Inheritance
II. Connections
a. Gene Locus & Disulfide Bridge: A disulfide bridge is a bond between sulfur atoms in neighboring cysteine amino acids. This bond occurs in protein folding to create different proteins. DNA in the nucleus code for the making of proteins. DNA strands are very long and can code for various genes. A gene locus is the specific location of certain genes.
b. Non-disjunction & 9-triplet Pattern: Non-disjunction is the failure of sister chromatids or homologous chromosomes to separate in meiosis or mitosis. This results in daughter cells having too many or too few chromosomes. The microtubules that form the spindle fibers that attach to the kinetochores of the chromosomes are made in a 9-triplet pattern.
c. Autosome & Steroid: Autosomes are the other chromosomes in body cells that are the same in both sexes. This is similar to the steroids all people have in common, such as cholesterol. Steroids, such as estrogen and testosterone, that are gender specific are similar to the sex chromosomes are specific chromosomes that determine gender.
d. Polygenic & Glycocalyx: Polygenic inheritance is the inheritance of multiple genes that affect the same trait. This helps influence genetic variations in DNA, that leads to the evolution of cells, similar to the evolution of eukaryotic cells. Because eukaryotic cells are more developed than prokaryotic cells, they do not have a glycocalyx, which is a ,eshlike capsul around the prokaryotic cell wall.
III. Few Essentials
a. Mendel's law of segregation states that genes of homologous chromosomes are separated from each other during meiosis, so that one version of each ends up in different gametes. Mendel's law of independent assortment states that genes are sorted individually from other genes during meiosis. Both laws give rise to genetic variations of traits. The law of segregation during meiosis, when the chromosomes are being pulled apart to opposite poles of the cell so that they end up in different gametes. The law of independent assortment occurs after meiosis, when the chromosomes have already been sorted for distribution, and occur independently from other types of genes.
Sunday, February 13, 2011
Friday, February 4, 2011
Ch. 10
Cell Reproduction
II. Connections
1. Homologous chromosome & Duplicated chromosome
At the beginning of a cell's life cycle, a cell has 23 pairs of homologous chromosomes. A homologous chromosome is one chromosome in a pair that have the same genes, but one version given from the mom and the other version given from the dad. A duplicated chromosome is a pair of chromosomes that are completely identical to each other. A cell has duplicated chromosomes after S-phase, when all the DNA in a cell is copied.
2. Kinetochore & Microtubule Organizing Center (MTOC)
In an animal cell, the MTOC is a centrosome. This is the place where microtubule spindle fibers develop and grow. They connect to the kinetochores attached to the centromeres of the chromosomes during the prophase stage. The spindle fibers shorten starting from the centrosomes, pulling the chromosomes apart.
3. Haploid & Somatic
A somatic cell is any cell in the body that is not a germ cell. The only cells in the body that are haploid are gametes, or reproductive cells. Haploid cells only have half of the DNA a normal cell, or diploid cell, has. This is because the reproductive cells from the mom and from the dad will come together during reproduction and fertilize a zygote, a diploid cell.
4. Nucleosome & Dehydration Reaction
A nucleosome is a small stretch of DNA wound twice around a spool of proteins called a histone. Proteins are made up of amino acids linked together by peptide bonds. They form in a dehydration reaction because the OH molecule on the carboxyl group and the H atom in the amino group bond together forming water, which is lost during this processs
III. Few Essentials
1. Chromosomes during Meiosis
A. Prophase 1: chromosomes are in thread-like form; homologous pairs are together; swap segments
B. Metaphase 1: homologous chromosomes line up next to each other along the midway line of the cell
C. Anaphase 1: spindle fibers pull apart homologous chromosomes
D. Telophase 1: homologous chromosomes are now in different ends of the cell; all chromosomes are still duplicated
E. Prophase 2: no new DNA replication has occurred; spindle fibers attach to each chromosome
F. Metaphase 2: all chromosomes line up along the midway of the cell
G. Anaphase 2: attachment between sister chromatids of each chromosome breaks; one of each type of chromosome is moving towards the ends of the cell
H. Telophase 2: 4 cells result with a haploid number of chromosomes
2. Outline 10.4
I. Crossing Over in Prophase 1
A. All chromosomes in a germ cell condense in the same way
1. drawn close to its homologue
2. chromatids of 1 become stitched to chromatids of another
a. favors crossing over
3. 2 "nonsister" chromatids swap genes
B. Genes come in different forms- alleles
1. crossing over: chance to swap slightly different versions of information on gene products
2. crossing over leads to recombinations among genes of homologous chromosomes, and eventually to variation in traits among offspring
II. Metaphase 1 Alignments
A. major shufflings of chromosomes: transition from prophase 1 to metaphase 1
1. no particular pattern to the metaphase 1 positions of chromosomes
2. either homologous partner can end up at either spindle pole
3. 8,388,608 possible combinations of chromosomes
3. Similarities & Differences
Similarities
II. Connections
1. Homologous chromosome & Duplicated chromosome
At the beginning of a cell's life cycle, a cell has 23 pairs of homologous chromosomes. A homologous chromosome is one chromosome in a pair that have the same genes, but one version given from the mom and the other version given from the dad. A duplicated chromosome is a pair of chromosomes that are completely identical to each other. A cell has duplicated chromosomes after S-phase, when all the DNA in a cell is copied.
2. Kinetochore & Microtubule Organizing Center (MTOC)
In an animal cell, the MTOC is a centrosome. This is the place where microtubule spindle fibers develop and grow. They connect to the kinetochores attached to the centromeres of the chromosomes during the prophase stage. The spindle fibers shorten starting from the centrosomes, pulling the chromosomes apart.
3. Haploid & Somatic
A somatic cell is any cell in the body that is not a germ cell. The only cells in the body that are haploid are gametes, or reproductive cells. Haploid cells only have half of the DNA a normal cell, or diploid cell, has. This is because the reproductive cells from the mom and from the dad will come together during reproduction and fertilize a zygote, a diploid cell.
4. Nucleosome & Dehydration Reaction
A nucleosome is a small stretch of DNA wound twice around a spool of proteins called a histone. Proteins are made up of amino acids linked together by peptide bonds. They form in a dehydration reaction because the OH molecule on the carboxyl group and the H atom in the amino group bond together forming water, which is lost during this processs
III. Few Essentials
1. Chromosomes during Meiosis
A. Prophase 1: chromosomes are in thread-like form; homologous pairs are together; swap segments
B. Metaphase 1: homologous chromosomes line up next to each other along the midway line of the cell
C. Anaphase 1: spindle fibers pull apart homologous chromosomes
D. Telophase 1: homologous chromosomes are now in different ends of the cell; all chromosomes are still duplicated
E. Prophase 2: no new DNA replication has occurred; spindle fibers attach to each chromosome
F. Metaphase 2: all chromosomes line up along the midway of the cell
G. Anaphase 2: attachment between sister chromatids of each chromosome breaks; one of each type of chromosome is moving towards the ends of the cell
H. Telophase 2: 4 cells result with a haploid number of chromosomes
2. Outline 10.4
I. Crossing Over in Prophase 1
A. All chromosomes in a germ cell condense in the same way
1. drawn close to its homologue
2. chromatids of 1 become stitched to chromatids of another
a. favors crossing over
3. 2 "nonsister" chromatids swap genes
B. Genes come in different forms- alleles
1. crossing over: chance to swap slightly different versions of information on gene products
2. crossing over leads to recombinations among genes of homologous chromosomes, and eventually to variation in traits among offspring
II. Metaphase 1 Alignments
A. major shufflings of chromosomes: transition from prophase 1 to metaphase 1
1. no particular pattern to the metaphase 1 positions of chromosomes
2. either homologous partner can end up at either spindle pole
3. 8,388,608 possible combinations of chromosomes
3. Similarities & Differences
Similarities
- starting cell is a diploid cell
- all chromosomes are duplicated from interphase
- both use spindles to sort and move chromosomes
Differences
- mitosis ends with 2 diploid cells; meiosis ends with 4 haploid cells
- mitosis happens in any part of the body; meiosis only occurs in the reproductive organs
- mitosis: basis of asexual reproduction and growth and tissue repair; meiosis: required step before the formation of gametes or sexual spores
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