mcq biology

DNA Repair Mechanisms: Biology MCQ 019 with Answer Key (Model Questions for CSIR NET and GATE Life Sciences Examination, December 2015)

MECHANISTIC STUDIES OF DNA REPAIR

1. Which of the following DNA repair mechanism is known as the ‘cut and patch mechanism’?

a.       Photoreactivation
b.      Nucleotide excision repair
c.       Base excision repair
d.      Mismatch repair

2. DNA helicase enzyme involved in base excision repair mechanism is______.

a.       DNA helicase I
b.      DNA helicase II
c.       DNA helicase III
d.      DNA helicase IV

3. In mismatch repair mechanism, which of the following protein recognize DNA mismatches in the genomic DNA?

a.       MutH
b.      MutS
c.       MutL
d.      UvrD

4. The main difference between nucleotide excision repair  (NER) and base excision repair (BER) is:

a.       In NER double strand breaks are repaired where as in BER single strand breaks repaired
b.      NER is a light dependent reaction whereas BER is light independent process
c.       In NER phosphodiester backbone is first cleaved where as in BER phosphodiester backbone is cleaved later
d.      All of these

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Botany lecture notes

Life Cycle in Algae (Haplontic, Diplontic, Haplodiplontic, Haplobiontic and Haplo-diplobiontic Life Cycles)


Life Cycle of Algae

Nature is a machine. The family is a machine. The life cycle is like a machine.

Ray Dalio

What is life cycle?

The growth and development consists of a number of distinct morphological and cytological stages. The sequence of these orderly changes is called as LIFE CYCLE. It is the sequence of all different phases or events through which an organism passes from a diploid zygote of one generation to the zygote of the next generation through haploid gametes.

There are five different types of life cycles in algae based on the number of haploid and diploid generations.

life cycle in algae

Haplontic Life Cycle

1. Haplontic life cycle

2. Diplontic life cycle

3. Haplodiplontic life cycle

4. Haplobiontic life cycle

5. Haplo-diplobiontic life cycle

(1). Haplontic life cycle:

Ø  Most common type of life cycle in algae

Ø  Life cycle is diphasic (two phases)

Ø  The prominent phase is haploid gametophytic phase

Ø  The diploid (sporophytic) phase in the life cycle is represented by the ZYGOTEContinue reading

Botany lecture notes

Algae: General Characters (with Power Point Presentation – PPT)


Important Characteristics of Algae

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“The life of the planet began the long, slow process of modulating and regulating the physical conditions of the planet. The oxygen in today’s atmosphere is almost entirely the result of photosynthetic living, which had its start with the appearance of blue-green algae among the microorganisms”

                                                                     Lewis Thomas, 1984


General appearance of algae

An Algal Bloom of Blue Green Algae

What are algae?

Algae is a group of chlorophyll containing thalloid plants which bear unicellular or multicellular sex organs and the sex organs are NOT protected in the sterile jacket cells. An undifferentiated plant body is known as ‘thallus’. In thalloid plants, there is no differentiation of plant body into true roots, stem and leaves.

The study of algae is known as PHYCOLOGY. The one who study algae is called Phycologist

General characters of algae

Ø  Thalloid plant body

Ø  In Eichler’s system of classification, algae are placed in the Division Thallophyta along with Fungi and Lichens.

Ø  Algae are autotrophs (synthesize food using light energy)

What is thallus?

Spirogyra Thallus *

Ø  Algae differ from fungi in:

⊕. Presence of photosynthetic pigment – chlorophyll
⊕. Mode of nutrition (autotrophs)

Ø  Majority of algae are in aquatic habitat (fresh water or marine), some algae are terrestrial also

Ø  Algae are present in all parts of the world including Arctic and Antarctic regions (universal occurrence)

Ø  Sex organs are unicellular or multicellularContinue reading

Zoology lecture notes and study materials

Classification of Arthropoda with Identification Characters for Each Sub-Phylum and Class


How Arthropods further classified

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Arthropods are classified into five sub-phylum and each then subdivide into classes (a total of 16 classes according to recent classification of animal taxa).

Phylum Arthropoda:

I.   Sub-phylum: Trilobitomorpha (extinct arthropods)

Class 1: Trilobita

II.   Sub-phylum: Chelicerata (spiders, horseshoe crabs)

Class 1: Arachnida
Class 2: Merostomata
Class 3: Pycnogonida

III.  Sub-phylum: Myriapoda (centipedes, millipedes)

Class 1: Chilopoda
Class 2: Diplopoda
Class 3: Pauropoda
Class 4: Symphyla

IV.  Sub-phylum: Crustaceae (crabs, prawns, shrimps)

Class 1: Branchiopoda
Class 2: Remipedia
Class 3: Cephalocarida
Class 4: Maxillopoda
Class 5: Ostracoda
Class 6: Malacostraca

V.   Sub-phylum: Hexapoda (insects)

Class 1: Insecta
Class 2: Entognatha

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Botany lecture notes

Vascular Bundles: Structure, Composition and Classification


Plant Vascular Tissue System

“It is not so much that the cells make the plant; it is rather that the plant makes the cells”
Heinrich Anton de Bary

easybiologyclass what are vascular bundlesWhat are vascular bundles?

Vascular bundles (VB) are the components of vascular tissue system in plants. They are also called as ‘fascicle’. They are the part of TRANSPORT system in plants. It is one of the PRIMARY tissue systems in plants. More than that is a perfect example for a COMPLEX tissue system in plants. (Complex tissue = composed of more than one type of cells)

What are the components of vascular bundles?

Vascular bundle consists of TWO main parts.

@. Xylem: the water conducting tissue

@. Phloem: the food conducting tissueContinue reading