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. 

Chapter Nine: Patterns of Inheritance

Questions:

1. What are most human genetic disorders caused by?
2. What are some dominant disorders?
3. What is the chromosome theory of inheritance?

Answers:

1. Most human genetic disorders are recessive.  They range in severity from relatively mild, such as albinism (lack of pigmentation), to life-threatening, such as cystic fibrosis.  Most people who have recessive disorders are born to normal parents who are both heterozygotes.  That is, they are carriers of the recessive allele for the disorder but are phenotypically normal. 
2. One serious dominant disorder is achondroplasia, a form of dwarfism.  In people with this disorder, the head and torso of the body develop normally, but the arms and legs are short.  Another is Huntington's Disease, a degenerative disorder of the nervous system that usually does not appear until 35 to 45 years of age.
3. The chromosome theory of inheritance states that genes occupy specific loci on chromosomes and it is the chromosomes that undergo segregation and independent assortment during meiosis.  Thus, it is the behavior of chromosomes during meiosis and fertilization that accounts for inheritance patterns.

Important Facts:

1. The rule of addition is the probability that an event can occur in two or more alternative ways is the sum of the separate probabilities of the different ways. 
2. An organism's appearance does not always reveal its genetic composition.  An organism's physical traits are called its physical traits.  It's genetic makeup is its genotype.
3. The law of independent assortment states that each pair of alleles segregates independently of other pairs of alleles during gamete formation.
4. Pleiotropy is the property that most genes influence multiple characters.
5. Polygenic inheritance are the additive effects of two or more genes on a single phenotypic character.

Key Terms:
Hybrids- the offspring of two different varieties.
P Generation- the true-breeding parental plants.
F1 Generation- P generation's hybrid offspring.
F2 Generation- offspring when F1 plants self-fertilize or fertilize each other.
Alleles- the alternative versions of a gene.
Homozygous- when an organism has two identical alleles for a gene, it is homozygous for that gene.
Heterozygous- when an organism has two different alleles for a gene, it is heterozygous for that gene.
Dominant allele- allele that determines the organism's appearance.
Recessive allele- allele that has no noticeable affect on the organism's appearance.
Law of Segregation-  A sperm or egg carries only one allele for each inherited character because allele pairs separate from each other during the production of gametes.

Diagram: This diagram is used to predict an outcome of a particular cross or breeding experiment. It is named after Reginald C. Punnett, who devised the approach, and is used by biologists to determine the probability of an offspring having a particular genotype. The Punnett square is a summary of every possible combination of one maternal allele with one paternal allele for each gene being studied in the cross.

Relevant Video:
http://www.youtube.com/watch?v=oVl8OH_7QSc&feature=related

Summary: This chapter focuses first on Mendelian genetics and crosses.  It then discusses more human genetics before moving on to genes and chromosomes.  It talks about the chromosomal basis of inheritance.  The chapter then details sex chromosomes and sex-linked genes.

Chapter Eight: The Cellular Basis of Reproduction and Inheritance

Questions:

1. What are the various steps of mitosis and meiosis?
2. What are the two methods of reproduction?
3. What is the difference between cytokinesis in plant and animal cells?

Answers:

1. The steps of mitosis are interphase, prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis.  Meiosis first begins with meiosis I.  During meiosis I, prophase I, metaphase I, anaphase I, and telophase I all occur.  Meiosis II follows meiosis I without chromosome duplication.
2. The two methods of reproduction are asexual reproduction and sexual reproduction.  In asexual reproduction, offspring are identical to the original cell or organism.  The offspring also inherits all  its genes from one parent.  In sexual reproduction, offspring are similar to parents, but show variations in their traits and involve the inheritance of unique sets of genes from two different parents.
3. A ring of microfilaments pinches an animal cell in two, a process called cleavage.  In a plant cell, membranous vesicles form a disk called the cell plate at the midline of the parent cell, cell plate membranes fuse with the plasma membrane, and a cell wall grows in the space.  

Important Facts:

• Somatic cells have pairs of homologous chromosomes, receiving one member of each pair from each parent.  Homologous chromosomes are matched in length, centromere position and gene locations.  
• Cancer cells escape control on the cell cycle.  They divide rapidly, often in the absence of growth factors.  They spread to other tissues through the circulatory system.  The growth is not inhibited by other cells and tumors form.
• The factors that control cell division include: presence of essential nutrients, growth factors, proteins that simulate division, presence of other cells causes density-dependent inhibition, and contact with a solid surface, as most cells show anchorage dependence.
• Separation of homologous chromosomes during meiosis can lead to genetic differences between gametes.  Homologous chromosomes may have different versions of a gene at the same locus.  One version was inherited from the maternal parent, and the other came from the paternal parent.  Since homologues move to opposite poles during anaphase I, gametes receive either the paternal or maternal version of the gene.
• An imbalance in chromosome number results in Down Syndrome, which is characterized by characteristic facial features, susceptibility to disease, shortened life span, mental retardation, and variation in characteristics.

Key Terms:
Fertilization- the union of sperm and egg
Chromatin- DNA and proteins.
Cell Cycle- an ordered sequence of events for cell division.  Consists or interphase and Mitotic phase.
Interphase- duplication of cell contents.
Mitotic phase- division of cell.  Includes mitosis (division of the nucleus) and cytokinesis (division of cytoplasm)
Centrosomes- Structures in the cytoplasm that produce a mitotic spindle required to divide the chromosomes.  They organize micro-tubule arrangement and contain a pair of centrioles in animal cells.
Cell Cycle Control System- A set of molecules, including growth factors, that triggers and coordinates events of the cell cycle.
Diploid Cells- have two homologous sets of chromosomes.
Haploid Cells- have one set of chromosomes.
Nondisjunction- the failure of chromosomes or chromatids to separate during meiosis.


Relevant Diagram:  This diagram shows the whole process of meiosis.  Meiosis is the process of cell division in germ line cells to form gametes. This process furthers sexual reproduction because each gamete has half the number of chromosomes of normal cells, so that when two gametes (one from each parent) combine, the correct number of chromosomes is preserved in the resulting zygote organism. This process is unlike mitosis, where the cells are simply replicated, preserving the number chromosomes.

Relevant Video:
http://www.youtube.com/watch?v=BFWelOJ7fW0

Summary:
This chapter mainly discusses cell division/reproduction.  The chapter begins with mitosis, detailing first the role of chromosomes and then moving on to the different phases of mitosis.  It talks about cell cycle control and then moves on to meiosis and homologous chromosomes.  The many phases of meiosis are discussed in great detail.  The chapter then finishes with genetic variation and chromosome number which directly affects mutation.

Chapter Seven: Photosynthesis: Using Light to Make Food

Questions:

1. What are the similarities and differences between the two photo systems in photosynthesis?
2. Why does a poison that inhibits an enzyme of the Calvin cycle also inhibit the light reactions?
3. How might phytochemicals benefit a cell?

Answers:

1. Both photosystems have primary accepters and both accept light power from electrons.  They both  take place in the thylakoid membrane.  They both use ATP.  Photosystem 2 takes place before Photosystem 1.  They also use different wavelengths.  Photosystem 2 takes in water and releases oxygen and hydrogen.  Photosystem 1 does not do this.    
2. The light reactions require ADP and NADP+, which are not recycled from ATP and NADPH when the Calvin cycle stops.  
3. Phytochemicals can act as antioxidants that protect from reactive forms of oxidative molecules.

Important Facts:

1. Photosynthesis occurs in two metabolic stages.  One stage involves the light reactions.  H+ ions reduce NADP+ to NADPH, which is an electron carrier similar to NADH.  The Calvin cycle is the second stage that occurs in the stroma.  It is a cyclic series of reactions that builds sugar molecules from CO2......NADPH produced by the light reactions provides the electrons for reducing carbon in the Calvin cycle.  ATP from the light reactions provides chemical energy for the Calvin cycle, which is often known as a dark reaction.
2. In photosynthesis, electrons gain energy by being boosted up an energy hill.  Light energy captured by chlorophyll molecules provides the boost for the electrons.  As a result, light energy is converted to chemical energy, which is stored in the chemical bonds of sugar molecules.
3. Cellular respiration uses redox reactions to harvest the chemical energy stored in a glucose molecule.  This is accomplished by oxidizing the sugar and reducing O2 to H2O.  The electrons lose potential as they travel down an energy hill, the electron transport system.  In contrast, the food producing redox reactions of photosynthesis reverse the flow and involve an uphill climb.
4. Chemiosmosis is the mechanism that not only is involved in oxidative phosphorylation in mitochondria but also generates ATP in chloroplasts.  ATP is generated because  the electron transport chain produces a concentration gradient of hydrogen ions across a membrane.  ATP synthase couples the flow of H+ to the phosphorylation of ADP.  The chemiosmotic production of ATP in photosynthesis is called phosphorylation.
5. The energy released by electrons is conserved as it is passed from one molecule to another.  All of the components to accomplish this are organized in thylakoid membranes in clusters called photosystems.  Photosystems are light-harvesting complexes surrounding a reaction center complex.  Energy is passed from molecule to molecule within the photosystem.  The energy finally reaches the reaction center where a primary electron acceptor accepts these electrons and consequently becomes reduced.  This solar- powered transfer of an electron from the reaction center pigment to the primary electron acceptor is the first step of the light reactions.
   

Key Terms: 
Photosynthesis- Process that converts solar energy to chemical energy.  Plants use water and atmospheric carbon dioxide to produce a simple sugar and liberate oxygen.  This sugar is food for humans for and animals.
Autotroph- an organism that makes its own food, thereby sustaining itself without eating other organsims or their molecules.
Cloroplasts- organelles consisting of photosynthetic pigments, enzyme, and other molecules grouped together.
Chlorophyll- a green pigment located within the chloroplasts of plants, algae, and certain prokaryotes.
Electromagnetic Spectrum- the entire spectrum of radiation.
Mesophyll- the middle layer of tissue inside a leaf.
Photoautograph- an organism that obtains energy from sunlight and carbon from CO2 by photosynthesis.
Thylakoid- one of the number of disk-shaped membranous sacs inside a chloroplast.
Stomata- tiny pores in the leaf that allow carbon dioxide to enter and oxygen to exit.
Stroma- the dense fluid within the chloroplast that is contained in two membranes.

Diagram: The light-dependent reactions are the first stage of photosynthesis, the process by which plants capture and store energy from sunlight. In this proces, light energy is converted into chemical energy, in the form of the energy-carrying molecules ATP and NADPH.

Relevant Video: http://www.youtube.com/watch?v=GR2GA7chA_c

Summary: This chapter begins by detailing the stages of photosynthesis.  It then continues to discuss the light reactions and the converting of solar energy to chemical energy.  It mentions photosystems and photophosphorylation.  The chapter then discusses the Calvin cycle and the converting of CO2 to sugars.  It details C3, C4, and CAM plants before discussing solar radiation and the Earth's atmosphere.