Bio exam 3 writing

What is the difference between a tissue and an organ?

A tissue is a group of cells working together to perform a specific function in the body, like muscle tissue or nervous tissue, while an organ is made up of 2 or more different types of tissues working together to perform a larger and more complex role, like our lungs and heart

Describe the DNA replication process during the cell cycle.

It has 4 checkpoints: G1 phase, where the cell begins to grow and carries out its normal metabolic process; S phase, where the cell makes identical copies of the DNA and makes instructions for future cells; G2 phase, where the cell will grow even more and double-check that the cell is ready for separation; M phase, when the cell separates into 2 identical cells.

DNA replication

DNA helicase attaches itself to the double helix strand and breaks down the hydrogen bonds of the nucleotide bases and unzips or unwinds the strand; then DNA polymerase moves along each side of the strand to match free nucleotides floating in the nucleus to the complementary partners on the original strand. A leading strand is built in a 5’-‘3 direction towards the replication fork, while the lagging strand is built in short, choppy segments called Okazaki fragments away from the replication fork in a 3’-5’ direction. These are later glued together by DNA ligase. DNA polymerase proofreads the strands and fixes mismatched base pairs, ending with 2 identical DNA molecules ready to be put into 2 separate daughter cells during mitosis.

What is an Allele and the characteristics of an allele?

A different form of a gene, like different traits in a person. There are dominant alleles that are represented by an uppercase letter and recessive alleles that are represented by a lowercase letter.

List and briefly describe all the different types of mutations?

Silent mutation: a substitution mutation that changes a single nucleotide base pair but causes no physical harm. Missense mutation: a mutation in which a single nucleotide is changed, and it causes another amino acid to be added to the chain. Nonsense mutation: a change in the DNA sequence that makes a stop codon and ends the process early, and ends with a short, nonfunctional protein

Describe the structure of the cytoskeleton and its contribution/function?

Protein fibers that stretch throughout the cytoplasm of a cell, made up of microfilaments, thin fibers made of protein, intermediate filaments, medium-sized fibers made of different fibrous proteins, and microtubules, thick  fibers shaped like hollow tubes made of a protein called tubulin that can grow and shrink

List and describe the different phases of the cell cycle? part 2

Mitosis (Prophase, Metaphase, Anaphase, Telophase): Chromosomes condense and align at the cell's equator, then sister chromatids are pulled to opposite poles, culminating in the formation of two new nuclei.

List and describe the different phases of the cell cycle? part 3

In an animal cell, the cytoplasm physically pinches in the middle, dividing the cell into 2 genetically identical daughter cells, while in plant cells, brick-shaped cells get pulled apart down the middle internally

Describe the cellular junction, the different types and their function?

Cellular junctions are connections that hold cells together or allow them to communicate with each other. Tight junctions act like waterproof seals; they help protect organs and tissue from harmful substances Desmosomes hold tightly together, like when you interlock your knuckles together; they provide strength and support tissue to handle stretching and pulling. Gap junctions tube like tiny channels between neighboring cells that help them communicate.

Semiconservative replication

A DNA replication mode where each daughter molecule consists of one newly synthesized strand and one parental strand

Binary fission

The process by which prokaryotic cells divide, involving DNA replication, DNA segregation, and division into 2 cells

Describe what cyclins are

Regulatory proteins that control the progression of cells through the cell cycle by binding to and activating enzymes called cyclin-dependent kinases CDK