31 Years NEET Previous Year Questions: Heredity And Variation - 2 - NEET MCQ

Haemophilia is sex linked recesive disease in which a simple protein that is a part of protein cascade involved in clotting of blood is affected. Due to this, in an affected individual a simple cut will result in non stop bleeding.

Tightly linked genes show more linkage then crossing over.

In Co-dominance F₁ generation resemble both the parents. Ex : Blood group inheritance.

ABO blood group system in human beings is an example of codominant, dominant recessive and multiple alletes. Blood groups are controlled by the gene I located on 9^th chromosome that has 3 multiple alleles, out of which any two are found in a person. In codominance both gene express it self completely.

A test cross, first introduced by Gregor Mendel, is used to determine if an individual exhibiting a dominant trait is homozygous or heterozygous for that trait. It takes place between F1 - Generation and recessive parent.

Change in single base pair of DNA is also a type of mutations called point mutations. It is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide of the genetic material, DNA or RNA. For example, a point mutation is the cause of sickle cell disease.

Colour blindness is a X-linked disease. So, woman whose father was colourblind will be carrier for the disease. So, possibility of a colourblind daughter (i.e., X^cX^c in F₁ generation is 0%.)

Blood group O acts as universal donor.

Two X chromosomes would lead to the birth of normal human female child.

Bacteriophage was used by Hershey and Chase to prove DNA as genetic matterial.

In test cross, genotype of an organism showing dominant phenotype is determined by crossing it with homozygous recessive genotype.

Type Oblood group is considered the universal donor blood group. It can potentially be transfused to any patient regardless of their blood type. In emergency situation, this type of blood can be given to the patient.

Mutation can be induced by gamma radiation.

Heterosis or hybrid vigor occurs when two unrelated individuals or lines are crossed, the performance of F1 hybrid, which is often superior to both is parents.

In grasshopper the males lack a Y-sex chromosome and have only an X-chromosome. They produce sperm cells that contain either an X chromosome or no sex chromosome, which is designated as O.

Infections proteins are rich in prions. Prions are made of proteins without nucleic acid. It is the causal agent of scrapie disease of sheep.

Linkage is the inheritance of genes of same chromosome together and capacity of these genes to retain their parental combination in subsequent generation. The strength of linkage between two genes is inversely proportional to the distance between the two. This means, two linked genes show higher frequency of recombination if the distance between them is higher and lower frequency if the distance is smaller.

Test cross is the cross of an individual with an individual having recessive phenotype. It is used to determine the genotype of a plant showing the dominant phenotype, that means to determine whether the individual exhibiting dominating characters are homozygous or heterozygous.

According to Mendel’s law of Dominance, out of two contrasting allelomorphic factors only one expresses itself in an individual. The factor that expresses itself is called dominant while the other which has not shown its effect in the heterozygous individual is termed as recessive. The option (c) in the given question cannot be explain-ed on the basis of law of dominance. It can only be explained on the basis of Mendel’s Law of independent assortment, according to which in a dihybrid cross, the two alleles of each character assort independently of the alleles of other character and separate at the time of gamete formation.

A point mutation is a simple change in one base of the gene sequence. This is equivalent to changing one letter in a sentence, such as this example, where we change the ‘e’ in cat to an ‘h’: Original: The fat cat ate the wee rat. Point Mutation: The fat hat ate the wee rat.

Baldness is a sex influenced trait. The dominance of alleles may differ in heterozygotes of the two sexes.

The correct option is Option B.

Haemoglobin is made of four polypeptide chains two α-chains which are 141 amino acid long and two β-chains which are 146 amino acids long. Sickle cell anaemia is due to inheritance of a defective allele coding for β-globin. It results in the transformation of HbA into HbS in which glutamic acid (Glu) is replaced by valine (Val) at sixth position in each of two β globin chain of haemoglobin. The substitution of amino acid in the globin protein results due to the single base substitution at the sixth codon of the beta globin gene from GAG to GUG.

So, it is caused by the substitution of valine by glutamic acid in the beta globin chain of haemoglobin.

By introducing bone marrow cells producing ADA into cells at early embryonic stages, the genetic defect adenosine deaminase (ADA) deficiency may be cured permanently. It is due to mutation.

The chart shows the inheritance of a condition like phenylketonuria as an autosomal recessive trait. Parents’ needs to be heterozygous as two of their children are known to be sufferer of the disease. It cannot be recessive sex linked inheritance because then the male parent would also be sufferer.

Klinefelter's syndrome is a genetic disorder affecting men in which an individual gains an extra X chromosome, so that the usual Karyotype of XY is replaced by one of XXY. Symptoms of  Klinefelter's syndrome  named after us physician H.P. Klinefelter, include female characteristics (such as breast enlargement).