Wednesday, November 30, 2011
Tuesday, November 29, 2011
This is the process of DNA becoming tRNA.
- DNA Replication- Before a cell divides, it must first duplicate its DNA- replication
- Transcription- A molecule of DNA is copied into a complementary strand of mRNA
- Translation- tRNA anticodons (3 nucleotides) complement the mRNA and bring in the corresponding amino acids
- Protein Synthesis- Amino acid are bonded together to form a polypeptide
- ribose sugar
- 1 strand
- Uracil instead of Thymine
- smaller size than DNA- can go inside/outside nucleus
- 3 types- messenger- mRNA, transfer- tRNA, ribosomal- rRNA(its the one that form ribosomes)
1. Initiation- RNA polmerase attaches to the DNA promoter nucleotide sequence on DNA. RNA is synthesized
2. RNA elongation- RNA grows longer, peels away from DNA, DNA strands come back together (uses DNA as a template)
3. Termination- RNA polymerase reaches the terminator- end of the gene. polymerase molecule detaches from RNA molecule and the gene
in prokaryotes, RNA is ready(mRNA)
in eukaryotes, it needs to process it, add extra nucleotides
- cap and tail protect RNA from enzymes and help ribosomes recognize it as mRNA
- introns-non coding regions (useless junk)
- exons-are the coding regions
introns are removed before RNA leaves the nucleus=RNA splicing
- mRNA is now ready
Steps of Translation
- a mRNA binds to small ribosomal subunit. tRNA with attached amino acid (Met) (UAC) binds to start codon, AUG on mRNA
- large ribosomal subunit binds to small one, creating a functional ribosome
2. elongation- amino acids are added one by one to the first amino acid
3. a stop codon (UGA, UAG, UAA) does not code for an amino acid. tells translation to stop. Polypeptide is freed ( several hundred amino acid) ribosome splits into its subunits
DNA->RNA->Protein. genes determine the protein, which makes your appearance and your cell capabilities
- change in nucleotide sequence of DNA-a. base substitution- replacement of one base for another. no change, or critical, bad or good~b. base insertion or deletions- adding or subtracting nucleotides. often disastrous results- can disrupt entire sequences of triple pairing (insertions are always bad)
- mutagens- physical and chemical agents, such as UV light, x-rays, chemicals, carcinogens. can cause mutations. Can also lead to diversity. DNA errors are also due to unknown causes.
next scribe Dana
Monday, November 28, 2011
In class today we did notes for the new DNA packet on pages 1-10. We also watched a video about DNA crime solving techniques and how much more complex and complicated they are then the tv shows make them appear to be.
Thursday, November 17, 2011
Today in period 3 biology. Mrs. Andrews had the class turn in lab 35 which dealt with the previous lesson, pedigrees. The class than took guided notes on gene linkage and Theory of Inheritence. New terms and concepts were introduced such as gene linkage which refers to alleles that travel together on the same chromosome. An example of gene linkage would be orange hair and freckles. In humans many people who have red/organge hair also have freckles. This is due to both of the alleles being carried on the same chromosome. Another new concept was more of a revision of a previous one. The Theory of ineritence deals with the old concept that genes are located on chromosomes. The new part of this Theory was that the behavior of chromosomes during meiosis accounts for inheritence patterns.
Ms. Andrews also went over information about the Y chromosome. The Y chromosome is not a new concept but has never been studied by our class until now. Lots of new information about the Y chromosome were introduced. Some of these new facts include...
- The y chromosome is 1/3 the size of the x chromosome
- It only carries 1/100 as many genes as the x chromosome
- Evolved from autosomal, once a homologous pair until inversion occured.
- Y genes have dissapeared over the past 1 million years,shrinking the chromosome
(Notes are on moodle and on pgs. 14-15 in our genetic notes packet)
After the notes were taken the class recieved a list of papers to help study and review for this unit. The class was than given time to work on these worksheets and the assigned homework.
Homework: Pgs. 73-77+ 81-88 (due Monday)
EC. pgs. 79-80 (due Friday)
Study for quiz (Friday) and Test (Tuesday)
Next blogger..... Jack Stillman
Wednesday, November 16, 2011
Today Ms. Andrews explained Pedigrees. First she checked in UP pages 63-72. Then we went over the answers. If you missed it, try to check the answers with a friend. There is a quiz on punnet squares on Friday.
Tuesday, November 15, 2011
Sunday, November 13, 2011
- test crossing: the mating between an individual of unknown genotype and an individual of a homozygous recessive genotype
- test crossing is used to determine the unknown genotype
- probability: what is the chance that the offspring will exhibit a particular genotype of phenotype?
- What is the chance that two parents will have two girls? There is a 50% chance that each baby is female because the father can give the child either an X (the child is female) or Y chromosome (the child is male). Multiply 50% (or 1/2) by 50% (1/2) to get 25%. There is a 25% that both children will be girls.
- Punnett Squares are used to find the different possibilities of phenotypes and genotypes in the offspring of two parents.
Wednesday, November 9, 2011
-After the meiosis quiz we worked on UP pg. 41 & 42.
- First find out if you have that gene, then look on the back of the page (page 42) and figure out what letter corresponds with that trait.
- If you do have the gene write the capital letter, then an underscore. EX- for tongue rolling if you can roll your tongue write R_ because you could have RR or Rr, but you wouldn't know which combination you have unless you looked back a few generations and traced the gene.
- If you can't roll your tongue you would write rr because tongue rolling is a dominant gene and if you are unable to roll your tongue you have the recessive gene.
- The capitol letter is the dominant gene, and the lowercase letter is the recessive gene. If you have at least one dominant gene then you will get the dominant trait, so to have a recessive gene you must have both genes be recessive, or lowercase.
- Gregor Mendel was the 1st to analyze the patterns of inheritance scientifically
- He studied this while working with peas in a garden
- He realized that some of the pea plants had different characteristics such as flower color, stem length, flower position, and pod color
- By taking some of the pollen from the purple flowered peas and replacing it with pollen from the white flowered peas he discovered
-all of the first generation peas had purple flowers, and in the second generation one out of four of the pea plants had white flowers.
-the stem length, pod color, seed shape, seed color and other traits were randomly picked
Mandel's Two Principles:
- Mandel's principle of segregation: Pairs of alleles separate during gamete formation. (fuse again at fertilization)
- Mandel's principle of independent assortment: each pair of alleles segregates independently of the other pairs during gamete formation.
-key points to know about genetics:
- genes are inherited (passed on) from parents
- genes retain individuality generation after generation
- self vs. cross fertilization- self means only one organism is need, cross requires two organisms to reproduce
- hybrids are offspring of two different true breeding varieties (purebreds), EX. AA or aa
- Monohybrid crosses are one trait
- alleles are alternative forms of genes EX. A=purple flowers, and a=white flowers
- dominant vs. recessive, dominant genes mask recessive genes, so an Aa would look the same as someone who has AA
- Genotypes are the letters for the trait- AA, Aa, aa
- Phenotypes are the traits you can see (physical traits)
- Homozygous is the same- AA or aa vs. Heterozygous which is different- Aa
If you are confused, read UP pages 43 and 44
- Read ch. 9 Genetics, pg. 142-168
- Read over UP pg. 43 and 44
Tuesday, November 8, 2011
Today in class we: (1) Finished some notes and (2) did the Karyotype Lab. (3) Homework
(1) We finished the "mistakes" notes. We briefly reviewed the last page, Breakage of a chromosome. Here are the notes we finished today if you missed them...
It is pretty straightforward, the only "side-note" we took on this page was on "Translocation"-- we said that "trans" means "change". So, that side-note can help understand what Translocation is: if a fragment changes location/reattaches to a non-homologous chromosome.
--What is a non-homologous chromosome?
First of all, a homologous chromosome is simply a pair of chromosomes which are similar in size, and each one is from mom and dad (thus, 2). In addition to, homologous chromosomes have genes that call for similar characteristics (i.e. eye color). A non-homologous chromosome is one that is not a pair of chromosomes, is not from mom and dad, and that do not call for similar characteristics.
(2) Next, we started the Karyotype Lab (pgs. 19-37). In class, we only did pg. 19-23 (using your cutouts). For homework, we have to finish the rest up to pg. 37*
--What are karyotypes?
Now that homologous chromosomes are explained, karyotypes are basically just the arrangement of homologous pairs. On the right is a picture of a Male karyotype. Although the two pairs don't look exactly the same in shape (some a twisted, for example, more than others), they are the same. This is kind of what the finished lab looked like.
So, in the karyotype lab we matched the different chromosomes that we cut out and taped them onto pg 23. The chromosomes in this lab were in metaphase because in it, the chromosomes are in "best length for identification".
Study for Quiz
Finish UP p. 19-37
(EC: UP p. 39-40)
Read CH 9 p. 142-168
*Depending on the letter she assigned you (A, B, C, D)-- NOT ALL OF THEM!
≈NEXT SCRIBE: Maddy
Monday, November 7, 2011
- Independent Assortment- this is when each homologous chromosome pair is decided during metaphase 1 by chance. Each pair arranges itself independently of the other pair. This allows for much variety in the resulting gametes.
- Random fertilization- the random chance of which of the 8000 possible sperm will fertilize the egg
- Crossing Over- genetic recombination that occurs during prophase 1. It's when parts of the homologous chromatids exchange or switch.
- homologous chromosome - (in drawings, they are the chromosome pairs that look like little X's next to each other) 2 chromosomes that match are the same in size , shape, and sequence of gemes
- gametes-a haploid cell created as a result of meiosis (the four cells that we see at the end of meiosis diagrams are gametes
- haploid cell- cell with half the number of chromosomes
Friday, November 4, 2011
Today we started notes for meiosis. You should have read Chapter 8 in the textbook already, which talks about mitosis and meiosis. Mitosis is still very important to know about, so GO BACK AND STUDY IT! Here are some of the important parts of today's notes:
(Note: know what the terms in purple mean)
- Mitosis has two divisions. The first division is the reduction of chromosomes and the second division is when the sister chromatids separate. The stages in the first division are:
- Interphase: G1 (when the replication of chromosomes has not happened yet); S (synthesis - the DNA replicates); G2 (final preparation)
- Prophase 1: There are 4 chromosomes in the parent cell, which means that there are 8 chromatids
- Metaphase 1: Homologous chromosomes (chromosome pairs) line up (differently from mitosis, as shown in the picture - they line up with their pair).
- Anaphase 1: The homologous chromosomes separate. The chromatids stay together because the centromeres are still intact
- Telophase 1/Cytokinesis: The nuclear envelope comes back and 2 daughter cells are produced
There is no second interphase GI or S between the two divisions
The second division is similar to mitosis. The stages of the second division are:
- Prophase 2: Each daughter cell has 2 chromosomes (which is why the first division is a "reduction") and 4 chromatids
- Metaphase 2: The chromosomes line up (this time, the same as mitosis)
- Anaphase 2: The chromatids separate
- Telophase 2: In each of the 4 daughter cells, there are 2 chromosomes and no chromatids (this is because a chromatid is held together to a sister chromatid by a centromere). Each of the 4 daughter cells are genetically different
- Meiosis is the production of egg and sperm cells (which are gametes). It is sexual reproduction and produces a variation of offspring
- Each sperm or egg (sex cell) has half the number of chromosomes (23) as somatic - body - cells (46)
- Homologous chromosomes are 2 chromosomes that match in size, shape, and sequence of genes (remember that "homo" means "same")
- A tetrad is when 2 homologous chromosomes pair together. They are most likely to cross over during Prophase 1 (it is improbable, but not impossible for them to not cross over)
- Crossing over is essential for genetic variation (so you can look similar to your mom/dad but not identical)
- There are sex chromosomes (usually 2, non-matching pair) and autosomes (body cells, usually 44 in a human, paired)...2 + 44 = 46 chromosomes
- Diploid: the total number of chromosomes
- Haploid: half the number of chromosomes
- There is only 1 duplication of chromosomes but 2 divisions in meiosis
- At the end of Meiosis 1, there is haploid number, but there are still double chromosomes
- At the end of Meiosis 2, there are 4 daughter cells (genetically different), haploid, and single chromosomes
- The variety in species is because of:
- Independent assortment - when homologous chromosomes pair at Metaphase 1, it is by chance. The effect is that the resulting gametes have a variety. Each one has 2 to the 23rd, or 8 million possible combinations!
- Random fertilization - 1 egg/8 million fertilized by 1 sperm/8 million is about 4 trillion combinations!
- Crossing over - the exchange of segments by homologous chromatids in genetic recombination, happens during prophase
Homework: Finish Spice Lab Report, UP 3-7, UP 9-11, cut out UP 21 (don't lose any - put them in an envelope, bring to class on Tuesday 11/8), UP 15-16B, and study mitosis and meiosis
Next Scribe: Vinise