protein synthesis and gene expression
introduction to protein synthesis
A monomer is a molecule that can bind to other monomers to form a polymer. Amino acids are the monomers of a protein. The DNA sequence contains the instructions to place amino acids into a specific order. When the amino acid monomers are assembled in that specific order, proteins are made, a process called protein synthesis. In short, DNA contains the instructions to create proteins. But DNA does not directly make the proteins. Proteins are made on the ribosomes in the cytoplasm, and DNA (in an eukaryotic cell) is in the nucleus. So the cell uses an RNA intermediate to produce proteins. Each strand of DNA has many separate sequences that code for a specific protein. Insulin is an example of a protein made by your cells ( Figure 1.1). Units of DNA that contain code for the creation of a protein are called genes.
cells can turn genes on or off
There are about 22,000 genes in every human cell. Does every human cell have the same genes? Yes. Does every human cell make the same proteins? No. In a multicellular organism, such as us, cells have specific functions because they have different proteins. They have different proteins because different genes are expressed in different cell types (which is known as gene expression). Imagine that all of your genes are "turned off." Each cell type only "turns on" (or expresses) the genes that have the code for the proteins it needs to use. So different cell types "turn on" different genes, allowing different proteins to be made. This gives different cell types different functions. Once a gene is expressed, the protein product of that gene is usually made. For this reason, gene expression and protein synthesis are often considered the same process.
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amino acids are the monomers of proteins.
--> a. true b. false
dna makes proteins.
a. true --> b. false
about how many genes are in every human cell?
a) 1,000 b) 10,000 --> c) 20,000 d) 100,000
which best defines a gene?
a) a gene is a unit of protein that contains the genetic code. --> b) a gene is a unit of dna that contains code for the creation of one protein. c) a gene is a unit of dna that contains the code for the creation of amino acids. d) none of the above
why do different cells have different functions?
a) because different cells have different dna. b) because different cells have different genes. --> c) because different cells have different proteins. d) all cells have the same functions.
what does it mean by cells turn on different genes?
--> a) cells will only turn on, or express, the genes whose proteins are needed. b) all cells turn on different genes, giving them different functions. c) all cells have different genes, giving them different functions. d) all of the above
which of the following statements is true?
a) genes are made of amino acids. b) dna is made out of genes. --> c) gene expression and protein synthesis can be considered the same. d) all of the above statements are true.
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