Studied by 21 peopleWhat is the cell cycle?
Sequence of events that includes growth, DNA synthesis, and cell division.
What are the two phases of the Cell Cycle?
Interphase and the Mitotic Phase
What is Interphase?
Phase in which cells grow, DNA is replicated, and cell performs normal metabolic processes in preparation for division
How many and what are the subphases are in Interphase?
G1, Synthesis, and G2.
What is G1?
A subphase of Interphase
The cell grows, proteins are made, and routine metabolic processes are performed
What is Synthesis?
A subphase of Interphase
DNA is replicated
What is G2?
A subphase of Interphase
Final preparations are made to divide and organelles are copied
What stage of the cell cycle do Eukaryotic cells spend most of their time in?
Interphase
What are regulatory proteins?
Proteins that control the cell cycle at specific checkpoints
How many checkpoints are their in the cell cycle?
3
When and what occurs at the Cell Growth Checkpoint?
Occurs in the middle of G1
Regulatory proteins decide if the cell is eligible to move forward in the cycle.
When and What occurs at the S Checkpoint?
Occurs in the middle of S phase
Regulatory proteins check to see if the DNA was replicated properly
Why are the daughter cells created from Mitosis genetically identical?
Because of DNA replication in the S phase
Where does DNA replication occur?
The nucleus
What type of proteins makes DNA replication happen?
Enzymes
What does Helicase do in regards to DNA replication?
An enzyme that unwinds the 2 stranded DNA and breaks the hydrogen bonds between nitrogenous bases
What structure is formed during DNA replication?
A DNA replication fork
What does DNA polymerase do in regards to DNA replication?
An enzyme that goes along the DNA strands and builds a complementary strand to the exposed base pairs of the parent DNA
What does Primase do in regards to DNA replication?
an enzyme that builds a short RNA primer on the lagging strand of DNA
What happens when the DNA Replication Fork is created?
A leading and lagging strand of DNA is established with the lagging strand being on top and the leading stand being on the bottom.
What is the lagging strand of DNA?
The DNA strand that is above the leading strand which is put together using a primase and okazaki fragments.
3’ to 5’ direction
What is the leading strand of DNA?
The DNA strand that DNA polymerase constructs in the 5’ to 3’ direction
What is DNA Replication?
The process in which a cell’s entire DNA is copied
What are Okazaki Fragments?
short fragments of DNA that comprise the lagging strand of DNA
What does 3’ to 5’ and 5’ to 3’ have to do with DNA replication?
Each DNA strand (the lagging and leading strands) have a direction.
A 5’ end has a terminal phosphate group.
A 3’ end has a -OH group.
What is a summary of DNA Replication?
DNA helicase unwinds the DNA. Proteins hold the two DNA strands apart while DNA polymerase creates a complementary DNA strand to the leading strand. Primase and Okazaki fragments work together to create complementary DNA strands to the lagging strand. Replication continues until new DNA has been made consisting of old/original DNA and new DNA.
All cells in an organism (except gametes)…
have the same DNA
What is Fertilization?
When egg and sperm (in humans) meets
What is the result of Fertilization?
A Zygote
When do Stem cells begin being made?
After the cells in a Zygote divide 4-8 times
What type of stem cells are made after 4-8 divides in a Zygote?
Embryotic Stem Cells
What are Embryotic Stem Cells?
A type of stem cell which can make all kinds of cells
Are referred to as totipotent
What does totipotent mean?
means they can make all types of cells
What are pluripotent stem cells?
A type of cell that can make one of the three primary groups of cells
What are the three types of pluripotent stem cells?
Ectoderm, Mesoderm, and Endoderm
What are multipotent stem cells?
A type of stem cell that can only make a certain type of cell
Example. Muscle Stem Cell or Skin Precursor Cell
What are unipotent stem cells?
A type of stem cell that can only make more of itselfs (can’t differentiate)
Example. Cheek Cell or Red Blood Cell
What is the scale for Stem Cell Differentiation?
Embryonic Stem Cell (totipotent) → pluripotent →multipotent→unipotent
What is cell differentiation?
The process by which stem cells produce specialized cells
What occurs to make cell differentiate?
Segments of genetic material is activated or repressed making cells more and more differentiated
What are homologous chromosomes?
Similar chromosomes with the same genes but different alleles
What are alleles?
Are alternate forms of genes found on chromosomes
What does the sequence of your DNA determine?
Determines how proteins are made and what your traits are (physically)
What are diploid cells?
Cells that have two sets of chromosomes equalling 46 total
What are haploid cells?
Cells that only have one set of chromosomes equalling 23 total
What type of cell are the majority of your body cells?
Diploid
What type of cell are gametes?
Haploid
What is Meiosis?
A type of cell division which produces gametes
How many rounds are in Meiosis?
2
What is the result of meiosis?
4 haploid cells which means each cell has 23 chromosomes, not pairs
Why are homologous chromosomes not identical?
Because of different alleles
What happens prior to meiosis?
DNA replicates
What occurs in Prophase 1?
Chromosomes line up together, crossing over may occur, chromosomes condense, and spindles form
What is crossing over?
A process which exchanges DNA between chromosomes resulting in a new combination of alleles
What occurs in Metaphase I?
Chromosomes line up at the equator of the cell and spindle fibers attach to the centromere of the chromosomes at random
What occurs in Anaphase I?
Chromosomes are pulled to each pole of the cell by the shortening of spindle fibers
What occurs in Telophase I?
The spindle fibers dissolve and the nuclear membrane does not reform.
What occurs after Telophase I?
Cytokinesis occurs almost instantly
What occurs in Prophase II?
Chromosomes recondense
What occurs in Metaphase II?
Chromosomes line up at the equator of the cell and spindle fibers attach to the centromere
What occurs in Anaphase II?
Sister chromatids separate as the spindle fibers shorten
What occurs in Telophase II?
Nuclear membrane begins forming around the around the newly separated chromosomes
What occurs right after Telophase II?
Cytokinesis occurs creating four gametes that are genetically different
What is gel electrophoresis?
a laboratory method that is used to separate DNA, RNA, and proteins according to molecular size
What does electrophoresis mean?
the movement of charged particles through the gel through a electric field
What types of charges are used during gel electrophoresis and what are their purpose?
A positive and negative charge is used.
The negative charged is used to repel the DNA molecules because DNA is also negatively charged.
The positive charge is placed at the end of the gel so the DNA moves towards it.
What is a mutation?
A change in nitrogenous bases of DNA or RNA
What is a Mutagen?
Something that causes a mutation
What is a Germline Mutation?
A mutation in a gamete and can be passed to offspring
What is a Somatic Mutation?
A mutation that occurs in a somatic (non-gamete) cell
Not serious and only occurs in one cell or daughter cells Cannot be passed onto offspring
What is Chromosomal Alteration?
A mutation that changes chromosome structure/genetic material
Occurs when part of a chromosome breaks off and doesn't rejoin correctly
Can occur because of deletion, duplication, inversion, insertion, or translocation
What is a Point Mutation?
A mutation that changes one nucleotide
Less serious
Several Types
What is a Frameshift Mutation?
A mutation in which a nucleotide is deleted or inserted causing everything to shift over, greatly impacting protein synthesis
What is a Genetic Disorder?
A disease caused by a gene mutation
What causes a mutation?
Most are accidental and random but some can be caused by mutagens.
What are some examples of a mutagen?
Chemicals (Cigarette smoke, Barbecuing) Infectious Agents (HIV) Radiation (UV radiation, X-Rays)
How many different types of point mutations are their and what are they?
Silent Mutation, Missense, and Nonsense
What is a Silent Mutation?
A type of point mutation, in which a mutated codon (a nitrogenous base gets changed) codes for the same amino acid
What is a Missense Mutation?
A type of point mutation, in which a mutated codon (a nitrogenous base gets changed) codes for a different amino acid
What is a Nonsense Mutation?
A type of point mutation, in which a mutated codon (a nitrogenous base gets changed) codes for a stop codon, ending the protein synthesis early
What is nondisjunction?
A type of chromosomal alteration that occurs when chromosomes or sister chromatids do not separate equally in anaphase I or anaphase II.
What are so examples of nondisjunction?
Trisomy 21 (having an extra 21 chromosome: causes down syndrome)
Trisomy 18 (having an extra 18 chromosome: causes edwards syndrome)
Klinefelter’s Syndrome (a male having two X chromosomes)
Turners Syndrome ( a female with one X chromosome)
What occurs during gel electrophoresis?
A negative current of electricity is used to move DNA through a semipermeable gel towards a positive current, resulting in DNA being sorted by size.
What are the 5 steps in gel electrophoresis?
Make the gel
Set up the gel apparatus
Load the DNA sample into the gel
Hook up the electrical currents and “run” the gel
Stain the gel and analyze the results
When the results of gel electrophoresis are printed on paper, there are dark bands present to indicate the results. What do these dark bands represent?
They represent the different molecular sizes of the DNA fragments tested
What are the centrioles?
An organelle that is only present during cell division, that spindle fibers are attached too
Also called a spindle apparatus
What charge is placed on the top of the gel apparatus?
A negative charge
What charge is placed on the bottom of the gel apparatus?
A positive charge
Note
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