Test: Heredity And Variation 6 - From Past 28 Years Questions - NEET MCQ

The women is heterozygous as albinic condition is recessive hence when she marries an albinic man, the offsprings are 50% normal and 50% albinic.

Genotype is the genetic make up of an organism. The given 4 genotypes are present in 1 : 2 : 2 : 4 ratio.

Inbreeding leads to the expression of recessive characters, most of the time which are harmful.

The two factors of each trait arrange or assort at random and are independent of each other in their distribution into the gametes and in the progeny.

Tall (T) - 12;     Dwarf (D) - 4

AB blood group possess the genotype I^AI^B. The alleles I^A and I^B are codominant as both express themselves when together in an individual.

A gynandromorph is an organis  that contains both male and female characteristics. These characteristics can be seen in butterflies, where both male and female characteristics can be seen physically because of sexual dimorphism. A gynandromorph can have bilateral symmetry, one side female and one side male, or they can be mosaic, a case in which the two sexes aren’t defined as clearly.

Holandric genes are present on the differential region of the Y-chromosome. The differential regions carry completely sex linked genes and they do not undergo crossing over.

The pseudoalleles are two genetic loci producing identical phenotypes in cis as well as trans position.

A barr body is one of the X-chromosomes in somatic cells of females. If there are more X-chromosomes, then there will be more barr bodies.

Polytene chromosomes are also called giant chromosomes. They consist of numerous parallel identical chromatids due to repeated duplication without division. They were first time observed by Balbiani in the salivary glands of Chironomus.

Sickle cell anaemia (in which nucleotide triplet CTC is changed to CAC) affects the β-globin chain of haemoglobin. Since these changes occur at a particular locus or point of a chromosome where specific gene is located, they are called as point mutation.

The change in the colour of peppered moth is due to the mutation of single mendelian gene for the survival in the smoke-laden industrial environment. It is called Industrial melanism.

Epistasis is the suppression of  the normal phenotypic expression of the gene by a non-allelic gene. Complimentary genes are two independent genes present on different  gene loci which assist each other in expressing a trait . Supplementary genes are two independent genes present on different gene loci, each of which may produce its own trait and interact when present together in dominant state to produce a new trait.

Hermaphrodite or bisexual refers to an organism having both male and female sex organs. Gynandromorphs are individuals who exhibit both male and female characteristics.

According to the principle of dosage compensation, one of the two X chromosomes  in a female are inactivated at random. The inactivate X chromosome appears as the barr body.

Klinefelter's syndrome is formed by the union of an XX egg and a normal Y sperm or normal X egg and abnormal XY sperm. The individual has 47 chromosomes (44 + XXY).

The daughters receive one X chromosome from the father and one X chromosome from the mother. Since all the daughters suffer from their father’s disease, the X  chromosome from the father must be carrying a dominant trait.

H.J. Muller - study of effect of radiation on the living organisms. He was awarded the nobel prize for discovering that ionizing radiations can induce  gene mutations.

In sex determination, the male specific chromosome will have half as much chance as the other to enter the egg cell. Hence the proportion will be 1 : 1.

Male sterlity occur due to cytoplasmic or cytoplasmic- genenic inheritance, i.e., due to DNA present in mitochondrion or chloroplast under the i.e. control of extra-nuclear gene.

Allosomes or sex chromosomes determine the sex of the individual. The rest of the chromosomes are known as autosome. Nucleolus is a cell organelle involved in synthesis of ribosomes.

Down’s syndrome develops due to trisomy of chromosome number 21. In Turner’s syndrome, the effect appears due to fusion of a gamete without sex chromosome and a gamete with one X-chromosome (44 + X). Klinefelter individuals are phenotypically males. The defect appears due to fusion of egg having unreduced sex complement (A + X X) with a gamete carrying Y chromosome (44 + XXY). Gynandromorphism occur among Drosophila. In such individuals one half  of the body shows male characters and the other half shows female characters.

Mental retardness is usually found when there are more than two X chromosomes. About 1% of all mentally defective men have one or more extra X chromosomes.

Inversion is a change in chromosomal architecture in which part of the chromosome gets inverted in its position so that the sequence of the genes in the inverted region is reversed. In deletion a segment of a chromosome breaks and is lost. Monosomy is a type of deletion involving deficiency of one chromosome (2n - 1). In reciprocal translocation there is a mutual exchange of segments between two non homologous chromosomes.