Exam 3

Question 1

Mitosis

Answer 1

The division of the nucleus

Question 2

Cytokinesis

Answer 2

Division of the cell where the cell membrane and cytoplasm divide into 2 cells, each containing a full complement of organelles and DNA. Usually accompanies mitosis, but not always. In some species, it is a separate process entirely from mitosis. In animal cells, the cell membrane “pinches in” to completely surround each new daughter cell, each of which will have the same number of chromosomes as the parent cell. In plant cells, a new cell wall grows between the two daughter nuclei.

Question 3

Cell division

Answer 3

Not the same as mitosis! The process by which a cell reproduces itself.

Question 4

Why is cell division important?

Answer 4

For normal growth, development, and repair of an organism: cell replacement since most cells have a finite lifespan, to heal wounds by replacing cells lost to injury. In unicellular organisms cell division is a means of reproduction.

Question 5

What are the phases of The Cell Cycle?

Answer 5

Broadly, interphase and mitosis+cytokinesis. Specifically within interphase: G1 Phase (cell enlarges, creates additional cytoplasm, and begins to produce new organelles), S Phase (s stands for synthesis, and DNA replication occurs, with each chromosome being replicated to produce 2 identical sister chromatids), G2 Phase (the final prep stage in which the cell prepares for division and checks if all chromosomes replicated properly). Mitosis is referred to as M Phase.

Question 6

Where does the cell cycle begin?

Answer 6

Interphase, where cells spend ~90% of their life span. Specifically, in the G1 Phase of interphase, where the “parent” cell begins the preparation for dividing into two new daughter cells.

Question 7

Describe the relationship of chromosome replication steps to each other

Answer 7

Standard chromosome is a single “arm”
/line” which means it is unreplicated. The famous chromosome X picture is actually of sister chromatids, still attached at their centromere, and after replication is finished, the sister chromatids separate from one another, setting up the two identical nuclei of the daughter cells.

Question 8

Sister chromatids

Answer 8

1/2 of a replicated chromosome. Product of DNA replication. Slide definition: one of the two identical DNA molecules that make up a duplicated chromosome following DNA replication.

Question 9

How many chromosomes are present in slide 10 of the lecture notes, in both cells?

Answer 9

6 in the first, 6 in the second. The second has 12 sister chromatids.

Question 10

Can you have mitosis without cytokinesis?

Answer 10

Yes, while it’s the exception and not the rule, it is not uncommon. Common example is human muscle cells, which contain multiple nuclei.

Question 11

Centromere

Answer 11

The place where sister chromatids are joined together: commonly depicted at the center, but can be anywhere.

Question 12

Interphase

Answer 12

Each chromosome replicates in late interphase (S-phase) resulting in two sister chromatids connected at the centromere
-chromosomes are loosely gathered in the nucleus

Question 13

Phases of mitosis: (definitions in following cards)

Answer 13

-prophase
-prometaphase
-metaphase
-anaphase
-telophase

Question 14

Prophase: (remember that for each part he wants to know what’s happening with the DNA, the mitotic spindle, and the nuclear envelope).

Answer 14

Here the DNA condenses into visible chromosomes (coiling up), and the protein fibers (microtubules) of the mitotic spindle begin to form.

Question 15

Mitotic spindle

Answer 15

A special organization of microtubules from the cytoskeleton that attach to the cell’s poles and attaches to the sister chromatids’ centromere and pull them apart during mitosis.

Question 16

Describe the significance of the nuclear envelope and cytoskeleton in mitosis:

Answer 16

DNA is housed in the nucleus. The cytoskeleton is in the cytoplasm. For the mitotic spindle to access DNA, the nuclear envelope must ”get out of the way.”

Question 17

Prometaphase:

Answer 17

The nuclear envelope begins to disassemble, and the spindle microtubules attach to chromosomes on both sides of the chromosome’s centromere.

Question 18

Metaphase

Answer 18

Chromosomes align along the middle of the cell (on the metaphase plate). Spindle fibers attached at opposite ends of the cell pull on chromosomes.

Question 19

Anaphase

Answer 19

Microtubules shorten and pull sister chromatids to opposite poles of the cell.

Question 20

Telophase (remember it’s 3 parts)

Answer 20

Chromosomes uncoil and return to the loosely packaged form they were in during interphase, spindle fibers disassemble (these microtubules return to their usual structural and transport function), and the nuclear envelope re-forms around each set of chromosomes, forming the daughter cell nuclei.

Question 21

Cell cycle checkpoints

Answer 21

These ensure that each stage of the cell cycle is completed accurately: a system of checkpoints regulates the cell’s progression to the next stage, making sure the current was accurately finished.

Question 22

Apoptosis

Answer 22

Programmed cell death which happens when a normal cell has irreparable damage.

Question 23

Cancer

Answer 23

Disease of unregulated, uncontrolled cell division. Cells divide inappropriately and accumulate, in some instances forming a tumor. Cancer cells have damaged checkpoint mechanisms, allowing them to divide when they shouldn’t. These damaged cells also bypass apoptosis, passing damaged DNA to each daughter cell. Caused commonly by mutation, radiation, carcinogens.

Question 24

Chemotherapy

Answer 24

Takes out every rapidly-dividing cell including healthy ones, not just cancer. This is why SEs are so awful, especially in digestive tract, hair follicles, and bone marrow.

Question 25

Radiation therapy

Answer 25

XRT babyyyy

High-energy radiation beams are used to kill dividing cells, severely damaging molecules and DNA to trigger apoptosis.

Question 26

Basic overview of flow of genetic information

Answer 26

-information content of DNA is in the form of specific sequences of nucleotides.
-the DNA inherited by an organism encodes proteins which control specific traits.
-As he likes to say, DNA encodes proteins and proteins do stuff!

Question 27

Genotype

Answer 27

Genetic makeup of that organism

Question 28

Phenotype

Answer 28

The physical characteristics of the organism

Question 29

Gene

Answer 29

A sequence of DNA that contains the instructions to make a protein, specifically a section containing a nucleotide sequence with instructions to make at least one protein. Chromosomes consist of many genes along their length. Each gene carries instructions to make at least one protein.

Question 30

My own gene expression definition

Answer 30

The process by which information stored in a gene is used to synthesize a functional product such as protein or RNA molecule.

Question 31

His slide definition of gene expression

Answer 31

When the cell uses DNA instructions to make proteins. When a gene is turned “on,” or expressed, the encoded protein is produced. Broadly the process of converting the genetic information of DNA into the sequence of a protein. It has two main steps: transcription and translation.

Question 32

The Central Dogma of molecular biology/protein synthesis

Answer 32

genetic information only flows in one direction: DNA->mRNA->protein.

Question 33

Translation

Answer 33

The synthesis of a protein, occurring under the direction of mRNA. There are 4 elements: the producing ribosome, mRNA, tRNA, and the resulting protein. In eukaryotic cells, the mRNA copy leaves the nucleus after RNA polymerase has unzipped the DNA double helix and copied the specific gene that is needed to build a specific protein (process of transcription). mRNA then enters the cytoplasm and is taken to the ribosomes where rRNA binds to mRNA, and then transfer tRNA with the complementary anticodon to the the mRNA codon brings the next amino acid specified by mRNA. The next amino acid is covalent bonded to the growing protein. Then when the protein is finished (stop codon), it detaches from the ribosome and folds into its 3D shape.

Question 34

Protein

Answer 34

A macromolecule made of repeating subunits known as amino acids. Remember, the shape of a protein determines its function. To some extent, changing the shape changes the function, but only in some cases.

Question 35

Amino acids

Answer 35

There are 20 different amino acids, all of which have the same basic core structure, but each also has a unique chemical side group. Amino acids determine the shape and function of a protein. The sequence of amino acids is unique to each protein, and the amino acid chain folds into a 3D protein based in the sequence. They bind together with covalent bonds.

Question 36

Where does gene expression occur?

Answer 36

-transcription occurs in the nucleus of eukaryotic cells (the mRNA copy leaves the nucleus and enters cytoplasm) and occurs in the cytoplasm of prokaryotic cells.
-translation occurs on ribosomes, the cellular machinery used for protein synthesis.

Question 37

What are the two parts of genes and their definitions?

Answer 37

-regulatory sequences: determine when and how much protein a gene makes; controls timing, location, and amount of gene expression.
-coding sequences: determine the amino acid sequence of the encoded protein, which determines the protein’s shape and thus function.

Question 38

What are the steps of transcription?

Answer 38

-RNA polymerase binds to the regulatory sequence upstream of the coding sequence, and unwinds the DNA double helix
-RNA polymerase moves along the DNA strand, “reading” and synthesizing a complementary mRNA strand
(NOTE that RNA has uracil instead of thymine, meaning adenine pairs with uracil. Cytosine and guanine still pair to each other.)
-the complementary mRNA forms from a DNA template according to the rules of base pairing
-as mRNA strand is formed, it detaches from the DNA sequence, and the DNA re-forms its double-stranded helix
-once mRNA molecule is complete, it leaves the nucleus. The gene remains part of the chromosome in the nucleus where it can be transcribed again and again.

Question 39

What are the steps of translation?

Answer 39

-after leaving the nucleus, mRNA associates with a ribosome which binds to mRNA at a specific sequence known as the start codon, usually AUG.
-initiator tRNA carrying methionine bonds to start codon.
-ribosome “moves” along mRNA, reading it in groups of three nucleotides (codons), each codon specifying a particular amino acid to be added to the growing chain, and ribosome moves to next codon
-when finished, the amino acid chain, now a new protein, detaches from the ribosome and folds into its 3D shape.

Question 40

Alleles

Answer 40

Alternative versions of the same gene that have slightly different nucleotide sequences. They influence phenotype.

Question 41

Transgenic definition and how to make a transgenic organism.

Answer 41

Referring to an organism that carries one or more proteins, aka GMO.

To make one, you “cut out” the gene of interest (the coding sequence for the gene you want to express) and paste it next to the organism’s regulatory sequence that you want to produce the specific protein. The damn antithrombin goats, or GMO plants.

Question 42

Chromosome

Answer 42

DNA wrapped around protein, consisting of many genes along their length.

Question 43

RNA polymerase

Answer 43

The main enzyme responsible for transcription.

Question 44

What is the structure of tRNAs and their role in translation?

Answer 44

Each tRNA has a 3 base anticodon one one side that binds to a specific codon in the mRNA. On the other end, each tRNA carries one specific amino acid.

Question 45

Anticodon

Answer 45

A sequence of 3 nucleotides found on tRNA. They are complementary to the 3 nucleotide sequence (codon) found on mRNA during translation. They are how the ribosome “knows” to stop the process of translation.

Question 46

Mutation: how can it lead to dz?

Answer 46

A change in the DNA sequence. It can lead to disease if it changes the proteins that were encoded by DNA, so they no longer fulfill the original purpose they were meant to carry out. Cystic fibrosis, sickle cell.

Question 47

Is it possible for a mutation to have no effect, and why?

Answer 47

Yes. 1) because 98% of our DNA does not encode proteins, so if a mutation occurs within a DNA sequence that doesn’t encode protein, it probably won’t have an effect. 2) some other mutations that don’t have an effect are silent mutations. These are because as long as the correct amino acid was added to the protein during translation, even if it’s added with a different codon than originally needed, the correct protein will still be built.

Question 48

Why do many scientists not consider viruses to be living?

Answer 48

Because viruses cannot reproduce or metabolize without a host.

Question 49

Why do virologists think viruses are living organisms?

Answer 49

Because they contain genetic information, protein, and sometimes a nuclear envelope.

Question 50

What is the structure of viruses and what differences can there be?

Answer 50

Standard: nucleic acid surrounded by a protein coat (capsid) and sometimes a membranous envelope.

Variety exists bc not all viruses have a membranous envelope, made of a protective but fragile phospholipid barrier, which has usually been stolen from the last cell the virus infected. Viruses with a membranous envelope are fragile (SARSCOV2, influenza) vs something like the tobacco mosaic virus, which can live on a surface for a long time and still infect a tobacco plant.

Question 51

Obligate intracellular parasite

Answer 51

Fancy term for virus!

Question 52

How do viruses reproduce?

Answer 52

After a virus gains entry to a host cell by its glycoproteins binding to special receptor proteins on the host cell’s surface, the virus then hijacks DNA polymerase to replicate viral DNA, then hijacks RNA polymerase to replicate viral mRNA, then hijacks the ribosomes to assemble its own viral proteins.

Question 53

Glycoproteins

Answer 53

Part carbohydrate, part protein. They are short polysaccharides covalently linked to a protein.

Question 54

What is host range with viruses?

Answer 54

The spectrum of different species and cell types the virus can infect. Largest known host range belongs to rabies.

Question 55

The difference between eukaryotic and prokaryotic transcription?

Answer 55

Since prokaryotes do not have a nucleus, transcription occurs all over the cytoplasm, whereas in eukaryotes, transcription occurs at the nucleus where pre-mRNA is formed and undergoes RNA processing prior to leaving the nucleus to undergo translation at a ribosome.