Bio 7

Name the amino acids that each of the following codons would code for

A codon is a three-nucleotide sequence that encodes one amino acid. • Each amino acid is specified by a codon • 64 codons are possible • Some amino acids have more than one possible codon o CAA: Glutamine. o UCA: Serine. o GGU: Glysine. o CCC: Proline.

What 3 types of RNA interact to produce proteins? Briefly describe each type.

A. Messenger RNA (mRNA): carries the information that specifies a protein. Each group of three mRNA bases specifies a codon. B. Ribosomal RNA (rRNA): forms part of a ribosome C. Transfer RNA (tRNA): "connectors" that bind an mRNA codon to the corresponding amino acid

What is the building block of a DNA molecule? What do these building blocks consist of?

A. Nucleotides. nucleotide consists of: B. One sugar (deoxyribose). C. One phosphate group. D. And one of four bases: adenine, guanine, thymine, or cytosine (A, G, T, or C).

Why are viruses not considered alive?

A. Viruses are noncellular. They are obligate, intracellular parasites • Non-living • No membrane-bound organelles • No ribosomes • No cytoplasm • No energy sources • No cellular respiration • No ATP production B. Can only replicate within a host. C. Viral genes contain instructions for making viruses. Viral replication: • Virus attaches to host. • Virus penetrates cell and releases its DNA. • Host transcribes and translates viral DNA as if it were its own. • New viruses assemble. • Viruses leave the cell.

Who was involved in the discovery of the double helix?

Annalee Newitz. It's commonly believed that James Watson and Francis Crick discovered the double helix shape of DNA

Does the RNA that leaves the nucleus contain introns, exons, or both?

Exons. Introns are removed during splicing.

True or False: All mutations are harmful.

False. mutations are not always harmful! Mutations create different versions of alleles, which are alternative versions of the same gene. Genetic variation is important for evolution. • Mutations have been important to evolution because they are the only means through which completely new genetic information can be added to a species' genome. • The accidental re-orderings of DNA sequences that mutations bring about can, in rare instances, produce new proteins that are useful to organisms. • ...in this way they produce the raw variation that natural selection acts upon.

Complementary strands of DNA are held together by what kind of bonds?

Hydrogen bonds connect complementary DNA strands.

transcription

Transcription occurs in the nucleus and produces an RNA copy of one gene. • Transcription has three steps: • Initiation: RNA polymerase binds to the promoter, which is the beginning of the gene. Enzymes unzip the DNA. The DNA template strand encodes the RNA molecule. • Elongation: RNA polymerase moves along the template strand, making an RNA copy. RNA molecule is complementary to the DNA template strand. • Termination: RNA polymerase reaches the terminator, which is the end of the gene. RNA, DNA, and RNA polymerase separate. DNA becomes a double helix again. The cell produced an RNA copy of a gene! • Transcription rewrites the DNA code into RNA, using the same nucleotide "language"

translation

Translation Builds the Protein • Translation also occurs in three steps: • Initiation: Small ribosomal subunit binds to mRNA. Small ribosomal subunit binds to mRNA. First tRNA molecule binds. tRNA complementary base pairs to mRNA. tRNA already carries an amino acid (Met). • Elongation: The second tRNA enters the ribosome next to the first tRNA. Amino acids covalently bond. The first tRNA leaves. The ribosome moves to the right, and a third tRNA comes in. the amino acids remain bonded together! This process continues and the protein grows. • Termination: The ribosome reaches the stop codon. A release factor binds. The polypeptide detaches from the mRNA and folds into a functional protein. Translation is efficient when multiple ribosomes attach to an mRNA molecule simultaneously. • Translation involves switching from the nucleotide "language" to amino acid "language"

Mutation

a permanent alteration in a cell's DNA base sequence.

Substitution

changed nucleotide(s)

point mutation

changes one or a few base pairs in a gene.

Frameshift

mutations affect multiple codons

Insertion

nucleotide(s) added. Insertion of one nucleotide changes every codon after the insertion.

Deletion

nucleotide(s) deleted. Deletions or insertions of three nucleotides add or delete entire codons, but do not affect other codons.

Wild type

original nucleotide sequence

What characteristics do DNA and RNA share?

• Both DNA and RNA are nucleic acid polymers. • The monomers of both DNA and RNA are composed of three parts: a phosphate group, a pentose (5-carbon sugar), and a nitrogenous base. • Both DNA and RNA use a form of ribose as their sugar (RNA uses ribose itself; in DNA, a single oxygen atom has been removed from the 2' carbon of ribose, to form deoxyribose). • Both DNA and RNA use the bases adenine, cytosine, and guanine. • Both DNA and RNA undergo complementary base pairing (DNA usually between two different strands, and RNA usually between two regions of a single strand). • Both DNA and RNA are synthesized in the 5' to 3' direction.

How does RNA differ from DNA?

• DNA contains the sugar deoxyribose, while RNA contains the sugar ribose. The only difference between ribose and deoxyribose is that ribose has one more -OH group than deoxyribose, which has -H attached to the second (2') carbon in the ring. • DNA is a double stranded molecule while RNA is a single stranded molecule. • DNA is stable under alkaline conditions while RNA is not stable. • DNA and RNA perform different functions in humans. DNA is responsible for storing and transferring genetic information while RNA directly codes for amino acids and as acts as a messenger between DNA and ribosomes to make proteins. • DNA and RNA base pairing is slightly different, since DNA uses the bases adenine, thymine, cytosine, and guanine; RNA uses adenine, uracil, cytosine, and guanine. Uracil differs from thymine in that it lacks a methyl group on its ring.

Drugs and Vaccines Help Fight Viral Infections

• Vaccines "teach" your immune system to recognize a virus. • Antiviral drugs are difficult to develop because of viruses high mutation rate. • Antibiotics do NOT work against viruses. Some Viruses Linger for Years