Chapter 9: Patterns of Inheritance

Three questions about the chapter:
1.When did the modern science of genetics begin and who was its founder?
The modern science of genetics began in the 1860s, when an Augustinian monk named Gregor Mendel deduced the fundamental principles of genetics by breeding garden peas.
2.What does the law of segregation states?
It states that a perm or egg carries only one allele for each inherited charcater because allele pairs separate from each other during the production of gametes.
3.Do sex-linked disorders affect more men or women?
Sex-linked disorders affect mostly males.

Five main facts from the reading:
1. The science of genetics has ancient roots.
2.Genetic traits in humnas can be tracked through family pedigrees
3.Many inherited disorders in humans are controlled by a single gene.
4.Many genes have more than two alleles in the population.
5.A single character may be influence by many genes.

Diagram:

This is an example of a Punnet square, which represents the fertilization between a male and female flower.












Link: http://bio8.wikispaces.com/4%29Mendelian+Genetics


Summary:
     The introduction section of the chapter talks about that there are many different types of dogs, due to the fact that when one type of a dog fertilizes another type of a dog, the production is a new type of a dog, similar to its parents. Genetics is the science of heredity and it has ancient roots. The first person to purpose an explanation to genetics was the physician Hippocrates, and even though he was not right, he put the basis of genetics. Experimental genetics began in an abbey garden. The modern science of genetics began in the 1860s, when an Augustinian monk named Gregor Mendel deduced the fundamental principles of genetics by breeding garden peas. He correctly argued that parents pass on to their offspring discrete heritable factors. A heritable feature that varies among individuals, such as flower color, is called a character. Each variant for a character, such as purple or white flowers, is called a trait. Perhaps the most important advantage of pea plants as an experimental model was that Mendel could strictly control matins. Consequently, pea plants usually self-fertilize in nature. That is, sperm-carrying pollen grains released from the stamens land on the egg-containing carpel of the same flower. He also used cross-fertilization sometimes, which is fertilization of one plant by pollen from a different plant. Mendel worked with his plants until he was sure he had true-breeding varieties - that is, varieties for which self-fertilization produced offspring all identical to the parent. In the language of plant and animal breeders and geneticists, the offspring of two different varieties are called hybrids, and the cross-fertilization itself is referred to as a hybridization, or simply a cross. The true-breeding parental plants are called the P generation, and their hybrid offspring are the F1 generation. When F1 plants self-fertilize or fertilize each other, their offspring are the F2 generation. Mendel's law of segregation describes the inheritance of a single character. A cross between a pea plant with purple flowers and one with white flowers is called a monohybrid cross, because the parent plants differ in only one character. There are alternative versions of genes that account for variations in inherited characters. For example, the gene for flower color in pea plants exists in two versions, one for purple and the other for white. The alternative versions of a gene are now called alleles. For each character, an organism inherits two alleles, one from each parent. These alleles may be the same or different. An organism that has two identical alleles for a gene is said to be homozygous for that gene. An organism that has two different alleles for a gene is said to be heterozygous for that gene. If the two alleles of an inherited pair differ, then one determines the organism;s appearance and is called the dominant allele; the other has no noticeable effect on the organism;s appearance ans is called the recessive allele. A sperm or egg carries only one allele for each inherited character because allele pairs separate from each other during the production of gametes. Because an organism's appearance does not always reveal its genetic composition, geneticists distinguish between an organism;s expressed, or physical, traits, called its phenotype, and its genetic makeup its genotype. Homologous chromosomes bear the alleles for each character. The law of independent assortment is revealed by tracking two characters at once. A dihybrid cross is a mating of parental varieties differing in two characters. Each pair of alleles segregates independently of other pairs of alleles during gamete formation. This is called Mendel's law of independent assortment. Geneticists use the testcross to determine unknown genotypes. A testcross is a mating between an individual of unknown genotype and a homozygous recessive individual. Mendel's laws reflect the rules of probability. Genetic traits in humans can be tracked through family pedigrees, by going back to the previous generations and finding out if they had the trait or not. many inherited disorders in humans are controlled by a single gene. Most human genetic disorders are recessive. They range in severity from relatively mild, such as albinism, to life-threatening, such as cystic fibrosis. Most people who have recessive disorders are born to normal parents who are both heterozygous - that is who are carriers of the recessive allele for the disorder but are phenotypically normal.Although many harmful alleles are recessive, a number of human disorders are caused by dominant alleles. New technologies can provide insight into one's genetic legacy. There are several ways of testing: genetic testing, fetal testing, fetal imaging, which uses ultrasound imaging, newborn screening, and ethical considerations. Incomplete dominance results in intermediate phenotypes. The F1 offspring of Mendel's pea crosses always looked like one of the two parental varieties. This situation is called complete dominance; the dominant allele has the same phenotypic effect whether present in one or two copies. But for some characters, the appearance of F1  hybrids falls between the phenotypes of the two parental varieties, an effect called incomplete dominance. Many genes have more than two alleles in the population. For instance, the ABO blood group phenotype in humans involves three alleles of a single gene. A single gene may affect many phenotypic characters. Most gene influence multiple characters, a property called pleiotropy. A single character may be influenced by many genes. Mendel studied genetic characters that could be classified on an either-or basis, such as purple or white flower color. However, many characteristics, such as human skin color and height, vary in a population along a continuum. Many such features result from polygenic inheritance, the additive effects of two or more genes on a single phenotypic character. The environment also affects many characters. Chromosome behavior accounts for Mendel's laws. Genes on the same chromosome tend to be inherited together. Genes located close together on the same chromosome tend to be inherited together and are called linked genes. Crossing over produces new combinations of alleles.  Geneticists use crossover data to map genes. Chromosomes determine sex in many species. Many animals, including all mammals, ahve apir of sex chromosomes, designed X and Y, that determine an individual's sex. Sex-linked genes exhibit a unique pattern of inheritance. A sex-linked gene is a gene located on either sex chromosome, and it is a lot different than a linked-gene. Sex-linked disorders affects mostly males. Hemophilia, red-green color blindness. and Duchenne muscular dystrophy are disorders caused by sex-linked genes, and they are seen more often in males, than in females. The Y chromosome is also very valuabe, because provides clues about human male evolution.

Key Terms:
1.Character - a heritable feature that varies among individuals, such as flower color.
2.Trait - each variant for a character, such as purple or whit flowers.
3.Hybrids - the offspring of two different varieties.
4.Alleles - the alternate versions of a gene.
5.Homozygous - an organism that has two identical alleles for a gene.
6.Heterozygous - an organism that has two different alleles for a gene.
7.Achondroplasia - a serious dominant disorder; a form of dwarfism.
8.Huntington's diseas - a degenerative disorder of the nervous system that usually does not appear until 35 to 45 years of age.
9.Complete dominance - the dominant allele has the same phenotypic effect whether present in one or two copies.
10.Incomplete dominance - the appearance of F1 hybrids falls between the phenotypes of the two parental varieties.

Chapter 8: The Cellular Basis of Reproduction and Inheritance

Three questions about the chapter:
1.Where do cells arise from?
Cells arise only from preexisting cells.
2.What are the two main stages of the cell cycle?
The cell ycle consists of two broad stages: a growing stage (called interphase) and the actual cell division (called the mitotic phase).
3.What can happen if a person has an extra copy of chromosome 21?
There is a chance that this person might have the Down syndrome.

Five main facts from the reading:
1.Prokaryotes reproduce by binary fission.
2.The large, complex chromosomes of eukaryotes duplicate with each cell division.
3.The cell cycle multiplies cells.
4.Cell division is a continuum of dynamic changes.
5.Cytokinesis differ for plant and animal cells.

Diagram:

      



    This diagram shows an example of binary fission of a prokaryotic cell.











Link: http://www.tutorvista.com/biology/transverse-binary-fission 


Summary:
     The introduction of the chapter talked about people who are trying to safe different plant species, because they are not very many of these kinds left. It also talked about life cycle, which is the sequence of stages leading from the adults of one generation to the adults of the next. Sperm and egg each carry one set of genetic information - one copy of the organism's genome.Like begets like is an adage that applies only to asexual reproduction, the creation of genetically identical offspring by a single parent, without the participation of sperm and egg. For example an amoeba is an organism which duplicates its chromosomes, the structures that contain most of the organism's DNA. Offspring produced by sexual reproduction generally resemble their parents more closely than they resemble unrelated individuals of the same species, but they are not identical to their parents or to each other. Cells arise only from preexisting cells. The reproduction of cells is called cell division. Prokaryotes reproduce by a type of cell division called binary fission.The large, complex chromosomes of eukaryotes duplicate with each cell division. These cells are more complex and generally much larger than prokaryotic cells, and they have many more genes. Almost all the genes in the cells of humans, and in all other eukaryotes, are found in the cell nucleus, grouped into multiple chromosomes. Most of the time, chromosomes exist as a diffuse mass of long, thin fibers.This material, called chromatin, is a combination of DNA and protein molecules. Before a eukaryotic cell begins to divide, it duplicates all of its chromosomes. The DNA molecule of each chromosome is copied, and new protein molecules attach as needed. The result is that each chromosome now consists of two copies called sister chromatids,w hich contain identical copies of the DNA molecule. Two chromatids are joined together especially tightly at a narrow "waist" called the centromere. The cell cycle multiplies cells. It is an ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division into two cells. The cell cycle consists of two broad stages: a growing stage (called interphase), during which the cell roughly doubles everything in its cytoplasm and precisely replicates its chromosomal DNA, and the actual cell division (called the mitotic phase). The mitotic phase is divided into two stages, called mitosis and cytokinesis, although the second stage begins before the first one ends. In mitosis, the nucleus and its contents, including the duplicated chromosomes, divide ad are evenly distributed to form two daughter nuclei. During cytokinesis, the cytoplasm is divided in two. Mitosis is a continuum of changes, but there are five main distinguished stages: prophase, prometaphase, metaphase, anaphase, and telophase. Cytokinesis differs for plant and animal cells. Anchorage, cell, cell density, and chemical growth factors affect cell division. A growth factor is a protein secreted by certain body cells that stimulates other cells to divide. The effect of a physical factor on cell division is clearly seen in density-dependent inhibition, a phenomenon in which crowded cells stop dividing. Growth factors signal the cell cycle control system. This system is a cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle. Growing out of control, cancer cells produce malignant tumors.A tumor is an abnormally growing mass of body cells. If the abnormal cells remin at the original site, the lump is called a benign tumor. In contrast, a malignant tumor can spread into neighboring tissues and other parts of the body, displacing normal tissue and interrupting organ function as it goes. The spread of cancer cells via the circulatory system beyond their original site is called metastasis. In short, mitosis provides for growth, cell replacement, and asexual reproduction. In humans, a typical body cell, called a somatic cell, has 46 chromosomes. They are matched in homologous pairs. X and Y chromosomes are called sex chromosomes. The other 22 pairs of chromosomes are called autosomes. Gametes are the egg and sperm cells, and they have a single set of chromosomes. Any cell with two homologous sets of chromosomes is called a diploid cell. A cell with a single chromosome set is called a haploid cell. Meiosis is a type of cell division that produces haploid gametes in diploid organisms. Mitosis and meiosis have many important similarities and differences. Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring. Homologous chromosomes can carry different versions of genes. Crossing over is an exchange of corresponding segments between two homologous chromosomes. A karyote is a photographic inventory of an individual's chromosomes. If a person has 47 chromosomes, instead of 46, the condition is called trisomy 21. An extra copy of chromosome 21 causes Down syndrome. Accidents during meiosis can alter chromosome number. Abnormal numbers of sex chromosomes do not usually affect survival. New species can arise from errors in cell division. Alternations of chromosome structure can cause birth defects and cancer.

Key Terms:
1.Life cycle - the sequence of stages leading from the adults of one generation to the adults of the next.
2.Asexual reproduction - the creation of genetically identical offspring by a single parent, without the participation of sperm and egg.
3.Cell division - the reproduction of cells.
4.Chromatin - a combination of DNA and protein molecules.
5.Cell cycle - an ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division into two cells.
6.Cytokinesis - a process during which the cytoplasm is divided in two.
7.Cleavage furrow - a shallow groove in the cell surface.
8.Growth factor - a protein secreted by certain body cells that stimulates other cells to divide.
9.Tumor - an abnormally growing mass of body cells.
10.Metastasis - the spread of cancer cells via the circulatory system beyond their original site.

Chapter 7: Photosynthesis

Three questions about the chapter:
1.What process do plants use that eukaryote organisms do not, to get energy?
 Photosynthesis.
2.Where does photosynthesis occur?
It occurs in the chloroplasts in plant cells.
3.What are the two stages of photosynthesis?
The first one is the light reactions, and the second one is the Calvin cycle, or the dark reactions.

Five main facts from the reading:
1.Autotrophs are the producers of the biosphere.
2.Plants produce oxygen by splitting water.
3.Photosynthesis is a redox process,as is cellular respiration.
4.Photosynthesis uses light energy, carbon dioxide, and water to make food molecules.
5.Photosynthesis moderates global warming. 

Diagram:

 This diagram is a simple overview of the two stages of photosynthesis that take place in a chloroplast.
















Link: http://www.calpoly.edu/~mforte/dream/p3.html


Summary:
     In the introduction of the chapter, we learned that scientists are trying to use plant power as fuel source. Photosynthesis is one of the oldest energy pathways on the planet. In this process, green plants, algae, and certain bacteria transform light energy to chemical energy stored in the bonds of the sugar they make from carbon dioxide and water. After this we learned that autotrophs are the producers of the biosphere. Producers are the organisms that produce their own food supply. All organisms that produce organic molecules from inorganic molecules using the energy of light are called photoautotrophs. Photosynthesis occurs in the chloroplasts in plant cells. Plants' green color is from chlorophyll, a light-absorbing pigment in the chloroplasts that plays a central role in converting solar energy to chemical energy. Chloroplasts are concerned in the cells of the mesophyll, the green tissue in the interior of the leaf. Carbon dioxide enters the leaf, and oxygen exits, by way of tiny pores called stomata. Water absorbed by the roots is delivered tot he leaves in veins. An envelope of two membranes encloses an inner compartment in the chloroplast, which is filled with a thick fluid called stroma. Suspended in the stroma is a system of interconnected membranous sacs, called thylakoids. In some places thylakoids are concentrated in stacks called grana. Plants produce oxygen by splitting water. Photosynthesis is a redox process, as is cellular respiration. It has two stages and they are linked by ATP and NADPH. The light reactions include the steps that convert light energy to chemical energy and produce oxygen. The reactants in this process are water sunlight energy, ADP, and NADP+. The products are ATP, NADPH, and oxygen. This process takes place in the thylakoids in the chloroplast. The Calvin cycle occurs in the stroma of the chloroplast. It is a cyclic series of reactions that assembles sugar molecules using carbon dioxide and the energy-containing products of the light reactions. The reactants of this process are carbon dioxide, ATP, and NADPH. The products are NADP+, ADP, and sugar. The process takes place in the stroma in the chloroplast. Visible radiation drives the light reactions. An electromagnetic spectrum is the full range of electromagnetic wavelengths from the very short gamma rays to the very long-wavelength radio waves. The distance between the crests of two adjacent waves is called a wavelength. A photon is a fixed quantity of light energy. Photosystems capture solar power. A photosytem consists of a number of light-harvesting complexes surrounding a reaction center complex. The reaction center complex contains a pair of chlorophyll "a" molecules and a molecule called the primary electron acceptor, which is capable of acdpeting electrons and becoming reduced. There two photosystems in the light reactions process. Photosystem 2 (P680) and photosytem 1 (P700). The two photosystems are connected by an electron transport chain and generate ATP and NADPH. Chemiosmosis powers ATP synthesis in the light reactions. In photosynthesis the chemiosmotic production of ATP is called photophosphorylation. ATP and NADPH power sugar synthesis in the Calvin cycle. Adaptations that save water in hot, dry climates evolved in C4 and CAM plants. In most plants, initial fixation of carbon occurs when the enzyme rubisco adds carbon dioxide to RuBP. Such plants are called C3 plants because the first organic compound produced is the three-carbon compounds 3-PGA. In certain plant species, alternate modes of carbon fixation have evolved that save water without shuttling down photosynthesis. C4 plants are so named because they precede the Calvin cycle by first fixing CO2 into a four-carbon compound. When the weather is hot and dry, a C4 plant keeps its stomata mostly closed, thus conserving water. CAM plants are species adapted  to very dry climates. A CAM plant conserves water by opening its stomata and admitting carbon dioxide only at night. Photosynthesis moerates global warming.

Key Terms:
1.Autotrophs - organisms that make their own food and thus sustain themselves without consuming organic molecules derived from any other organisms.
2.Mesophyll - the green tissue in the interior of the leaf.
3.Stomata - tiny pores by which carbon dioxide enters the leaf, and oxygen exits.
4.Stroma - a thick fluid filled in an envelope of two membranes in the chloroplast.
5.Thylakoids - a system of interconnected membranous sacs suspended in the stroma.
6.Grana - stacks in which thylakoids are concentrated.
7.Light reactions - include the steps that convert light energy to chemical energy and produce oxygen.
8.Calvin cycle - occurs in the stroma of the chloroplast, and it is a cyclic series of reactions that assembles sugar molecules using carbon dioxide and the energy-containing products of the light reactions.
9.Photosystem - consists of a number of light-harvesting complexes surrounding a reaction center complex.
10.Photon - a fixed quantity of light energy.