Ch.9 Patterns of Inheritance

WHAT WERE EXPERIMENTS MENDEL CONDUCT AND WHAT WERE HIS RESULTS?
Mendel conducted pea plant experiment. He crossed different plants and came out mostly with the same result, but some had different phenotypes. Je experimented with thousands of pea plants and recorded the phenotypic and genotypic traits of both using Punnet Squares. Mendel's finding showed that phenotypic traits in pea plants were inherited in discrete packages and at predictable frequencies. Mendel stated two laws, law of independent segregation, which states that a parent plant passed only one copy of a trait to the offspring. His second law was the Law of independent assortment that states that these traits met randomly in the offspring. 

WHY DO MORE MEN THAN WOMEN HAVE COLOR BLINDNESS?

Women have the sex chromosomes XX, while men have the chromosomes XY. The gene for normal color vision is found on the X-chromosome. If a woman has one X-chromosome with the gene and one without it, she will not be color blind. On the other hand, a man with an X-chromosome that is missing the gene has no backup. He will be color blind. Color blind women have both X-chromosomes missing the color vision gene. This has less probability than having just one X-chromosome missing the gene.

WHAT ARE THE MENDELIAN LAWS?
1) Law of segregation: pair of characteristics only one can be represented in a gamete. In another words,  for any pair of characteristics there is only one gene in a gamete even though there are two genes in ordinary cells.
2) Law of independent assortment: two characteristics the genes are inherited independently.
 If you had the genotype AaBb, you would make four kinds of gametes: they would contain the combinations of either AB, Ab, aB, or ab.

SUMMARY:
Genetic materials are only transported to offsprings. In another words, no matter how hard you work out to build your arm muscles, the offsprings will not get the muscle unless you have muscle cells that build muscles faster and easier than normally. In 1859, Mendel published a paper that says that the heritable factors retain their individuality generation after generation. He choose garden pea flower to study, using method that prevented fertilization, to cross fertilize the stamenless flower the carpel developed into a pod, and he planted. The seeds grew into offspring plants. Through these methods, Mendel was always sure of the parentage of new plants. He worked until he was sure he had true-breeding varieties. Mendel's law of segregation describes the inheritance of a single character. This starts with a cross between two parents and cross them to expect how offsprings are going to look like, using punnett square. We are able to describe phenotype and genotype of offsprings. Mendel's law of segregation states that pairs of alleles segregate during gamete formation. Homologous chromosomes state that alleles of a gene reside at the same locus on homologous chromosomes. Mendel's law of independent assortment states that each pair of alleles segregates independently of other pairs of alleles during gamete formation. From crossing P generations using punnett square, we are able to distinguish the percentage of phenotype and genotype of offsprings that will be born.
Genetic traits in humans can be tracked through family pedigrees. To analyze the pedigree, the geneticist applies logic and the Mendelian laws. Dominant traits are usually easier to occur, such as having freckles, widow's peak, and free earlobe. However people do have recessive traits, opposite of dominant traits, such as no freckles, straight hairline, and attached earlobe. Many inherited disorders in humans are controlled by a single gene. For example of recessive disorders, if both parents have gene of deaf, 25% of offsprings have possibilities to be deaf. The most common fatal genetic disease in the United states is cystic fibrosis. The CF allele is carried by about one in 25 people of European ancestry. The probability increases greatly if close relatives marry and have children. People with recent common ancestors are more likely to carry the same recessive relatives, called inbreeding, which is more like to produce offspring many types of inbred animals.
New technologies are able to provide insight into someone's genetic legacy. Genetic testing, fetal testing, fetal imaging, and ethical considerations are used. There is an incomplete phenotype. For example, if you cross red flower and white flower, there are probabilities of pink flower to be born between them.
Many genes have more than two alleles in the population. Most genes can be found in populations in more than two versions, known as multiple alleles. Although any particular individual carries, at most, two different alleles for a particular gene, in cases of multiple alleles, more than two possible alleles exist in the wider population. For example, blood group phenotype. There are four blood types, A, B, O, and AB. These letters refer to two carbohydrates, designated A and B, that may be found on the surface of red blood cells. Genotypes will be ii for O, IAIA or IAiA for A, IBIB or IBiB for B, and IAIB for AB. If I is a capital, it is a codominant; both alleles are expressed in heterozygous individuals.
Chromosome behavior accounts for Mendel's laws. The chromosome theory of inheritance was emerging. It 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. Genes located close together on the same chromosome tend to be inherited together and they are called linked genes. They do not generally follow Mendel's law of independent assortment. Crossing over is very useful. They are used to produce new combinations of alleles, see the percentage of it, and also its data can be used to map genes.
Many animals have a pair of sex chromosomes, designated X and Y that determine and individual's sex. A gene located on either sex chromosome is called a sex-linked gene. By using punnett square, whether an individual is a male or a female is also able to be determined. Disorders can affect mostly males. For example, hemophilia, red-green color blindness, and duchenne muscular dystrophy.


KEY TERMS:
-self-fertilize: sperm-carrying pollen grains released from the stamens land on the egg containing carpel of the same flower.
-cross-fertilization: fertilization of one plant by pollen from a different plant.
-hybrids: the offspring of two different varieties
-P generation: the true-breeding parental plants
-F1 generation: true-breeding parental plants' hybrid offsprings
-F2 generation: offsprings of when F1 plants self-fertilizeor fertilize each other
-testcross: a mating between an individual of unknown genotype and a homozygous recessive individual
-phenotype: offsprings' composition, geneticists distinguish between an organism's expressed, or physical, traits
-genotype: genetic makeup such as PP, Pp, pp
-rule of addition: the probability that an event can occur in two or more alternative ways is the sum of the separate probabilities of the different ways.

This punnett square shows that both parents have gametes that can be showed as  RrYy cross over. And it shows the probabilities of offspring whether if it is going to have round yellow, round green, wrinkled yellow, or wrinkled green. In this punnett square, 1/16 have RRYY, RRyy, rrYY, or rryy, 2/16 have RRYy, rrYy, Rryy, or RrYY, and 4/16 have RrYy. This is genotype of offsprings. And 9/16 have round yellow, 3/16 have round green, or wrinkled yellow, and 1/16 have wrinkled green. It is phenotype of offsprings. 
http://www.youtube.com/watch?v=-2YPAt8hOmE

5FACTS:

1) Phenotype shows the physical looking of organism, and genotype shows the alleles.

2) Mendel's laws are valid for all sexually reproducing species, but genotype often does not dictate phenotype in the simple way his laws describe.

3) Sex chromosomes determine sex in many species. If a specie has Y, it is a male, and if it has XX, it is a female.

4) Genes are located on chromosomes, whose behavior during meiosis and fertilization accounts for inheritance patters.

5) Crossing over can separate linked alleles, producing gametes with recombinant chromosomes.

Ch.8 The Cellular Basis of Reproduction and Inheritance

HOW DO PROKARYOTIC CELLS PERFORM CELL DIVISION WITHOUT NUCLEUS?
--> Cell division in prokaryotic organisms is simpler than in eukaryotes. This is because prokaryotes have much less complex DNA, and they don't have to worry about ensuring that each of the new cells receives an approximately equal number of organelles. All cells reproduce by dividing the middle until the cell membrane pinches closed and two new daughter cells are formed. In prokaryotes,once the DNA of the cell is replicated, each copy moves toward an opposite side of the cell by attaching to the cell membrane. The cell then elongates until it is approximately double its original size. At the end, the cell membrane on either side pinches inward and forms two new cells. 

WHY CAN'T PROKARYOTIC CELLS PERFORM MITOSIS?
--> Prokaryotic cells cannot go through mitosis. This is because mitosis is a division of nucleus into nuclei containing the same number of chromosomes. However, prokaryotic cells do not have nucleus, thus making it impossible.


WHAT HAPPENS TO THE NUMBER OF CHROMOSOMES WHEN FERTILIZATION HAPPENS?
--> A sperm has 23 chromosomes, and an egg also has 23 of them. When they fertilize, there will be 46 chromosomes. An offspring that is going to be made will have 46 chromosomes at the end. But its sex will only have 23 of them. That is how a human is like. This offspring will have 46 chromosomes but they are all mixed of 23 chromosomes from the sperm, and the other 23 from the egg. Also when meiosis occurs, all the chromosomes perform cross over, so it all depends on which sperm and egg fertilizes. This is why there is no identical people in the world because the possibility is almost 0%. It is almost impossible to happen to make two identical people.


SUMMARY:
There are two ways of reproduction for living things. Asexual reproduction, offsprings are identical to the original cell or organism. It only requires one parent, and sexual reproduction, it requires two parents and offsprings get genes from both of the parents. Cell division is the reproduction of cells. Roles of Asexual reproduction are reproduction of an entire single-celled organism, growth of a multicellular organism, growth from a fertilized egg into an adult, and repair and replacement of cells in an adult. For sexual reproduction is that sperm and egg production.
Binary fission is a type of cell division which occurs in prokaryotic cells. Two identical cells arise from one cell. Cell cycle consists of two stages. Interphase, duplication of cell contents, which includes G1, S, and G2, and mitotic phase, the division of duplicated contents, which includes mitosis and cytokinesis.
There are two types of reproduction of eukaryotic cells. Mitosis and Meiosis. Mitosis progresses through a series of stages. Interphase, prophase, prometaphase, metaphase, anaphase, telophase. Cytokinesis often overlaps telophase. During interphase, cytoplasmic contents are duplicated and two centrosomes form in the cytoplasm, and in the nucleus, chromosomes duplicate during the S phase. During prophase, in the cytoplasm, microtubules begin to emerge from centrosomes, forming the spindle. In the nucleus, chromosomes coil and become compact, and nucleoli disappears. During metaphase, spindle is fully formed, and chromosomes align at the cell equator, kinetochores of sister chromatids are facing the opposite poles of the spindle. During anaphase, sister chromatids separate at the centromeres, daughter chromosomes are moved to opposite pole of the cell, and the cell elongates due to lengthening of nonkinetochore microtubules. During telophase, the cell continues to elongate, the nuclear envelope forms around chromosomes each pole, establishing daughter nuclei, the spindle disappears, and chromatin uncoils. In cytokinesis, cytoplasm is divided into separate cells. Cleavage furrows is formed for animal cells for division, and cell plate is formed for plant cells.
Cancer cells escape controls on the cell cycle. They divide quickly. often in the absence of growth factors. They spread to other tissues through the circulatory system. Tumors get formed. There are three classifications of cancer by origin, carcinomas, sacromas, leukemias, and lymphomas.
Meiosis is a reproduction of sex cells. It also consists a series of stages but they perform twice. During prophase I, contents in nucleus duplicate. During metaphase I, tetrads align at the cell equator. During Anaphase I, homologous pairs separate and move toward the end of the cell. During telophase I, duplicated chromosomes have reached the poles and a nuclear envelope forms around them. Next stage is meiosis II, which follows meiosis I without chromosomes duplication. During metaphase II, duplicated chromosomes align at the cell. During anaphase II, sister chromatids separate and chromosomes move toward opposite poles. During telophase II, chromosomes have reeached the poles of the cell, and a nuclear envelope forms around each set of chromosomes.

KEY TERMS:
-chromatin: DNA+ proteins
-centromere: a join of sister chromatids. Made of protein
-cell cycle: an ordered sequence of events for cell division
-mitosis: division of the nucleus
-cytokinesis: division of cytoplasm
-mitotic spindle: composed of microtubules, produced by centrosomes to divide the chromosomes
-centrosomes: structures in the cytoplasm that organize microtubule arrangement, only in animal cells
-growth factor: proteins that stimulate division
-cell cycle control system: a set of molecules, including growth factors, that triggers and coorinates events of the cell cycle
-carcinomas: a type of cancer that arise in external or internal body coverings
-sarcomas: a type of cancer that arise in supportive and connective tissue
-leukemias/lymphomas: a type of cancer that arise from blood-forming tissues

This diagram shows movement of chromosomes during mitosis. The first step is prophase, when the chromosomes are form and nuclear envelope begins to dissolve. The second step is metaphase, when chromosomes line up in the middle of the cell. Spindles get attached to the centromere. During anaphase, the chromosomes are pulled apart from each other toward the end of the cell. During the last step, telophase, cleavage furrows are formed, and at the same time nuclear envelope begin to reform. The result of this step is two identical daughter cells.

http://www.youtube.com/watch?v=3kpR5RSJ7SA

This video shows more details about mitosis.

5 FACTS:
1) Mitosis is a reproduction of cells, and meiosis is a reproduction of sex cells.
2) Cytokinesis is division of cytoplasm.
3) Cells control how many cells they will reproduce, but cancer cells do not.
4) Animal cells form cleavage furrow, and plant cells form cell plate.
5) There are 46 chromosomes in human cells. After duplication it will go up to 92, and after division of sex cells, each will have 23.