Detailed explanations in West Bengal Board Class 10 Life Science Book Solutions Chapter 3B Some Common Genetic Diseases offer valuable context and analysis.
WBBSE Class 10 Life Science Chapter 3B Question Answer – Some Common Genetic Diseases
Short Answer Type Questions : 2 Marks
Question 1.
What is genetical disease?
Answer:
The disease which arises due to mutation of genes or chromosomes and is inherited, then the disease is known as genetical disease.
Question 2.
What do you mean by autosomal and sex linked inheritance.
Answer:
Autosomal inheritance : When the gene is transmitted through autosomes from one generation to the next, then the situation is known as autosomal inheritance.
Sex linked inheritance: When the gene is transmitted through sex chromosome from one generation to the next therr the situation is known as sex linked inheritance.
Question 3.
Give examples of autosomal and sex-chromosomal disease.
Answer:
- Autosomal : Thalassemia
- Sex-chromosomal : Haemophilia
Question 4.
What is the cause of Thalassemia?
Answer:
Mutational change in 16th and 11th autosome causes defective structure of haemoglobin.
Question 5.
Write two symptoms of thalassemia.
Answer:
- Digestive disorder and frequent fever.
- Enlargement of spleen.
Question 6.
What is causes of haemophilia?
Answer:
Recessive gene of ‘X’ chromosome does not produce anti-coagulant in the blood, causing not to clot in the body any time.
Question 7.
Write two symptoms of ‘haemophilia?
Answer:
- Blood does not coagulate.
- After birth body may be died due to excessive bleeding.
Question 8.
What do you mean by haemophilia A and B ?
Answer:
Haemophilia A : Due to the absence of anti-haemophilic gene globulin (AHG) or factor (VII) ; the blood does not clot, there is injury in the body. 80% of the patient is of this type.
Haemophilia B : Due to the absence of christmas factor, or factor IX, the blood can’t coagulate when there forms an injury in or outside the body.
Question 9.
What is colour blindness?
Answer:
Colour blind is a genetical disease caused by a sex linked recessive gene in human being. The normal gene is C+ and its mutant recessive form, which hampers the activity of C+. The male carries C in his ‘ X ‘ chromosome and becomes colour blind. He is unable to detect red and green light.
Question 10.
What is genetic counselling?
Answer:
Consultation about genetic inheritance and probability of occurring genetical disease like thalassemia is known as genetic counselling.
Long Answer Type Questions : 5 Marks
Question 1.
What do you mean by autosomal and X linked inheritance in Human.
Answer:
Autosomal: The gene responsible for the phenotype is located on one of the 22 pairs of autosomes (non-sex determining chromosomes). Dominant: conditions that are manifest in heterozygotes (individuals with just one copy of the mutant allele). Recessive: conditions are only manifest in individuals who have two copies of the mutant allele (are homozygous).
Autosomal Dominant Conditions:
- Huntington Disease
- Acondroplasia (short-limbed dwarfism)
- Polycystic kidney disease
Affected individuals are indicated by solid black symbols and unaffected carriers are indicated by the half black symbols. Autosomal recessive diseases:
- Cystic fibrosis
- Tay-Sachs
- Haemochromatosis
- Phenylketonuria (PKU)
X linked: The gene that encodes for the trait is located on the X chromosome. X linked Recessive Disorders:
- Duchenne muscular dystrophy
- haemophilia A
- X linked severe combined immune disorder (SCID)
- some forms of congenital deafness
Question 2.
What is Thalassemia trait?
Answer:
Thalassemia Trait : Thalassemia is a genetic disease. This means that a person can only get thalassemia disease or trait by inheriting the genes for thalassemia from their parents. Genes determine what we look like, such as hair colour, and are also responsible for many diseases. Inheritance of thalassemia happens purely by chancethere is nothing that parents do, or do not do, that will cause their child to inherit thalassemia. Thalassemia is never ‘caught’ by another person in the way that a cold or flu is transmitted. People with thalassemia disease and trait are born with it.
Thalassemia trait is not and never will become thalassemia disease. There are two main types of thalassemia trait: Alpha Thalassemia trait and Beta Thalassemia trait. Most types of thalassemia trait cause the red blood cells to be smaller in size than usual, but there is no scientific evidence that thalassemia trait causes health problems. Individuals with thalassemia trait have some level of protection from malaria. Therefore, although thalassemia trait is found in all populations, it is most common in people from region where malaria occurs.
Question 3.
What do mean by the Inheritance of Thalassemia?
Answer:
The Inheritance of Thalassemia
Haemoglobin is made of heme, alpha globins, and beta globins. At least 9 different genes direct the production of heme. Changes in these genes may lead to disorders of heme production, a group of conditions separate from the thalassemias. Alpha thalassemia occurs when a mutation in the gene that codes for alpha globin results in reduced or absent production of alpha globins. Beta thalassemia occurs with a corresponding change in the beta globin gene. Therefore, the thalassemias are a result of quantitative mutations in the globin genes.
Below is a karyotype, a picture of all of an individual’s genetic information as seen through a microscope. There are 22 pairs of numbered chromosomes (autosomes) and one pair of sex determining chromosomes. A male carries both an X- and a Ychromosome, whereas a female has two X-chromosomes. Because a man can pass down either an X – or a Y-chromosome, he is the one who randomly determines the sex of the baby. The instructions for alpha globin production are present in duplicate, two genes on each chromosome 16 for a total of four. The instructions for beta globin production are on chromosome 11 , one gene on each chromosome for a total of two.
Half of a woman’s genetic information goes into each egg, including one chromosome 11 and one chromosome 16. The same is true in the formation of sperm. At conception, the total of 46 chromosomes is restored in which chromosome 11 or 16 is passed down is determined randomly. There is nothing that a mother or father does (or does not do) to direct which chromosome, and therefore which allele, is transmitted to his or her children.
Recessive Inheritance : In recessive conditions, a benign trait or carrier state can exist in which an individual has both a normal and a mutated copy of the gene. The term “normal” is a convention to simply describe the copy of the gene, called an allele, that is seen most often in the general population. The normal allele is able to compensate for the missing or altered function of the mutant allele. Therefore, the individual with trait does not have the symptoms seen in the disease. It is generally thought that each one of us carries 7-8 of these recessive traits, which would cause disease if present in a “double dose.”
It is not uncommon for a person with a recessive disease to be the first individual in his or her family to have the condition. Typically, this occurs when both parents are carriers of the trait. This is different from a dominantly inherited condition in which members of a family in several consecutive generations are affected. Some Recessive Conditions:
- Attached earlobes
- Sickle cell anemia
- Cystic Fibrosis
- Thalassemia
Some Dominant Conditions :
- Tongue rolling
- Huntington’s disease
Question 4.
Write about the inheritance of Haemophilia.
Answer:
The genes – or instructions – for blood clotting are found on the X chromosome, which means that haemophilia is described as an X-linked disorder. Since girls have two X chromosomes, they usually receive a healthy gene on the second X chromosome. The healthy gene will be dominant, meaning that girls who inherit the gene for haemophilia remain carriers, but do not usually show symptoms as their healthy gene can generally produce enough clotting factor for their blood to clot properly. However, this is not the case for boys who inherit the gene for haemophilia, because they only inherit one X chromosome. This means that they have no “back up” set of instructions for the clotting factor so are unable to produce very much, or in some cases none at all.
It can be quite complicated to visualise how haemophilia is inherited and what the chances are of someone having haemophilia or being a carrier, so it is worth looking at the diagram and reading the explanation. And remember, with the same parents, the likelihood of having a child with haemophilia is the same for each pregnancy.
Diagram of haemophilia inheritance (where is the gene for haemophilia A)
When a man with an affected gene on his X chromosome and a woman with two healthy genes have a child (see part (a) of the inheritance diagram), a daughter will receive one affected gene (from their father) and one healthy gene (from their mother), making them a ‘carrier’ of the condition, although they will not suffer from it. No son receives the affected gene as they must inherit the Y chromosome (not the X
chromosome) from their father. If the mother is a carrier and the father has healthy genes (see part (b) of the inheritance diagram), each son has a 50 per cent chance of receiving the affected gene from the mother. Any daughter has 50 per cent chance of receiving one affected gene and one healthy gene (therefore becoming a carrier) or of receiving two healthy genes. It is worth to note that in 30 per cent of newly diagnosed children their haemophilia is caused by a new mutation in the X chromosome, either in the mother or the child, where there is no previous family history of haemophilia. If the altered gene occurs in the mother it can also be passed to other children that she has, as detailed above. In addition, it may have arisen in her mother so her sisters, aunts and cousins may also be carriers.
Question 5.
Write about the inheritance pattern of Haemophilia.
Answer:
Inheritance Pattern of Haemophilia
The following diagrams show how the haemophilia gene can be inherited. It is important to note that in one-third of people with haemophilia, there is no family history of the disorder.
Mother is a carrier
- 50% chance that each son will have haemophilia.
- 0% chance that each daughter will be a carrier of the haemophilia gene.
Father has haemophilia
- All daughters will carry the haemophilia gene.
- No sons will have haemophilia.
Mother is a carrier and
Father has haemophilia
- 50% chance that each son will have haemophilia.
- 50% chance that each daughter will be a carrier of the haemophilia gene.
- 50% chance that each daughter will have haemophilia.
Question 6.
What do you mean by Genetic Counselling? State its necessity, component and limitation in relation to Thalassemia.
Genetic Counselling
Genetic counselling is the communication process of providing information and support to individuals and families with a diagnosis and/or risk of occurrence of an inherited disorder. Culturally sensitive genetic counselling, with an emphasis on reproductive issues, is an integral and necessary component of comprehensive care for patients and parents affected by all forms of thalassemia disease and trait. Services should be provided by a licensed genetic counselor in states with licensed legislation and by an ABGC board-certified or board-eligible genetic counselor in all other states.
Genetic counselling is needed :
- at diagnosis and during adolescence
- prior to and after any genetic testing
- prior to pregnancy and/or as early in pregnancy as possible
- Annual follow-ups are needed to reinforce teaching.
Critical components of genetic counselling include :
obtaining a three-generation genetic family history (pedigree)
assessing risk for thalassemia in family members
identifying risk factors impacting medical management (e.g., family history of other haemoglobin traits or diseases, hereditary haemochromatosis, G6 PD deficiency, inherited thrombophilia, cardiovascular disease or its risk factors, cardiac conduction defects, diabetes, renal disease, ophthalmologic disorders, hearing loss, allergies, ethnicity, consanguinity)
incorporating psychosocial information impacting the family system and relationships (e.g., location of residence, disclosure/nondisclosure of diagnosis, reliable source of emotional/social support)
assisting patients in conveying information about genetic risk to other family members
providing informed consent, pre-and post-counselling for all genetic testing
alpha-globin genotyping: haemoglobin H-Constant Spring and other structural alpha-globin variants, possible modifying effects of alpha-globin deletions/triplications on beta-thalassemia
beta-globin genotyping: beta0/beta+, S, D, E, O, and other structural variants
The limitations of drawing genotype/phenotype correlations include:
- developmentally appropriate consent/education for minors
- reproductive genotype post-stem cell transplant or bone marrow transplant
- the possibility of revealing undisclosed adoption or alternative paternity
- discussing/facilitating appropriate screening and diagnostic tests for relatives
Genetic Testing
If HLA typing is performed when stem cell transplant or bone marrow transplant is an option, genetic counselling and education is vital due to ethical implications. A genetic counselor should provide initial and ongoing teaching regarding natural history and clinical manifestations; signs and symptoms of disease that warrant immediate medical attention; and available emotional and social support services. Genetic counselors should also provide available resources in collaboration with outreach coordinators and social workers (e.g. research studies, support groups, advocacy organizations, and patient-to-patient or parent-to-parent connections).
Multiple Choice Questions : 1 Mark
Question 1.
Both husband and wife have normal vision though their fathers were colour blind. The probability of their daughter becoming colour blind is
(a) 0%
(b) 25%
(c) 50%
(d) 75%
Answer:
(a) 0%
Question 2.
Which one is a hereditary disease?
(a) cataract
(b) leprosy
(c) blindness
(d) phenylketonuria.
Answer:
(d) phenylketonuria.
Question 3.
Haemophilia is more common in males because it is a
(a) recessive character carried by Y-chromosome
(b) dominant character carried by Y-chromosome
(c) dominant trait carried by X-chromosome
(d) recessive trait carried by X-chromosome.
Answer:
(d) recessive trait carried by X-chromosome.
Question 4.
A colour blind girl is rare because she will be born only when
(a) her mother and maternal grandfather were colour blind
(b) her father and maternal grandfather were colour blind
(c) her mother is colour blind and father has normal vision
(d) parents have normal vision but grandparents were colour blind.
Answer:
(b) her father and maternal grandfather were colour blind
Question 5.
A colour blind mother and normal father would have
(a) colour blind sons and normal/carrier daughters
(b) colour blind sons and daughters
(c) all colour blind
(d) all normal.
Answer:
(a) colour blind sons and normal/carrier daughters
Question 6.
The colour blindness is more likely to occur in males than in females because
(a) the Y-chromosome of males have the genes for distinguishing colours
(b) genes for characters are located on the sex-chromosomes
(c) the trait is dominant in males and recessive in females
(d) none of the above.
Answer:
(b) genes for characters are located on the sex-chromosomes
Question 7.
The genes, which remain confined to differential region of Y-chromosome, are
(a) autosomal genes
(b) holandric genes
(c) completely sex-linked genes
(d) mutant genes.
Answer:
(b) holandric genes
Question 8.
A genetically diseased father (male) marries with a normal female and gives birth to 3 carrier girls and 5 normal sons. It may be which type of genetic disease?
(a) sex-influenced disease
(b) blood group inheritance disease
(c) sex-linked disease
(d) sex-recessive disease.
Answer:
(c) sex-linked disease
Question 9.
A person whose father is colour blind marries a lady whose mother is a daughter of a colour blind man. Their children will be
(a) all sons colour blind
(b) some sons normal and some colour blind
(c) all colour blind
(d) all daughters normal.
Answer:
(d) all daughters normal.
Question 10.
A woman with two genes for haemophilia and one gene for colour blindness on one of the ‘X’ chromosomes marries a normal man. How will the progeny be?
(a) 50% haemophilic colour-blind sons and 50% normal sons
(b) 50% haemophilic daughters (carrier) and 50% colour blind daughters (carrier)
(c) all sons and daughters haemophilic and colour blind
(d) haemophilic and colour blind daughters.
Answer:
(b) 50% haemophilic daughters (carrier) and 50% colour blind daughters (carrier)
Question 11.
Haemophilic man marries a normal woman. Their offsprings will be
(a) all haemophilic
(b) all boys haemophilic
(c) all girls haemophilic
(d) all normal.
Answer:
(d) all normal.
Question 12.
A marriage between normal visioned man and colour blind woman will produce offspring
(a) colour blind sons and 50% carrier daughter
(b) 50% colour blind sons and 50% carrier daughter
(c) normal males and carrier daughters
(d) colour blind sons and carrier daughters.
Answer:
(d) colour blind sons and carrier daughters.
Question 13.
A diseased man marries a normal woman. They get three daughters and five sons. All the daughters were diseased and sons were normal. The gene of this disease is
(a) sex linked dominant
(b) sex linked recessive
(c) sex limited character
(d) autosomal dominant.
Answer:
(a) sex linked dominant
Question 14.
The recessive genes located on X-chromosome humans are always
(a) lethal
(a) sub-lethal
(c) expressed in males
(d) expressed in females.
Answer:
(c) expressed in males
Question 15.
A normal woman, whose father was colour blind is married to a normal man. The sons would be
(a) 75% colour blind
(b) 50% colour blind
(c) all normal
(d) all colour blind.
Answer:
(b) 50% colour blind
Question 16.
A woman with normal vision, but whose father was colour blind, marries a colour blind man. Suppose that the fourth child of this couple was a boy. This boy
(a) may be colour blind or may be of normal vision
(b) must be colour blind
(c) must have normal colour vision
(d) will be partially colour blind since he is heterozygous for the colour blind mutant allele.
Answer:
(a) may be colour blind or may be of normal vision
Question 17.
Which of the following is not a hereditary disease?
(a) cystic fibrosis
(b) thalassemia
(c) haemophilia
(d) cretinism.
Answer:
(d) cretinism.
Question 18.
Haemophilia is more commonly seen in human males than in human females because
(a) a greater proportion of girls die in infancy
(b) this disease is due to a Ylinked recessive mutation
(c) this disease is due to an X-linked recessive mutation
(d) this disease is due to an X-linked dominant mutation.
Answer:
(c) this disease is due to an X-linked recessive mutation
Question 19.
If a colour blind woman marries a normal visioned man, their sons will be
(a) all colour blind
(b) all normal visioned
(c) one-half colour blind and onehalf normal
(d) three-fourths colour blind and one-fourth normal
Answer:
(a) all colour blind
Very Short Answer Type Questions : 1 Mark
Question 1.
When the disease transmitted from one generation to next, the disease known as-
Answer:
Genetical disease.
Question 2.
Give example of one autosomal disease.
Answer:
Thalassemia.
Question 3.
Give two examples of sex linked disease.
Answer:
Haemophilia, Colour blindness.
Question 4.
Which chromosomes are involved in case of thalassemia?
Answer:
16th and 11th autosome.
Question 5.
Write the vision defect for colour blindness.
Answer:
Unable to detect red and green colour.
Question 6.
Which disease is also known as sea of blood?
Answer:
Thalassemia.
Question 7.
Name one disease for which genetic counselling is necessary.
Answer:
Thalassemia.
Question 8.
Excess iron causes diseases.
Answer:
Thalassemia.
Question 9.
Which factor is absent in haemophilia-A?
Answer:
Anti-haemophilia gene globulin (AHG) or factor VIII.
Question 10.
Which factor is absent in haemophilia-B?
Answer:
Christmas factor or factor IX.
Question 11.
Which disease is also known as haemoglobinopathy.
Answer:
Thalassemia.
Question 12.
What is the nature of gene for haemophilia?
Answer:
Recessive X chromosome linked.