Genetics Test

Time to apply what I've learned the last month (sigh... its only been 4 weeks of school?!!?).  I never like this part of learning... time restraints to solve questions.  Panic level just went up...

So, genetics.  Everything began somewhere, so let's start with the history:

1928: Griffith --> proteins do NOT carry traits

1952: Hershey and Chase --> DNA is the genetic material. Proteins are NOT the hereditary material

pyramidine - single ringed: cytosine, thymine

purine - double ringed: adenine, guanine

adenine = thymine

guanine ≡ cytosine

nucleotide = phosphate backbone, sugar, base

 

(difference of an OH group on carbon 2)

Bond types:

• glycosyl: sugar + nitrogenous base (CN) - intramolecular
• hydrogen bond: complementary nitrogenous bases; between nucleotides - intermolecular
• phosphodiester: sugar + phosphate (POC) - intramolecular

DNA replication is semi-conservative

1. helicase: unwinds DNA at replication fork
2. single-strand binding proteins (ssbps): attach to unpaired strands until replication begins
3. gyrase: enzyme that releases tension of unwinding but cutting the DNA strands and putting them back together again
4. primase: makes RNA primers --> signals elongation to
5. DNA polymerase III: elongates new DNA strands
6. DNA polymerase I: proofreads + converts RNA primers into DNA
7. ligase: joins gaps between Okazaki fragments (on lagging strand only)

DNA elongates ONLY in the 5' --> 3' direction

Template strand read 3' --> 5', creating a 5' --> 3' RNA strand

1. 5' TATA 3' box
2. transcription factors --> signals transcription to
3. RNA polymerase II: transcribes (don't want to stay in Toronto, but should go to University. Or else suffer getting disowned...) until
4. AATAA in the coding strand
5. 5'G cap
6. poly(A) tail
7. spliceosomes = snRNPs + snRNA: splice pre-RNA --> RNA
8. introns are OUT, exons are IN

This is pre-RNA/mRNA:

This is tRNA:

It is NOT from DNA. It floats.

RNA read in threes beginning at AUG --> Met

1. 5' AUG 3'
2. 40S ribosomal unit + 60S ribosomal unit = 80S ribosomal unit
3. P (Met), new tRNA at A, animo acid attaches to the one at A-->P-->E
4. stop codons (UAA, UGA, UAG)

Point mutation: change of ONE base pair of a gene

• base-pair substitution:
• silent mutation: no effect
• missense mutation: change amino acid
• nonsense mutation: stop codon
• frameshift mutation:
• insertion
• deletion
• inversion

(And now I have made my 10 points worth)

Deaf by Design

The first presentation of the year was given by Mr. Chung to show us what a Level 3 would look like.  If what he did was only a Level 3, then *sigh* we are going to have to work so much harder...
The presentation was on an article called Deaf by Design and was featured in Nature in 2004.  It introduced the situation of two couples with children opposite of what they wanted or expected (hearing couple with a deaf child and deaf couple with a hearing child) and a term called "deaf culture".  The controversial question behind the article was if a hearing fetus of a deaf couple should be aborted simply because it will be able to hear, or vice versa?
To me, when I was reading the article, I found the "deaf culture" to be very interesting.  It felt like it was a very unique group to be in.  While watching the video that was shown during the presentation, it was fascinating to watch all those hands and fingers dancing around, talking in a language that only certain people can use.  The video preserved the silence that they were in and there was a sense of calm in them not using their mouths but their hands.
Along with my fascination, I was enraged over the fact that expecting parents in the article would consider aborting their child due to something as small as being able to hear or not.  In my opinion, abortions should only be allowed if there are severe complications to the fetus.  I understand that deaf parents would be afraid of having a hearing child because it would mean that their child will be able to experience a side of the world that they never got a chance to.  Since they never experienced it, they fear that they might not be able to help their child and that will make their child drift further and further away from them.  However, if they teach the child and expose him/her to both hearing and non-hearing worlds, the child would get the best of both. They can live in the two societies and bridge the way for their parents to see the other side of the world.  The world is limitless, and losing one of the senses should not be a limiting factor.

BLAST FROM THE PAST: SBI3U

trait: a specific characteristic/feature represented by an organism

allele: a different form of the same trait

dominant: the form of a trait that always appear when an individual has an allele for it (BB or Bb)

recessive: the form of a trait that only appears when an individual has two (2) alleles for it (bb)

homozygous: an organism that has two (2) identical alleles of a gene (PP or pp)

heterozygous: an organism that has two (2) different alleles of a gene (Pp)

genotype: the combination of alleles for any given trait; the organism's entire genetic make-up   -----------------TRANSLATION----------------->

phenotype: the physical and physiological traits of an organism

Example: (respectively)

genotype: YY (homozygous dominant), Yy (heterozygous), yy (homozygous recessive)

phenotype: yellow seed, yellow seed [heterozygous: dominant is expressed], green seed

Parental (P) generation → First Filial (F₁) generation → Second Filial (F₂) generation

Punnett square: (a grid used to illustrate all possible genotypes of offsprings from genetic crosses)

test cross: a cross between a parent of unknown genotype and another of homozygous recessive genotype

Mendel's Law of Segregation: when gametes are formed, each must contain one allele from the two (2) of the parents

EXAMPLE: parent: Bb  possible gametes: B or b

Mendel's Law of Independent Assortment: if two (2) or more alleles are considered at the same time, the alleles have no influence over the separation of the others [disproven by linkage genes]

Law of Random Assortment: there is no telling in which gamete alleles will be in

incomplete dominance: first allele + second allele → new third allele (when heterozygous)

EXAMPLE: snapdragons (red + white → pink)

codominance: mix of first and second allele

EXAMPLE: roan horses/cows

multiple allelism: more than two (2) different alleles exist

EXAMPLE: blood types (A, B, O)

sex-linkage: alleles found only in the X chromosome has dominance over the Y chromosome

EXAMPLE: hemophilia

Cell → Nucleus → Chromosome → Chromatin → Gene → DNA→ Nucleotides ⤀ sugar, phosphate, nitrogenous bases

anti-parallel: 5-3 (other side) 3-5

Semi-conservative replication reduces the chance of genetic error because one strand of the original DNA is used as a template for the new, corresponding strand.