CBSE > Class 12 > Biology | CBSE Board | Homework Help

in lac operon lactose act as an inducer which regulates on and off of operon. it consist of structural gene (z y a) and regulatory gene (i) promoter (p) and operator (o) gene. In the absence of lactose(inducer) ....repressor protein is form by regulatory gene(i) which gets binds at operator gene (o)and prevent transcribing the operon... In the presence of lactose.....the repressor protein gets inactivated coz lactose binds on it ...due which transcription continues...and three structural gene: z form beta galactose y form premase a form transacetylase......!!!!

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Important que that can ask from evolution

Posted by Shivam Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

0 answers

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Exp amplicilin and tetracycline resistance gene in vector

Posted by Shivam Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Meghna Thapar 5 years, 5 months ago

The ampicillin resistance gene (ampr) codes for an enzyme (b-lactamase) that is secreted into the periplasmic space of the bacterium where it catalyzes hydrolysis of the b-lactam ring of the ampicillin. Thus, the gene product of the ampr gene destroys the antibiotic. pBR322 is 4361 base pairs in length and has two antibiotic resistance genes – the gene bla encoding the ampicillin resistance (AmpR) protein, and the gene tetA encoding the tetracycline resistance (TetR) protein. The pBR322 plasmid is a commonly used cloning vector that contains both the ampicillin and tetracycline resistance genes as selectable markers.

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How PCR help in detection of aids (hiv)

Posted by Shivam Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Prajjawal Sharma 6 years, 10 months ago

Pcr can amplify the no. Of infected cells under diagnoses and help in early stage recognition

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Explain aquired immunity in brief ?

Posted by Shivam Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

2 answers

Prajjawal Sharma 6 years, 10 months ago

Clonal selection is important

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Prajjawal Sharma 6 years, 10 months ago

It is pathogen specific Main part is its types antibodies mediated and cell mediated Antibodies by b lymphocytes and t lymphocytes help in the process

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Acc. To chargoff rule , a+t=c+g A/T = 1, A=T So A+T=A+A 2A =2C,as G/C=1 In this way A should also be equal to C

Posted by Nidhi Chauhan 6 years, 10 months ago

CBSE > Class 12 > Biology

2 answers

Shivam Jaiswal 6 years, 10 months ago

Purines and pyrimidines are equal in amounts If que is right u can suggest me ans

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Shivam Jaiswal 6 years, 10 months ago

Question has mistake Correct que is A+G=T+C

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What is Darwin fitness?

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Niyaz Ahmed 6 years, 10 months ago

It is darwin finches During his journey to galapagos island he observed that there were many varieties of small black birds later called darwin finches All the barieties he conjectured evolve on the island itself From the orignal seed- eating features many other form with altered beaks arose enabling them to become insectivorous and vegetarian finches This due to adaptive radiation ...... Thoda answer bda h pr pura h answer.

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What is Ex situ conservation?

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

2 answers

Niyaz Ahmed 6 years, 10 months ago

By moving them from there natural habitat

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Niyaz Ahmed 6 years, 10 months ago

Placing threatened animal and plant in special care units for their protection.

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What is population density?

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Rohit Dhariya 6 years, 10 months ago

Population per unit volume is called population density

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What is exons?

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Prajjawal Sharma 6 years, 10 months ago

The part of m rana that codes for polypeptide synthesis

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What is In situ conservation?

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Niyaz Ahmed 6 years, 10 months ago

It is conservation and protection of biodiversity in its natural habitat.

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ANSWER

What is 'fitness of an individual' according to Darwin ?

Posted by Arti Vishwakarma 6 years, 10 months ago

CBSE > Class 12 > Biology

2 answers

Yogita Ingle 6 years, 10 months ago

Darwinian fitness of a biological trait describes how successful an organism has been at passing on its genes.All organisms have the capacity to reproduce at a very high rate,but some reproduce more offspring while some less offspring. Hence, the species which produces more offspring are selected by nature.

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Inspi Sarkar 6 years, 10 months ago

According to the Darwin, it referce to ultimately and only to reproductive fitness. Those who are better fit in an environment level more progeny than others.

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We take a medicine after pasturation

Posted by Dharamveer Kumar 6 years, 10 months ago

CBSE > Class 12 > Biology

0 answers

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Could you please tell me a good investigatory project for biology class 12 semester

Posted by Christin Mathew 6 years, 10 months ago

CBSE > Class 12 > Biology

4 answers

Niyaz Ahmed 6 years, 10 months ago

Tardigrade.... One of the best topic for investigatory project

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Shivam Jaiswal 6 years, 10 months ago

Reproductive health, cancer , dna fingerprinting, microbes in human welfare , animal breeding etc

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Christin Mathew 6 years, 10 months ago

Any other suggestions

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A Jaiswal 6 years, 10 months ago

Plant breeding..... ☺

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Why meselaon and stahl used isotopes of N

Posted by Dikshant Kukreja 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Shivam Jaiswal 6 years, 10 months ago

Because purines and pyrimidines has nittogen Purines at position 1,3,7and 9 in double ring structure Pyrimidines at 1 and 3 position at single ring structure

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Guys tell me..... How many times you have revised biology?..... ☺

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

2 answers

A Jaiswal 6 years, 10 months ago

Hmmmm ?

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Dikshya Karki 6 years, 10 months ago

0. Gonna start from today

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Name an allergen and write the response of the human body when exposed to it.

Posted by Vinod Sharma Chhata 6 years, 10 months ago

CBSE > Class 12 > Biology

2 answers

Shivam Jaiswal 6 years, 10 months ago

Pollrn grain is allergen response is sneezing e.g carrot grass pollen grains

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Sadvi Slathia 6 years, 10 months ago

Dust is an allergen cause sniffing

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Microsporangia ....microspore....pollen grain ..in me kya difference h

Posted by Sangeeta Nara 6 years, 10 months ago

CBSE > Class 12 > Biology

0 answers

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What is menstruation cycle

Posted by Abhinav Tyagi 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Yogita Ingle 6 years, 10 months ago

The reproductive cycle starting from the one menstruation till the next one in the female primates is called menstrual cycle. The first menstruation which begins at puberty and is called menarche . The cycle is repeated at an interval of 28-29 days. Menstrual cycle involve three phases- menstrual phase, follicular phase and luteal phase.

Menstrual phase-

Menstrual flow occurs and lasts for about 3-5 days.
The endometrial lining of the uterus breaks along with the blood vessels which forms a red fluid and results in menstrual flow.
If the ovum is fertilized by a sperm menstrual flow does not occur and hence indicates pregnancy.

Follicular phase-

In this phase, the primary follicles in the ovary grow to become a fully matured graafian follicle.
Endometrium regenerates through proliferation.
Changes in Pituitary hormone and ovarian hormones induce the formation of graafian follicle and regeneration of endometrium.
The secretion of gonadotropins like luteinizing hormone and follicular stimulating hormone increases gradually during this phase and stimulates follicular development as well as secretion of estrogens by the growing follicles.
Both LH and FSH attain a peak level in the middle of cycle about 14th day.
Rapid secretion of LH leading to its maximum level during the mid-cycle called LH surge induces rupture of Graafian follicle and thereby the release of ovum known as ovulation

Luteal phase-

In this phase, the ruptured part of Graafian follicle transforms into yellow body called Corpus luteum.
The corpus luteum secretes large amounts of progesterone hormone which maintains the endometrium for implantation of the fertilized ovum.
During pregnancy all events of the menstrual cycle stop and there is no menstruation.
In the absence of fertilization, the corpus luteum degenerates hence causes disintegration of the endometrium leading to menstruation and a new cycle begins.

In human beings, menstrual cycles ceases around 50 years of age and known as menopause.

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ANSWER

Name two hormones that are constituents of contraceptives pills?

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

3 answers

A Jaiswal 6 years, 10 months ago

0Thank You

Yogita Ingle 6 years, 10 months ago

The two hormones that are constituents of contraceptive pills are:

1. Progestogen

2. Estrogen

They have high and effective contraceptive value as they inhibit ovulation and implantation as well as after the quality survical mucus to retard entry of sperm.

Example: Saheli is a non-steroidal oral pill.

1Thank You

Sayeda Iram Ateeq 6 years, 10 months ago

Estrogen and progesterone!

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If Anyone need help in biology then ask....? ☺

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

0 answers

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Anyone need help in biology then ask......? ☺

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

3 answers

A Jaiswal 6 years, 10 months ago

Kya Btau ..... ?

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Abhinav Tyagi 6 years, 10 months ago

Tell me about ******

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Sangeeta Nara 6 years, 10 months ago

Ans milega ?

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What is withdrawal syndrome ?

Posted by Arti Vishwakarma 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Muskan Garg 6 years, 10 months ago

Withdrawal syndrome is a set of symptoms when person leave taking drugs

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What is climax community ?

Posted by Snehashish Datta 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Azmat Ali 6 years, 10 months ago

It is that stable community of organisms which is obtained or which gets established after the invasion of pioneer species .

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What is plieotriphy?

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Muskan Garg 6 years, 10 months ago

When single gene controls many phenotypes , such genes are called pleiotropic genes and phenomenon of expressing pleiotrpic gene is known as pleitropy .

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What is polygenetic?

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Maniska Das 6 years, 10 months ago

It's having more than one grnetic source.

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Again..... ?What are some ethical issues in human diseases chapter?

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

0 answers

ANSWER

What are main features of HGP?

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology

1 answers

Arti Vishwakarma 6 years, 10 months ago

The main goals of the Human Genome Project were to provide a complete and accurate sequence of the 3 billion DNA base pairs that make up the human genome and to find all of the estimated 20,000 to 25,000 human genes. The Project also aimed to sequence the genomes of several other organisms that are important to medical research

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If anyone need help in biology then ask......? ☺

Posted by A Jaiswal 6 years, 10 months ago

CBSE > Class 12 > Biology