Crossing over happens in Meiosis 1 only. In Prophase 1 a cells chromatin (chromatin = chromosomes that have not condensed yet) condense and pair up forming homologous chromosomes (paired = XX (2 chromosomes together)). When this happens segments/ alleles of the chromosomes pairing up swap over. This creates genetic diversity as each chromosome is different, it has parts from its pair. This leaves every chromosome unique and individual.
I hope this helps, sorry some of the vocab is rather technical. By the way I would suggest watching the
'Crash Course: Meiosis' on YouTube, this really helped me when I was learning this topic. :D
I don’t know why they make everyone type more than 20 characters but B sounds like the most reasonable answer.
Answer:
Actually, cell division is the mechanism by which DNA is passed from one generation of cells to the next and ultimately, from parent organisms to their offspring. During meiosis, the cells needed for sexual reproduction divide to produce new cells called gametes.
Explanation:
A true-breeding<span> organism, sometimes also called a purebred, is an organism that always passes down certain phenotypic traits (i.e. physically expressed traits) to its offspring.</span>
I believe the correct answer is upwelling. Lets say we have producers such as plankton. well upwelling currents bring dead matter from the ocean floor up to the surface, creating plankton.