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fiasKO [112]
3 years ago
7

Describe the key features of the Watson-Crick model for DNA structure.

Biology
1 answer:
vagabundo [1.1K]3 years ago
5 0

Answer:

Watson and Crick proposed the double helical model of DNA.

Explanation:

- This model says that DNA exist as double helix. It has two polynucelotide strands running in opposite direction i.e the strands are anti-parallel.

- Each polynucleotide strand is made up of several nucleotide liknked together by phophodiester bonds.

- The two strands are not coiled upon each other but the double strand is coiled upon itself around a common axis like the spiral stair case. Here base pairs forms the stairs and backbone of two strands form railing. Back bone contains sugar and phosphate.

- The base pairing is specific, adenine always pairs with thymine and guanine always pairs with cytosine. Thus if we see any base pair, it consists of one purine and one pyrimidine.

- The two strands of DNA thus show complementary base pairing.

- The strands are held together because of hydrogen bonding between the bases in opposite strand.

- One full helical turn involves ten base pairs and the base pairs are stacked  3.4 A apart.

- This form is called as B-form of DNA.

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Describe the function of each organelle.
Elis [28]

Answer:

Cytoplasm: Fluid between the cell membrane and the nucleus. helps protect organelles

Nucleus: A part of the cell containing hereditary information and is responsible for growth and reproduction; the "command center" of the cell.

Ribosome: A small particle in the cell that can make proteins.

Endoplasmic Reticulum: A cell structure that forms a maze of passageways in which proteins and other materials are carried from one part of the cell to another.

Golgi Apparatus: A cell structure that helps make and package materials to be transported out of the cell or for storage inside the cell.

Lysosome: Cell organelle filled with enzymes needed to break down certain materials in the cell, such as large food particles or old parts of the cell. May be found only in animal cells.

Vacuole: Saclike storage structure in the cell. can store water, nutrients, and even toxic substances.

Mitochondrion: An organelle containing enzymes responsible for producing energy. (Metabolism/respiration)

Chloroplast: An organelle found in the cells of plants and some other organisms that captures the energy from sunlight and converts it into chemical energy (photosynthesis).

Cell membrane: The thin, flexible barrier around a cell; controls what enters and leaves the cell.

Cell wall: The structure outside of the cell membrane that is used to provide support and protection. Present in plants, algae, fungi, and many prokaryotes.

8 0
2 years ago
Which organism is most related to birds?
Lesechka [4]

Answer:

Crocodiles are actually the closest living relatives to birds

6 0
2 years ago
The process of phagocytosis involve all of the following except
evablogger [386]

Hello, I figured your question was missing its options so I went online to find them. Here they are:

The process of phagocytosis involves all of the following EXCEPT :

a. adhesion.

b. secretion of cytotoxins.

c. elimination.

d. vesicle fusion.

e. chemotaxis.

Answer:

The correct answer is: b) secretion of cytotoxins.

Explanation:

Phagocytosis is a mechanism performed by cells in which the plasma membrane engulfs a large particle. Phagocytosis is used by cells in the immune system to ingest pathogens like viruses and bacteria.

Phagocytosis consists of many steps:

  1. activation - the phagocytes that were resting are activated in the inflammatory response when a pathogen enters the body.
  2. chemotaxis  - this refers to the process in which the phagocyte moves to the pathogen by following the chemical factors released by these germs.
  3. adhesion - the phagocyte attaches to the pathogen.
  4. ingestion /vesicle fusion - the phagocyte sends pseudopods to engulf the pathogen, and places it in a phagosome, which is an endocytic vesicle. The phagosome and the phagocyte will fuse so the pathogen gets inside.
  5. elimination - the pathogen is destroyed in the phagocyte by the lysosomes present in it.

<u>The</u><u> secretion of cytotoxins</u><u> is not a part of the phagocytosis, and is a process exclusive to </u><u>T cells</u><u> (leukocytes that lack the ability to phagocyte).</u>

5 0
2 years ago
What would be the best source of information for an essay about sharks
serg [7]
A verified animal source such as animal planet or any website that doesn't have ads and has accurate info
8 0
3 years ago
Observe an ecosystem near your home and describe the biodiversity of your chosen ecosystem. PLZZZ HELPP idc if its from a photo
murzikaleks [220]

Answer:

A garden is a ecosystem that is near my house.  the biodiversity of garden is fresh green leaves for caterpillars, and floral resources (pollen and nectar) for pollinators.

Explanation:

Hope it helps!!!!!

Mark me brainlist plzzzzzzzzzzzzzzzzzzzzzzzzz

5 0
2 years ago
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