KCET 2010 Biology Question Paper with Answer and Solution

(D) Both the statements $A$ and $B$ are correct and $A$ is not the reason for $B$.
$Statement A$ is correct; $DNA$ synthesis occurs during the $S$-phase of interphase. During this time,the amount of $DNA$ per cell doubles.
$Statement B$ is also correct; each chromosome consists of two sister chromatids joined at the centromere during metaphase.
However,$Statement A$ is not the direct reason for $Statement B$,as the formation of two chromatids involves the replication of the entire chromosome structure,not just $DNA$ synthesis alone.

(A) The correct answer is $A$.
In non-cyclic photophosphorylation,both photosystems ($PS \ I$ and $PS \ II$) participate in the electron transport chain.
Option $B$ is incorrect because both $ATP$ and $NADPH$ are produced during this process.
Photolysis of water occurs at $PS \ II$ to provide electrons,and as a byproduct,$O_2$ is released.

(B) neither $O_2$ is used,nor $CO_2$ is liberated.
During lactic acid fermentation,oxygen is not consumed,and carbon dioxide is not produced.
This is an anaerobic process where glucose is converted into lactic acid without the involvement of oxygen or the release of carbon dioxide.
The chemical equation is:
$C_6H_{12}O_6 \longrightarrow 2C_3H_6O_3 + 2ATP$

(A) matrix of mitochondria.
The pyruvate dehydrogenase complex,which is essential for the oxidative decarboxylation of pyruvic acid into acetyl $CoA$,is located in the mitochondrial matrix.
This reaction serves as a crucial link between glycolysis (which occurs in the cytoplasm) and the $Kreb's$ cycle (which occurs in the mitochondrial matrix).

(A) The correct option is $A$.
In the electron transport system $(ETS)$ located in the inner mitochondrial membrane:
$1$. Coenzyme $Q$ (ubiquinone),labeled as $A$,acts as a mobile electron carrier that transfers electrons from Complex $I$ ($NADH$ dehydrogenase) and Complex $II$ (succinate dehydrogenase) to Complex $III$ (cytochrome $bc_1$ complex).
$2$. Cytochrome $c$,labeled as $B$,is a small protein attached to the outer surface of the inner membrane and acts as a mobile carrier for electrons between Complex $III$ and Complex $IV$ (cytochrome $c$ oxidase).

(D) $2$-chloroethylphosphonic acid,commonly known as $Ethrel$,is used to promote synchronized flowering in pineapples.
It acts as an ethylene-releasing compound,which induces flowering.

(B) The correct answer is $(B)$.
Erythroblastosis fetalis is a condition that occurs when an $Rh$-negative mother carries an $Rh$-positive fetus.
During the first pregnancy,the mother's blood is exposed to the $Rh$ antigens of the fetus during delivery,causing her to produce anti-$Rh$ antibodies.
In subsequent pregnancies,if the fetus is again $Rh$ positive,these maternal antibodies cross the placenta and destroy the fetal red blood cells (hemolysis).
This risk specifically arises when the mother is $Rh$ negative and the father is $Rh$ positive,as the fetus may inherit the $Rh$ positive trait.

(B) The correct answer is $O$.
Blood group $O$ individuals do not have $A$ or $B$ antigens on the surface of their red blood cells $(RBCs)$.
However,their blood serum contains both anti-$A$ and anti-$B$ antibodies.
When $RBCs$ containing both $A$ and $B$ antigens (such as those from an $AB$ blood group individual) are mixed with serum containing anti-$A$ and anti-$B$ antibodies,the antibodies bind to the antigens,causing the cells to clump together,a process known as agglutination.
Therefore,if agglutination occurs,the serum must contain these antibodies,which is characteristic of blood group $O$.

(C) The correct answer is $C$.
Insulin is a hypoglycemic hormone that lowers blood glucose levels.
It increases the permeability of cell membranes to glucose and promotes the oxidation of glucose in cells.
It also stimulates glycogenesis,which is the formation of glycogen from excess glucose in the liver and muscles.
Option $C$ is incorrect because the conversion of glycogen to glucose (glycogenolysis) is stimulated by the hormone glucagon,not insulin.

(B) By observing the provided diagram of the fish,we can identify the labeled parts as follows:
$A$ points to the Nostril.
$B$ points to the Eye.
$C$ points to the Dorsal fin (located on the back).
$D$ points to the Caudal fin (the tail fin).
$E$ points to the Anal fin (located on the ventral side near the tail).
$F$ points to the Pectoral fin (located on the side behind the operculum).
$G$ points to the Pelvic fin (located on the ventral side).
Comparing these identifications with the given options,option $C$ correctly labels all parts: $A$-Nostril,$B$-Eye,$C$-Dorsal fin,$D$-Caudal fin,$E$-Pectoral fin,$F$-Anal fin,$G$-Pelvic fin. Note: In the provided diagram,$E$ is the anal fin and $F$ is the pectoral fin. Therefore,the correct sequence is $A$-Nostril,$B$-Eye,$C$-Dorsal fin,$D$-Caudal fin,$E$-Anal fin,$F$-Pectoral fin,$G$-Pelvic fin,which matches option $B$.

(A) is the correct answer.
Butterflies and moths both belong to the order $Lepidoptera$.
Butterflies typically possess long,thin antennae that end in a club-like shape,whereas moths generally have feathery or comb-like antennae.
Both insects possess two pairs of wings.
Generally,moths are nocturnal (active at night),while butterflies are diurnal (active during the day).
Both groups possess compound eyes,though their visual structures can vary in complexity.

(D) The correct answer is $D$.
Lactose is a disaccharide sugar composed of two monosaccharide units: $D$-glucose and $D$-galactose.
It is naturally found in milk and dairy products,acting as a primary source of energy for infants and young mammals.

(B) exine of pollen grain.
Sporopollenin,found in the exine of pollen grains,is one of the most resistant organic materials known. It is highly resistant to extreme temperatures,strong acids,and alkali,and no enzyme that degrades sporopollenin is known so far. In contrast,the intine of pollen grains is composed of cellulose and pectin. The endothecium of the anther aids in dehiscence,while the tapetum provides nourishment to the developing pollen grains.

(D) micropropagation.
To meet societal demands for large numbers of plantlets quickly,the technique used in floriculture and horticulture is called micropropagation.
This method allows for the rapid production of multiple plantlets from a small tissue sample in a controlled environment.
$A$ Hybridoma technology is used for producing monoclonal antibodies.
$B$ Somaclonal variation refers to genetic variation in plants regenerated from tissue culture.
$C$ Somatic hybridisation involves the fusion of somatic cells to create hybrids.

(C) The correct sequence for the production of humulin is $(i), (iv), (v), (ii), (vi), (iii)$.
$1$. First,the gene for human insulin is synthesized artificially $(i)$.
$2$. Then,this gene is inserted into a plasmid $(iv)$.
$3$. The recombinant plasmid is introduced into $E. coli$ $(v)$.
$4$. The $E. coli$ is then cultured in bioreactors to produce the insulin protein $(ii)$.
$5$. The recombinant insulin protein is extracted from $E. coli$ $(vi)$.
$6$. Finally,the product is purified to obtain pure humulin $(iii)$.

(B) Kaziranga National Park.
Kaziranga National Park, located in Assam, India, is world-renowned for hosting two-thirds of the world's population of the one-horned rhinoceros, also known as the Indian rhinoceros $(Rhinoceros \text{ } unicornis)$.

(D) keystone species.
In an ecosystem,certain species have a disproportionately large effect on their environment relative to their abundance. Even if they are insignificant in number,they play a critical role in maintaining the structure and diversity of the community. Such species are known as $keystone$ $species$.

(D) habitat destruction.
Habitat destruction is the primary threat to most endangered species,as it leads to the loss of living spaces and essential resources.
While over-hunting,acid rain,and competition with introduced species are significant threats,habitat destruction is recognized as the most widespread and critical issue causing the decline of biodiversity globally.

(A) The correct answer is $A$.
In the absence of an acrosome,the sperm cannot penetrate the egg.
The acrosome is a cap-like structure present at the tip of the sperm head.
It contains hydrolytic enzymes,such as hyaluronidase and acrosin,which are essential for digesting the protective layers of the ovum (zona pellucida and corona radiata).
Without these enzymes,the sperm is unable to penetrate the egg,and fertilization cannot occur.

(A) The correct answer is $A$.
During the process of gastrulation,the embryo forms a structure called the gastrula.
The gastrula contains an opening or pore known as the $Blastopore$.
$Blastopore$ is the first opening formed in the early embryo,which later develops into either the mouth or the anus depending on the organism (protostomes or deuterostomes).

(A) The correct answer is $A$.
$1$. When a sperm with $22A + XY$ fertilizes a normal egg with $22A + X$,the resulting zygote has a chromosome composition of $44A + XXY$. This condition is known as Klinefelter's syndrome.
$2$. When a sperm with $22A + O$ fertilizes a normal egg with $22A + X$,the resulting zygote has a chromosome composition of $44A + XO$. This condition is known as Turner's syndrome.

(D) sex has no influence on the dominance of traits.
Mendel's observation that reciprocal crosses produce identical results led him to conclude that the inheritance of traits is not influenced by the sex of the parent.
This means that the dominance of a trait is independent of whether the allele comes from the male or female parent,leading to the conclusion that sex has no influence on the dominance of traits.

(A) In genetic fingerprinting,a 'probe' is a radioactively labelled single-stranded $DNA$ molecule that is complementary to the specific variable number tandem repeat $(VNTR)$ sequences being analyzed.
These probes hybridize with the target $DNA$ fragments on a membrane,allowing for the visualization of specific $DNA$ patterns through autoradiography.
Therefore,the correct option is $(A)$.

(C) The statement "$UAA$ codon codes for lysine" is incorrect.
$UAA$ is a stop codon (also known as the ochre codon), which does not code for any amino acid and signals the termination of protein synthesis.
Lysine is actually coded by the codons $AAA$ and $AAG$.

(B) is the correct answer: to identify and sequence all the genes present in human $DNA$.
The main aim of the Human Genome Project $(HGP)$ was to map and sequence the entire human genome.
This involved identifying all the genes present in human $DNA$ and determining the complete nucleotide sequence of the $3 \times 10^9$ base pairs that make up human $DNA$.
The project did not focus on introducing new genes (gene therapy),developing forensic comparison techniques,or removing disease-causing genes as its primary objective.

(A) $DNA$ gyrase is a type of $DNA$ topoisomerase that relieves the torsional strain caused by the unwinding of $DNA$ during replication.
It introduces negative supercoils to counteract the positive supercoils that form ahead of the replication fork.

(C) Statement $A$ is correct and $B$ is wrong.
In eukaryotic cells,the primary transcript (pre-mRNA) produced during transcription must undergo post-transcriptional modifications,such as capping,polyadenylation,and splicing,to become functional mRNA for translation. It is not used directly.
Statement $B$ is incorrect because $RNA$ splicing is the process of removing introns (non-coding sequences) and joining exons (coding sequences) together to form mature mRNA. Exons are not removed; they are retained.

(B) The correct answer is $B$. According to Darwin,evolution is a slow,gradual,and continuous process. Darwin proposed that evolution occurs gradually over long periods of time,where small,heritable variations accumulate,eventually leading to the emergence of new species.

(D) The correct matching is as follows:
$A$. Natural active immunity: This occurs when the body encounters a pathogen and develops an immune response naturally,i.e.,$s$. Fighting infections naturally.
$B$. Artificial passive immunity: This involves the administration of pre-formed antibodies (antiserum) to provide immediate protection,i.e.,$r$. Injection of antiserum to travellers.
$C$. Artificial active immunity: This is induced by introducing antigens into the body through vaccination to stimulate an immune response,i.e.,$t$. Induced by vaccination.
$D$. Natural passive immunity: This occurs when antibodies are transferred from mother to foetus through the placenta or via colostrum,i.e.,$q$. From mother to foetus through placenta.
Therefore,the correct combination is $A-s, B-r, C-t, D-q$.