Principles of Inheritance and Variation — BIOLOGY STD 12 Science — Question

What is placenta? Draw well labelled diagram of human embryo showing placenta in uterus and also write its four functions.

Replication was allowed to take place in the presence of radioactive deoxynucleotides precursors in E.coli that was a mutant for DNA ligase. Newly synthesised radioactive DNA was purified and strands were separated by denaturation. These were centrifuged using density gradient centrifugation. Which of the following would be a correct result?

Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.

The following is the illustration of the sequence of ovarian events (a – i) in a human female.

Explain the changes that occur in the uterus simultaneously in anticipation.

Describe the characteristics a cloning vector must posses.

Discuss the process of translation in detail.

Rohan and his friends emptied all the overhead tanks, which were not in use for last few months. Some people did not like this. Rohan and his friends explained and convinced them about the hygienic benefits of their act.

1. What was the objective behind their act?
2. Explain in brief the stages of life cycle of a malarial parasite in human body.
3. Which pathogen is responsible for malaria?
4. What values did Rahul and his friends promote?

1. Given below is the TS of human ovary. Identify the following in the diagram:

• Corpus luteum.
• Secondary oocyte.
• Antrum.
• Primary follicle.
• Primary oocyte.

2. Explain the changes the primary oocyte undergoes while in different follicular stages before ovulation.

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What is the role of animal husbandary in human welfare? Explain with examples.

Briefly describe the following: Translation