What can cause mutations?
Mutations arise spontaneously at low frequency owing to the chemical instability of purine and pyrimidine bases and to errors during DNA replication. Natural exposure of an organism to certain environmental factors, such as ultraviolet light and chemical carcinogens (e.g., aflatoxin B1), also can cause mutations.
Are there good mutations?
Mutational effects can be beneficial, harmful, or neutral, depending on their context or location. Most non-neutral mutations are deleterious. In general, the more base pairs that are affected by a mutation, the larger the effect of the mutation, and the larger the mutation’s probability of being deleterious.
Which best describes genetic mutations?
Which best describes genetic mutations?
| A) Genetic mutations that cause diseases are always passed on to offspring. | B) Some inherited genetic mutations can be good for the offspring. |
|---|---|
| C) Different genetic mutations cause few forms of cancer. | D) Somatic mutations can be inherited from parents or acquired during life. |
Which best describes somatic mutations?
An alteration in DNA that occurs after conception. Somatic mutations can occur in any of the cells of the body except the germ cells (sperm and egg) and therefore are not passed on to children. These alterations can (but do not always) cause cancer or other diseases.
Are mutations always bad quizlet?
Are all mutations harmful? No, some have no effect, some may be beneficial.
What prevents Lac genes?
The lac repressor is a protein that represses (inhibits) transcription of the lac operon. It does this by binding to the operator, which partially overlaps with the promoter. When bound, the lac repressor gets in RNA polymerase’s way and keeps it from transcribing the operon.
What is the first thing that happens during transcription?
Initiation is the beginning of transcription. It occurs when the enzyme RNA polymerase binds to a region of a gene called the promoter. This signals the DNA to unwind so the enzyme can ”read” the bases in one of the DNA strands. The enzyme is now ready to make a strand of mRNA with a complementary sequence of bases.
What are the 3 steps of transcription?
Transcription takes place in three steps: initiation, elongation, and termination. The steps are illustrated in Figure 2.
What are the four steps of transcription?
Transcription involves four steps:
- Initiation. The DNA molecule unwinds and separates to form a small open complex.
- Elongation. RNA polymerase moves along the template strand, synthesising an mRNA molecule.
- Termination. In prokaryotes there are two ways in which transcription is terminated.
- Processing.
What are the six steps of transcription?
Stages of Transcription
- Initiation. Transcription is catalysed by the enzyme RNA polymerase.
- Elongation. One DNA strand (the template strand) is read in a 3′ to 5′ direction and so provides the template for the new mRNA molecule.
- Termination.
- 5′ Capping.
- Polyadenylation.
- Splicing.
What does DNA provide the code for?
The DNA code contains instructions needed to make the proteins and molecules essential for our growth, development and health. The cell reads the DNA code in groups of three bases. Each triplet of bases, also called a codon, specifies which amino acid? will be added next during protein synthesis.
What happens if an Anticodon is mutated?
For example, mutations in the anticodon region of a tRNA gene can result in a tRNA that sometimes inserts an amino acid at an erroneous stop codon; if the original mutation is caused by a stop codon, which arrests translation at that point, then a tRNA anticodon change can insert…
What is the anticodon for AAA?
The anticodon is a sequence of three bases that are complementary to a mRNA codon and will bind to it. For example, if you have the codon for phenylalanine on the mRNA (UUU), the tRNA that carries phenylalanine will have the anticodon (AAA), the complement of UUU(see figure below).