Answer:
O type blood (ii) and AB type Blood (IAIB) 50% of their children will have type A blood (IAi) and 50% will have type B blood (IBi)
Explanation:
Answer:
Over 95% of incoming ultraviolet radiation is absorbed in :
A. The Stratosphere.
Explanation:
- Stratosphere is the second layer of the earth's atmosphere that lies next to the troposphere.
- This layer experiences very little turbulence of air and is very significant because of the presence of Ozone layer in it.
- The UV rays entering the Earth's atmosphere, photo dissociates ozone into O₂ and O. But these molecules quickly recombine to form ozone.Thus, stabilizing the concentration of ozone in the atmosphere.
- During this photo dissociation UV radiations loses much of its energy. Thus, 95% of incoming Ultraviolet radiation gets absorbed in the Stratosphere.
- Absorption of ozone UV radiation increases exponentially with the thickness of ozone layer.
Answer:
The letters of DNA pair up because they form hydrogen bonds: each contains hydrogen atoms, which are attracted to nitrogen or oxygen atoms in their partner
Explanation:
Nucleotide bases are added to DNA strands in a 5' to 3' direction.
What is DNA replication?
When a cell divides, DNA copies itself through a process called replication.
- Generally speaking, DNA replication involves uncoiling the helix, strand separation by rupturing the hydrogen bonds between the complementary strands, and synthesis of two new strands through complimentary base pairing.
- The origin of replication, which is a precise location in the DNA, is where replication starts.
- From the point of origin, DNA replication is bidirectional.
- The two parent DNA strands unwind and split apart at the origin of replication to generate two "Y-shaped" replication forks in order to start DNA replication.
- These unwinding enzymes are known as DNA helicases.
- The real location of DNA copying is at these replication forks.
- Proteins that destabilize helices bind to the single-stranded areas to prevent the two strands from rejoining.
- To reduce stress on the helical molecule during replication, enzymes known as topoisomerases cause breaks in the DNA and then reunite them.
- The hydrogen bonding of free DNA nucleotides with those on each parent strand results in the formation of new complementary strands as the strands continue to unwind and split in both directions around the entire DNA molecule.
- The new nucleotides are joined by DNA polymerases using phosphodiester bonds as they align themselves opposite each parent strand using hydrogen bonds.
- Deoxynucleotide triphosphates, which are made up of a nitrogenous base called deoxyribose and three phosphates, are the actual nucleotides that are aligning through complementary base pairing.
- Two of the phosphates are withdrawn to provide energy for bonding as the phosphodiester bond forms between the 3' OH of the previous nucleotide in the DNA strand and the 5' phosphate group of the next nucleotide.
- In the end, two identical DNA molecules are created when each parent strand acts as a template for the synthesis of a complementary copy of itself.
Hence, nucleotide bases are added to DNA strands in a 5' to 3' direction.
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