Question

The genetic regulation of the various blood types observed in humans is a great example of

Select one:

a. Codominance

b. Epistasis

c. Incomplete dominance

d. Mendelian genetics

e. Polygenic inheritance

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The main replication enzyme involved in prokaryotic DNA copying is called

Select one:

a. Primase

b. DNA polymerase 1

c. DNA polymerase 2

d. Ligase

e. DNA polymerase 3

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The membrane that forms at the end of telophase to separate daughter cells at the end of mitosis in plants is known as

Select one:

a. Cleavage furrow

b. Cytokinetic constriction

c. Mitotic split

d. A septum

e. A cell plate

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The primers that are attached by DNA primase during DNA replication and made of RNA nucleotides

Select one:

a. False

b. True

Answer 1

ANSWER 1

e. Polygenic inheritance - In polygeneic inheritance, single trait is controlled by few genes. Contribution of each gene is usually additive to overall phenotype. For example, 14 genes are involved in person eye colour. Human blood type has three alleles. Person can have only two alleles. So, three genes are involved in human blood type (single trait or characteristics).

Incorrect options with Explanations

a. Codominance - When both alleles shows dominant effects, the phenomenon is called Co-dominance. For example, ABO blood groug has single gene with three alleles -  i, IA and IB. One allele is inherited from each parents. IA  gives blood group A and IB gives blood group B. And, i gives O blood group. IA and IB  is dominant over i. Person with following alleles will have corresponding blood groups:

Alleles	Blood Group
IAIA or IAi	A
IBIB or IBi	B
IAIB	AB
ii	O

Here, person with alllele IAIB will have blood group AB. Both alleles expressed and phenotypes are shown (expression of A and B antigen on blood cells). Such phenomenon is called Co-dominance.

b. Epistasis - It is a phenomenon in which expression of one gene is dependent on another gene or we can say that the effect of one gene mutation is dependent on muatation status of another gene (modifier gene).

c. Incomplete dominance - Phenomenon in which the dominant alllele is not completely dominant in phenotypic expression. It donot completely mask the recesssive alllele. As a result, phenotype of both alleles appear.

d. Mendelian genetics - It is a biological inheritance pattern which follows three principles laid by Mendel - laws of segregation and independent assortment. Discrete unit of inheritance, gene, is inherited from one of the parents and segregates into gametes with equal frequency.

ANSWER 2

e. DNA polymerase 3

DNA polymerase 3 is the main enzyme in prokaryotic DNA replication. It has 5' -> 3' polymerase activity and also proofreading activity. In addition, it has also 3' -> 5' exonuclease activity.

Incorrect Options with explanation

a. Primase - Primase is an enzyme which synthesise RNA primer to initiate DNA replication. It is RNA polymease which synthesise short RNA strectch on DNA template.

b. DNA polymerase 1 - It also has 5' -> 3' polymerase activity. But mainly involved in gap filling left after RNA primer removal, removal of RNA primer itself and also in DNA repair. It has both 5' -> 3' and 3' -> 5' exonuclease activity.

c. DNA polymerase 2 - It also has 5' -> 3' polymerase activity and mainly involved in DNA repair. Like DNA pol 3, it has 3' -> 5' exonuclease activity.

d. Ligase - Ligase is an enzyme which join two DNA strands by making phosphodiester bond between 3'OH group of one DNA strand and 5' phosphate of another strand. So, it fills the gaps created during DNA eplication. It is also involved in DNA repair.

ANSWER 3

e. A cell plate - Cytokinesis in plants are mediated by cell plates formation. Vesicles from Golgi comes up at the center of dividing cell. Cell plate grows and fuse with the pasma membrane (center outwards). Thereby producing two daughter cells. This membrane that forms at the end of telophase to separate daughter cells at the end of mitosis in plants is known as cell plate.

Incorrect Options with explanation

a. Cleavage furrow - For cytokinesis to occur, the cell membrane invaginates inside at the equitorial plane of the cell. This indicates the start of cytokinesis in animals.

b. Cytokinetic constriction - During cytokinesis, there is an cnstriction of cell due to constriction of a contractile actomyosin ring. This actomyosin ring generates tension in cell, as a results contriction of cell occurs to divide cells.

c. Mitotic split - During mitosis, the duplicated chromosomes are split in an ordered manner. Because cells with unusual chromosome numbers do not function normally.

d. A septum - It is structure in bacterial cell division. At the site of cell division, a septal ring is formed which contain many proteins. Polymer of protein FtsZ form foundation for septal ring.

ANSWER 4

b. True - The primers that are attached by DNA primase during DNA replication and made of RNA nucleotides. DNA primase is a type of RNA polymerase which sythesise short RNA stretch so that DNA polymerase 3 can use free 3'OH group to initiate DNA synthesis, complementary to template strand.

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