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Question
Why are thalassemia and haemophilia categorized as Mendelian disorders? Write the symptoms of these diseases. Explain their pattern of inheritance in humans.
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Solution
Thalassaemia and haemophilia are categorised as Mendelian disorders because these are determined by alternation or mutation in a single gene.
Symptoms of thalassaemia: The main symptoms of thalassaemia are anaemia, jaundice, hepatosplenomegaly, cardiac enlargement and skeletal deformities.
Symptoms of haemophilia: Haemophilia is also called bleeder’s disease in which a single cut leads to non-stop bleeding. It prevents clotting of blood. A seriously affected person may bleed to death after even a minor skin cut.
Inheritance pattern of haemophilia:
This is a sex-linked recessive disease which shows its transmission from an unaffected carrier female to some of the male progeny. It shows criss-cross inheritance. The heterozygous female (carrier) for haemophilia may transmit the disease to sons. The possibility of a female becoming a haemophilic is extremely rare because the mother of such a female would have to be at least a carrier and the father should be haemophilic.
Inheritance pattern of thalassaemia:
Thalassaemia is an autosomal, recessively inherited blood disorder transmitted to the offspring when both parents are heterozygous. The defect arises because of either mutation or deletion which results in the reduced rate of synthesis of one of the globin chains of haemoglobin.
RELATED QUESTIONS
Given below is the representation of amino acid composition not the relevant translated portion of β-chain of haemoglobin, related to the shape of human red blood cells
(a) Is this representation indicating a normal human or a sufferer from certain related genetic disease? Give reason in support of your answer.
(b) What difference would be noticed in the phenotype of the normal and the sufferer related to this gene?
(c) Who are likely to suffer more from the defect related to the gene represented the males, the females or both males and females equally? And why?
Why is pedigree analysis done in the study of human genetics? State the conclusions that can be drawn from it.
Write a note on Down’s syndrome.
Read the following statements and select the correct option.
i. Genetic disorders are broadly categorised as, Mendelian disorders and chromosomal disorders.
ii. Mendelian disorders are caused due to absence or excess of one or more chromosomes or their abnormal arrangement.
iii. Chromosomal disorders are mainly caused due to alteration or mutation in the gene.
Identify the characteristics that are observed in an individual suffering from Klinefelter syndrome.
i. Gynaecomastia, under developed testis and no spermatogenesis.
ii. Voice pitch is harsh.
iii. They are tall with long arms.
Match the Column-I with Column-II and choose the CORRECT answer
| Column-I | Column-II | ||
| P. | Klinefelter syndrome | i. | Mutation in autosomal gene |
| Q. | Thalassaemia | ii. | Mutation sex chromosome linked gene |
| R. | Down syndrome | iii. | Trisomy of autosome |
| S. | Colour blindness | iv. | Trisomy of sex chromosome |
Sickle cell anaemia is ______.
Females with Turner’s syndrome have ______.
In Down's syndrome, karyotyping has shown that the disorder is associated with trisomy of chromosome number 21 usually due to ______.
Trisomy of 21st chromosome leads to a disorder ______.
