Mitosis and Meiosis

Cell division and reproduction can occur in two ways - mitosis and meiosis.

Mitosis is a process of cell duplication, or reproduction, during which one cell gives rise to two genetically identical daughter cells.

Meiosis, on the other hand, is a division of a germ cell involving two fissions of the nucleus and giving rise to four gametes, or sex cells, each possessing half the number of chromosomes of the original cell.

Mitosis is used by single celled organisms to reproduce; it is also used for the organic growth of tissues, fibers, and membranes. Meiosis is useful for sexual reproduction of organisms. The male and female sex cells, e.g. the spermatozoa and egg, fuse to create a new, singular biological organism.

Process Differences
Different Stages of Mitosis and Meiosis
Differences in Purpose

Mitosis is a method of reproduction for single celled organisms that reproduceasexually. An identical version of the organism is created through splitting of the cell in two. Meiosis may result in millions of spermazoa and egg cells with unique genetic patterns. The mating of the two cells formed by meiosis results in a unique genetic offspring of the same species. Meiosis is a major factor in evolution, natural selection, and biodiversity. The processes of cellular division shown in mitosis and meiosis are present in all manner of life forms including humans, animals, plants, fungi, and single celled organisms and species. Essentially any cell based organism of which all organic life is based will exhibit some form of mitosis and meiosis for growth and reproduction of the individual and species.

The different phases of meiosis are: Prophase, Metaphase, Anaphase and Telophase.

Both Meiosis and Mitosis are found in complex organisms which reproduce sexually. Mitosis may be used for human growth, the replenishment of depleted organs and tissues, healing, and sustenance of the body. Identical versions of cells can be created to form tissues through Mitosis. Meiosis is a special process reserved for the creation of the egg and sperm cells. The same patterns may be found in many species of plant and animal cell reproduction.

Significance

Meiosis	Mitosis
Definition	A type of cellular reproduction in which the number of chromosomes are reduced by half through the separation of homologous chromosomes, producing two haploid cells.	A process of asexual reproductionin which the cell divides in two producing a replica, with an equal number of chromosomes in each resulting diploid cell.
Function	sexual reproduction	Cellular Reproduction & general growth and repair of the body
Type of Reproduction	Sexual	Asexual
Occurs in	Humans, animals, plants, fungi	all organisms
Genetically	different	identical
Crossing Over	Yes, mixing of chromosomes can occur.	No, crossing over cannot occur.
Pairing of Homologs	Yes	No
Number of Divisions	2	1
Number of Daughter Cells produced	4 haploid cells	2 diploid cells
Chromosome Number	Reduced by half	Remains the same
Steps	The steps of meiosis are Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II and Telophase II.	The steps of mitosis are Interphase, Prophase, Metaphase, Anaphase, Telophase and Cytokinesis
Karyokinesis	Occurs in Interphase I	Occurs in Interphase
Cytokinesis	Occurs in Telophase I & Telophase II	Occurs in Telophase
Centromeres Split	The centromeres do not separate during anaphase I, but during anaphase II	The centromeres split during Anaphase
Creates	Sex cells only: Female egg cells or Male sperm cells	Makes everything other than sex cells

The importance of mitosis is the maintenance of the chromosomal set; each cell formed receives chromosomes that are alike in composition and equal in number to the chromosomes of the parent cell.

Your Inner Fish 6

Ectoderm: outer part of the body and nervous system
Endoderm: the inside layer, inner structures of the body
Mesoderm: our skeleton and our muscles.

Cell Tour

http://prezi.com/vt7bo_4oy0ns/?utm_campaign=share&utm_medium=copy

Special Genetics

Dihybrid Cross

Definition: A dihybrid cross is a breeding experiment between P generation (parental generation) organisms that differ in two traits.

Examples:

In this dihybrid cross, a plant with the dominant traits of green pod color and yellow seed color is cross-pollinated with a plant with the recessive traits of yellow pod color and green seed color.

If a true-breeding plant with green pod color (GG) and yellow seed color (YY) is cross-pollinated with a true-breeding plant with yellow pod color (gg) and green seeds (yy), the resulting offspring will all be heterozygous for green pod color and yellow seeds (GgYy).

Prezi - Parkinsons disease

http://prezi.com/wgkdr-qnfohk/parkinsons-disease/

Mendel

Introduction

Gregor Mendel (1822-1884) was an Austrian monk who discovered the basic rules of inheritance. From 1858 to 1866, he bred garden peas in his monastery garden and analyzed the offspring of these matings. The garden pea was good choice of experimental organism because:

• many varieties were available that bred true for clear-cut, qualitative traits like
• seed texture (round vs wrinkled)
• seed color (green vs yellow)
• flower color (white vs purple)
• tall vs dwarf growth habit
• and three others that also varied in a qualitative — rather than quantitative — way.

• peas are normally self-pollinated because the stamens and carpels are enclosed within the petals. By removing the stamens from unripe flowers, Mendel could brush pollen from another variety on the carpels when they ripened.

The first cross

Mendel crossed a pure-breeding round-seeded variety with a pure-breeding wrinkled-seeded one.

Our interpretation

The parents (designated the P generation) were pure-breeding because each was homozygous for the alleles at the gene locus (on chromosome 7) controlling seed texture (RR for round; rr for wrinkled).

The results

All the peas produced in the second or hybrid generation were round.

Operon System

In genetics, an operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single regulatory signal or promoter.[1][2] The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo trans-splicing to create monocistronic mRNAs that are translated separately, i.e. several strands of mRNA that each encode a single gene product. The result of this is that the genes contained in the operon are either expressed together or not at all. Several genes must be both co-transcribed and co-regulated to define an operon.[3]

Originally, operons were thought to exist solely in prokaryotes, but since the discovery of the first operons in eukaryotes in the early 1990s,[4][5] more evidence has arisen to suggest they are more common than previously assumed.[6] In general, expression of prokaryotic operons leads to the generation of polycistronic mRNAs, while eukaryotic operons lead to monocistronic mRNAs.

Protein Synthesis

Proteins are assembled from amino acids using information encoded in genes. Each protein has its own unique amino acid sequence that is specified by the nucleotide sequence of the gene encoding this protein. The genetic code is a set of three-nucleotide sets called codons and each three-nucleotide combination designates an amino acid, for example AUG (adenine-uracil-guanine) is the code for methionine. Because DNA contains four nucleotides, the total number of possible codons is 64; hence, there is some redundancy in the genetic code, with some amino acids specified by more than one codon.[6] Genes encoded in DNA are first transcribed into pre-messenger RNA (mRNA) by proteins such as RNA polymerase. Most organisms then process the pre-mRNA (also known as a primary transcript) using various forms of Post-transcriptional modification to form the mature mRNA, which is then used as a template for protein synthesis by the ribosome. In prokaryotes the mRNA may either be used as soon as it is produced, or be bound by a ribosome after having moved away from the nucleoid. In contrast, eukaryotes make mRNA in the cell nucleus and then translocate it across the nuclear membrane into the cytoplasm, where protein synthesis then takes place. The rate of protein synthesis is higher in prokaryotes than eukaryotes and can reach up to 20 amino acids per second.[7]

The process of synthesizing a protein from an mRNA template is known as translation. The mRNA is loaded onto the ribosome and is read three nucleotides at a time by matching each codon to its base pairing anticodon located on a transfer RNA molecule, which carries the amino acid corresponding to the codon it recognizes. The enzyme aminoacyl tRNA synthetase "charges" the tRNA molecules with the correct amino acids. The growing polypeptide is often termed the nascent chain. Proteins are always biosynthesized from N-terminus to C-terminus.[6]

The size of a synthesized protein can be measured by the number of amino acids it contains and by its total molecular mass, which is normally reported in units of daltons (synonymous with atomic mass units), or the derivative unit kilodalton (kDa). Yeast proteins are on average 466 amino acids long and 53 kDa in mass.[5] The largest known proteins are the titins, a component of the muscle sarcomere, with a molecular mass of almost 3,000 kDa and a total length of almost 27,000 amino acids.[8]

DNA Replication

DNA replication is the process of producing two identical copies from one original DNA molecule. This biological process occurs in all living organisms and is the basis for biological inheritance. DNA is composed of two strands and each strand of the original DNA molecule serves as template for the production of the complementary strand, a process referred to as semiconservative replication. Cellular proofreading and error-checking mechanisms ensure near perfect fidelity for DNA replication.[1][2]

In a cell, DNA replication begins at specific locations, or origins of replication, in the genome.[3] Unwinding of DNA at the origin and synthesis of new strands results in replication forks growing bidirectionally from the origin. A number of proteins are associated with the replication fork which assist in the initiation and continuation of DNA synthesis. Most prominently, DNA polymerase synthesizes the new DNA by adding complementary nucleotides to the template strand.

DNA replication can also be performed in vitro (artificially, outside a cell). DNA polymerases isolated from cells and artificial DNA primers can be used to initiate DNA synthesis at known sequences in a template DNA molecule. The polymerase chain reaction (PCR), a common laboratory technique, cyclically applies such artificial synthesis to amplify a specific target DNA fragment from a pool of DNA.

http://upload.wikimedia.org/wikipedia/commons/8/8/DNA_replication_en.svg

Unit 3 Lab

https://sites.google.com/site/unit3dna/unit-3--dna/pglo

Homework 11/5

This flower is different from other flowers that surround it. According to the book Survival of the sickest, we can hypothesize that this flower's genes had occurred some mutations, so it helps to protect itself.

These extra finger are a result of the mirror- image duplication. The sonic hedgehogs genes were placed  wrongly into in the body,

DNA Replication Enzymes

DNA Replication Enzymes

1.     Helicase: DNA helicases bind to ssDNA at the replication forks and move into the adjacent double stranded regions forcing the two strands apart and unwinding the helix. Helicases require ATP as an energy source

2

.     DNA Polymerase III: In prokaryotes, chain elongation is catalyzed by DNA Polymerase III on both strands. The high processivity of the polymerase is the result of the β-subunit of the polymerase acting as a sliding clamp on the DNA template. On the lagging strand, Pol III elongates until it encounters a RNA primer.

3

.     DNA Polymerase I: DNA repair and some replication. Highest concentration

4

.     RNA Primase: Replicates/synthesizes the start of a new strand, the primer. Uses RNA in a 3'-5' way

5. Ligase:    Supplies final phosphodiester bond that seals the new strands together.

Survival of Sickest chapter 6 summary

    DNA can be purposely modified or just by random mutation. Barbara McClintock discovered the “ jumping genes” – whole sequences of DNA that moved from one place to another during times of some environmental stress.  These jumping genes are constantly “cut and paste” and “copy and paste. Also, what we consider as the “junk” DNA ( DNA that does not code for proteins) actually is the main source of jumping genes.

    Retroviruses are made of RNA, and can be written into DNA.  For example, HIV is a retrovirus and the drug “cocktail” therapy used to resist HIV by stopping the enzyme that helps the retroviruses become part of DNA. The retroviruses that are part of our DNA are called HERV, and it’s function is to produce a healthy placenta 

“ From Atoms to Traits”

Kevin Lin 

Mr. Quick 

A Block 

“ From Atoms to Traits”

1. One of these principles, now called Mendel's law of segregation, states that allele pairs separate or segregate during gamete formation, and randomly unite at fertilization.

 A gene can exist in more than one form.

Organisms inherit two alleles for each trait.

When gametes are produced (by meiosis), allele pairs separate leaving each cell with a single allele for each trait.

When the two alleles of a pair are different, one is dominant and the other is recessive.

2. Watson and Crick first discover the structure of DNA.

3.

1) The substitution of a single letter for another at a particular position in the polymer

Example:

ACTGCC…

ACGCCC…

Every three letters is a amino acid, so it could cause the change of protein

 2) Insertion: The addition of extra base pairs in the sequence

Example: A smooth pea and a wrinkled pea

 3) Gene Copy Number: Difference in the number of duplication of an entire sequence

Example: the genes for starch digestion in chimpanzees and humans

 4) Duplication: Difference in the number of duplication of a base pair

Example: Signal receptor for pigment cells in pigs

 5) Regulatory changes: the change in the formation of gene sequences during the organism's development

Example: …

4. Evolutionary developmental biology (evolution of development or informally, evo-devo) is a field of biology that compares the developmental processes of different organisms to determine the ancestral relationship between them, and to discover how developmental processes evolved. It addresses the origin and evolution of embryonic development; how modifications of development and developmental processes lead to the production of novel features, such as the evolution of feathers; the role of developmental plasticity in evolution; how ecology impacts development and evolutionary change; and the developmental basis of homoplasy and homology.

5.   If a person has been constantly rejecting lactose products while he was growing up, then he will be lactose intolerant because his body lacks the mutant form of lactase enzyme. 

“Traces of a Distant Past”

Kevin Lin

Mr. Quick

A Block

Oct 22^nd

     Darwin knew that individuals were variable, so each individual in a population carried a unique set of traits. However, he did not discover that the reason behind it is genetic differences. Variation in the genes of individuals arises from several sources. Mutation, the alteration of existing genes to form new alleles, can arise from copying errors during DNA replication, DNA damage, and repair or recombination during cell division. Varation also arises from sexual reproduction, wherein new combinations of DNA are created through the independent assortment of genes. 

   In the Documentary movie “ The Journey of Man”, Spencer Wells, a geneticist, adheres to the out of Africa theory in which all of mankind stemmed from a single person who originated in Africa 60,000 years ago. His question is that how human possibly travelled from Africa and end up spread out in the rest of the world and also to find genetic evident to backup his theory. He is also wondering what caused human immigration. From his basis understanding, he believes that on genetic markers in Y chromosomes, which are only found in males. The idea behind this is that sons inherit Y chromosomes identical to that of their fathers. However occasionally mutations occur in the DNA and form a genetic marker which can be traced. By looking for different markers and analysing DNA in people all over the world today, a picture can be formed of where our ancestors were at certain points in time and this enables us to track their journey and the origins of man.

The article “Traces of a Distant Past” once again proof Spencer Wells idea that humans left Africa and gradually fanned out across Asia to Australia and then up to Europe; and then say 15,000 years ago, they crossed over what was then a land bridge to the Americas and gradually worked their way down to South America. Also, due to fast speed of globalization, discovering how genetics related to evolution is becoming an important issue. That has been the perspective of a number of population geneticists who have felt that we really need to carry out this research as soon as possible because of globalization, because of the mixing of peoples. That was the reason that in the early '90s, a very well-known population geneticists, Luca Cavalli-Sforza, suggested that at the same time that we begin a Human Genome Project, we begin something called the Human Genome Diversity Project that would go out and collect samples from many, many different indigenous populations from around the world and then have a basis for comparing that genetic diversity for researching the hypothesis that we're talking about, that humans originated in Africa and gradually spread out with this decreasing genetic diversity. There was a problem with that. Many of the people who they approached were not eager to have their blood sampled or to give samples of sputum because they felt that, one, this may be taking something that is intrinsic to their own belief systems, which is there are some groups that believe that taking the blood is in essence robbing the soul in some ways. Others had had bad experience with people coming and wanting to take plants and other types of materials that they've been using and patenting them.

Class 11 quiz

Class 11 Quiz

1.   This picture demonstrates the evolution of whale. 55 million years ago, Mesonychid was a mammal that lived on land. Its four limbs allowed it to walk. Ambulocetus evolved from Mesonychid. The structure of its head is flatter and its mouth was longer and sharper. The limbs of Ambulocetus adapted to amphibian environment that it was able to go to near land area yet still hunt in the water. The eyes of Ambulocetus were on the sides so that they can see better in the water. Rodhocetus evolved from Ambulocetus. The body structure of Rodhocetus was more streamlined, allowing it to swim in water. Its tail was divided into two parts to balance the body while swimming. The limbs changed to fins because fingers were not needed in water. Finally, Basilosaurus evolved from Rodhocetus. The structure of the body was more streamlined. All four of the fins grew smaller.

2.     E.

3.     Dragonfly, birds and bats are all able to fly. However, bats  is the only organism have finger structure in the wings. The limbs of birds are more stronger than bats and dragonfly because they need to stand on their feet. The neck of bird is long so it allows the bird to pick up its food from the ground. The long tail of dragonfly also allows it to balance its body

4.     The sequences of Cytochrome C of different organisms demonstrate the relationship between them. The fewer differences between two organisms, the more closer they are to the common ancestor because DNA mutations take place over time. The less time available for mutations to happen, the closer two organisms are to their more recent common ancestor. For example, there is only one difference in amino acid between human and Rhesus monkey.

5.     Homology shows two organisms have similar structures or genes which indicates that they share a common ancestor. For example, modern toothed whale and Rodhocetus have the same tail structures. 

3rd Class

  Agua

1.     Oxygen - atom in water that attracts electrons more strongly

2.     Polar - a molecule with an uneven distribution of charge

3.     Water - an example of a polar molecule

4.     Hydrogen bond - attraction of a hydrogen for a more negatively charged atom such as oxygen or nitrogen

5.     Cohesion - attraction between molecules of the same kind

6.     Adhesion - attraction between molecules of different kinds

7.     Capillarity or capillary action - tendency of water to rise in a narrow tube due to adhesion and cohesion

8.     Molecular Motion - Molecular motion is how the molecules move and the energy associated with the movement affects the physical properties of a chemical. Molecules can move in three ways, transitional, rotational, and vibrational.