Biology Vocabulary Review

Intro to Biology

To be alive, an object needs to meet certain criteria which biologists call the characteristics of life.
Eight characteristics of life:
- Made of cells: Being made up of one or more cells, the basic unit of life.
- Growth and development: An organism increasing in size and complexity over time.
- Response to their environment (stimulus): Detecting and reacting to changes in the environment.
- Based on a universal genetic code: Passing on genetic information from parent to offspring.
- As a group, evolve over time: Gradual change over time, referring to the process where characteristics within a population change across generations due to natural selection
- Require nutrients and energy (metabolism): Chemical processes within an organism to acquire and use energy.
- Homeostasis: Maintaining a stable internal environment despite external changes.
- Reproduce: The ability to create new individuals of the same species.

Experimental Design

Independent Variable: The variable that the researcher actively changes or manipulates to observe its effect on another variable; considered the "cause" in a cause-and-effect relationship.
Dependent Variable: The variable that is measured or observed to see how it is affected by changes in the independent variable; considered the "effect" in a cause-and-effect relationship.
Controlled Variable: A variable that is kept at the same level in every group so comparisons can be made to see if changes in the dependent variable are due only to changes in the independent variable.
Control Group: A group in an experiment that does not receive the experimental treatment or variable being tested, serving as a baseline for comparison with the experimental group
Example field study examining how artificial light at night (light pollution) affects the behavior of nocturnal insects in a local forest ecosystem:
- Hypothesis: The higher the intensity of artificial light, the greater the number of nocturnal insects attracted, because brighter lights are more likely to disrupt their natural behaviors and attract them.
- Independent variable: intensity of light
- Dependent variable: number of insects attracted per min
- Variables that needed to be controlled (held constant): type of insects, humidity of air, temperature of air
- Experimental group: insects exposed to different intensities of light
- Control group: insects not exposed to artificial light. Without the control group, differences in the experimental groups might just be the normal range of insect behavior, so it provides a baseline.

Biodiversity

Biodiversity refers to the variety of life on Earth at all its levels, from genes to ecosystems, and can encompass the evolutionary, ecological, and cultural processes that sustain life.
Biodiversity is essential for the processes that support all life on Earth, including humans.
Without a wide range of animals, plants and microorganisms, we cannot have the healthy ecosystems that we rely on to provide us with the numerous ecosystem services like pollination, pest control, nutrient cycling, and maintaining a stable food web, which are vital for the overall health and resilience of the environment; a diverse ecosystem is better equipped to adapt to changes and withstand disturbances compared to one with low biodiversity.
Biodiversity, or the variety of life on Earth, is a central concept in ecology, evolution, and genetics because it reflects the complexity and adaptability of living systems:
- In ecology, biodiversity contributes to the stability and resilience of ecosystems. A greater variety of species means more ecological roles are filled, allowing ecosystems to maintain functions such as nutrient cycling, pollination, and energy flow, even under stress or change.
- In evolution, biodiversity is both a cause and effect of natural selection. Over time, genetic variation within populations leads to the emergence of new species. The diversity of life forms reveals the history of adaptation to different environments and changing conditions.
- In genetics, biodiversity is rooted in the genetic variation within and between populations. This variation provides the raw material for evolution and allows populations to adapt to environmental changes, resist diseases, and avoid loss of genetic diversity through inbreeding.

Ecology

Five factors that can impact the growth of a population:
- Food availability - biotic
- Water availability - abiotic
- Habitat space - abiotic
- Shelter/ nesting sites - may be either
- Predator/prey interactions - biotic
- Diseases - biotic (exception viruses, abiotic)
- Natural disasters (abiotic)
“Energy flows but matter cycles.”
- Energy flows – energy is neither created nor destroyed, but passes from organism to organism as one eats another, as well as out into the atmosphere. Most energy is lost as heat. The source of all energy on earth is the sun.
- Matter cycles – Matter is neither created nor destroyed; All of the carbon $(C)$ , hydrogen $(H)$ , oxygen $(O)$ , nitrogen $(N)$ and phosphorus $(P)$ on earth was here when earth formed. All matter gets incorporated into living things, is passed from organism to organism as one eats another and is put back into the earth when organisms die and decompose.
The type of organism that is always at the start of a food chain is a producer because Producers always start the food chain as they are the only organisms capable of converting energy from the sun into glucose (photosynthesis).
California Chaparral biome food chain: chamise (leaf) → mule deer → mountain lion → California condor (vulture)
- Autotroph (producer): chamise
- Heterotrophs (consumers): mule deer, mountain lion, condor
- Secondary consumer: mountain lion
- Herbivore: mule deer
- Scavenger: condor
The processes of photosynthesis and cellular respiration both allow organisms to obtain energy.
- In photosynthesis, producers obtain energy from the sun and convert solar energy into chemical energy in the form of glucose.
- In cellular respiration, glucose is broken down and in the process, ATP (cellular energy) is created. Plants do not need consumers to live, as they create their own energy. However, consumers must consume, or eat, in order to obtain energy.
- Organisms that have chloroplasts: eukaryotic producers
- Organisms that have mitochondria: eukaryotic producers and consumers
Ecological Pyramid:
- An ecological pyramid can have more or fewer than three trophic levels. The number of trophic levels in an ecosystem depends on the complexity of the food web and the availability of energy.
- There aren’t usually more than 4-5 levels because of the 10% rule, which states that only about 10% of the energy from one trophic level is transferred to the next level. The rest is lost as heat, used for metabolism, or left behind in waste. By the time you reach the 4th or 5th level, there’s not enough energy left to support another level of consumers. This energy loss limits the number of trophic levels most ecosystems can support.
Biological magnification is the process in which the concentration of polluting chemicals increases in successive trophic levels of a food. The toxin builds up most in organisms at the top of the food chain, as they consume the largest concentration of that toxin. So, for example, condors would have more of the hazardous chemical than any other organism in the food chain, since they eat the organisms that eat producers (who incorporate the chemical in the first place).
The carbon cycle:
- Carbon is in the atmosphere as CO2 gas
- Only producers can incorporate carbon dioxide and use it to build other molecules.
- Producers use carbon dioxide during photosynthesis to make glucose.
- Consumers get the carbon they need from the foods they eat (we eat producers and/or consumers that have carbon in the form of carbohydrates, lipids, proteins, and nucleic acids), and we use the carbon to build all of our biological molecules.
- All organisms (producers and consumers) that conduct cellular respiration release carbon back into the atmosphere as carbon dioxide. Carbon is also released as CO2 by humans burning trees and fossil fuels.
Competition is when organisms or species interact to obtain a resource that is in limited supply.
Difference between a habitat and a niche:
- A habitat is the physical location where an organism lives, like a forest or a coral reef, while a niche is the specific role an organism plays within its environment, including its food sources, behavior patterns, and interactions with other species; essentially, its "job" in the ecosystem; two species cannot occupy the same niche because they would directly compete for the exact same resources, leading to one species outcompeting the other; the niche is more relevant for competition as it defines how an organism interacts with its environment and other species within that environment.
Niche partitioning example:
- In the African savanna, zebras, wildebeest, and gazelles all graze on grass, but they partition their niche by primarily eating different heights of grass at different times, effectively reducing competition for the same food source; zebras tend to eat taller grasses immediately after rain, while wildebeest graze on shorter grasses left behind by zebras, and gazelles may then eat even shorter grass later in the season once the other herbivores have moved on.
Significance of a keystone species in an ecosystem:
- A keystone species, like the sea otter, plays a disproportionately large role in maintaining the balance of an ecosystem, meaning their presence significantly impacts the biodiversity of the area by controlling populations of other species, like in the case of sea otters regulating sea urchin populations, which allows kelp forests to thrive and support a diverse range of marine life; without sea otters, kelp forests would be decimated, drastically reducing biodiversity in the ecosystem.
Lynx (predator) and a population of hare (prey):
- The solid line represents the hare, and the dashed line represents the lynx. We know this because prey populations are always larger than predator populations, and predator population curves always lag behind prey population curves. The lag is due to the time it takes predator populations to reproduce.
Carrying Capacity:
- When a population reaches its carrying capacity, it essentially stabilizes, meaning the population size remains relatively constant as the available resources in the environment can only support that number of individuals; this occurs because the birth rate tends to balance out with the death rate at this point, preventing further population growth or decline.
- A carrying capacity is not a completely flat line because real populations in nature fluctuate around the theoretical maximum, meaning they dip below or exceed the carrying capacity due to factors like resource availability fluctuations, predator prey cycles, competition with other species, or natural disasters, resulting in a more "bumpy" line on a graph rather than a perfect horizontal line.

Evolution

Evolution: change over time; the process by which modern organisms have descended from ancient organisms
Variation: differences in traits or characteristics among individuals within a population
Adaptation: heritable characteristic that increases an organism’s ability to survive and reproduce in an environment
Fitness: how well an organism can survive and reproduce in its environment
Natural selection: process by which organisms that are most suited to their environment survive and reproduce most successfully; also called survival of the fittest
Homologous structures: anatomical features found in different species that share a similar basic structure and origin, indicating a common evolutionary ancestor, even if they serve different functions in the present-day organisms due to different environments/niches
Analogous structures: anatomical features that perform similar functions in different species that do not share a common ancestor, due to their similar environment/niches
Divergent evolution: species with a shared ancestry evolve different adaptations based on their respective environments
Convergent evolution: species adapt to similar environmental pressures in similar ways; similar traits are not due to a common ancestor
Sexual selection: a type of natural selection that arises from differences in reproductive success based on certain traits that increase an individual's chances of attracting mates or successfully reproducing. These traits may enhance mating opportunities but do not necessarily improve survival.
Species: group of similar organisms that can breed and produce fertile offspring
VIDA - explain how each term is involved in natural selection
- Variation: Individuals in a population have natural differences in their traits.
- Inheritance: Traits are passed down from parent to offspring.
- Differential survival and reproduction: Organisms that are best suited to their environment are more likely to survive and reproduce, passing on their traits to their offspring.
- Adaptation/change in frequencies: Over time, the frequency of favorable traits increases in a population leading to adaptation in that environment
Natural selection causes a population to evolve by favoring individuals with traits that increase their chances of survival and reproduction in a given environment. Within a population, individuals show variation in traits, some of which may give them an advantage when facing environmental challenges known as selection pressures—such as predators, climate, or competition.
- Individuals with advantageous traits tend to have higher fitness, meaning they are more likely to survive and reproduce. These beneficial traits, known as adaptations, are passed on to the next generation. Over time, as these adaptations become more common and less advantageous traits are lost, the genetic makeup of the population changes, resulting in evolution of that species.
- Divergent evolution occurs if two related species were found to have structures that were similar in form and position but had different functions in each.
- Those types of structures are called homologous structures.
- Example: The human arm and a dolphin’s flipper are evidence that divergent evolution occurred and both species descended from a common ancestor.
Convergent evolution is exhibited when organisms evolve similar traits because of adaptation to similar environmental conditions rather than inheriting them from a common ancestor.
- Analogous structures are evidence of convergent evolution. These structures may have a different form and position but serve the same function.
- Examples: Bird wings and insect wings; snail shell and turtle shell; fins in dolphins (mammals) vs penguins (birds)
Over time, honeybees have developed hairs on the back of their legs which pick up pollen, and flowers have developed extremely sticky pollen. This is an example of coevolution.
- Coevolution is a pattern of evolution in which two species adapt in response to each other. A species interaction must be present in order for coevolution to occur. In this example, there is a mutualistic relationship between the plant and the honey bee. Because the plant is immobile, it needs help transmitting its gametes to other plants. The plant offers the bee a protected and rich food source. Both benefit. Over time the plant evolves to attract bees more and ensure that other organisms can’t steal the bees’ food while the bee evolves feed exclusively on flower pollen and nectar and to become efficient pollinators.

Cellular Systems

A prokaryotic cell lacks a nucleus and other membrane-bound organelles, while a eukaryotic cell has a well-defined nucleus where its DNA is stored, along with other membrane-bound organelles that compartmentalize cellular functions.
An organelle is a structure within a cell that has one or more specific jobs to perform in the cell, much like an organ does in the body.
Four components that all cells have in common: cell membrane, cytoplasm, DNA, ribosomes
Function of each of these organelles:
- i) mitochondria- Convert glucose into ATP energy using cellular respiration
- ii) chloroplasts- Convert energy in sunlight into glucose using photosynthesis
- iii) ribosomes- Protein production
- iv) cell membrane- Separates the cell from its environment
- v) cell wall- Provides structural support and protection to a cell
Atoms interact in ionic and covalent bonds.
- Ionic bonds form when one atom transfers electrons to another atom. Covalent bonds form when two atoms share electrons. A molecule is a group of atoms connected with covalent bonds.
The muscle cells in a hummingbird’s body, particularly those in its wings, would contain the most mitochondria because This is because mitochondria generate ATP through cellular respiration, and wing muscles require a high energy supply to sustain the rapid, continuous contractions needed for flight.
One important property of water is its polarity.
- A molecule of water contains covalent bonds, where electrons are shared between atoms. In water $(H₂O)$ , the oxygen atom shares electrons with two hydrogen atoms, but oxygen pulls the shared electrons more strongly than hydrogen. This causes the electrons to be closer to oxygen, creating an uneven distribution of charge.
- Because oxygen pulls electrons more strongly, it becomes slightly negative $(δ–)$ , and the hydrogen atoms become slightly positive $(δ+)$ . This uneven distribution of electrons across the water molecule makes it polar, resulting in the water molecule having a slightly positive end and a slightly negative end.
- The positive hydrogen of one water molecule is attracted to the negative oxygen of another water molecule. This weak attraction between molecules is called a hydrogen bond.
The polarity of water contributes to its importance in biological systems:
- cohesion and adhesion of water are crucial to its importance in biological systems because they allow water to effectively transport nutrients and move throughout organisms, particularly in plants, by enabling water molecules to stick to themselves (cohesion) and to other surfaces (adhesion), facilitating processes like capillary action and water transport from roots to leaves against gravity.
- Water’s ability to act as a universal solvent is crucial in biological systems because it transports nutrients and minerals. This property arises from water’s polarity, which allows it to dissolve a wide range of substances. This allows substances to be transported throughout the environment and within an organism’s body.
Biological macromolecules:
- Carbohydrates
  - Example polymer: Glycogen, starch, cellulose
  - Subunit/ Monomers: monosaccharides
  - Example monomer: glucose
  - Functions: Store and release energy (also structural support)
- Lipids
  - Example polymer: Triglyceride
  - Subunit/ Monomers: Fatty acids and glycerol
  - Example monomer: ATP
  - Functions: Long term energy (also as membranes and insulation)
- Nucleic Acids
  - Example polymer: DNA, RNA
  - Subunit/ Monomers: Nucleotides
  - Functions: Store and transmit genetic info
- Proteins
  - Example polymer: Keratin
  - Subunit/ Monomers: Amino acids
  - Example monomer: Tyrosine, alanine, serine
  - Functions: Serve a huge variety of functions due to their high diversity
Diffusion- movement of molecules from an area of high concentration to low concentration. It happens naturally and does not require energy
Polar - A molecule that has uneven sharing of electrons, resulting in partial positive and negative ends. Polar molecules mix well with water (hydrophilic).
Non-polar - A molecule where electrons are shared evenly, so there are no charged ends. Non-polar molecules do not mix well with water (hydrophobic).

Cell Functions

Cell Cycle:
- Interphase:
  - G1 (first cell growth phase): Grows and performs its normal functions; Organelles and proteins are made
  - S (Synthesis): Replicates its DNA, making an identical copy of each chromosome
  - G2 (second cell growth phase): Continues to grow; Produces proteins and organelles needed for mitosis
- M phase
  - Mitosis
    - Prophase: Chromosomes condense and become visible. Spindle fibers start to form and attach to centromeres; The nuclear envelope breaks down.
    - Metaphase: Chromosomes line up in the middle of the cell (equator) based on pulling by the spindle
    - Anaphase: Sister chromatids are pulled apart by the spindle fibers. They move to opposite ends (poles) of the cell.
    - Telophase: Chromatids reach the poles and begin to uncoil back into chromatin. Nuclear envelopes re-form around each set of DNA.
  - Cytokinesis: Cytoplasm divides, creating two separate daughter cells
Mitosis is the division of the nucleus and its chromosomes into two identical nuclei. Cytokinesis is the division of the cytoplasm, resulting in two separate cells.
Role of checkpoints in the cell cycle:
- Checkpoints ensure the cell is ready to move to the next phase of the cell cycle. They help prevent errors like damaged DNA or incomplete replication.
  - G1 Checkpoint: Checks for cell size, nutrients, growth signals, and DNA damage.
  - S/G2 Checkpoint: Ensures all DNA is replicated correctly and checks for damage.
  - M (Spindle) Checkpoint: Ensures chromosomes are properly attached to the spindle before anaphase.
Cancer cells are often described as “immortal.” Cancer cells ignore normal cell cycle controls. Mutations in genes that regulate cell division (like checkpoints) can cause cells to divide uncontrollably, forming tumors.
- In cancer cells, mitosis occurs more quickly and is often unregulated. Checkpoints may be faulty or bypassed, allowing cells with DNA errors to continue dividing.
Angiogenesis is the formation of new blood vessels. Tumors need blood supply to get oxygen and nutrients for cell respiration, so they stimulate angiogenesis to keep growing.
Reactants are substances that enter a chemical reaction. Products are substances formed by the reaction. Activation energy is the minimum energy needed to start a chemical reaction.
Enzymes affect the rate of chemical reactions in the body.
- Enzymes are proteins.
- Enzymes lower the activation energy, allowing reactions to happen faster and more efficiently.
Enzymes and substrates are often described using a lock-and-key model. Lock = Enzyme, Key = Substrate. Just like only the right key fits a lock, only the correct substrate fits into an enzyme’s active site. The enzyme’s shape determines its function. If the shape changes, the substrate may not fit in the active site, and the enzyme won't work.
Enzyme denaturation is when an enzyme loses its shape, making it unable to bind to its substrate. Changes in temperature, salt concentration and pH levels can cause denaturation.
- Hydrogen bonds help maintain the enzyme’s shape. When they break, the enzyme unfolds and loses function. Covalent bonds are usually unaffected during denaturation.
Reactants and products of cellular respiration:
- glucose + oxygen -> carbon dioxide + water
- $C6H{12}O6 + 6 O2 \longrightarrow 6 CO2 + 6 H2O$
Reactants and products of photosynthesis:
- carbon dioxide + water -> glucose + oxygen
- $6 CO2 + 6 H2O \longrightarrow C6H{12}O6 + 6 O2$
- Carbon dioxide from the air (enters through stomata). Water from the soil (absorbed by roots). Light energy from the sun (captured by chlorophyll in leaf cells).
- Carbon in glucose produced in photosynthesis comes from carbon dioxide in the air.
Cellular respiration requires oxygen.
- Metabolic processes that require oxygen are called aerobic.
- Cells make ATP if they are low on oxygen through fermentation.
Plants need to perform cellular respiration to convert glucose energy to ATP energy, just like animals.
- Glucose from photosynthesis (made in chloroplasts and transported through the plant).
- Oxygen from the air (enters through stomata and diffuses into cells).
Mammals need to perform cellular respiration to convert glucose energy to ATP energy.
- Oxygen from the air (breathed into the alveoli in the lungs, diffused into capillaries, then transported by blood to cells).
- Glucose from food (digested in the digestive system, absorbed into blood, then delivered to cells).
Amylase breaks down starch into glucose, which cells use in cellular respiration to make ATP. Without digestion, starch would be too big to be absorbed into the bloodstream.

Meiosis & Genetics

The diagram illustrates the process of:
- meiosis (a)
- production of gametes (b)
- production of haploid cells (c)
- All of the above (d)
The first time there are cells with the haploid number of chromosomes is shown in step: D
Metaphase II occurs in step: E
The appearance of tetrads occurs in step: B
The significance of the process shown is that it results in: reproductive cells that are genetically different from each other
Step A is a diagram of: one chromosome
Step B is a diagram of crossing over
The following statement explains the significance of the process pictured above: a new combination of alleles is produced
Structures of the male reproductive system:
- penis, vas deferens, urethra, bladder, rectum, prostate gland, ureter, testes, seminal vesicle, epididymis
- Organ that delivers semen to the female reproductive tract: penis
- Where sperm are produced: testis
- The tube that carries sperm from the epididymis to the urethra: vas deferens
- The tube that carries both sperm and urine down the penis: urethra
- Organs that contribute 90% of the semen: accessory glands
- Tubules where sperm are stored: epididymis
Structures of the female reproductive system:
- ovary, fallopian tube, cervix, vagina, uterus
- Chamber that houses the developing fetus: uterus
- Muscular canal that extends from the vulva to the cervix: vagina
- Usual site of fertilization: fallopian tube
- Duct through which the ovum travels to reach the uterus: fallopian tube
- The opening of the uterus leading to the vagina: cervix
- Where the ova (eggs) are produced: ovary
Definitions:
- gene - A segment of DNA that contains the instructions to make a specific protein
- allele - A different version of a gene
- genotype - The combination of alleles an organism has for a trait (e.g., TT, Tt, or tt)
- phenotype- The physical trait that shows up, based on the genotype (e.g., tall or short)
- dominant - An allele that shows its effect even if only one copy is present (written as a capital letter, like T)
- recessive - An allele that only shows its effect if both copies are the same (written as a lowercase letter, like t)
- homozygous allele pair - Two of the same alleles for a gene
- heterozygous allele pair - Two different alleles for a gene
- incomplete dominance - inheritance where neither allele is completely dominant, so the result is a blended/ in between phenotype
- codominance - Both alleles are fully and equally expressed in the phenotype
- sex-linked gene - inheritance of a gene on the X chromosome. These traits often show up more in males because they have only one X
Problems:
- P = purple, p = white
- Genotype of the purple flower in the P generation: PP
- Genotype of the white flower in the P generation: pp
- Genotype of the flowers in the F1 generation: Pp
- The ratio of possible genotypes of individuals in the F2 generation: 1 PP: 2 Pp: 1pp
- The ratio of possible phenotypes of individuals in the F2 generation: 3 purple: 1 white
- Kate and Joe are the parents of Curtis and Anne. Curtis is color blind, but his sister Anne, isn’t. Neither of his parents is colorblind. Color blindness is caused by a recessive sex-linked gene.
- If N = normal vision and n = color blind, then Kate is XNXn and Joe is XNY
- Anne most likely genotype is could be XNXN or XNXn
- If Anne was colorblind, her genotype have to be XnXn
- Anne’s parents’ genotypes have to be for Anne to have been born color blind: XNXn and XnY OR XnXn and XnY
- Curtis cannot pass his colorblind allele to his son because males pass their Y chromosome to the sons. However, if Curtis had a son with a woman who was colorblind (XnXn) or carried the colorblind allele (XNXn), his son could be colorblind.
- The red allele and white allele show incomplete dominance.
- If a short plant with pink flowers is crossed with a heterozygous tall plant with red flowers, what are the genotypes of the plants?
  - Short pink = Rrtt
  - Tall red = RRTt
  - Phenotypic ratio = 1 Red tall: 1 red short: 1 pink tall: 1 pink short

Population Genetics & Gene Expression

Hardy-Weinberg equation: $p^2+ 2pq+ q^2 = 1$
- frequency of the recessive allele: q
- frequency of the dominant allele: p
- frequency of the homozygous recessive genotype: $q^2$
- frequency of the homozygous dominant genotype: $p^2$
- frequency of the heterozygous genotype: 2pq
In a population of 1,000 rabbits, 160 show the recessive phenotype (white fur, genotype ff). The dominant allele (F) codes for gray fur. Assume Hardy-Weinberg conditions.
- frequency of the f allele: 0.4
- frequency of the F allele: 0.6
- expected genotype frequencies:
  - FF = 0.36
  - Ff = 0.48
  - ff = 0.16
Conditions for a population to be in Hardy-Weinberg equilibrium:
- No mutations – The DNA of individuals must not change.
- Random mating – Individuals must pair by chance, not by choosing certain traits.
- No natural selection – All traits must give equal chances of survival and reproduction.
- Extremely large population size – To prevent changes by chance (genetic drift).
- No gene flow – No new individuals can enter or leave the population.
- Why real populations rarely meet all conditions: In nature, mutations happen, individuals choose mates, natural selection favors some traits, populations are often small, and there is usually movement in and out of populations. Because of these factors, allele frequencies often change, and most real populations are not in perfect equilibrium.
population of beetles has a higher-than-expected number of heterozygotes because of heterozygote advantage — meaning individuals with one dominant and one recessive allele have a better chance of surviving or reproducing than either homozygote. This indicates that natural selection is acting on the population, favoring heterozygous individuals.
DNA:
- Steps of DNA Replication:
  - Unzipping – The DNA double helix is unwound by helicase. Hydrogen bonds between base pairs are broken, creating two single strands.
  - Building – DNA polymerase adds complementary DNA nucleotides to the original strands.
  - Proofreading – DNA polymerase checks for and corrects errors.
- DNA must be replicated in the S (synthesis) phase so that each new daughter cell gets a full set of genetic information after cell division. Without replication, cells would lose DNA with each division.
- mRNA that was 336 nucleotides long has 111 amino acids in the protein produced.
- The triplet that codes for the start of protein production:
  - DNA triplet = TAC
  - Start codon = AUG, which also codes for the amino acid methionine.
    Transcription is the process of making mRNA using the DNA template; translation is the process of making a polypeptide chain using the mRNA.
Molecule Table:
- DNA
  - Type of sugar: deoxyribose
  - Nitrogenous bases: A, T, C, G
  - Strands: double
  - Groups of three name: triplet
- mRNA
  - Type of sugar: ribose
  - Nitrogenous bases: A, U, C, G
  - Strands: single
  - Groups of three name: codon
- tRNA
  - Type of sugar: ribose
  - Nitrogenous bases: A, U, C, G
  - Strands: single
  - Groups of three name: anti-codon
Three main types of mutations:
- Substitution (Point Mutation): One nucleotide is replaced by another. May result in a different amino acid, or sometimes no change at all (silent mutation).
- Insertion: One or more nucleotides are added to the DNA sequence. This can cause a frameshift, changing the way the codons are read during translation and resulting in a new set of amino acids.
- Deletion: One or more nucleotides are removed from the DNA sequence. Like insertion, this can cause a frameshift and significantly change the resulting protein.
Gel:
- Lane 1 contains the largest molecule because it migrated the shortest distance. Lane 3 contains the smallest molecule because it migrated the greatest distance.
- The molecules are negatively charged. They might be DNA fragments because the phosphate groups in the DNA backbone carry a negative charge. We can tell because during electrophoresis, they moved toward the positive electrode (opposites attract), showing that the molecules are negatively charged.
- Restriction enzymes cut DNA at specific sequences. This creates DNA fragments of different lengths. When used in gel electrophoresis, these fragments are separated by size, allowing scientists to compare DNA samples or analyze genetic differences.
Stem cells are unspecialized cells that can divide and become many different types of differentiated cells. In regeneration, stem cells help replace damaged or lost tissues by turning into the needed cell types (like skin, nerve, or muscle cells).
In different cells of an organism, All cells in an organism have the same DNA. However, different cells turn on (express) different genes depending on their function (e.g., muscle vs. nerve cells).
Gene regulation allows cells to use only the genes they need for their specific job. This is important so that different cells perform different functions, and the body works properly. It also helps cells respond to changes in the environment or signals from other cells.
PCR (Polymerase Chain Reaction) is a technique that makes millions of copies of a specific DNA segment. It's useful for things like DNA testing, disease detection, forensics, and research where only a small DNA sample is available.
CRISPR is a gene-editing tool that allows scientists to cut and modify specific DNA sequences in an organism. It is useful for fixing genetic disorders, studying genes, modifying crops, and developing treatments for diseases.