Posted by: mrborden | May 13, 2012

DNA Replication and Mitosis


Friday May 18
Meiosis – process that produces sex cells with half the number of chromosomes ( heredity)
Copy page 596 picture
Genes – are characteristics of an organism, units of heredity
Dominant genes – stronger genes Recessive Genes – weaker genes because they dissappear when thay are paired with a dominant gene
Law of segregation – one allele (trait) from each parent segregates or separates into each sex cell
Law of independent assortment – all gene traits are inherited independently of all other genes or traits (ex. Blue eyes – brown hair)
Some genes are co-dominant where both traits are expressed (blood) called incomplete dominance
Pheno type – The physical appearance of a gene or visible characteristics
Geno Type – the genetic makeup of an individual ex XX XY BB bb
EX Man has an X and Y chromosome
Woman has 2 X chromosomes
Mutations occur when there is a change in the gene expressions or in the chromosomes
Genetics – study or science behind heredity and the probability to predicting offspring (children)studied by Gregory Mendel in 1860
Homozygous Dominant – 2 dominant genes ex BB, PP, GG
Homozygous recessive – 2 recessive genes ex bb, pp, gg
Hybrid or Heterozygous – 1 dominant gene and 1 recessive gene and expresses the dominant gene ex Bb, Pp, Gg
Punnett Squares – a process to determine the probability of a gene expression in gametes


Thursday May 17
DNA replication
is the process of copying a double-stranded DNA molecule. Both strands serve as templates for the reproduction of the opposite strand. This process occurs in all life forms with DNA.[1] There are some differences in the control of DNA replication in prokaryotic and eukaryotic organisms.

In a cell, DNA replication begins at specific places in the genome, called origins.[2] As the DNA unwinds at the origin, the synthesis of new strands forms at a replication fork. In addition to DNA polymerase,[3] other enzymes at the fork help to start and continue the DNA synthesis
The rules of base pairing (or nucleotide pairing) are: • A with T: the purine adenine (A) always pairs with the pyrimidine thymine (T)
• C with G: the pyrimidine cytosine (C) always pairs with the purine guanine (G)

This is consistent with there not being enough space (20 Å) for two purines to fit within the helix and too much space for two pyrimidines to get close enough to each other to form hydrogen bonds between them.

But why not A with C and G with T?

The answer: only with A & T and with C & G are there opportunities to establish hydrogen bonds (shown here as dotted lines) between them (two between A & T; three between C & G). These relationships are often called the rules of Watson-Crick base pairing, named after the two scientists who discovered their structural basis.

The rules of base pairing tell us that if we can “read” the sequence of nucleotides on one strand of DNA, we can immediately deduce the complementary sequence on the other strand.

The rules of base pairing explain the phenomenon that whatever the amount of adenine (A) in the DNA of an organism, the amount of thymine (T) is the same (called Chargaff’s rule). Similarly, whatever the amount of guanine (G), the amount of cytosine (C) is the same.

The C+G:A+T ratio varies from organism to organism (particularly among the bacteria), but within the limits of experimental error, A = T and C = G

Notes
DNA molecule – looks like a twisted ladder and contains the genetic code of an individual or organism and passes down genetic information from parent to off spring
DNA Replication= Deoxyribo nucleic acid and consists of a sugar, a phosphate group, and a nitrogen base and As the DNA unwinds at the 3′ side, the synthesis of new strands forms at a replication fork by adding new nitrogen bases.(599)
Nitrogen Bases – A with T: adenine (A) always pairs with thymine (T)
• C with G: cytosine (C) always pairs with guanine (G)
Replication – molecule first unzips and then 2 new DNA molecules form by adding free form nitrogen bases
1) nitrogen bases on one side are: AGTTCTCCAG what is the order on the other side?
2) If you have 23 pairs of chromosomes, how many are in every human cell? How many genes are on each chromosome?
3) How many are in every sex cell?
Meiosis – process that produces sex cells with half the number of chromosomes ( heredity)
Copy page 596 picture
Genes – are characteristics of an organism, units of heredity
Dominant genes – stronger genes Recessive Genes – weaker genes because they dissappear when thay are paired with a dominant gene
Law of segregation – one allele (trait) from each parent segregates or separates into each sex cell
Law of independent assortment – all gene traits are inherited independently of all other genes or traits (ex. Blue eyes – brown hair)
Some genes are co-dominant where both traits are expressed (blood) called incomplete dominance
Pheno type – The physical appearance of a gene or visible characteristics
Geno Type – the genetic makeup of an individual ex XX XY BB bb
EX Man has an X and Y chromosome
Woman has 2 X chromosomes
Mutations occur when there is a change in the gene expressions or in the chromosomes
Genetics – study or science behind heredity and the probability to predicting offspring (children)studied by Gregory Mendel in 1860
Wednesday May 16
QUIZ 1
QUIZ 2

Monday May 14 and Tues May 15
DNA replication

is the process of copying a double-stranded DNA molecule. Both strands serve as templates for the reproduction of the opposite strand. This process occurs in all life forms with DNA.[1] There are some differences in the control of DNA replication in prokaryotic and eukaryotic organisms.

In a cell, DNA replication begins at specific places in the genome, called origins.[2] As the DNA unwinds at the origin, the synthesis of new strands forms at a replication fork. In addition to DNA polymerase,[3] other enzymes at the fork help to start and continue the DNA synthesis
The rules of base pairing (or nucleotide pairing) are: • A with T: the purine adenine (A) always pairs with the pyrimidine thymine (T)
• C with G: the pyrimidine cytosine (C) always pairs with the purine guanine (G)

This is consistent with there not being enough space (20 Å) for two purines to fit within the helix and too much space for two pyrimidines to get close enough to each other to form hydrogen bonds between them.

But why not A with C and G with T?

The answer: only with A & T and with C & G are there opportunities to establish hydrogen bonds (shown here as dotted lines) between them (two between A & T; three between C & G). These relationships are often called the rules of Watson-Crick base pairing, named after the two scientists who discovered their structural basis.

The rules of base pairing tell us that if we can “read” the sequence of nucleotides on one strand of DNA, we can immediately deduce the complementary sequence on the other strand.

The rules of base pairing explain the phenomenon that whatever the amount of adenine (A) in the DNA of an organism, the amount of thymine (T) is the same (called Chargaff’s rule). Similarly, whatever the amount of guanine (G), the amount of cytosine (C) is the same.

The C+G:A+T ratio varies from organism to organism (particularly among the bacteria), but within the limits of experimental error, A = T and C = G



Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly equal shares of these cellular components. Mitosis and cytokinesis together define the mitotic (M) phase of the cell cycle—the division of the mother cell into two daughter cells, genetically identical to each other and to their parent cell. This accounts for approximately 10% of the cell cycle.

Mitosis occurs only in eukaryotic cells and the process varies in different species. For example, animals undergo an “open” mitosis, where the nuclear envelope breaks down before the chromosomes separate, while fungi such as Aspergillus nidulans and Saccharomyces cerevisiae (yeast) undergo a “closed” mitosis, where chromosomes divide within an intact cell nucleus.[1] Prokaryotic cells, which lack a nucleus, divide by a process called binary fission.

The process of mitosis is fast and highly complex. The sequence of events is divided into stages corresponding to the completion of one set of activities and the start of the next. These stages are prophase, prometaphase, metaphase, anaphase and telophase. During mitosis the pairs of chromatids condense and attach to fibers that pull the sister chromatids to opposite sides of the cell. The cell then divides in cytokinesis, to produce two identical daughter cells which are still diploid cells.[2]

Because cytokinesis usually occurs in conjunction with mitosis, “mitosis” is often used interchangeably with “mitotic phase”. However, there are many cells where mitosis and cytokinesis occur separately, forming single cells with multiple nuclei. This occurs most notably among the fungi and slime moulds, but is found in various groups. Even in animals, cytokinesis and mitosis may occur independently, for instance during certain stages of fruit fly embryonic development.[3] Errors in mitosis can either kill a cell through apoptosis or cause mutations that may lead to certain types of cancer.





DNA replication – DNA is the basic sunstance of heredity and stores and passes on genetic information from one gerneration to the next.
Watson and Crick discovered the sturcture of DNA in 1962
Nitrogen Bases – Adenine pairs with thymine, and Guanine pairs with cytosine
DNA Replication – process in which DNA makes an exact duplicate of itself
Allele – a form of a gene that expresses itself
Nondisjunction – the failure of chromosomes to separate from each other
Amniocentesis – the removal of a small amount of fluid from the sac surrounding the baby while it is still in the mother to determine if anything is wrong in the childs development
Gregor Mendel – the father of modern genetics who studied pea plants and determined that there are dominant and recessive genes
Genes – characteristics of an organism or units of heredity
Dominant genes – those genes that are expressed when present
Recessive Genes – those traits that are wesker and expressed less often

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Responses

  1. were can we watch the videos about moose jones

    • osmosis jones , scroll down to last week at bottom

  2. i ❤ math


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