Chapter Eleven: How Genes are Controlled

Questions:

1. What are some disadvantages of cloning?
2. What does RNA interference accomplish?
3. What are homeotic genes?

Answers:

1. Cloning does not increase genetic diversity.  And cloned animals may face health problems related to abnormal gene regulation.  
2. It prevents expression of a gene by interfering with translation of its RNA product, involves binding of small, complementary RNAs to mRNA molecules and leads to degradation of mRNA or inhibition of translation.
3. Homeotic genes are master control genes that determine the anatomy of the body, specifying structures that will develop in each segment.

Key Terms:
Gene Expression- the overall process of information flow from genes to proteins.
Operon- a group of genes under coordinated control in bacteria. 
Repressor- can bind and block RNA polymerase action. 
Regulatory Gene- codes for a repressor protein.
Activators- enhance RNA polymerase binding to the promoter.
Transcription factors- promote RNA polymerase binding to the promoter.
Silencers-repressors that inhibit transcription.
Signal transduction pathway- a series of molecular changes that converts a signal at the cell's surface to a response within the cell.
Reproductive cloning- used to produce animals with desirable traits.
Adult stem cells- can produce many but not all types of cells.


Important Facts:

1. Eukaryotic chromosomes undergo multiple levels of folding and coiling, called DNA packing.  DNA packing can prevent transcription.  
2. Control of gene expression occurs with breakdown of mRNA, initiation of translation, protein activation, and protein breakdown.
3. Nuclear transplantation is the replacing of the nucleus of an egg or zygote with a nucleus from an adult somatic cell.
4. Cloned animals can show differences from their parent due to the variety of influences during development. 
5. Carcinogens are cancer-causing agents that damage DNA and promote cell division.

Relevant Video:
http://www.youtube.com/watch?v=FVuAwBGw_pQ

Diagram-

Chapter Ten: Molecular Biology of the Gene

Questions:

1. What is DNA composed of?
2. What occurs during transcription?
3. What is elongation?

Answers:

1. DNA is composed of two nucleotide chains joined together by hydrogen bonding between bases, twisted into a helical shape.  The sugar phosphate backbone is on the outside.
2. The two DNA strands separate.  One strand is used as a pattern to produce an RNA chain, using specific base pairing.  RNA polymerase catalyzes the reaction.
3. Elongation is the addition of  amino acids to a polypeptide chain.  Each cycle has three steps: codon recognition, peptide bond formation, and translocation.

Important Facts:

1. DNA replication follows a semi-conservative model. The two DNA strands separate and then each strand is used as a pattern to produce a complimentary strand, using specific base pairing. Each new DNA helix has one old strand with one new strand.  
2. A gene is a sequence of DNA that directs the synthesis of a specific protein.  DNA is transcribed into RNA and then RNA is translated into a protein.  The actions of proteins determine the phenotype of an organism.
3. The one gene–one enzyme hypothesis was based on studies of inherited metabolic diseases.  The one gene-one protein hypothesis expands the relationship to proteins other than enzymes. 
4.  Initiation brings together the components  needed to begin RNA synthesis.  It occurs in 2 steps.  mRNA binds to a small ribosomal subunit, and the first tRNA binds to mRNA at the start codon.  A large ribosomal subunit joins the small subunit, allowing the ribosome to function.
5. Emerging viruses cause human diseases through mutation, contact between species, and spread from isolated populations.  

Key Terms:

Bacteriophage- viruses that infect bacterial cells.

Viruses- invaders that sabotage our cells.

DNA polymerase- adds nucleotides to a growing chain.

DNA ligase- joins small fragments into a continuous chain.

Messenger RNA- contains codons for protein sequences.

Introns- interrupting sequences. 

Exons- the coding regions. 

RNA Splicing- removal of introns and joining of exons to produce a continuous coding sequence.

Transfer RNA- match an amino acid to its corresponding mRNA codon.

Anticodon- allows the tRNA to bind to a specific mRNA codon, complementary in sequence.

 

Diagram:

Relevant Video: 

http://www.youtube.com/watch?v=-mtLXpgjHL0

Chapter Fourteen: The Origin of Species

Questions:

1. How is gene flow between populations prevented and reduced?
2. Who is Charles Darwin?

Answers:

1. Gene flow is initially prevented by a geographic barrier such as a mountain or river.  It can be reduced by polyploidy, habitat differentiation, or sexual selection.x
2. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.

Key Terms:
Species- a group of organisms whose members can breed and produce fertile offspring, but who donot produce fertile offspring with members of other groups.
Speciation- the emergence of a new species.
Taxonomy- the branch of biology that names and classifies species and groups them into broader categories. 
Reproductive Barriers- isolate a species gene pool and prevent inbreeding.
Polyploidy- the multiplication of the chromosome number due to errors in cell division.
Hybrid Zones- where members of different species meet and mate to produce hybrid offspring.
Adaptive Radiation-when many diverse species evolve from a common ancestor.
Sympatric Speciation- when a new species may arise within the same geometric area as a parent species.
Allopatric Speciation- when populations of the same species are geographically separated, separating their gene pools.
Prezygotic Barriers- prevent mating and fertilization between species.

Key Facts:   
1. The biological species concept defines a species as a population or group of populations whose members have the potential to interbreed in nature and produce fertile offspring.
2. The morphological species concept classifies organisms based on observable phenotypic traits.  It can be applied to asexual organisms, fossils, and in cases when we donít know about possible interbreeding.
3. The ecological species concept defines a species by its ecological role or niche.  The morphological species concept classifies organisms based on observable phenotypic traits.
4. The phylogenetic species concept defines a species as a set of organisms representing a specific evolutionary lineage. 
5. The process of speciation depends on whether reproductive barriers prevent gene flow between populations.

Diagram:

Relevant Video:
http://www.youtube.com/watch?v=LEGQu3cm3CE 


Summary:



 

 



 

Chapter Thirteen: How Populations Evolve

Questions:

1. What is the Hardy-Weinberg Principle?
2. What are the three main causes of evolutionary change?
3. d

Answers:

1. The Hardy-Weinberg Principle states that allele and genotype frequencies within a sexually reproducing, diploid population will remain in equilibrium unless outside forces act to change those frequencies. 
2. The three main causes of evolutionary change are natural selection, genetic drift, and gene flow.  If individuals differ in their survival and reproductive success , natural selection will alter their allele frequencies.  Genetic drift is a change in the gene pool of a population due to chance.  Gene flow is the movement of individuals between populations and can alter frequencies in a population.
3. d

Key Terms:
Biogeography- the study of the past and present distribution of organisms.
Homology- similarity in characteristics resulting from a shared ancestry.
Microevolution- a change in a population's gene pool over generations.
Mutation- a change in the nucleotide sequence of an organism's DNA.
Paleontologist- a scientist who studies fossils.
Natural Selection- The primary mechanism of evolution producing adaptation of organisms to their environment.
Comparative Anatomy- the comparison of body structures in different species.
Molecular Biology- comparisons of DNA and amino acid sequences between different organisms reveal evolutionary relationships.
Population- a group of individuals of the same species living in the same place at the same time.
Evolution- is the change in heritable traits in a population over generations.

Important Facts:

1. Natural selection can amplify or diminish only heritable traits.  Acquired traits cannot be passed on to offspring.  
2. Evolution is not goal directed and does not lead to perfection, and favorable traits vary as environments change. 
3. Chromosomal duplication is an important source of genetic variation.  If a gene is duplicated, then the new copy can undergo mutation without affecting the function of the original copy.
4. Directional selection acts against individuals at one of the phenotypic extremes.  It is common during periods of environmental change, or when a population migrates to a new and different habitat. 
5. Most animal species show sexual dimorphism, which is when males and females are distinctly different in appearance.