rna

three rnas

DNA contains the instructions to create proteins, but it does not make proteins itself. DNA is located in the nucleus, which it never leaves, while proteins are made on ribosomes in the cytoplasm. So DNA needs a messenger to bring its instructions to a ribosome located outside of the nucleus. DNA sends out a message, in the form of RNA (ribonucleic acid), describing how to make the protein. There are three types of RNA directly involved in protein synthesis: Messenger RNA ( mRNA) carries the instructions from the nucleus to the cytoplasm. mRNA is produced in the nucleus, as are all RNAs. The other two forms of RNA, ribosomal RNA ( rRNA) and transfer RNA ( tRNA), are involved in the process of ordering the amino acids to make the protein. rRNA becomes part of the ribosome, which is the site of protein synthesis, and tRNA brings an amino acid to the ribosome so it can be added to a growing chain during protein synthesis. There are numerous tRNAs, as each tRNA is specific for an amino acid. The amino acid actually attaches to the tRNA during this process. More about RNAs will be discussed during the Transcription and Translation Concepts. All three RNAs are nucleic acids, made of nucleotides, similar to DNA ( Figure 1.1). The RNA nucleotide is different from the DNA nucleotide in the following ways: RNA contains a different kind of sugar, called ribose. In RNA, the base uracil (U) replaces the thymine (T) found in DNA. RNA is a single strand molecule. A comparison of DNA and RNA, with the bases of each shown. Notice that in RNA, uracil replaces thymine.

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instructional diagrams

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questions

dna is located in the nucleus, and proteins are made in the cytoplasm.

-->  a. true

b. false

rna contains the bases a, c, u, and t.

a. true

-->  b. false

how is rna different from dna?

-->  a) rna is single stranded.

b) dna contains the base uracil.

c) rna has a phosphate group.

d) all of the above

which rna carries information from the nucleus to the cytoplasm?

a) rrna

b) trna

-->  c) mrna

d) irna

which rna brings amino acids to the ribosome?

a) rrna

-->  b) trna

c) mrna

d) arna

which of the following statements is true?

a) dna contains the instructions to make proteins.

b) dna is located in the nucleus.

c) dna needs a messenger to take its instructions to the cytoplasm.

-->  d) all of the above are true.

which of the following statements is true?

a) mrna is part of the ribosome.

b) trna transfers the message to the ribosome.

c) rrna relays amino acids to the ribosome.

-->  d) mrna is made in the nucleus.

diagram questions

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