Mitosis
What happens during Prophase?
The cell's loose DNA condenses into tight, visible X-shaped chromosomes.
What are the correct complementary nucleotide base-pairings? DNA vs RNA?
In DNA, A pairs with T (think apple and tree) and C pairs with G (think car and garage). In RNA, U replaces T, to be U and A.
What are the 4 steps of DNA extraction?
1. Break open the cells: cells are lysed (broken down) using a detergent that breaks down the cell membrane
2. Remove cell debris: separate unwanted materials, such as proteins and pieces of cell membranes, from the DNA
3. Precipitate the DNA: the liquid containing the DNA is transferred to a clean tube
4. Collect the DNA
What are the differences between prokaryotic and eukaryotic genomes?
Eukaryotes have a nucleus, while prokaryotes don't. Prokaryotes don't have membrane bound organelles. Prokaryotes only have circular DNA, eukaryotes have linear, double-stranded DNA.
Prophase 1: matching chromosomes pair up and exchange pieces of DNA, this is called crossing over.
Metaphase 1: nucleus condenses, matching chromosome pairs line up in the metaphase plate and the spindle fibers start to pull the chromosomes apart.
Anaphase 1: the spindle fibers pull the chromosomes apart to opposite poles of the cell. Their sister chromatids stay attached.
Telophase 1: the cell starts to split into two separate cells, each with half the original number of chromosomes, the nucleus reforms
Cytokenesis: the cell splits into two separate haploid daughter cells
What happens during Metaphase?
The chromosomes line up single-file right down the middle of the cell.
Describe the structure of a DNA nucleotide.
It is made up of a phosphate, a deoxyribose sugar, and a base.
What are the 3 steps of the Polymerase Chain Reaction (PCR)?
1. Denaturation (separate): the DNA is heated so the two strands separate from each other
2. Primer Annealing (attach): the mixture cools; short pieces of DNA (primers) attach to the target DNA
3. Primer Extension (copy): an enzyme called DNA polymerase adds DNA building blocks to make new DNA strands
Describe “G0.” Why would a cell enter this phase, and what might cause it to come out of G0?
A cell would enter G0 if it doesn't want to replicate, for example you don't want to replicate heart or brain cells. It would come out of G0 if the cell receives any signals that it needs to duplicate.
What happens during Meiosis 2?
Prophase 2: a new spindle fiber forms in each haploid cell around the duplicated chromosomes, nucleus condenses
Metaphase 2: chromosomes line up individually at the center of each haploid cell, spindle fibers start separating the pairs
Anaphase 2: spindle fibers separate sister chromatids and move toward opposite poles in each cell
Telophase 2: nucleus reforms and each of the two cells starts to split into two
Cytokinesis: the cells fully split to end up with four genetically different haploid daughter cells
What happens during Anaphase?
The sister chromatids are pulled apart by the spindle fibers twoard opposite ends of the cell.
How is complementary base-pairing important to replication?
If all the pairs were the same, there would be no way to distinguish between them. A always pairs with T, and C always pairs with G, so this way it is a smooth process to replicate the DNA.
What is whole genome sequencing?
Sequencing all the A's, T's, C's, and G's.
Why is cancer described as "unregulated cell division"?
When the cell passes through a checkpoint and something is wrong, but the checkpoint doesn't know that, then the cell duplicates but because there is a mutation in the cell, you don't want it to duplicate, so that is what causes cancer.
What are the sources of genetic variation?
Crossing over, mutations, independent assortment, segregation, sexual reproduction
What happens during Telophase?
The chromosomes end up at opposite ends of the cell and start to separate back into loose DNA strands. Two brand new nuclear membranes form around each of the two new sets of DNA.
What is meant when we say that DNA replication is semi-conservative?
It means that DNA strands are complementary, meaning that one strand is a template for DNA.
What are the steps of Molecular Cloning? What are the steps of whole organism cloning using somatic nuclear transfer?
Molecular Cloning:
1. Find & isolate the gene you want to copy
2. Cut the gene and the plasmid with restriction enzymes
3. Join the gene to the plasmid to create recombinant DNA
4. Insert the plasmid into bacteria so the bacteria carry the new DNA
Whole Organism Cloning:
1. Take a body cell from the animal you want to clone
2. Take an egg cell from another animal and remove its nucleus
3. Insert the nucleus from the body cell into the egg cell without a nucleus
4. Stimulate the egg cell so it begins dividing and developing into an embryo
5. Place the embryo in the surrogate mother where it can continue developing
6. The surrogate gives birth to a cloned animal if successful
How do proto-oncogenes and tumor suppressor genes relate to the cell cycle?
Proto-oncogenes promote regular cell growth and the more there are, the cell is less likely to develop cancer and pass inspection. If a checkpoint detects cancer then the tumor suppressor genes make sure the cell explodes.
Explain DNA Replication including leading and lagging strand
1. Unzip the DNA: the enzyme called helicase breaks the hydrogen bonds between complementary bases, separating the two DNA strands and creating a replication fork.
2. Prepare the strands for copying: the enzyme primase makes short RNA primers. These provide a starting point for the DNA polymerase because it can't begin building a new strand from scratch.
3. Build the new DNA strands: the enzyme DNA polymerase adds complementary DNA nucleotides using the original strands as templates. A pairs with T. C pairs with G. DNA polymerase can only build a new strand in the 5' to 3' direction. This is the leading strand, it's made continuously.
The lagging strand is made discontinuously in short pieces called Okazaki fragments. Each fragment is made in the 3' to 5' direction and each fragment needs its own RNA primer
What is Cytokenesis?
The actual cytoplasm splits into two independent cells.
Explain the Central Dogma of Biology.
DNA codes for RNA which codes for Protein.
What are the 4 steps of CRISPR?
1. Find the target DNA: scientists design a guide RNA that matches the DNA section they want to edit; guides the CRISPR system to the right spot
2. Locate the DNA: the guide RNA helps a protein called Cas9 find the matching DNA sequence
3. Cut the DNA: Cas9 acts like molecular scissors and cuts the DNA at the target location
4. Repair and edit the DNA
Describe binary fission in prokaryotes. How is it different from cell division in eukaryotes.
Binary fission in prokaryotes means that it’s how prokaryotes replicate DNA, it is asexual reproduction. It can happen with just one bacteria, it doesn’t need another one to help reproduce.
Explain Mendel’s findings in terms of modern genetics
1. Law of Dominance: Some alleles are dominant and can mask the effects of recessive alleles. For example, a plant with one purple-flower allele and one white-flower allele may have purple flowers.
2. Law of Segregation: Each individual has two alleles for a gene but passes only one allele to each offspring through its gametes (egg or sperm cells). The two alleles separate during meiosis.
3. Law of Independent Assortment: Alleles of different genes are distributed independently into gametes when the genes are unlinked or far apart on the same chromosome.