The gene encoding VEGFR2, the main receptor that binds and is activated by VEGF-A, is transcribed in almost every tissue type, but the VEGFR2 protein is rarely present. List and describe one mechanism that cells could use to reduce VEGFR2 protein levels despite high levels of transcription.

The RNA interference (RNAi) mechanism

Explanation:

RNA interference (RNAi) is a biological process by which endogenous non-coding RNAs (ncRNAs) sequences target messenger RNAs in order to inhibit gene expression and translation. The regulatory ncRNAs bind by complementary base pairing to specific mRNAs and thus promote gene silencing by both posttranscriptional (mRNA degradation, block translation, etc) and by transcriptional (recruiting of histone/DNA modifying enzymes) pathways. The most common types of evolutionarily conserved ncRNAs found in plant and animal cells are 1-small interfering RNAs (siRNAs), 2-microRNAs (miRNAs), 3-piwi interacting RNAs (piRNAs, only present in animal cells) and 4-long noncoding RNAs (lncRNAs).

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!