Kendriyavidyalaya No. 1 Salt Lake

KendriyaVidyalaya No. 1 Salt Lake

Class XI - Unit Test 1 -2015-16

Subject: Biotechnology (Set 2)

Max. Marks – 40 Time: 1 ½ hours

Section A (1x5=5)

1. Which was the first protein to be completely sequenced? And by whom?

Insulin by Frederick Sanger

1. The example for multiple allelism is ______.

Blood group in humans

1. Name one protein for each of the functions: a) defense protein b) enzyme

a) Defense protein – Immunoglobulin

b) Enzyme – trypsin/amylase or others

1. What are alleles? Give an example.

Alleles are alternate forms of a gene. T and t for height of plants

1. Indicate one disease caused by a mutant protein.

Sickle cell anaemia

Section B (2x5=10)

1. Define an International unit of enzyme activity. Mention any two conditions required for enzyme activity.

An International unit of enzyme activity is defined as the activity of the enzyme which can catalyse the conversion of 1µ mole of substrate to product in one minute at room temperature.

Two conditions required for enzyme activity are pH and temperature.

1. What are amphipathic molecules? Give an example.

Amphipathic molecules are molecules that have both hydrophilic and hydrophobic regions. Example – lipid molecules

1. Differentiate between homopolysaccharides and heteropolysaccharides.

1. What are the different forms of RNA? Which is the most abundant form?

The different forms of RNA are mRNA, tRNA and rRNA. The most abundant form of RNA in the cell is rRNA found in association with ribosomes.

1. What protein is used to make bullet-proof vests? Why?

The protein used to make bullet proof vests is fibroin from webs of certain spiders. It is composed of mostly β-pleated sheets and is therefore strong and non-extensible.

Section C (3x5=15)

1. Explain the strategy used in the N-terminal to C-terminal sequencing of proteins.

The N-terminal amino acid of a polypeptide is chemically labelled and is specifically released leaving the rest of the protein shortened by one residue. The labelled amino acid is identified by a chromatographic technique. This procedure is repeated as many times as the number of resideues the protein contains. Hence, the identity of each released amino acid from the N-terminal of the protein will lead to the sequence of the protein read from N-terminal to C-terminus.

Diagram 3 on page 36.

1. Briefly explain the different forms of DNA.

A – DNA: right handed helix, formed at lower humidity conditions, larger diameter, lower pitch than B-DNA, 9 bases per helical turn

B- DNA – dominant form in-vivo, right handed helix, 10 bases per helical turn

Z-DNA – left handed helix, zig-zag appearance, 11 bases per helical turn

1. Differentiate between α-helix and β-pleated sheet.

1. Differentiate between complete and incomplete dominance.

1. Represent the cross showing complementary gene interaction for flower colour in 4 O’ clock plant.

Cross between AAbb(white) and aaBB(white) plant showing F1AaBb (purple), which is selfed to give 9(purple): 7 (white).

Section D (5x2=10)

1. Who discovered the structure of DNA? With the help of a neat labelled diagram, explain the details.

The structure of DNA was discovered by James D Watson and Francis Crick in 1953.

The following are the details of the double-helical structure of DNA:

1. DNA is a double stranded structure.
2. The two strands associate in an anti-parallel manner, one strand runs 5’ to 3’ while the other runs in a 3’ to 5’ direction.
3. The base sequence on one strand is complementary to the base sequence on the other strand because of the base pairing rule – adenine on one strand forms two hydrogen bonds with thymine on the other strand; cytosine on one strand forms three hydrogen bonds with guanine on the other strand.
4. The backbone of the double-helix is made up of sugar phosphate groups and the nitrogenous base pairs are towards the inside of the helix.
5. The distance between two nitrogenous base pairs is 0.34nm, the helix makes a complete turn after 3.4nm, the diameter of the helix is 2nm.

Diagram 9 on page 42.

1. Taking a suitable example, explain the Law of Independent Assortment.

Law of Independent Assortment states that in a cross considering two or more characters, the alleles of different characters segregate independent of each other.

Dihybrid Cross between plants with round, yellow peas and plants with wrinkled green peas produce F1 hybrids with round and yellow peas (RrYy). In the F2 generation Mendel obtained four classes of phenotypes in the ration 9:3:3:1. 9 plants were round, yellow peas (parental combination), 3 with round, green and wrinkled yellow each (non-parental combinations), and 1 with wrinkled green (parental combination). These observations suggest that the parental characters cba be split and non-parental combination can be obtained in F2 generation. However, the segregation ratio 9:3:3:1 in the dihybrid cross clearly shows that thte two paris of characters segregate in an independent manner.

Cross showing the dihybrid cross with Punnett square. (fig 3 page 50)

KendriyaVidyalaya No. 1 Salt Lake

Class XI - Unit Test2 -2015-16

Subject: Biotechnology (Set 1)

Max. Marks – 40 Time: 1 ½ hours

Section A (1x5=5)

1. Name the bond that links the monomers in a) polysaccharides b) nucleic acids

a) Glycosidic linkages b) phosphodiester

1. What is meant by primary structure of the proteins?

The complete amino acid sequence of a protein read from amino to carboxyl terminus is called the primary structure of a protein.

1. Name the scientists who invented a method for protein sequencing.

PehrEdman& Fred Sanger

1. Name one protein for each of the functions: a) defense b) contraction

a) Immunoglobulin b) actin and myosin

1. Show the genotype of a double heterozygote and a double homozygote taking a suitable example.

Double heterozygote – RrYy

Double homozygote – RRYY or rryy

Section B (2x5=10)

1. Differentiate between RNA and DNA.

1. How do enzymes differ from inorganic catalysts? Give any two differences.

1. Draw a neat labelled diagram of biomembrane showing the amphipathic nature of lipids.

Figure 8, page

1. What is a test cross? Why is it used?

A test cross is a cross between a F1hybrid(or any test organism) and the recessive parent. It is used to identify the genotype, ie. Homozygous or heterozygous condition of the organism.

1. What is multiple allelism? Give an example.

The existence of more than two forms of alleles for the same gene is called multiple allelism. Example, blood group in humans.

Section C (3x5=15)

1. Explain the strategy used in the sequencing of proteins.

The N-terminal amino acid of a polypeptide is chemically labelled and is specifically released leaving the rest of the protein shortened by one residue. The labelled amino acid is identified by a chromatographic technique. This procedure is repeated as many times as the number of resideues the protein contains. Hence, the identity of each released amino acid from the N-terminal of the protein will lead to the sequence of the protein read from N-terminal to C-terminus.

Diagram 3 on page 36.

1. Briefly explain the Law of Segregation.

Mendel’s law of segregation states that the paired hereditary determinants separate or segregate during gamete formation such that each gamete is equally likely to get either.

When Mendel crossed a tall and dwarf pea plant, the progeny of the F1 generation were all tall and no dwarf plants were obtained. When the tall plants of the F1 were selfed, he obtained both tall and dwarf plants in the ratio 3:1. This clearly shows that the alleles segregate randomly during gamete formation and are brought together in the next generation.

Monohybrid cross in figure 2, page no. 49.

1. Differentiate between α-helix and β-pleated sheet.

1. Briefly discuss the different forms of RNA.

Messenger or mRNA: contains information to make a protein. It is unstable and comprises 5% of total RNA. Its length is highly variable, of the range 75-3000 nucleotides.

Transfer RNA or tRNA: it is a small molecule and is involved in the transfer of amino acids to the site of protein synthesis. It is about 90 nucleotides long. It comprises about 15% of total RNA and forms 3D structure.

Ribosomal RNA or rRNA: associated with the ribosomes. It comprises 80% of the total RNA. Length varies from 120-3000 nucleotides.

1. How does the phenomenon of incomplete dominance deviate from mendelism? Explain.

Incomplete dominance is a phenomenon where the heterozygote offspring of the F1 generation does not show the character of either parent but produces an intermediate phenotype. The phenomenon is found in the inheritance of flower colour in 4 O’clock plant. A cross between red (RR) and white (rr) plants yields F1 plant which is pink (Rr) in colour. Upon selfing, it yields red, pink and white plants in the ration 1:2:1, the Mendelian monohybrid genotypic ratio.

It is a deviation from Mendelism because in Mendel’s experiments, the cross between parents with contrasting characters produces offsprings with one of the parental characters, i.e. the dominant character.

Section D (5x2=10)

1. Who discovered the structure of DNA? With the help of a neat labelled diagram, explain the details.

The structure of DNA was discovered by James D Watson and Francis Crick in 1953.

The following are the details of the double-helical structure of DNA:

1. DNA is a double stranded structure.
2. The two strands associate in an anti-parallel manner, one strand runs 5’ to 3’ while the other runs in a 3’ to 5’ direction.
3. The base sequence on one strand is complementary to the base sequence on the other strand because of the base pairing rule – adenine on one strand forms two hydrogen bonds with thymine on the other strand; cytosine on one strand forms three hydrogen bonds with guanine on the other strand.
4. The backbone of the double-helix is made up of sugar phosphate groups and the nitrogenous base pairs are towards the inside of the helix.
5. The distance between two nitrogenous base pairs is 0.34nm, the helix makes a complete turn after 3.4nm, the diameter of the helix is 2nm.

Diagram 9 on page 42.

1. Explain the inheritance of flower colour in sweet peas.

The inheritance of flower colour in sweet peas follows complementary gene interaction. Here two varieties of pea plants with AAbb (white flower) and aaBB (white flower) are crossed. The F1 plants will produce purple flowers with genotype AaBb. This is because flower colour requires the production of the pigment anthocyanin. Anthocyanin is produced only when a dominant allele from each gene is present. When the F1 hybrid is selfed, the F2 produced purple and white flower plants in the ratio 9:7. 9/16 of the plants will carry atleast one dominant allele of both ‘A’ and ‘B’ genes. The other 7/16 will be unable to produce the pigment as they may not contain both the dominant alleles.

Cross shown in figure 9, page 55.