Question

chapter 6 molecular biology
6.10 mutation effects

1. what are the 3 reasons most neither negative or positive?
2. what are two enzymes involved in dna repair?
3. mutations that lead to new versions of proteins that help organisms adapt to changes in their environment
4. a disease caused by a mutation in one or a few genes
5. disease in which cells grow out of control and form abnormal masses of cells

6.11 gene expression

1. regulatory protein that switches a gene on
2. regulatory proteins which turn a gene off
3. transcription factors that help position rna polymerase at the start of a gene
4. how can a mutation in a cis - regulatory region affect protein synthesis?

6.12 prokaryotic gene regulation

1. a region of dna that consists of one or more genes that encode the proteins needed for a specific function
2. a region of the operon where regulatory proteins bind
3. how is lac operon regulated?
4. what is lactose?
5. what so the proteins made by the lac operon do?

6.13 eukaryotic gene regulation

1. distant regions of dna that can loop back to interact with a gene’s promoter
2. a regulatory element that is part of the promoter of most eukaryotic genes, has a core sequence of tataaa and forms a multi - protein complex
3. genes that regulate development
4. regulatory gene, helps control cell division, when mutated can cause cancer
5. regulatory gene, prevents cells with damaged dna from dividing, when mutated can cause cancer

Explanation:

1. Most mutations are neutral because: 1) They occur in non-coding DNA regions with no protein impact; 2) They are silent mutations that code for the same amino acid; 3) They alter a protein but do not change its function.
2. Two common DNA repair enzymes are DNA ligase (seals breaks in DNA strands) and DNA polymerase (proofreads and corrects mismatched bases during repair).
3. These are beneficial adaptive mutations, which enhance an organism's fitness in a changing environment.
4. This is a single-gene (monogenic) disorder, caused by mutations in one or a small number of genes.
5. This describes cancer, a disease characterized by uncontrolled cell proliferation and abnormal cell mass formation.
6. This is an activator protein, a regulatory factor that initiates gene transcription.
7. These are repressor proteins, regulatory factors that inhibit gene transcription.
8. These are general transcription factors, which assist in positioning RNA polymerase at the gene's promoter to start transcription.
9. A mutation in a cis-regulatory region can alter binding sites for regulatory proteins, either increasing or decreasing gene transcription, which changes the amount of protein produced (it does not change the protein's structure, only its expression level).
10. This is an operon, a cluster of functionally related genes under a single regulatory region in prokaryotes.
11. This is the operator, the region of an operon where repressors or activators bind to regulate transcription.
12. The lac operon is regulated by lactose and glucose levels: 1) In the absence of lactose, a repressor binds the operator, blocking transcription; 2) When lactose is present, it is converted to allolactose, which binds the repressor, releasing it from the operator to allow transcription; 3) High glucose levels lower cyclic AMP (cAMP) levels, reducing binding of the catabolite activator protein (CAP) to the promoter, which slows transcription even if lactose is present.
13. Lactose is a disaccharide sugar composed of glucose and galactose, found in milk, used as an energy source by some bacteria.
14. The lac operon produces three proteins: 1) β-galactosidase, which breaks down lactose into glucose and galactose; 2) Permease, which transports lactose into the bacterial cell; 3) Transacetylase, which modifies toxic lactose derivatives.
15. These are enhancers, distant DNA sequences that interact with the promoter via looping to increase gene transcription.
16. This is the TATA box, a core promoter element that binds transcription factors to form a complex that recruits RNA polymerase.
17. These are homeotic (Hox) genes, highly conserved genes that regulate the body plan and developmental pattern of organisms.
18. This is a proto-oncogene; when mutated, it becomes an oncogene, which promotes uncontrolled cell division and cancer.
19. This is a tumor suppressor gene (like p53); it normally halts division of damaged cells, and loss-of-function mutations allow damaged cells to divide, leading to cancer.

Answer:

1. 1) Mutation in non-coding DNA; 2) Silent mutation (same amino acid); 3) No change to protein function
2. DNA ligase and DNA polymerase
3. Beneficial adaptive mutations
4. Monogenic (single-gene) disorder
5. Cancer
6. Activator protein
7. Repressor proteins
8. General transcription factors
9. It alters regulatory protein binding, changing the amount of protein produced (not the protein's structure)
10. Operon
11. Operator
12. Regulated by lactose (repressor binding) and glucose (CAP/cAMP) levels: repressor blocks transcription without lactose; lactose inactivates repressor; high glucose reduces transcription even with lactose
13. A disaccharide sugar (glucose + galactose) found in milk
14. β-galactosidase (breaks down lactose), permease (transports lactose), transacetylase (modifies toxic lactose derivatives)
15. Enhancers
16. TATA box
17. Homeotic (Hox) genes
18. Proto-oncogene (mutates to oncogene)
19. Tumor suppressor gene (e.g., p53)