Cell Division & Molecular: IB content

Mother Cell

The original cell that is divided to produce daughter cells originate. Also called the parent cell

Cleavage furrows

The region that pinches an animal cell during cytokinesis

Cell plate

The new cell wall that is built to split up a replicated plant cell in cytokinesis

Contractile actin & myosin proteins

The ring that pinches an animal cell during cytokinesis.

• the ring is made of the former

• The former is made of the latter

Vesicles for division

These carry additional cell membrane and cell wall parts to build the cell plate

Anuculeate cells

Cells without a nucleus

Elongated DNA

Another term for chromatin

Condensation

The process where loose DNA is packaged into chromosomes

Histones

The proteins DNA supercoils around during cell replication

Supercoiling

A ± value that represents how tightly wound packaged DNA is. Most DNA is slightly -.

• + : over-winding

• - : under-winding

Microtubules

Structural hollow tubes that form the cytoskeleton of a cell, giving it structure and forming the spindle fibers

Microtubule motors

Proteins that transport all kinds of cargo along microtubules (it’s the cvnty walking protein from the memes)

Down-syndrome

A genetic disorder with an additional 21 chromosome caused by non-disjunction. Called trisomy-21

Recombinant chromatids

The term for chromatids having undergone the crossing over

Proliferation for growth

Fancy term for the fact that cells replicate so the organism can grow

Biosynthesis of cell components

When cells produce molecules (lipids, proteins, nucleic acids) to carry out their functions and build structures

Cyclins

A group of proteins that control the cell’s progression through the cell cycle.

They bind to CDKs so they can act as enzymes

CDKs

Cyclin-dependent protein kinases.

When bound to cyclins, they can act as enzymes for the cell cycle, telling the cell to proceed to the next stage of interphase

Checkpoints

The points in the cell cycle where CDKs are activated

Proto-oncogenes

A cell that has the potential to become an oncogene

Oncogenes

A section of genes that can mutate the become cancerous by causing cells to divide more frequently than they should

Tumour suppressor genes (TSGs)

Code for proteins that regulate the cell cycle and prevent cells from becoming cancerous

Metastasis

A pathogen or tumour that has spread from its original location to another location on the organism

Benign

Cells are forming a tumour but they’re not spreading to the rest of the body

Malignant

If the cells rupture the organ they’re in and spread to the rest of the body

1° tumor

One that occurs at the original site of the cancer

2° tumor

One that has spread from the original site to a new one

Mitotic index

The ratio of cells undergoing mitosis over the amount of cells

Chimpanzee chromosome #

Diploid cells: 48

Haploid cells: 24

Karyotyping

A test to map the genes of a cell

Karyograms

A visual representation of a cells chromosomes arranged in a standard format

Genomes

All the genetic information in a cell

Single-nucleotide polymorphisms

Where a single nucleotide differs in at least 1% of the population.

Personalized medicine

AKA precision medicine, when medical professionals use the known genetic sequence of their patients to help prescribe more effective treatments

Parthenogenesis

Females reproducing asexually

Covalently bonded atoms

• a strong bond between two or more non-metal elements

• In DNA, molecules within the strands are this, and hydrogen bonds connect the bases

Nucleotide

One building block of DNA

Contains:

• a phosphate group

• A deoxyribose sugar

• A nitrogenous base (A, T, C, or G)

Nucleosomes

During cell replication, a DNA packaging unit comprised of ~146 base pairs around 8 round histones and held by one long histone

Hershey-Chase

An experiment that proved DNA is the genetic material being inserted by viruses during infection using radioactvity

Chargaff’s Rule

DNA contains equal amounts of A & T, and equal amounts of C & G

“Problem of induction”

A philosophical problem, that questions the justification for our belief in future events based off past observations. We cannot logically prove the future will resemble the past.

“Certainty of falsification”

A philosophical concept; things can only be seen as true so long as it has not been proven false, and every scientific law we observe holds a disclaimer that it will only be a law so long as we haven’t found proof of its falsity.

Tetra-nucleotide hypothesis

Suggested that nucleic acids were composed of the repeating sequence of four nucleotides with equal amounts of each of the four bases ATCG

• this theory led scientists to believe DNA was too simple to hold genetic material, instead believing proteins were the source.

70s Ribosomes

The smaller than eukaryotes ribosomes found in prokaryotes (bacteria, archaea), mitochondria and chloroplasts

Naked Circular DNA

Prokaryotes have a continuous loop of DNA without histones

Polymers of nucleotides

Think about the breakdown of those individual words

DNA and RNA

Helicase

The enzyme responsible for unwinding and unzipping DNA

DNA polymerase I

• removes RNA primers

• Fills those gaps with DNA nucleotides

• Repairs damaged DNA

• Slow

DNA polymerase III

• Main replication enzyme

• Synthesizes new DNA strands 

• Completes long stretches very quick

Polymerase chain reaction (PCR)

A lab technique using a thermocycler machine to make many copies of a small amount of DNA

Taq DNA polymerase

a polymerase from a bacterium found in hot springs (withstands heat), one of the components to run a PCR

Gel electrophoresis

A lab technique used to separate DNA fragments to identify its origin. Enzymes chop up DNA so that it can be put into an electrical chamber that separates them into wells. 

How we can do paternity tests

Continuous vs. Discontinuous replication of the strands

leading strand vs lagging strand

DNA proofreading

Done by the DNA polymerases

RNA polymerase

The enzyme that opens up DNA for the creation of mRNA and synthesizes mRNA

Degeneracy

For each amino acid, there may be more than one codon

Universality

With a few exceptions, all life shares the same genetic code

Small vs. Large ribosome subunit

Small: mRNA bonds to this

Large: where the tRNA and their proteins come in

Elongation

The Taq polymerase catalyst the building of new DNA strands by extending the primers

5’ to 3’ transcription

During the formation of mRNA, the 5’ end of the mRNA is synthesized

3’ to 5’ translation

During the formation of proteins, the mRNA is read from the 3’ end to the 5’ end

Telomeres

Useless ends of chromosomes that exist to protect the actual important stuff from famage

Genes for rRNAs

• found in the DNA of all cells

• transcribed to form rRNA molecules and the proteins made form ribosomes

Genes for tRNAs

• transcribed from DNA to form tRNA

Splicing

Process of removing sections of introns from primary mRNA to make sure its ready.

5’ caps

• Protective strand on the 5’ end of mRNA

• Helps move the mRNA from nucleus to ribosome

• Helps ribosomes attach to mRNA

3’ polyA tails

• Protective strand on the 3’ end of mRNA

• Helps move the mRNA from nucleus to ribosome

• Helps mRNA be efficiently translated into proteins

Stabilize mRNA transcripts

To make sure mRNA doesn’t degrade:

• 5’ caps

• Poly-A tail

• RNA binding proteins

A binding sites for tRNA on the ribosomes

The first binding site

• holds the the tRNA carrying the next amino acid to be added to the polypeptide chain

P binding sites for tRNA on the ribosomes

Second binding site

• Holds the tRNA carrying the growing polypeptide chain

E binding sites for tRNA on the ribosomes

Third binding site

• Discharges the tRNA that has lost its amino acid

Pre-proinsulin vs. Proinsulin vs. Insulin

In order, these three things are what forms the final product

Through a process of removing a signal peptide it 1 becomes 2

2 is exposed to enzymes that break peptide bonds to form 3, which is pretty small.

Proteasomes

The cellular organelle that breaks down marked (damaged or unused) proteins into amino acids

Single-nucleotide polymorphisms (SNPs)

When a genetic sequence is altered by one letter only

Chemical mutagens

When exposure to certain chemicals damages genetic material

Mutagenic forms of radiation

when exposure to radioactivity causes bases in genetic material to rearranged

Commercial genetic tests

Tests run to detect genetic mutations, find ancestry and paternity

(Not always 100% accurate)

Gene knockout

When we render a gene inoperable in to see what happens to learn what it’s responsible for

Inoperative

Unable to carry out its normal function

CRISPR

A process the can perform cut, copy and paste with any gene

Clustered Regularly Interspaced Short Palindromic Repeats (the mini sections that are this things namesake)

Still novel, with some ethical issues, but it has potential to fix genetic disorders

Enzyme Cas9

Works as DNA scissors in the CRISPR process

Gene editing

A process done to modify genetic sequences, often for improvement

Conserved sequences in genes

DNA stretch that has changed very little of over evolutionary time

Highly conserved sequences in genes

DNA sequences that is nearly identical across many species

Promoters

• A region of DNA that determines which strand will be the template

• On any gene, the promoter is always on the same strand

• A short sequence of bases that is not transcribed 

Enhancers

Tells the DNA when a genetic sequence should be expressed

Transcription factors

Proteins that regulate gene expression by promoting or inhibiting the binding of RNA polymerase to DNA

Nucleases

Enzymes that break down nuclear acids by hydrolysis the bonds between the nucleotides

Degradation of mRNA

A process to destroy mRNA that is unnecessary

Epigenesis

The process that results in the formation of organs and specialized tissue from a single undifferentiated cell.

Genome

All the genetic information of an organism

Transcriptome

All the RNA that a cell makes for its specific region

Proteome

The entire set of proteins that is or can be expressed by a cell, tissue or organism

DNA Methylation

The process by which a methyl group is added to a DNA nucleotide

Epigenetic tags

A methyl group that flags part of the DNA, sometimes making certain parts of the DNA unable to be expressed

• if on the cytosine in the DNA of a promoter, the rest of the gene can’t be read

Histone modification

Chemical changes to these proteins that alter chromatin structure and regulate gene transcription

Alteration of methyl tags

Adding or removing these on DNA or histones to regulate gene expression without changing the DNA sequence

Tigons/ligers

• Male tiger + female lion = smaller hybrid

• Male lion + female tiger = enormous hybrid

Monozygotic twins

Another term for identical twins

Tryptophan in bacteria

Acts as a corepressor that binds to the trp repressor protein, enabling it to inhibit transcription of the trp operon