Science exam terms

DNA sequence

It is the specific order of nitrogen bases (A, T, G, C). It carries genetic instructions. It has the order of the four DNA bases (letters):
A = Adenine
T = Thymine
G = Guanine
C = Cytosine

Complementary DNA strand

Where each base pairs with a specific partner:

A ↔ T and G ↔ C.

Example: If one strand is A-T-G-C, the complementary is T-A-C-G.

Nucleotide parts

It includes the following:

• A phosphate group
  

• A deoxyribose sugar
  

• A nitrogen base (A, T, C, or G)

DNA base pairing

The rules:

• Adenine (A) goes with Thymine (T)
  
  

• Guanine (G) goes with Cytosine (C)

characteristics

Traits are determined by genes inherited from parents. These include physical traits like eye color or height.

monohybrid cross

A punnett squeare involving one trait (e.g., eye color).

Example: Crossing Bb × Bb gives a 3:1 dominant-to-recessive phenotype ratio.

x-linked traits

Traits found on the X chromosome.

Males (XY) are more likely to show X-linked disorders because they have only one X chromosome.

Females (XX) can be carriers.

heterozygous crosses

Where combination of traits has one dominant and one recessive allele (e.g., Aa).
Aa × Aa → 75% show dominant trait, 25% show recessive.

codominance

Where both alleles show up equally in the phenotype.
Example: Blood type AB shows both A and B alleles.

physical feature

It is a (phenotype) is influenced by genotype and sometimes the environment

natural selection

Four key components:

• Variation

• Inheritance

• Overproduction

• Survival of the fittest (selection)

 mutations

A change in DNA sequence. It can be helpful, harmful, or neutral — and may cause genetic disorders or create variation.

biotechnology

using bio systems, living organisms, or parts of them to develop products, processes, or services

GMOs

any living thing whose genetic code (DNA) has been changed to improve the way it grows, thrives, looks or tastes (genetically modified organisms)

DNA analysis

the process of examining an individual's deoxyribonucleic acid (DNA) characteristics, often used for identification, forensics, or genetic research

chemical reactions

- process in which atoms of one

or more substances are rearranged to form different

substances

- break food down into nutrients

that the body can use.

- are in our everyday life, from

the plastics we use to the synthetic fibres that we

wear and the healthcare products we put on

ourselves.

ionic and covalent compounds

-They form when electrons are transferred between metals and nonmetals. Covalent compounds form when electrons are shared between two nonmetals.

- atoms give electrons to become stable. In covalent bonds, atoms share electrons.

Lewis diagrams

- Drawings that show an atom’s valence electrons.
- Dots represent electrons around element symbols. They help show bonding between atoms.

Oxygen

-It is is a gas that supports life and helps things burn.
- In breathing and burning, oxygen reacts with other substances to release energy.

chemical reaction

-A process where substances change into new substances.
- Atoms rearrange and form new bonds, creating products.

chemical reaction

-A reaction that makes something new.
-Reactants change by breaking and forming chemica

 Balancing a chemical reaction

-Making sure both sides of a chemical equation have the same number of each atom.
- You add coefficients to match the number of atoms on both sides (reactants = products).

endothermic reaction

reaction that absorbs heat.
- It feels cold because energy is taken from the surroundings.

-Reactants are lower than the products

Photosynthesis

 -A process where plants make food using sunlight.
-Plants use sunlight, carbon dioxide, and water to make sugar and oxygen.

energy level diagram

- Shows how energy is absorbed or released in a reaction.
-It shows reactants, products, and energy changes (up for endothermic, down for exothermic).

decomposition reaction

-A reaction where one compound breaks into simpler parts.
-One substance breaks into two or more products.

single replacement reaction

-A reaction where one element swaps with another in a compound.
-A more reactive element takes the place of another in a compound.

pH scale

-Goes from 0–14 that measures how acidic or basic a substance is.
-Low pH = acid, high pH = base, 7 = neutral (like water).

neutralization reaction

-Reaction between an acid and a base that forms water and a salt.
- The acid's H⁺ and base's OH⁻ combine to form water.

predicting products of a reaction

Figuring out what new substances will form in a chemical reaction.
Use reaction types and rules to guess what products will form.

type of chemical reaction

-The category a reaction fits into (e.g., synthesis, decomposition).
-Reactions follow patterns you can match to known types.

potential/kinetic energy

-where one has stored energy and the other has energy of movement.
-A still object has potential energy; a moving one has kinetic.

conservation of energy

-Where energy cannot be created or destroyed, only changed.
-Energy transforms (like potential to kinetic) but total stays the same.

potential energy calculation

-Energy due to position (height).
-Formula: PE = mgh (mass × gravity × height)

 kinetic energy calculation

-Energy of motion.
-Formula: KE = ½mv² (½ × mass × velocity squared)

 kinetic energy, solving for mass

-Rearrange KE formula: m = (2 × KE) ÷ v²

kinetic energy, solving for velocity

- Rearrange KE formula: v = √[(2 × KE) ÷ m]

fuel cells

- Devices that make electricity from chemical reactions.
- Hydrogen reacts with oxygen to make electricity and water.

nuclear reactor

-A machine that produces energy from nuclear reactions.
-Splits atoms to release heat, which makes steam to turn turbines.

energy

-Different forms and how energy is transferred or transformed.

radiant energy

Energy from light or electromagnetic waves.
Comes from the sun and can be absorbed or reflected.

fossil fuel concerns

Problems with using coal, oil, and gas.
Burning them releases pollution and carbon dioxide, harming the planet.

fuel cells

Devices that make electricity from chemical reactions.

Hydrogen reacts with oxygen to make electricity and water.

nuclear reactor

A machine that produces energy from nuclear reactions.
Splits atoms to release heat, which makes steam to turn turbines.

energy transfer

Moving energy from one place or object to another.
Like heat moving from a stove to a pot of water.

circulating heat

Heat moving in fluids by convection.
Hot fluids rise, cold fluids sink, creating a cycle.

clouds

Water vapor condensed in the sky.
Water vapor cools and sticks to particles to form clouds

water cycle

The movement of water through Earth’s systems.
Includes evaporation, condensation, precipitation, and runoff.

 water

A liquid made of hydrogen and oxygen (H₂O).
Essential for life, used in reactions and as a solvent.

past study of sky objects

Ancient people studied stars to tell time and navigate.

Used constellations and star patterns to track seasons.

celestial sphere

An imaginary dome where sky objects appear to move.
Helps map positions of stars and planets in the sky.

ecliptic

The path the sun appears to take through the sky.
Based on Earth’s orbit; used to track seasons.

movement of celestial objects

Planets and stars move across the sky due to Earth’s rotation.
Sun rises in the east and sets in the west.

retrograde motion

When a planet looks like it moves backward in the sky.
Happens because Earth moves faster than outer planets.

azimuth

The direction along the horizon (measured in degrees).
Tells you which direction to look to find an object.

astronomical units

A unit of distance in space (1 AU = distance from Earth to Sun).
Used to measure distances in the solar system.

star formation

Stars form from clouds of gas and dust.
Gravity pulls gas together until nuclear fusion starts.

Study of universe

Astronomy is the study of stars, planets, and galaxies.
Uses telescopes and models to understand space.

galactic speed

How fast galaxies move away from each other.
Measured by redshift; faster speed = farther away.

Universe radiation

Background energy left over from the Big Bang.
Detected as microwave signals everywhere in space.

Hubble constant

The rate at which the universe is expanding.
Helps calculate the age and size of the universe

• Genotype

• Is the genetic code of an organism.

  It describes the combination of alleles (versions of genes) an organism has.

  Example: Aa, BB, tt

• phenotype

• The phenotype is the physical trait or observable feature caused by the genotype.

• It shows how the genes are expressed.

• Example: Brown eyes, curly hair, tall plant