Heredity And Variation 7 - From Past 28 Years Questions Free MCQ Practice

Multiple alleles control inheritance of blood groups in human. A, B, O blood group system is found in humans where the allele I^A for A antigen is codominant with the allele I^B for the B antigen. Both I^A and I^B are completely dominant to the allele P Hierarchy of dominance relationships is symbolised as(I^A = I^B) > I^O.

I^AI^O × I^AI^B gives us the following genotypes I^AI^A, I^OI^B, I^AI^B.

The genotype of the mother was to be either X^C X^C or X^CX and that of father X^CY so that the daughter becomes colour blind.

Homozygous individuals have identical mendelian factors or genes for a character (TT or tt). They are always pure for a particular trait (character).

At anaphase I, actual segregation occurs, but two similar alleles occur in the dyad chromosome which separate at anaphase II.

Genotype is the genetic make up of an individual irrespective of the mendelian characters or genes impressing.

Epsitasis is the phenomenon of masking or supressing the phenotypic impression of a gene pair by a non allelic gene pair which impresses its own effect.

Dominant alleles expresses itself in the homozygous as well as heterozygous condition. It is denoted by capital letter.

The genotype of the child would be IºIº (recessive). Hence the genotype of the father can only be I^BI^O.

Turner syndrome encompassess several chromosomal abnormalities, of which monosomy X is the most common. It occurs in 1 out of every 2500 female births. Instead of the normal XX sex chromosomes for a female, only one X chromosome is present and fully functional. This is called 45,X or 45,X0, although other genetic variants occur. In Turner syndrome, female sexual characteristics are present but generally underdeveloped.

Down's syndrome is due to non-disjunction of chromosomes. Non-disjunction means absence of sepration of two homologous X chromosomes during anaphase-I of meiosis. Both X-chromosomes go together to same pole. Other pole will receive no X-chromosome.

When a colour blind woman marries a normal man the recessive homozygous gene is expressed in sons whereas the daughters become carriers.

In Neurospora , products of meiosis remain linearly arranged and undergo one mitosis. Crossing over occurs in four strand stage.

Plasma genes present in the maternal cytoplasm are transmitted to offspring hence this type of inheritance is termed as cytoplasmic or maternal inheritance.

Law of independent assortment is applicable to only those factors or genes which are located on different chromosomes. Probably the characters were present on same chromosome and showed linkage which Mendel might not have studied.

Polygenic inheritance show cumulative effect i.e. two independent dominant genes produce additive effect on an individual.

The four histone proteins constituting the core of nucleosome are H2A, H2B, H3, H4.

Sex of human body is determined by the karyotype of the zygote or fertilized egg. Sex of the baby depends upon the sperm which fertilizes the ovum.

It was genetically modified to get high lipid contents.

The haploid organisms readily express the phenotypes of the new mutations because there is no hindrance of dominance.

Chromosome mapping is based on the fact that genes are linearly arranged on the chromosome and frequency of crossing over is directly proportional to the distance between two genes. Dominant genes show cis arrangement. At 50 map units cis is changed to trans & vice-versa hence no fixed linkage is present.

Since half the sons are haemophilic so the genes for haemophilia is located on X-chromosome of mother.

Due to linkage the genes present on same chromosome stay together during transmission. All other combinations except AABB × aabb show recombination which do not show linkage and hence not suitable for experiments on linkage.

Genotype of Mr. Kapoor will be Bb d-hence one fourth of the sperms will have Bd.

On crossing carrier colour-blind woman with a normal man, the sons become colour blind. This is an example of criss cross inheritance. The genes for colourblindness is coming from mother's father.