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Biology Test

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By analysing a number of somatic cell hybrid lines for enzyme activities and their human chromosome constitution, the doctors can find out

  1. the number of chromosomes in the human genome

  2. the number of human chromosomes in each cell

  3. the location of gene on the chromosome that produces a specific enzyme

  4. the number of ribosomes in each cell


Correct Option: C
Explanation:

It is possible to correspond enzyme activity with a specific chromosome in a somatic cell hybrid.

Which of the following is NOT a method applied in humans' genetic analysis?

  1. Karyotyping

  2. Pedigree analysis

  3. RFLP analysis

  4. Test cross


Correct Option: D
Explanation:

Deliberate crosses are not used in studying the inheritance patterns of human beings.

In a cross between a white-eyed female dragonfly and red-eyed male, how many female progenies will inherit white eyes?(White eyes are X-linked recessive)

  1. 0%

  2. 25%

  3. 50%

  4. 75%


Correct Option: A
Explanation:

All the female eggs will have X chromosome with the white-eye mutation while the sperm will posses either a normal X chromosome or a Y chromosome. By using Punnett square, we can predict the outcome of this cross. Female progenies will receive X chromosome from both the sperm and egg cells. All females receive the dominant, red-eyed allele from their fathers and the recessive, white-eyed allele from their mothers.

In a cross between red-eyed female dragonfly and a white-eyed male dragonfly what percent of the male progenies will have white eyes? (White eyes are X-linked recessive)

  1. 75%

  2. 50%

  3. 25%

  4. 0%


Correct Option: D
Explanation:

The pure breed female is homozygous with the normal X chromosome and the white-eyed male is hemizygous for the X chromosome with a white eye mutation. Therefore, all male and female progenies are red-eyed.

A couple has a daughter suffering with Tay Sachs disease, and 4 normal children. Neither parent nor any of the four biological grandparents of the affected daughter had this disease. The most likely genetic condition leading to Tay Sachs disease is

  1. sex-linked recessive

  2. autosomal recessive

  3. autosomal dominant

  4. sex-linked dominant


Correct Option: B
Explanation:

It must be recessive because both parents are normal, but one or both parents must have passed the disease allele to their daughter. Since one or both parents are heterozygous and are not affected by the Tay-Sachs allele, the disease must be recessive.

A white-eyed female fruitfly is crossed with a red-eyed male fruitfly. Red eyes are dominant, and X-linked. What are the expected phenotypes of their children?

  1. 100% females will have red eyes while 50 % males will have red eyes, and 50% males will have white eyes.

  2. 100% females and 100% males will have white eyes.

  3. 100% females will have red eyes & 100% males will have white eyes.

  4. 100% females and 100% males will have red eyes.


Correct Option: C
Explanation:

As per the question, all of the females are red-eyed and heterozygous. All of the males are white-eyed and hemizygous.

A human male bearing an allele for a trait on the X chromosome is termed as

  1. heterozygous

  2. homozygous

  3. hemizygous

  4. monozygous


Correct Option: C
Explanation:

Human males are termed as hemizygous for any X-chromosome genes, meaning that there are only half (hemi) as many alleles as normally present for a diploid individual. As a result, if males inherit X-linked recessive trait from their mothers, they will show the recessive phenotype.

When RFLP investigation is used to examine a human gene, the approach is to first find out

  1. a known gene on the same chromosome

  2. a homozygous individual with a simple RFLP pattern

  3. particular DNA sequence located on the same chromosome

  4. particular DNA sign co-inherited with the specific genetic trait


Correct Option: D
Explanation:

Genes and anonymous DNA markers located near each other on the same chromosome are linked and do not segregate independently during meiosis.

Interpretation of chromosome aneuploidy of a foetus is typically done by the combination of amniocentesis, cell culture, and

  1. karyotyping

  2. RFLPs analysis

  3. enzyme assay

  4. pedigree analysis


Correct Option: A
Explanation:

A karyotype is used to demonstrate the number, types and appearance of chromosomes. Analysis of chromosomes of the developing foetus can be carried out with cells obtained from the amniotic fluid within the mother's uterus.

Klinefelter's syndrome in humans is an archetype of chromosomal aneuploidy. It is diagnosed by

  1. somatic cell genetics

  2. biochemical analysis

  3. behavior analysis

  4. karyotyping


Correct Option: D
Explanation:

A karyotype is used to show the number, types and appearance of chromosomes. Therefore, an extra X chromosome in a Klinefelter's person could be readily diagnosed by karyotyping.

Which among the following explanations regarding the Down's syndrome is false?

  1. The frequency increases severely in mothers after the age of 40.

  2. The genesis is a nondisjunction when chromosomes do not separate during the first meiotic division.

  3. Affected persons have an extra autosome.

  4. None of these


Correct Option: D
Explanation:

All statements are correct.

The logic behind the general prediction that half of the human babies born will be boys and half will be girls

  1. as a consequence of segregation of the X and Y chromosomes during male meiosis

  2. as a consequence of the segregation of the X chromosomes during female meiosis

  3. as the human eggs contain only X chromosomes

  4. approximately, half of human eggs produce females


Correct Option: A
Explanation:

It is the true statement because in humans the sex is determined by the sex chromosome in the sperm that fertilizes the female egg. Half of the sperm have a X-chromosome and half have a Y-chromosome.

Barr body is defined as

  1. an inactivated X chromosome

  2. an amplified gene

  3. a polytene chromosomes

  4. a ribonucleoprotein particle


Correct Option: A
Explanation:

One of the two X chromosomes in female somatic cells is foreseed as a densely staining body within the nucleus known as Barr body.

Which of the following individuals are mosaics?

  1. 47,XXX

  2. 45,X

  3. 47,XYY

  4. 47,XXY


Correct Option: B
Explanation:

This condition arises due to nondisjunction or loss of a structurally abnormal X or Y chromosome. Many are mosaics, with a cell line containing 46 chromosomes with a structurally abnormal X or Y.

Which of the following is an useful token for genetic or physical mapping of human chromosomes?

  1. RFLP

  2. EST

  3. STS

  4. All of the above


Correct Option: D
Explanation:

All are useful tokens for genetic or physical mapping of human chromosomes.

In Maharashtra, in a small nuclear family, red nose proved to be an inherited trait due to a single genetic locus. The man's mother and one sister also had red nose but his father, his brother and two other sisters had normal nose. The man and his normal-nosed wife had seven children, including four boys and three girls. Two girls and two boys had red nose. The red nose trait is most probably

  1. autosomal dominant

  2. autosomal recessive

  3. sex-linked dominant

  4. sex-linked recessive


Correct Option: A
Explanation:

Since this genetic trait has been passed from generation to generation from both fathers to daughters and mothers to daughters, therefore it is typically autosomal dominant trait.

Palpebral fissures, furrowed tongue, short fingers and toes, and incurved fifth finger are the symptoms of

  1. Trisomy 13 (Patau syndrome)

  2. Trisomy 18 (Edwards syndrome)

  3. Trisomy 21 (Down syndrome )

  4. Trisomy 17 (Mosaicism)


Correct Option: C
Explanation:

Newly born are hypotonic at birth and may have congenital anomalies, especially cardiac and gastrointestinal. Facial features include flat occiput, up-slanting palpebral fissures, furrowed tongue, short fingers and toes, and incurved fifth finger. 

The syndrome resulting from the microdeletion of chromosome 22q11.2. is

  1. Velo-cardio-facial syndrome

  2. Prader-Willi syndrome

  3. Angelman syndrome

  4. Williams syndrome


Correct Option: A
Explanation:

It results from the microdeletion of chromosome 22q11.2. Usually it is not visible cytogenetically, but detectable by FISH or comparative genomic hybridization.

Which of the following explains a particular type of polymorphism taking place within the gene that causes Huntington's disease in humans?

  1. Sequence-tagged sites (STSs)

  2. Short tandem repeat polymorphisms (STRPs)

  3. Expressed sequence tag (EST)

  4. Restriction fragment length polymorphism (RFLP)


Correct Option: B
Explanation:

The autosomal dominant gene leading to Huntington's disease has a mutation due to the extension of a triplet sequence of (CAG) within the coding region of the gene. Since the arrangement of the entire gene is now known, primers on either side of the tandem repeat arrangement of (CAG)n can be used to modify the region using the polymerase chain reaction and determine the size, i.e. number of times CAG is repeated. The triplet repeat arrangement is known as a STRPs, or short tandem repeat polymorphisms.

Which of the following syndromes arises due to mutation in the TP53 tumor suppressor gene?

  1. Cowden syndrome

  2. Li-Fraumeni syndrome

  3. Hereditary breast and ovarian cancer

  4. Hereditary non-polyposis colon cancer (HNPCC)


Correct Option: B
Explanation:

It is an autosomal dominant disease. It arises due to the mutation in the TP53 tumor suppressor gene. Its symptom includes cancers involving multiple sites including soft tissue sarcoma, osteosarcoma, etc.

Which among the following is a X-linked dominant disorder?

  1. Incontinentia pigmenti

  2. Ectodermal dysplasia

  3. Albinism

  4. Epidermolysis bullosa


Correct Option: A
Explanation:

It is a X-linked dominant disease. It results from the loss of function mutation of IKBKG gene. Primarily affects females and is lethal to hemizygous males in utero.

The mutation in SERPINA1 gene causes

  1. hemochromatosis

  2. Wilson disease

  3. Cystic fibrosis

  4. α1-antitrypsin deficiency


Correct Option: D
Explanation:

It is an autosomal recessive disease. It results from the mutation in SERPINA1 gene, which encodes α1-antitrypsin, a protease inhibitor. Lack of α1-antitrypsin in the lung leads to pulmonary damage due to inflammation.

The autosomal dominant disorder resulting from the mutation in NF1 gene on chromosome 17 is

  1. neurofibromatosis

  2. tuberous sclerosis complex

  3. multiple endocrine neoplasia

  4. retinoblastoma


Correct Option: A
Explanation:

It is an autosomal dominant disease. It results from the mutation in NF1 gene on chromosome 17. It is associated with development of tumors of the nerve sheath. Other features of NF1 include café-au-lait spots, optic glioma, learning disability, and increased risk of malignancy or vascular disease.

In which of the following syndromes, an individual develops sun-sensitive rashes on the face, hands, and forearms?

  1. Hippel-Lindau syndrome

  2. Noonan syndrome

  3. CHARGE syndrome

  4. Bloom syndrome


Correct Option: D
Explanation:

People with Bloom syndrome have low birth weight and proportionate short stature as they grow. There are distinctive facies, with underdeveloped malar bones and a sun-sensitive rash appears on the face, hands, and forearms.

Which disorder is associated with memory loss and hallucinations?

  1. Huntington disease

  2. Holoprosencephaly

  3. Canavan disease

  4. Alzheimer disease


Correct Option: D
Explanation:

Alzheimer disease is associated with memory loss and confusion, and may include language problems, poor judgment, agitation, and hallucinations. Brain atrophy is seen by MRI. There are no physical signs of the disease.

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