A women with albinic father marries an albinic man. The proportion of her progeny is
The women is heterozygous as albinic condition is recessive hence when she marries an albinic man, the offsprings are 50% normal and 50% albinic.
In a dihybrid cross AABB × aabb, F2 progeny of AABB, AABb, AaBB and AaBb occurs in the ratio of
Genotype is the genetic make up of an organism. The given 4 genotypes are present in 1 : 2 : 2 : 4 ratio.
The process of mating between closely related individuals is
Inbreeding leads to the expression of recessive characters, most of the time which are harmful.
A cross between pure tall Pea plant with green pods and dwarf Pea plant with yellow pods will produce short F2 plants out of 16
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
A child of blood group O can not have parents of blood groups
AB blood group possess the genotype IAIB. The alleles IA and IB are codominant as both express themselves when together in an individual.
A fruitfly exhibiting both male and female traits is
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.
Genes located on Y-chromosome are
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.
When two genetic loci produce identical phenotypes in cis and trans position, they are considered to be
The pseudoalleles are two genetic loci producing identical phenotypes in cis as well as trans position.
Barr body in mammals represents
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.
The polytene chromosomes were discovered for the first time in
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.
The most striking example of point mutation is found in a disease called
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 of the light-coloured variety of peppered moth (Biston betularia) to its darker variety (Biston carbonaria) is due to
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.
Alleles that produce independent effects in their heterozygous condition are called
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.
An individual exhibiting both male and female sexual characteristics in the body is known as
Hermaphrodite or bisexual refers to an organism having both male and female sex organs. Gynandromorphs are individuals who exhibit both male and female characteristics.
Barr body in human female is formed by
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.
A person with 47 chromosomes due to an additional Y chromosome suffers from a condition called
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).
A man with a certain disease marries a normal woman. They have eight children (3 daughters and 5 sons). All the daughters suffer from their father's disease but none of the sons are affected. Which of the following mode of inheritance do you suggest for this disease?
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 was awarded Nobel Prize for his
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.
A fruit fly is heterozygous for sex-linked genes. When mated with a normal female fruit fly, the male-specific chromosome will enter egg cells in the proportion of
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.
After crossing between two plants, the progenies are found to be male-sterile. This phenomenon is found to be maternally inherited and is due to some genes which are present in
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.
Genetic identity of a human male is determined by
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.
A person with the sex chromosomes XXY suffers from
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.
In Down's syndrome, Karyotyping has shown that the disorder is associated with trisomy of chromosome number-21 usually due to
Down’s syndrome caused by trisomy 21, arises due to an occassional non disjunction during meiosis when a gamete comes to possess an extra chromosome (n+1). Fusion with a normal gamete [n + (n+1)] produces trisomy.
Mental retardation in man associated with sex chromosomal abnormality is usually due to
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.
The formation of multivalents at meiosis in a diploid organism is due to
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.