hybrid strain results with a genome that is ___ n = ___. This strain is then referred to as a(n) ___ or a(n) ___. Addition or deletion of one or more single chromosomes is described by the genetic term ___, while possessing additional sets of chromosomes is described by the genetic term ___. Most cases of Down Syndrome are ___ AND result from ___, but a few rare cases are ___ AND result from ___ .

Answer 1

Question Number 1:

1. A duplication is the occurrence of a segment of a chromosome in two or more copies per genome.
2. Duplications may be-tandem duplications, Reverse tandem, Displaced tandem, Transposition and Extra chromosomal.
3. When duplicate is located just following the original copy, it is called tandem duplication. Reverse tandem duplications result in genes arranged arranged in the opposite opposite order of the original. Tandem duplication duplication at the end of a chromosome is a terminal tandem duplication.
4. In displaced tandem the segment is repeated somewhere away from its original location but on the same or other arm of the chromosome of same chromosome.
5. In transposed duplications the segment id duplicated on the non homologous chromosome and extrachromosomal duplications involve centromere.

Question Number 2:

1. “Cri-du-chat” means “cry of the cat is a human disorder that results from deletion of short arm of chromosome number 5.
2. The larynx develops abnormally due to the chromosome deletion. This affects the sound of the child’s cry.
3. The condition affects an estimated 1 in 50,000 live births and is more common in females.

   Question Number 3:,

4. A person who wishes to reveal regions of the chromosomes that are rich in A-T base pairs in a karyotype preparation, should use Giemsa stain (named after Gustav Giems).
5. Gemsa stain is used in Giemsa banding (G-banding) to stain chromosomes for karyotype preparation. It is specific for the phosphate groups of DNA and attaches itself to regions of DNA where there are high amounts of A-T bonding.
6. G-banding, G banding, or Giemsa banding is a technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes.
7. The condensed chromosomes in metaphase are treated with trypsin (to partially digest the chromosome) and stained with Giemsa stain. The heterochromatic regions (representing genetically less active sites ) which are rich in A-T base pairs stain darkly in G-banding and less condensed regions which are rich in G-C base pairs and are transcriptionally stain lightly in G-banding.

8. Question Number 4:

9. The number, sizes and shapes of the metaphase chromosomes constitute the karyotype or karyogram, which is distinctive for each species.
10. Karyotype consisting of all the metaphase chromosomes in homologous pairs according to decreasing length and position of centromere is described as ideogram.
11. Human karyotype consists of 23 pairs or 46 chromosomes.
12. Of the 23 pairs, 22 are perfectly matched in both males and females, and are called autosomes. The remaining pair of chromosomes constitutes a pair of sex chromosomes. Males have two dissimilar sex chromosomes-XY and females have two similar chromosomes-XX.