- Describe different types of aberrations caused due to change in chromosome number.
- What is aneuploidy? Give its different types.
- What is polyploidy? Give its different forms.
- What is deletion? Give its different types.
- What is Duplication? Give its different types.
- What is inversion? Give its different types.
What are chromosomal aberrations? How are they
Ans: Any numerical or structural change in the usual chromosome
complement of a cell or organism is called chromosome aberration. There are to types of chromosomal aberrations: Changes in the number.of chromosomes: Aneuploidy and euploidy Changes in structure of chromosome: deficiency (deletion), duplication, inversion and translocation.
- What is aneuploidy? How is it caused?
Ans: The random abnormal number of chromosomes in the animals is called as aneuploidy. Aneuploidy is mostly caused by nondisjunction.
- What is monosomic?
Ans: If a chromosome is missing the aneuploidy is monosomic.
Therefore. the cell has 2n — I chromosomes.
- What is mosaic Mosaic trisomy? Give example.
Ans: In this case, an extra chromosomal material exists in only
some of the organism’s cells. –ale most common types of
trisomy that survive without spontaneous abortion in humans are: Trisomy 21 (Down syndrome).
- What are Tertrasomics?
Ans: If the chromosome is present in tetrad form in the fertilized
egg the aneuploid cell is called tertrasomics for that chromosome. The cell has a total of 2n + 2 chromosomes.
- What are the effects of aneuploidy?
Ans: Affects of aneuploidy
Aneuploidy is produced in sperm or egg. Later it is transmitted to the zygote. Mitosis transmits the aneuploidy to all embryonic cells. Such organism may not survive. If the organism survives, it becomes abnormal. Nondisjunction can also occur during mitosis. The early aneuploid condition is passed to a large number of cells by mitosis. It has greater effect on the organism.
- What is polyploidy?
Ans: A condition in which the organisms have more than two
complete sets of chromosomes is called polyploidy.
- Differentiate between autopolyploidy and alloploidy
Ans: Autopolyploids are polyploids in with chromosomes derived from a single species. Allopolyploids are polyploids with chromosomes derived from different species.
- What is triticale?
Ans: Triticale is an example of an allopolyploid. It has six
chromosome sets. Four are taken from wheat (Triticum
turgidum) and two are taken from rye (Secale cereale).
10-Name some tetraploid crops.
Ans: Tetraploid crops: wheat, maize., cotton, potato, cabbage,
leek, tobacco, peanut.
11-Give comparison of Comparison of aneuploidy and polyploidy.
Ans: Polyploids are more normal in appearance than aneuploids. Most of polyploids are fertile. One extra (or missing) chromosome disrupts genetic balance in aneuploids.
12-Differentiate between Interstitial deletions and Terminal deletion.
Ans: In case of interstitial deletion, internal part of a chromosome is missing. In case of terminal deletion, there is only one break and the homologous chromosome fail to rejoin. Thus tip of the chromosome is lost in cell division.
13-What is Cri du chant syndrome?
Ans: A deletion of part of the short arm of chromosome–5 results
in Cri du chat. It is also known as “cry of the cat” syndrome. It is found in I in 50.000 live births. The surviving infants have a distinctive cry, severe mental retardation, and shortened life span.
14-What is pseudo dominance? How is it caused?
Ans: Heterozygous deletion may cause pseudo-dominance. In this case, dominant allele is missing. Therefore, recessive allele expresses itself.
15-What is duplication?.
Ans: In this case, the fragment joins to the homologous chromosome , with a duplication of genes. It adds one or more gene in the chromosome. therefore. the organism carries same gene repeated in its haploid chromosome.
16-What is Tandem duplication?
Ans: In this case. the duplication is adjacent to the normal chromosome. It has same order as the original order. It is believed that the homoloeous chromosomes tnerlap each other. Therefore, the segments break simultaneously at different points.
17-What is Heterokaryotypic duplication?
Ans: In some cases, part of chromosomes bend back and join with the duplicated sequence on the same chromosome. Such individuals with tt,t,o chromosomal types are called heterokaryotypie. ‘Ellis duplication is called heterokaryotypic duplication.
18-What are paralogs and orthoglous genes?
Ans: The two genes that exist after a gene duplication event are
called paralogs. Paralogs code for proteins with a different function and structure. This is different from orthologous genes. Ortholgous genes code. for proteins with similar Iii nctions but exist in different species.
19. Differentiate between Paracentric and Paracentric inversions.
Ans: Paracentric inversions do not include the centromere. Both breaks occur in one arm of the chromosome. Pericentric inversions includes the centromere and there is a break point in each arm.
20-Differentiate between Reciprocal and Robertsonian translocations?
Ans: It is caused due to an exchange of material between non-homologous chromosomes. Reciprocal translocations are found in about I in 600 newborns. Robertsonian translocations of rearrangement involves two acrocentric chromosomes.these chromosomes Rise ‘tear the centromere region with loss of the short arms.