bio 3

Mitosis

Mitosis

two daughter cells produced are identical and produced from parent. Prokaryotes

what triggers life cycle in cells

this happens when a signal is made that a cell needs replaced/cells need made. If injured, this signal is sent to replace the cells that died/were injured. They are in g1 and enter next phase when signal is sent.

most cells are in this phase and they do ____

g1 phase - they function/grow in this phase

how does cancer happen/why is it so hard to treat

something dignals the cell to come out of g1 and mvoe into the growth phase. Hard because unsure of what causes it, so cant stop it.

Interphase

S portion (synthesis of DNA occurs) and G2

happens to eukaryotic diploid cells

you have chromosomes in the nucleus, and the chromosomes replicate.

microtubules hold it all together

diploid

pair of chromosomes pauses in this phase and enters G2 phase.

centromere

structural protein that holds the chromosomes together.

kinetochore

part on centromere where the spindle fibers attach to chromosomes

sister chromatids

the DNA replicates

G1

growing/functioning - preparatory phase

M phase

mitotic cell phase - actual division

S phase

Actual duplication/synthesis occurs

G2 phase

very short, known as lag phase. cell with 2 copies of DNA

Parts of M (mitotic) phase

prophase

metaphase

anaphase

telephase

• then cytokinesis happens, but not formal part of this phase

Prophase

Chromosomes condense (DNA is unwound, but here specifically made to wrap around proteins to keep organized during division)

nuclear envelope breaks down

microtubles attach to kinetochore

Metaphase

all sister chromotids are moved to the central plane/metaphasal plate.

all chromosome pairs line up via microtubules moving them around

Anaphase

sister chromatids (chromosome pairs) move away from eachother and go towards poles (they break apart)

Telophase

nuclear envelope reforms; microtubules release grip on chromatids

Cytokenesis

cell physically divides into 2

Meiosis

this is one parent cell thats a diploid produces 4 haploid cells (reproductive cells egg/sperm or egg/pollen). This actually has variation and is used by many eukaryotes while mitosis is used by prokaryotes.

What happens prior to Meiosis 1

the DNA replicates (S phase)

Meiosis 1

the sister chromotids crossover, meaning that their genetic information gets shuffled. This leads to variety in the DNA, therefore making them not clones. This reshuffling is what differentiates Meiosis from mitosis (prokaryotes). Reshuffling is critical in reproduction. This contains a prophase, a metaphase, and a telophase

• chiasmata formation

• prophase 1 is when recombination occurs

• metaphase 1 is when the homologous chromosomes stay. They don’t line up on any plate or anything

• telophase 1 is when this parent cell is split into 2 cells

Chiasmata

the sister chromatids line up in this (chiasmata) they recombine in prophase 1. This is the position that allows for recombination

Meiosis 2

Prophase 2: As the sister chromotids are still attached, the nuclear envelope breaks down

Metaphase 2: the nuclear envelope completely dissapates

Anaphase 2: Now the sister chromotids finally break/split apart via spindle fibers pulling them apart

Telophase: cell divides, now there are 4 cells compared to the 2 that started Meiosis 2 and 1 that started Meiosis 1. There are now 4 haploid cells (gametes/not paired/egg/sperm/pollen)

Gregor Mendel

Austrian Monk that did work in 1880. Worked with plants, particular garden peas and snapdragons, while working in the monestary. He would cross plants and pollenate them with a brush instead of letting bees do it.

Mendelian genetics focuses on ____.

focuses on diploid eukaryotes

genotype

actual DNA code like PP or Pp or pp

phenotype

physical expression or genotype (purple, pink, white, yellow, green, tall, short, etc)

gene

a piece of DNA that codes for a trait. Many genes in one strand of DNA.

allele

a form of the trait (ex: purple is a form of flower color, tall is a form of flower height)

How did Mendel try to ensure accuracy/eliminate potential contamination or inconsistencies

he isolated his plants for years to make them homozygous so there were no carriers. true breeding plants = homozygous.

example of a haploid gamete/diploid gamete

P in PP (only 1 P, one contribution of sperm/egg/pollen). PP together is diploid (both contributions)

Di-hybrid in relation to Mendel

he did a di-hybrid for color and seed shape. complete dominance

Sex linked traits

attached to the X and Y. Example is hemophilia. Hemophilia is recessive and carried on X. Men are far more suseptible to this because they dont have a second X to potentially have a dominant trait (no hemophiia/normal clotting) and mask the hemophilia.

Epistasis

Common in nature. When there are 2 genes; coat color for example and whether pigment is expressed. example is labs (Black BBE_, brown bbE_, yellow doesn’t matter what the B/bs are, just that there is no pigment (__ee)

Incomplete dominance

RED, Pink, white

Co-dominance

both show up equally but not mixed; roan cows

DNA Synthesis

happens in S phase (S for Synthesis)

• Each original strand serves as the template for a new strand

1) DNA strands (2 together to form that iconic helix) unwind/split. this is done using helicase (an enzyme) Helicase splits at replication forms/replication bubbles

2) DNA polymerase does to replication fork and reads the exposed nucleotide bases It adds the appropriate complementary strand (a-t, c-g)

3) Rule of DNA replication is that a new nucleotide base cant be added to a 5’ end.

4) Ligase fills in any missing fragments of DNA on lagging strand, therefore completing the complementary strand.

5) now have 2 copes of original DNA strand

why is there a 5’ and a 3’ end/what dictates that

5’: this happens when the phosphate coems off the 5th carbon

3’: this happens when the phosphate comes off the 3rd carbon

amount of chromosomes and how many are somatic/sex

23 pairs (46 total) in each cell

22 of those pairs are somatic (coding for body parts and stuff

1 pair is sexual (XX or XY)

what type of bond is formed between the bases on the DNA strand

hydrogen bonds

3 main key points for DNA Synthesis

1) OG strands serve as templates

2) Helicase (unzipping DNA strand), DNA Polymerase adds free floating nucelotides to form new strand, Ligase assembles the Okazaki Fragments on the lagging strand and zips these strands back together

3) All of this occurs during the S phase

Nucelotides for DNA can only be added to what end

they can only be added to the 3’ end - why there is a lagging strand

Semi-conservative replication of DNA

considered this because the new DNA strand is only ½ replication and ½ older DNA strand that already existed

DNA replication takes about how long in mammals and is about how accurate

about one hour - only 1 error out of 1 billion nucleotides (known as mutation or error rate)

what happens after DNA replication

the new DNA molecules are checked over for mistakes. Mistake usually is a nucleotide mismatch. this is corrected using a mismatch repair. This mismatch will occur on the new strand when the free floating nucleotides are being added.

How does correction occur after DNA Synthesis

the cell can note the difference between nucelotide bases. Theyll mark this mismatch using a methyl group similarly to how people circle test questions they want to go back to. Cell later comes back to the mismatches (marked using Methyl group) and removes/replaces them.

Okazaki Fragments

new strand on DNA can only be built in 3’ to 5’ direction. DNA Polymerase only goes one direction. This works out for one strand because this stand would be 3 to 5 and DNAPoly would be moving 3 to 5 as well. The other strand would be 5 to 3 though, so as DNA Polymerase moves, It needs to kind of backtrack. This leaves gaps in lagging strand that Ligase fills later.

Protein Synthesis Overview

Process happens in three stages: Transcription, Translation, and Elongation

This involves taking genetic code and turning it into a protein

DNA serves as template for this, but RNA is eventually used/necessary.

RNA is single strand and uses Uracil for Thymine

Protein Synthesis Step 1: Transcription

Happens in nucleus

1) DNA is unzipped using Helicase. It is only unzipped where the gene/DNA is that is being transcribed

2) one DNA strand serves as template. This process starts where the promoter site/primer is (promoter site serves as a signal to tell RNA Polymerase where to begin transcription) This site is sey by primase enzyme

3) new strand is made using RNA Polymerase. RNA Poly pulls in free floating nucleotides, using Uracil instead of Thymine. This creates a strand of Messenger RNA

4) mRNA transcript leaves nucleus and moves to ribosomes, there protein synthesis occurs

In Protein Synthesis, DNA serves as the template. Can that template be reused?

The DNA strand serving as a template can be reused several times. This is good for (example) when someone needs lot of lactate, etc. This template can be reused to make process more efficient.

Prime ends direction

reads strand in 3-5 direction. forms new strand in 5-3 direction to complement 3-5 original strand.

Protein Synthesis Stage 2: Translation

1) the mRNA strand that was made in transcription attaches to ribosomes. ribosomal RNA (rRNA) acts as the structural portion of the ribosome.

2) the mRNA strand is read and the corresponding Amino Acids are assembled on the ribosome (the mRNA strand in read in codons, each set of 3 nucleotides being a codon. Each Codon codes for an amino acid (table showed in class) or a stop codon

• mRNA is laid on the ribosome’s small subunit that is in 3 sections (starting at the E site, then P site, then A site). In each of these three sections is one codon.

• the ribosome moves along the mRNA strand reading the codons. The codons click into place in these three sections.

• Amino acids are brought to ribosome. How? tRNA (transfer RNA) has an anti codon attached to correct amino acid via peptide bond. If the codon is AUG, then the tRNA anticodon will be UAC

Methionine

AUG and means “START” during protein synthesis process

Protein Synthesis Stage 1a

between transcription and translation. the mRNA is processed. the non-coding sections (known as intervening regions or introns) are removed. After removal, the mRNA is now processed. This processed mRNA is now comprised of exons only (sections that do code/stay), and the mRNA moves from nucleus and ribosome

Universal Genetic Code

chart in class. Ex: Pro is Prolene. UAA is stop, etc

Protein Synthesis Stage 3: Elongation

This is the elongation of the amino acid chain. As each tRNA brings the amino acids to the ribosome, the amino acids are in close proximity to eachother. They are so close that they form peptide bonds (the A.A. that are adjacent to eachother form Peptide bonds). This bonding creates a chain. This continues, and the chain of AA becomes longer as more are brought by tRNA and bonded because of proximity. This AA/protein chain grows until the “STOP” codon is reached. This stop codon says to stop adding AA and to release chain. The chain is then released, and it folds into a 3D shape/large protein of tertiary nature

Why is genetic coding so accurate?

proofreading and redundancy in genetic code. In a codon, there are 3 nucleotide bases. That third Nucleotide base rarely matters. UCU, UCA, UCG, and UCC all code for the same thing (serine). If there is a mistake in the last nucleotide base, it will almost definitely go unnoticed. Known as silent mutation. If in the first 2, there may be noticeable difference/mutations.

Mendels Law of Segregation

Mendels work lead to laws of inheritence, particularly law of segregation. Law of Segregation states that the alleles in diploid adults segregate/seperate from eachother when forming gametes that are haploid. EX: PPxpp forms Ppx4. The 2 P’s in PP seperate, the 2 p’s in pp seperate and go into the haploid Pp.

Backbone of DNA

sugar, phosphate group, hydroxyl group, ?

Relationship between DNA and Protein Synthesis (?)

DNA has genetic code, but is unable to carry it out for the most part. Protein is about to take that code, transform it into a usable form, and uses it to carry out bodily functions. DNA is template, but protein is needed to actually put that code to any use/apply it.