KCET 2016 Biology Question Paper with Answer and Solution

(B) The correct answer is $B$.
In a taxonomic hierarchy,the categories are arranged from higher to lower ranks as Kingdom,Phylum,Class,Order,Family,Genus,and Species.
As we move from the higher category (Kingdom) to the lower category (Species),the organisms within the group share more common characteristics.
Therefore,the number of common characters increases as we go from Kingdom to Species.

(B) The correct answer is $B$.
During the pachytene stage of prophase-$I$ of meiosis,the process of crossing over occurs.
Crossing over involves the exchange of genetic material between non-sister chromatids of homologous chromosomes.
This process is mediated by the enzyme 'recombinase',which facilitates the breakage and reunion of $DNA$ strands.

(D) The correct answer is $D$.
In the process of photosynthesis,the carbon source is $CO_2$,which is incorporated into the glucose molecule during the Calvin cycle.
Since the plant is supplied with the radioactive isotope $^{14}CO_2$,the carbon atoms in the resulting glucose molecule will be radioactive (labelled).
Oxygen released during photosynthesis is derived from the photolysis of water $(H_2O)$,not from $CO_2$.
Therefore,the oxygen released will be normal $(^{16}O)$ and not labelled.

(A) The correct answer is $A$.
Apical dominance is the phenomenon where the growing apical bud suppresses the growth of lateral or axillary buds.
This process is primarily regulated by the phytohormone $Auxin$,which is synthesized at the shoot apex and transported downwards,inhibiting the development of axillary buds.

(C) vasopressin.
Antidiuretic hormone $(ADH)$,also known as vasopressin,is released by the neurohypophysis (posterior pituitary gland).
It acts on the distal convoluted tubules $(DCT)$ and collecting ducts of the nephron to increase the permeability of water.
This process is known as facultative water reabsorption,which helps in the concentration of urine and prevents water loss from the body.

(A) The correct answer is $A$.
$A$ sarcomere is defined as the functional unit of muscle contraction.
Structurally,it is the segment of a myofibril located between two successive '$Z$' lines (also known as '$Z$' discs).
These '$Z$' lines are elastic fibres that bisect the '$I$' bands and serve as the anchor points for actin filaments.

(C) - pineal.
The pineal gland secretes a hormone called melatonin,which is an amine hormone.
Melatonin plays a very important role in the regulation of the $24$-hour (diurnal) rhythm of our body,such as the sleep-wake cycle and body temperature.

(D) The correct matches are as follows:
$1$. $(A)$ Prothallus: It is the free-living,photosynthetic,thalloid gametophyte stage found in Pteridophytes $(q)$.
$2$. $(B)$ Microsporophyll: These are leaf-like structures that bear microsporangia,characteristic of Gymnosperms $(s)$.
$3$. $(C)$ Protonema: It is the creeping,green,branched,and filamentous stage in the life cycle of mosses,which are Bryophytes $(p)$.
$4$. $(D)$ $PEN$ (Primary Endosperm Nucleus): It is formed by triple fusion during double fertilization,which is a unique feature of Angiosperms $(r)$.
Therefore,the correct matching is $A-q, B-s, C-p, D-r$.

(A) The correct answer is $A$.
In apple,the fruit is a false fruit $(pseudocarp)$.
In false fruits,the thalamus contributes to fruit formation along with the ovary.
The fleshy,edible part of the apple is the modified thalamus.

(D) The correct answer is $D$.
In plants,lateral roots are endogenous in origin,meaning they arise from internal tissues.
Specifically,they originate from the pericycle,which is a layer of cells located just inside the endodermis in the root.
The pericycle cells undergo division to form the root primordium,which eventually pushes through the cortex and epidermis to emerge as a lateral root.

(C) The correct answer is $C$.
In a polysaccharide,individual monosaccharide units are linked together by a glycosidic bond.
This bond is formed through a dehydration synthesis reaction between the hydroxyl group of one monosaccharide and the carbon atom of an adjacent monosaccharide.

(B) It declines the enzyme action.
When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme,it is known as a competitive inhibitor.
Because the inhibitor competes with the substrate for the active site,the substrate cannot bind effectively.
As a result,the overall rate of enzyme action declines.
An example is the inhibition of succinic dehydrogenase by malonate,which closely resembles the substrate succinate in structure.

(B) The correct statement is that $Cleistogamous$ flowers always exhibit autogamy.
In $Cleistogamous$ flowers,the flowers do not open at all.
Because the anthers and stigmas lie very close to each other within the closed flower,pollination occurs within the same flower,which is known as autogamy.
This ensures seed set even in the absence of pollinators.

(C) dithecous anther consists of $4$ pollen sacs (microsporangia).
Each $MMC$ (Microspore Mother Cell) undergoes meiosis to produce $4$ haploid microspores (pollen grains).
Number of $MMC$ per pollen sac = $1000$.
Number of pollen grains per pollen sac = $1000 \times 4 = 4000$.
Since there are $4$ pollen sacs in a dithecous anther,the total number of pollen grains = $4 \times 4000 = 16000$.

(A) Plants produced through tissue culture are genetically identical to the original plant because they are derived from somatic cells through asexual reproduction (mitosis).
These genetically identical individuals are collectively referred to as $Somaclones$.
Therefore,the correct option is $A$.

(B) molecular farming.
Molecular farming refers to the production of recombinant proteins using genetic engineering from live animals and plants. In this process,transgenic animals or plants are used as bioreactors to produce pharmaceutical proteins,enzymes,or other valuable biological products on a large scale.

(D) $Mutualism$ is a biological interaction where both interacting species benefit from the relationship.
In $Lichens$,algae and fungi live in a mutually beneficial association.
In $Mycorrhiza$,fungi and roots of higher plants show a mutualistic relationship.
Pollination involves a mutualistic interaction between plants and animals,where plants get pollinated and animals get food (nectar/pollen).
However,the association between cattle egrets and grazing cattle is an example of $Commensalism$,not $Mutualism$. In this interaction,the egret benefits by finding insects disturbed by the cattle,while the cattle are neither benefited nor harmed.

(A) The correct answer is $A$ and $B$ only.
$A$ population is defined as a group of individuals of the same species that occupy a specific geographical area at a given time.
These individuals are capable of interbreeding and sharing or exchanging genetic information.
Option $(C)$ is incorrect because population density and dispersion are dynamic characteristics that change over time and space,rather than being constant or uniform.

(D) Competition.
In competitive interactions,members of the species strive to obtain the same limited resources,that is,they compete for resources.
In this type of interaction,both the interacting organisms do not necessarily need to live in close proximity to each other,as they may be competing for resources that are available in the same environment or habitat.

(B) . Competition.
It was observed that in the deeper zones,$Balanus$ barnacles could always outcompete $Chthamalus$ barnacles.
$Balanus$ barnacles used the resources of the deeper zone more efficiently than $Chthamalus$ organisms,even though $Chthamalus$ barnacles are able to survive there in the absence of their competitor.

(B) The correct answer is $B$ (secondary productivity).
Net primary productivity is the biomass available for consumers (herbivores and decomposers) for consumption.
These organisms (heterotrophs) also produce new organic matter,and this process is called secondary production because it depends on the production of autotrophic organisms.
The rate of production of organic compounds by heterotrophs is known as secondary productivity.
Since deer are herbivores (heterotrophs),the rate at which they form new organic matter is termed secondary productivity.

(C) The correct sequence of events in human reproduction is as follows:
$1$. Gametogenesis: Formation of gametes (sperm and ovum).
$2$. Insemination: Transfer of sperm into the female genital tract.
$3$. Fertilisation: Fusion of male and female gametes to form a zygote.
$4$. Implantation: Attachment of the blastocyst to the uterine wall.
$5$. Gestation: Embryonic development inside the uterus.
$6$. Parturition: Delivery of the baby.
Therefore,the correct sequence is Gametogenesis $\rightarrow$ Insemination $\rightarrow$ Fertilisation $\rightarrow$ Implantation $\rightarrow$ Gestation $\rightarrow$ Parturition.

(C) - Prolactin.
The placenta acts as an endocrine tissue and produces several hormones essential for maintaining pregnancy,including human chorionic gonadotropin $(hCG)$,human placental lactogen $(hPL)$,estrogens,and progestogens.
Prolactin is a hormone secreted by the anterior pituitary gland,not the placenta. Its primary function is to stimulate the mammary glands to produce milk.

(D) Bartholin's gland.
Bartholin's gland is an accessory gland found in the female reproductive system,not the male reproductive system.
The male accessory glands include the prostate gland,seminal vesicles,and Cowper's (bulbourethral) glands.

(C) Amniocentesis is a prenatal diagnostic technique based on the chromosomal pattern in the amniotic fluid surrounding the developing fetus.
It is primarily used to determine the sex of the fetus and to detect any chromosomal abnormalities or genetic disorders.
Due to the misuse of this technique for female foeticide,it is legally banned in many countries,including India,for the purpose of sex determination.

(B) is the correct answer.
Lactational amenorrhea refers to the absence of menstruation during the period of intense lactation following parturition.
As long as the mother breastfeeds the infant fully,the high levels of prolactin inhibit the release of gonadotropins ($LH$ and $FSH$) from the pituitary gland.
This inhibition prevents ovulation,thereby preventing conception.
This method is effective for up to $6$ months following parturition.

(B) The correct answer is $B$.
$1$. In the pedigree,unaffected parents produce an affected offspring (the second child in the first generation). This indicates that the trait is recessive,as it skips a generation and appears in the offspring of phenotypically normal parents.
$2$. Since the trait appears in both males and females and does not show a sex-linked pattern (e.g.,it is not exclusively passed from father to daughter or mother to son),it is classified as an autosomal recessive trait.

(A) The genotype of the human male is $AaBbX^{h}Y$.
Since the genes are on different chromosomes (autosomal and sex-linked),they assort independently.
The possible gametes are formed by the combination of alleles: $(A, a) \times (B, b) \times (X^{h}, Y)$.
This results in $2 \times 2 \times 2 = 8$ types of gametes: $ABX^{h}, ABY, aBX^{h}, aBY, AbX^{h}, AbY, abX^{h}, abY$.
Among these $8$ types,the genotype '$abh$' corresponds to the gamete $abX^{h}$.
Therefore,the probability of producing a sperm with the '$abh$' genotype is $1/8$,which is $12.5 \%$.

(D) The correct answer is $D$.
Haemophilia is an $X$-linked recessive disorder.
In males,there is only one $X$ chromosome. If a male is haemophilic,his genotype is $X^hY$.
During reproduction,a father passes his $Y$ chromosome to his son and his $X$ chromosome to his daughter.
Therefore,a haemophilic father $(X^hY)$ will always pass his $Y$ chromosome to his son,meaning he cannot pass the haemophilia gene to his son.

(B) Pleiotropy.
Phenylketonuria is a classic example of pleiotropy,where a single gene mutation affects multiple phenotypic traits,such as mental retardation,reduction in hair pigmentation,and skin pigmentation.

(C) The correct answer is $C$.
The genetic code is said to be degenerate because some amino acids are coded by more than one codon.
In this case,both $UUU$ and $UUC$ code for the same amino acid,phenylalanine.
Note: The term 'non-ambiguous' means that one codon codes for only one amino acid,which is also a property of the genetic code,but the specific phenomenon of multiple codons coding for a single amino acid is defined as degeneracy.

(B) The given $DNA$ template strand sequence is: $3$' $TAC$ $ATG$ $GGT$ $CCG$ $5$'.
During transcription,the mRNA is synthesized complementary to the $DNA$ template strand in the $5$' to $3$' direction.
The mRNA sequence will be: $5$' $AUG$ $UAC$ $CCA$ $GGC$ $3$'.
The codons on the mRNA are $AUG$,$UAC$,$CCA$,and $GGC$.
The anticodons on the tRNA molecules that bind to these codons are $UAC$ (for $AUG$),$AUG$ (for $UAC$),$GGU$ (for $CCA$),and $CCG$ (for $GGC$).
Comparing the given tRNA complexes:
- $A$: $AUG$ (Anticodon for $UAC$)
- $B$: $UAC$ (Anticodon for $AUG$)
- $C$: $CCG$ (Anticodon for $GGC$)
- $D$: $GGU$ (Anticodon for $CCA$)
The sequence of binding to the mRNA codons ($AUG$,$UAC$,$CCA$,$GGC$) is $B$,$A$,$D$,$C$.

(D) The correct answer is $D$.
According to the Meselson and Stahl experiment,$E. coli$ cells grown in a medium containing $^{15}N$ (heavy isotope) incorporate it into their $DNA$.
When these cells are transferred to a medium containing $^{14}N$ (light isotope),the $DNA$ replication follows a semi-conservative model.
After the $1^{st}$ generation ($20$ minutes),all $DNA$ molecules are hybrid $(^{15}N^{14}N)$.
After the $2^{nd}$ generation ($40$ minutes),the hybrid $DNA$ molecules replicate to produce one hybrid $DNA$ molecule and one light $DNA$ molecule $(^{14}N^{14}N)$.
Therefore,the resulting population contains both hybrid and light $DNA$ in equal proportions.

(D) Statement $(A)$ is correct: In a transcription unit,the promoter is located at the $5'$ end of the coding strand (upstream).
Statement $(B)$ is incorrect: The template strand has a polarity of $3' \rightarrow 5'$,which allows $RNA$ polymerase to synthesize $RNA$ in the $5' \rightarrow 3'$ direction.
Statement $(C)$ is incorrect: $RNA$ polymerase binds to the promoter,not the operator,to initiate transcription.
Statement $(D)$ is correct: Single base $DNA$ differences occurring in humans are known as Single Nucleotide Polymorphisms $(SNPs)$.
Therefore,statements $(A)$ and $(D)$ are correct.

(D) is the mismatch: Genetic drift - Constant gene.
Genetic drift refers to the random fluctuation in the frequencies of alleles in the gene pool of a finite population due to chance events.
It occurs over a few generations.
If the change in allele frequencies is very drastic,it can lead to the formation of new species.
Therefore,genetic drift does not maintain a constant gene frequency; rather,it causes unpredictable changes in it.

(C) The Hardy-Weinberg principle states that the sum of all allele frequencies in a population is $1$,represented as $p + q = 1$.
When considering the genotype frequencies in a population at equilibrium,the equation is the binomial expansion of $(p + q)^2$,which is $p^2 + 2pq + q^2 = 1$.
Therefore,the correct representation of the Hardy-Weinberg law in terms of the binomial expansion is $(p + q)^2 = 1$.

(B) The correct statement is: The gametocytes develop in $RBC$.
$1$. The infective stage of $Plasmodium$ is the sporozoite,which is present in the salivary glands of the female $Anopheles$ mosquito.
$2$. When the mosquito bites a human,sporozoites enter the human blood along with the mosquito's saliva.
$3$. Inside the human body,the parasite undergoes asexual reproduction in liver cells and then in red blood cells $(RBCs)$.
$4$. In the $RBCs$,the parasite eventually develops into gametocytes (male and female gametocytes),which are then taken up by the mosquito during a blood meal.

(B) Rhinovirus.
The common cold,also known as rhinitis,is caused mainly by rhinoviruses.
These viruses infect the upper respiratory tract but do not affect the lungs.
The characteristic symptoms include nasal congestion,cough,headache,hoarseness,and sore throat.

(C) The correct answer is $C$.
An allergy is an exaggerated or inappropriate immune response to certain antigens present in the environment,such as dust,pollen,or dander.
When an individual is exposed to these allergens,the body's immune system produces specific antibodies of the $IgE$ type.
These $IgE$ antibodies bind to mast cells and basophils,triggering the release of chemicals like histamine,which leads to the symptoms of an allergic reaction.

(B) The incorrect statement is: $B$. Interferons kill viruses.
Interferons are glycoproteins produced by virus-infected cells. They do not kill viruses directly; instead,they protect non-infected cells from further viral infection by inhibiting viral replication.

(D) It acts as a clot buster.
Streptokinase is produced by the bacterium $Streptococcus$ and is modified by genetic engineering to be used as a 'clot buster' for removing clots from the blood vessels of patients who have undergone myocardial infarction (heart attack). It has a fibrinolytic effect,which helps in dissolving blood clots.

(B) Carbon dioxide.
The dough becomes puffy due to the presence of $CO_2$ gas liberated by bacteria during the process of fermentation.
In this metabolic process,bacteria break down carbohydrates into ethanol and $CO_2$ gas,which gets trapped in the dough,causing it to rise.

(B) The correct answer is $B$.
Elution is a process in biotechnology used during gel electrophoresis.
After the $DNA$ fragments have been separated on an agarose gel based on their size,the specific $DNA$ bands are cut out from the gel.
These cut $DNA$ fragments are then extracted from the gel piece.
This entire process of cutting and extracting the $DNA$ bands from the agarose gel is known as elution.

(D) The correct answer is $D$.
Plasmids are small,circular,double-stranded $DNA$ molecules that are distinct from a cell's chromosomal $DNA$.
They are found primarily in bacteria and are much smaller in size compared to the chromosomal $DNA$ of the host cell.
Therefore,the statement that plasmid $DNA$ is as long as chromosomal $DNA$ is incorrect.

(D) The correct answer is $D$. The statement 'The smaller $DNA$ fragments separate first' is technically incorrect in the context of the final separation pattern,as they migrate the fastest and reach the farthest point,but they do not 'separate first' in a chronological sense; rather,they are the ones that travel the furthest distance through the gel matrix.
Gel electrophoresis is a technique that uses an electric field to separate $DNA$ molecules based on their size.
Since $DNA$ molecules are negatively charged due to the phosphate backbone,they migrate towards the positive electrode (anode).
The rate of migration is inversely proportional to the size of the $DNA$ fragment.
Smaller $DNA$ fragments encounter less resistance from the agarose matrix and thus migrate faster and travel further than larger fragments.
Therefore,the band located farthest from the loading well represents the smallest $DNA$ fragment.

(A) The correct answer is $A$.
Biolistics,also known as the gene gun method,is the most suitable technique for introducing foreign $DNA$ into plant cells.
In this method,cells are bombarded with high-velocity micro-particles of gold or tungsten coated with $DNA$.
Microinjection is typically used for animal cells,lipofection is used for animal cells,and the heat shock method is primarily used for bacterial transformation.