The sex determination in honey bee is based on the number of sets of chromosomes an individual receives. An offspring formed from the union of a sperm and an egg develops as a female (queen or worker), and an unfertilised egg develops as a male (drone) by means of parthenogenesis. This means that the males have half the number of chromosomes than that of a female. The females are diploid having 32 chromosomes and males are haploid, i.e., having 16 chromosomes. This is called as haplodiploid sex-determination system Answer : (d)

Aneuploidy is a chromosomal variation due to a loss or a gain of one or more chromosomes resulting in the deviation from the normal or the usual number of chromosomes. The different conditions of aneuploidy are nullisomy (2N-2), monosomy (2N-1), trisomy (2N+1), and tetrasomy (2N+2). Down’s syndrome results in the gain of extra copy of chromosome 21. This condition is trisomy. Turner’s syndrome results due to loss of an X chromosome in human females. This conition is monosomy. Answer : (b)

A Barr body or X-chromatin is an inactive X chromosome in a cell with more than one X chromosome, rendered inactive in a process called lyonization, in species with XY sex-determination. Men with Klinefelter syndrome (47, XXY karyotype) have a single Barr body. Answer : (b)

Failure of segregation of chromatids during cell division cycle results in the gain or loss of a chromosome(s), called aneuploidy. Aneuploidy in sex chromosomes means additional copy of a chromosome may be included in an individual or an individual may lack one of any one pair of chromosomes. example: Turner’s Syndrome : Such a disorder is caused due to the absence of one of the X chromosomes, i.e., 45 with X0. Klinefelter’s Syndrome : This genetic disorder is also caused due to the presence of an additional copy of Xchromosome resulting into a karyotype of 47, XXY. Answer : (a)

Gamete	X	Xh
X	XX Normal daughter	X Xh Carrier daughter
Y	XY Normal boy	Xh Y Haemophilic boy

Haemophilia : This sex linked recessive disease, which shows its transmission from unaffected carrier female to some of the male progeny has been widely studied. Cross between haemophilic carrier woman and normal man will produce progeny as follows: 50% carrier daughter and 50% normal daughter. Answer : (a)

Answer : (b)

Answer : (b)

The father's sex chromosomes are labeled XY. The father only passes half of his sex chromosomes to the baby, either the X or the Y. If the baby gets the Y chromosome from the father it will be a boy. The son can get from the mother either her X chromosome with the hemophilia gene or her X chromosome with the normal blood clotting gene. If the son gets his mother's X chromosome with the hemophilia gene he will have hemophilia. If he inherits his mother's other X chromosome, he will have normal blood clotting. So a carrier's son has a 50% chance of having hemophilia. A baby girl will inherit an X chromosome with a dominant gene for normal blood clotting from her father. So the daughter will not have hemophilia. A daughter will get either her mother's X chromosome with the hemophilia gene or her mother's X chromosome with the normal gene for clotting. If she gets the X chromosome with the hemophilia gene she will be a carrier. So a carrier's daughter has a 50% chance of being a carrier. Answer : (b)

Hardy-Weinberg equation is p2 + 2pq + q2 = 1. Here p is the frequency of the "A" allele and q is the frequency of the "a" allele in the population. Hence, frequency of heterozygous genotype= 2pq= 2 x 0.6 x 0.4= 0.48. Answer : (d)

Sickle cell anaemia provides immunity against malaria. The sickle cells have membranes, stretched by their unusual shape, that become porous and leak nutrients that the parasites need to survive and the faulty cells eventually get eliminated quite fast by the organisms, destroying the parasite along the way. Answer : (d)

Answer : (c)

Chromosomes are made up of a DNA-protein complex called chromatin that is organized into subunits called nucleosomes. Protein content is same as in DNA. Answer : (d)

Gamete	X	X
XC	XCX Carrier normal vision girl	XC X Carrier, normal vision girl
Y	XY Normal boy	X Y Normal boy

A colour blind man has XCY and normal female has XX chromosomes. Progeny will be as follows: All normal vision progeny. Answer : (d)

Crossing over is a process that happens between homologous chromosomes in order to increase genetic diversity. During crossing over, part of one chromosome is exchanged with another. The result is a hybrid chromosome with a unique pattern of genetic material. This generation of non-parental gene combinations are known as recombinant. Answer : (a)

A laggard was defined as a chromosome that did not overlap along the long axis of the spindle with any of the properly segregating chromosomes. Dicentric chromosome is the cause of chromosome laggards in meiosis as it is an abnormal chromosome with two centromeres. Answer : (b)

Cytoplasmic male sterility can be defined as total or partial male sterility in plants due to specific nuclear and mitochondrial interactions. Genes responsible for this are present in mitochondrial genome. Answer : (b)

Failure of cytokinesis after telophase stage of cell division results in an increase in a whole set of chromosomes in an organism and, this phenomenon is known as polyploidy. Wheat, Triticum, has basic chromosome number is n= 7; thus the hexaploid species (Triticum aestivum) have 6n= 42. Monosomic =6n-1 = 41 Nullisomic = 6n-2 = 40 Trisomic = 6n+1 = 43 Haploid = 6n/2 = 21 Answer : (d)

Mutations can result from errors during DNA replication or induced by exposure to mutagens (like chemicals and radiation). Answer : (d)

During anaphase, sister chromatids (or homologous chromosomes for meiosis I), will separate and move to opposite poles of the cell, pulled by microtubules. In nondisjunction, the separation fails to occur causing both sister chromatids or homologous chromosomes to be pulled to one pole of the cell. Answer : (b)

In grasshoppers, males have 23 chromosomes and females have 24 chromosomes Answer : (d)

The term linkage is used to describe physical association of genes on a chromosome. The genes that are close to each other have a tendency to be more linked than those that are farther. The more the linkage lesser will be the recombination frequency. Answer : (c)

Huntington's disease is caused by an inherited defect in a single gene. Huntington's disease is an autosomal dominant disorder, which means that a person needs only one copy of the defective gene to develop the disorder. An inherited condition in which nerve cells in the brain break down over time. It typically starts in a person's 30s or 40s. Usually, Huntington's disease results in progressive movement, thinking (cognitive) and psychiatric symptoms. Answer : (a)

Chromosomes were discovered by Hofmeister (1848), studied by Strasburger (1875) and given the present name by Waldeyer (1888) after their staining by dyes like Janus Green. Answer : (b)

Base analogues are molecules that can substitute for normal bases in nucleic acids. Usually, substitution of a base analogue will result in altered base pairings and structural changes that affect DNA replication and transcription of genes. Examples of base analogues include 5-bromouracil, 2-aminopurine, 6-mercaptopurine, and acycloguanosine. Since 5-bromouracil can pair with either adenine or guanine, it also affects base pairing during DNA replication, which leads to mutations. Answer : (a)

Answer : (c)

Answer : (b)

In human pedigree analysis full-shaded symbols represent the affected individuals while the half-shaded stands for carriers. The square shape stands for a male individual while the circle stands for females. A diamond shape represents the unidentified sex. A square connected by two horizontal lines with circle represents the mating between relatives. Answer : (d)

A translocation occurs when a piece of one chromosome breaks off and attaches to another chromosome. Answer : (c)

Lesch-Nyhan syndrome is a condition that occurs almost exclusively in males. It is characterized by neurological and behavioral abnormalities and the overproduction of uric acid. Uric acid is a waste product of normal chemical processes and is found in blood and urine. Answer : (b)

Gamete	Xh	Xh
X	XhX Carrier daughter	X Xh Carrier daughter
Y	XhY Haemophilic boy	Xh Y Haemophilic boy

Haemophilia : This sex linked recessive disease. Cross between haemophilic woman and normal man will produce progeny as follows: All daughter will be carrier and all the sons are haemophilic. Answer : (c)

According to this theory of sex determination, if the ratio of the X chromosome to a total number of sets of autosomes X/A ratio < 0.5 gives supermale or metamale. Drosophila with 1 X chromosome and 3 set of autosomes have the (X/A = 1/3) ratio of 0.33 and is metamale. Answer : (d)

Phenylketonuria : This inborn error of metabolism is also inherited as the autosomal recessive trait. albinism is passed on in an autosomal recessive inheritance pattern. Answer : (a)

Haemophilia : This sex linked recessive disease. Female can be haemophilic when woman has hozygous pattern i.e. XhXh A homozygous recessive female express the disease but they do not survive due to impaired ability or inability of blood clotting which causes heavy blood loss even in the case of small injury. Answer : (b)

Down’s Syndrome : The cause of this genetic disorder is the presence of an additional copy of the chromosome number 21 (trisomy of 21). This disorder was first described by Langdon Down (1866). The affected individual is short statured with small round head, furrowed tongue and partially open mouth. Palm is broad with characteristic palm crease. Physical, psychomotor and mental development is retarded. The eyes of an individual with Down syndrome might slant upwards a little bit and are almond shaped. They might have small folds of skin at the inner corners, which are called Epicanthal Folds. Answer : (c)

Barbara McClintock,American scientist whose discovery in the 1940s and '50s of mobile genetic elements, or “jumping genes, won her the Nobel Prize for Physiology or Medicine in 1983. Answer : (b)

Colour Blindness : It is a sex-linked recessive disorder due to defect in either red or green cone of eye resulting in failure to discriminate between red and green colour. This defect is due to mutation in certain genes present in the X chromosome. For female to colour blindess, she should have homozygous defective allele, heterzygous makes a carrier. But for male, defect in X chromosomes can make then colour blind. Answer : (d)

40% Answer : (d)

Colchicine is an important mutagen that works by preventing the microtubules formation and doubles the number of chromosomes. It is commonly used to develop polyploid plants and functions as a mitotic poison by producing many mutagenic effects on plants Answer : (d)

A translocation occurs when a piece of one chromosome breaks off and attaches to another chromosome. An inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end-to-end. Answer : (d)

Each chromosome may produce two iso-chromosome, one for each arm; thus for each primary trisomic, two types of secondary trisomics are possible. Thus in Datura (2n – 24), 12 primary and 24 secondary trisomics are possible. Answer : (b)

Auxotrophy is the inability of an organism to synthesize a particular organic compound required for its growth. Auxotroph = mutant that cannot grow on minimal medium, requires certain supplement(s). Answer : (c)

Telomeres are nucleoprotein structures that protect and maintain chromosome ends. Answer : (d)

(p + q)2 = p2 + q2 + 2pq =1 where; p2 is the frequency of homozygous dominants. q2 is the frequency of homozygous recessive individuals. The 2pq in equation shows frequency of heterozygotes in the population. p+q=1. q=0.2 Then p = 0.8 p2 = (0.8)2 = 0.64 Answer : (a)

A translocation occurs when a piece of one chromosome breaks off and attaches to another chromosome. Answer : (a)

A gynandromorph is an organism that contains both male and female characteristics. Gynandromorph is an animal that's half male and half female when splitting at the midline. Meanwhile, a hermaphrodite is an animal that appears as male or female but has both male and female reproductive organs. Answer : (b)

Klinefelter’s Syndrome : This genetic disorder is also caused due to the presence of an additional copy of X chromosome resulting into a karyotype of 47, XXY. Such an individual has overall masculine development, however, the feminine development (development of breast, i.e., Gynaecomastia) is also expressed. Such individuals are sterile. Answer : (c)

Secondary spermatocytes are haploid (N) cells that contain half the number of chromosomes. Answer : (c)

Deuteranomaly (most common—6% of males, 0.4% of females): These individuals have a mutated form of the medium-wavelength (green) pigment. Protanomaly (2% of males, 0.01% of females): Having a mutated form of the long-wavelength (red) pigment Answer : (b)

A hallmark of UVC and UVB mutagenesis is the high frequency of transition mutations at dipyrimidine sequences containing cytosine. Because of these mutations, the connection between ultraviolet damage to DNA and cancer is quite clear. Answer : (a)

Hugo De Vries conducted his experiments on the plant Oenothera lamarckiana, the common name of this plant is “Evening Primrose”. Answer : (c)