Answer:
When homologous chromosomes form pairs during prophase I of meiosis I, crossing-over can occur. Crossing-over is the exchange of genetic material between homologous chromosomes. It results in new combinations of genes on each chromosome. It is obviously another source of genetic variation in offspring.
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Answer: Mouth.
Explanation:
The mouth is known to be performing both the tasks of chemical digestion and mechanical digestion.
The food is ingested through mouth and the teeth perform the process of mechanical digestion by breaking down the food particles into smaller particles.
Then the saliva gets mixed into the food and the enzymes(amylase) present in the saliva helps in the digestion of carbohydrates.
So, mouth is the organ that performs the process of both mechanical and chemical digestion.
Answer:
C) are sequence-specific DNA endonucleases
Explanation:
Restriction enzymes represent a type enzyme capable of recognizing short nucleotide sequences to cut at specific restriction sites in the DNA, these sites are known as target DNA sequences. Some of the most commonly used restriction enzymes are <em>EcoRI</em>, <em>BamHI</em> and <em>HindIII</em>, isolated from <em>Escherichia coli</em>, <em>Bacillus amyloliquefaciens</em> and <em>Haemophilus influenza</em>, respectively. Restriction enzymes are endonucleases because these enzymes only cleave the phosphodiester bond within the DNA chain, conversely to exonucleases, which cleave nucleotides from the end of the polynucleotide DNA strand.
Answer:
The option 'All cells contain a nucleus' is not a part of the cell theory.
Explanation:
The cell theory proposed by scientists illustrates that every organism whether prokaryotic or eukaryotic is made up of a cell or different kinds of cells. It also that explains that cells are made from living things. According to the cell theory, cells are termed as the basic unit of life, without which life is not possible.
The cell theory does not claim that every cell must have a nucleus because many cells like cells of prokaryotes lack nucleus. Their genetic material is dispersed in the cytoplasm.