EXAM 1 review Flashcards
What are the 3 phases of the Cell Cycle?
- Interphase
- Mitosis
- Cytokinesis
What are the divisions of Interphase?
- G1
- S
- G2
What occurs during the G1 phase of interphase?
- This is the longest section
- Here is where most of cells live & organelle making occurs (ribosomes & proteins)
What occurs during the S phase of interphase?
- “S” for DNA synthesis= replication
- 23 pairs of chromosomes turns to 46
What occurs during the G2 phase of Interphase?
-This is where the cell prepares for mitosis= making microtubules thats used to pull chromatids apart
What is the order of phases of Mitosis?
- *Prophase, Prometaphase, Metaphase, Anaphase, Telophase
- PMAT
What occurs during Prophase?
- Chromatids condense into chromosomes
- Mitotic spindle forms
- Nucleolus disappears
- Separation of Centrosomes
What occurs during Prometaphase?
- Nuclear envelope breaks apart due to lipid dissociation =fragmented
- Chromosomes form 2 kinetochores at the centrosome
- Microtubules are starting to attach to kinetochores
What occurs during Metaphase?
-The chromosomes line up on the metaphase plate
What occurs during Anaphase?
- Sister Chromatids separate & move to their respective poles
- If the checkpoint is passed=Anaphase Promoting Complex (APC) is produced
What occurs during Telophase?
- The cell elongates
- Nuclear envelope reforms
- Chromosomes unfold back into chromatin
- Nuclei reappear
What occurs during Cytokinesis?
- The cell starts to pinch= forming Cleavage Furrow
- Daughter cells are formed
What kind of cell has replication coupled w/ the segregation of genetic material, has 3 kai genes, has a compacted chromosome?
-It is a prokaryote
What kind of cell has solenoids, actin & myosin filaments that are involved in cytokinesis, sister chromatids that separate during segregation of genetic material?
- It has nucleosomes
- it also has an S phase
What is Kinetochore?
-It is made up of protein & is the site of microtubule attachment
What is a characteristic of Cyclin Dependent Kinase Molecules?
-They are a component of Maturation (mitosis) Promoting Factor=MPF
Where does the cell cycle checkpoint occur?
- at G1/S= restriction point=cdk &cyclin
- end of G2/beginning of P= MPF
- at Metaphase/ Anaphase transition=APC
What happens when you treat cells with Colchicine? an anticancer drug that binds to tubulin and blocks the assembly & polymerization of microtubules
chromosomes can not be moved to the metaphase bc they are reliant on the elongation of the microtubules
What are Primers?
-They are made of RNA & requires primase for their synthesis during replication
What is DNA Replication for the lagging strand?
-The lagging strand is made discontinuously using a template strand running from 5’ to 3’
What happens during DNA replication?
- Hydrogen bonds are normally formed between complementary bases on their interior helix
- Primase assists in the production of phosphodiester bonds
How is DNA unwound during DNA replication?
-It is unwound by Helicase to form the replication fork
When do alleles first segregate during Meiosis?
-Anaphase I
At what stage are Cohesins completely degraded in Mitosis?
Anaphase
At what stage are cells that contain 1 homolog of each chromosome produced?
- Meiosis II
- Meiosis I
What makes Mitosis and Meiosis similar?
- They both involve the segregation of genetic material
- They both have checkpoints
What is Crossing Over?
- Result in recombinant chromosomes
- Occurs during Prophase I
What should a pea plant that is homozygous for 3 different loci that assort independently make?
-It should only make 1 type of gamete bc its homozygous
What is the difference between Codominance & Incomplete Dominance?
- The heterozygote shows features of both the parents in Codimance
- In Incomplete Dominance, the heterozygote is intermediate between the 2 homozygotes
What is Hemizygous?
-It is a diploid organism that only has 1 copy of a gene
What is true about Keytruda? a drug that has successfully treated jimmy carter’s melanoma cancers?
- It activates immune cells
- it is an effective treatment for lung cancer
- it targets receptors on B cells
What are the key enzymes in DNA replication?
- Helicase
- DNA polymerase
- DNA Primase
- DNA Ligase
- Topoismerase
What is the job of Helicase?
- AKA unzipping enzyme
- It breaks through the H-bonds that hold the DNA bases together
What is the job of DNA Polymerase?
- AKA Bob the builder that only works in 5’ to 3’ direction of the old strand
- It replicates DNA molecules to build new strand of DNA by adding nucleotides
- Also has proofreading abilities to ensure no mistakes were made in matching the bases
What is the job of DNA Primase?
- AKA the initializer
- It makes the primer so that DNA polymerase can see where to start to work
What is Primase made of?
-RNA
What is the job of DNA Ligase?
- AKA the gluer
- It glues the Okazaki fragments together on the lagging strand by adding the phosphodiester bonds
What is the job of Topoisomerase?
- It helps unwind the tightly found helix by breaking up part of the backbone temporarily
- It is also the “clip” that keeps DNA from super-coiling
What is the process of DNA Replication?
1) replication starts at the origin
2) Helicase comes in & unwinds the DNA
3) Primase comes in & makes RNA primers on both strands
4) DNA polymerase builds new strand following the direction of the old strand= 5’ to 3’
5) The primers on the lagging strand get replaced w/ DNA bases
6) DNA Ligase glues the Okazaki fragments together
How many origins of replications do Eukaryotes have vs Prokaryotes?
-Eukaryotes have multiple while Prokaryotes have 1
What happens after Helicase comes in & unwinds the DNA?
-Single-Stranded Binding Proteins (SSB) bind to DNA strands to prevent them from touching again after the DNA strands are unzipped
How many primers does Primase make on the Leading Strand vs the Lagging Strand?
-The leading strand only needs 1 primer for DNA to get to work vs Lagging strand needs several since it is copied in fragments
How would the final result of DNA replication be defined as?
-Semiconservative bc each new DNA set has 1 old strand & 1 new strand
At what phases of the Cell Cycle would we have 2 chromatid chromosomes?
- G2
- Prophase
- Metaphase
At what phases of the Cell Cycle would we have 1 chromatid Chromosomes?
- Anaphase
- Telophase
- G1
What are the characteristics of Microtubules?
- Made of Protein Tubulin (made up dimers)
- Taking off dimers= shortening of the microtubule
What are the proteins that hold the sister chromatids together?
-Cohesion proteins
How are chromosomes compacted in Eukaryotic cells?
- The DNA is wrapped around Histone Proteins= H2A, H2B, H3 &H4
- These chains form a beaded necklace= Solenoid
What are Centromeres?
-They consist of short DNA sequences & hold the sister chromatids together
What are Telomeres?
-They are repeated short sequences of DNA at the tips of the chromosomes
What does Ploidy mean?
-It is the number of complete chromosomes in a cell
Eg; sperm & egg cells are haploid bc they only have 1 set
What are the 4 compaction levels of DNA?
1) Nucleosome= DNA wrapped around Histone protein
2) Solenoid= forms chromatin & associated during interphase= thread-like structure
3) Chromatin Loop
4) Rosettes of Chromatin Loop= forms rosettes on scaffold proteins forming highly condensed DNA
What are the 3 things that control the Cell Cycle?
- Cyclins
- Kinases
- MPF= Cyclin- cdk complex
What is the job of Cyclins in controlling the Cell Cycle?
-They are regulatory proteins which increase going into mitosis & decrease coming out
What is the job of Kinases in controlling the Cell Cycle?
-They are enzymes that phosphorylate (add phosphate groups) to other molecules so that they can work
What is the job of MPF?
- cdk is the Cyclin Dependent Kinases which are constant in the cell cycle but can’t work w/o cyclin
- Our MPF is high when we have cyclin (going into mitosis)
Which end of the DNA is the only place were nucleotides can be added?
-The 3’ end of DNA
How do you do a test cross?
-You would need to cross the genotype you want to know with the homozygous recessive version of it
What is the job of the Anaphase Promoting Complex (APC)?
- The APC has jobs in 3 different parts of the cell cycle
- In MITOSIS the APC helps digest the cohesion proteins that hold the sister chromatids together
- in MEIOSIS 1 the APC helps digest the synaptonemal complex to allow the homolog pairs to separate
- in MEIOSIS 2 the APC helps digest cohesion proteins to allow the sister chromatids to separate
Where is Cyclin & Kinase present in the Cell Cycle?
-Present during the G1/S transition which allows the Initial checkpoint to pass
Where is MPF & Kinase present in the Cell Cycle?
-Present during the G2/P transition which gets the cell ready for Mitosis
Where is APC present?
-Present during the A phase for anaphase
How is Meiosis described as?
-PMAT times 2
What are the different stages in Meiosis?
- Prophase I, Metaphase I, Anaphase I, Telophase I
- Prophase II, Metaphase II, Anaphase II, Telophase II
What does Interphase look like for Meiosis?
-There are 2 sets of chromosomes w/ 2 chromatids each
What occurs in Prophase I of Meiosis?
- The chromosomes undergo Synapsis= chromosome from mom & the chromosome from dad attach to each other via Synatomenal Proteins (tetrad)
- This is also where the chromosomes experience crossing over
What happens in Metaphase I of Meiosis?
- The homologous pairs line up on the metaphase plate independently
- The way they align can vary (blue with blue on same side or blue with red on the same side)
- The spindle also attaches to the centrosomes of the pairs
What happens during Anaphase I of Meiosis?
- The pairs are pulled apart= chromosome goes to their respective pole
- APC bites away at the Synaptomenal Proteins to help the pairs separate
What happens during Telophase I of Meiosis?
-The nuclei reforms at each side
What happens during Cytokinesis I?
-The cell divides= each daughter cell has 1 pair of chromosomes with 2 chromatids
What occurs during Prophase II of Meiosis?
- The nuclear envelope breaks down
- Spindle apparatus forms
- Centrioles are the ONLY THING that is replicated
What occurs during Metaphase II of Meiosis?
- The chromosomes are gonna line up on metaphase plate
- The spindle is gonna attach to the centromeres of the centrosomes
What occurs during Anaphase II of Meiosis?
-The sister chromatids are gonna be pulled apart and moved to their respective poles of the cell
What occurs during Telophase II of Meiosis?
-Nuclear membrane reassembles
What occurs during Cytokinesis II of Meiosis?
-The cells split again resulting in 4 haploid daughter cells that have 1 chromosome pair w/ 1 chromatid
What are the similarities between Prokaryotic & Eukaryotic cell division?
-They both involve DNA replication, segregation of genetic material, Division of the cytoplasm
What are the Differences between Prokaryotic & Eukaryotic cell division?
- Prokayotes divide via Binary Fission, They also couple their DNA replication & segregation
- Eukaryotes divide via Mitosis & they DON’T couple replication & segregation bc they occur at different times during the cell cycle
What kind of chromosomes do Prokaryotes have vs Eukaryotes?
- Prokaryotes have circular chromosmes= genophore which is compacted via supercoiling
- Eukaryotes have linear chromosomes that go through different phases of compaction
