Resources on Inheritance, Genes, Cell Division, Variation, and Natural Selection

Inheritance

The process by which genetic information is passed down from parents to offspring, determining traits like eye color, hair type, and other characteristics.

Chromosomes

Long strands of DNA that carry genetic information; humans typically have 46 chromosomes organized into 23 pairs.

Gene

A small section of DNA located on a chromosome, responsible for coding specific proteins that influence traits such as eye color or height.

DNA

The molecule that contains the genetic blueprint for living organisms, shaped like a twisted ladder (double helix) and made of four building blocks called bases.

Protein

Large, complex molecules made up of amino acids that perform various functions in the body, such as providing structure, speeding up chemical reactions, and regulating processes.

Nucleotide

The basic building block of DNA, consisting of a phosphate group, a sugar, and a nitrogenous base (A, T, C, or G).

Double helix

The spiral structure of DNA, which looks like a twisted ladder, with two strands wound around each other.

Bases

The four fundamental components of DNA (adenine, thymine, cytosine, and guanine) that pair up to form the steps of the DNA ladder.

Genetic code

The set of instructions encoded in DNA, where groups of three bases (triplets) correspond to specific amino acids, which are the building blocks of proteins.

Alleles

Different versions of a gene that may result in variations in traits, such as having blue or brown eyes.

ABO gene

The gene that determines blood type, which has three variations: Iᴬ (A), Iᴼ (O), and Iᴺ (B).

Phenotype

The observable physical characteristics of an organism, like height, color, and shape, resulting from the interaction between its genes and the environment.

Genotype

The genetic makeup of an organism, referring to the specific alleles it possesses for a particular trait.

Dominant allele

An allele that can express its trait even when only one copy is present in the genotype, overshadowing the effect of a recessive allele.

Recessive allele

An allele whose characteristic only shows up if two copies are present in the genotype, meaning the dominant allele is absent.

Homozygous

Having two identical alleles for a trait, either both dominant or both recessive.

Heterozygous

Having two different alleles for a trait, one dominant and one recessive.

Protein synthesis

The process by which cells create proteins based on the instructions found in DNA through two main stages: transcription (making RNA from DNA) and translation (building proteins from RNA).

Transcription

The first step in protein synthesis where the DNA sequence of a gene is copied into messenger RNA (mRNA), which carries the genetic information out of the nucleus.

Translation

The second step in protein synthesis where the ribosomes read the mRNA sequence and use it to string together amino acids in the correct order to form a protein.

mRNA (messenger RNA)

A type of RNA that carries the genetic instructions from the DNA in the nucleus to the ribosomes in the cytoplasm, where proteins are made.

Ribosomes

Cell structures that act as the site of protein synthesis, reading the sequence of mRNA and assembling amino acids into proteins.

Triplet

A group of three bases in mRNA that specifies a particular amino acid during the process of protein synthesis.

Amino acid

The building blocks of proteins; there are 20 different amino acids that combine in various sequences to form proteins.

Gene expression

The process by which a gene's instructions are turned into a functional product, such as a protein, in a specific cell type.

Haploid cells

Cells that contain one complete set of chromosomes; in humans, these are the egg and sperm cells, which have 23 chromosomes.

Diploid cells

Cells that contain two complete sets of chromosomes, one from each parent; all human body cells except gametes are diploid and have 46 chromosomes.

Gametes

The reproductive cells (sperm in males and eggs in females) that are haploid and combine during fertilization to form a new organism.

Mitosis

The process of cell division that results in two identical daughter cells, used for growth, tissue repair, and asexual reproduction.

Stem cells

Undifferentiated cells capable of dividing and developing into various specialized cell types in the body.

Zygote

The fertilized egg that forms when sperm and egg cells unite; it is the first stage of a new organism's development.

Meiosis

A specialized form of cell division that reduces the chromosome number by half, producing four genetically unique haploid gametes.

Reduction division

Another term for meiosis, emphasizing the halving of the chromosome number from diploid to haploid.

Punnett square

A tool used in genetics to predict the probability of an offspring inheriting particular traits based on the genotypes of the parents.

Monohybrid inheritance

Inheritance pattern that tracks the passing of a single trait controlled by one gene.

Codominance

A genetic situation where both alleles in a heterozygous genotype are fully expressed, leading to a trait that is a blend of both parent traits.

Sex chromosomes

The pair of chromosomes that determine an individual's sex; females typically have two X chromosomes (XX), while males have one X and one Y chromosome (XY).

Carrier

A person who has one recessive allele for a trait but does not show the trait; they can pass the recessive allele to their offspring.

Variation

Differences among individuals within a species, which can arise from genetic, environmental, or a combination of both factors.

Phenotypic variation

The range of physical traits observed within a population, such as variations in height, skin color, or disease resistance.

Continuous variation

A trait that can have many variations and is usually influenced by multiple genes and environmental factors, such as height or weight.

Discontinuous variation

A trait that has distinct categories with no intermediates, such as blood type or ability to roll one's tongue.

Genetic variation

The differences in DNA sequences among individuals, which contribute to unique traits and characteristics.

Environmental variation

Differences in traits among individuals caused by their environments, like temperature, nutrition, or exposure to sunlight.

Mutation

A change in the DNA sequence that can lead to new traits, some of which may be beneficial, harmful, or neutral.

Allele combination

The specific pairing of alleles received from both parents for a particular gene, which determines an individual's traits.

Recombination

The process during meiosis where genetic material is exchanged between paired chromosomes, creating new allele combinations.

Adaptive features

Traits that have evolved in response to environmental challenges, helping organisms survive and reproduce effectively.

Natural selection

The process where individuals with advantageous traits are more likely to survive and reproduce, passing those traits to the next generation.

Survival of the fittest

A phrase that describes how individuals best adapted to their environment are more likely to survive, reproduce, and pass on their traits.

Evolution

The gradual change in species over time, primarily driven by natural selection as populations adapt to changing environments.

Adaptation

The process through which populations develop traits that enhance their survival and reproductive success in a specific environment.

Artificial selection (Selective breeding)

The human practice of breeding animals and plants for specific traits, enhancing desirable qualities over generations.

Test cross

A breeding experiment to determine an unknown genotype by crossing it with a known homozygous recessive individual, revealing the offspring's traits.

Linked alleles

Genes that are located close together on the same chromosome and are typically inherited together.

Pedigree diagrams

Family trees that trace patterns of inheritance for specific traits or diseases across generations.

Homozygous dominant

Having two identical dominant alleles for a specific gene.

Homozygous recessive

Having two identical recessive alleles for a specific gene.

Pure breeding

Individuals that consistently produce offspring with the same traits because they are homozygous for those traits.

Mutation rate

The frequency at which mutations occur within a population or individual.

Gamete formation

The process through which gametes (sperm and eggs) are produced during meiosis.

Fertilisation

The combining of a sperm and an egg to form a zygote, marking the beginning of a new organism's life.

Chromosome pair

Matching pairs of chromosomes, one inherited from each parent, that carry genes for the same traits.

Sex determination

The biological mechanism that establishes the sex of an offspring based on the inherited sex chromosomes.

DNA base sequence

The order of nucleotides (A, T, C, G) in a DNA molecule that encodes genetic information.

Amino acid sequence

The specific order of amino acids in a protein, determining its structure and function.

Enzyme

A type of protein that accelerates chemical reactions within the body, making them occur faster and more efficiently.

Hormone

A signaling molecule produced by glands that regulates various physiological processes in the body.

Structural protein

Proteins that provide support and structure to cells and tissues, such as collagen found in skin and cartilage.

Antibody

A protein produced by the immune system that identifies and helps to fight off pathogens like bacteria and viruses.

Receptor

A molecule on the surface of cells that binds to signaling molecules, triggering specific cellular responses.

Nuclear pore

Tiny openings in the nuclear envelope that allow molecules to transfer between the nucleus and the cytoplasm.

Cytoplasm

The jelly-like substance inside a cell, excluding the nucleus, where various cellular processes occur.

Cell fibre

Structures that assist in the movement of chromosomes during cell division.

Recombinant chromosome

A chromosome that has been altered through recombination, resulting in a new arrangement of genetic material.

Antigen

A substance that triggers an immune response; in blood types, antigens A and B are present or absent depending on the genotype.

Linked genes

Genes that are located close to each other on the same chromosome usually inherited together.

X chromosome

One of the two sex chromosomes in humans; females have two X chromosomes, while males have one X and one Y chromosome.

Y chromosome

The sex chromosome found only in males; it determines male biological traits when paired with an X chromosome.

Genetic diagram

Visual representations used to show how genes are inherited, such as Punnett squares.

Family pedigree chart

A visual representation of the inheritance of a specific trait across generations in a family.

Test cross ratio

The ratio of phenotypes among offspring produced in a test cross, helping to determine the genotype of a parent with a dominant trait.

Codominant alleles

Alleles that both contribute to the organism's phenotype when present together, such as in blood type inheritance where both A and B can be expressed.

Sex

Linked recessive traits, which are determined by genes located on the sex chromosomes.

Mutation effect

The impact that a mutation has on an organism's phenotype, which can range from no visible effect to harmful or advantageous changes.

Spontaneous mutation

A mutation that occurs naturally without any external influences or known causes.

Induced mutation

A mutation that results from exposure to external factors, such as chemicals or radiation, that alter the DNA.

Adaptation mechanism

Specific features or behaviors that enhance an organism's ability to survive in its environment (e.g., a cactus's adaptations for conserving water).

Natural selection pressure

Environmental factors that impact the survival and reproduction of certain traits within a population, influencing evolution.

Selective breeding goal

The characteristics that breeders aim to enhance in plants or animals through selective breeding, like flavor in crops or appearance in pets.

Continuous trait

A characteristic that shows a range of variations, such as height, which can be measured on a scale.

Discrete trait

A characteristic that has limited variation, such as the presence of a gene for tongue rolling (either you can or cannot roll your tongue).

Genome

The complete set of genetic material contained within an organism, including all of its genes.

Mapping

The process of identifying the location of genes on chromosomes to better understand genetic traits.

Personalised Medicine

Medical care tailored to the individual characteristics, needs, and preferences of a patient, often based on genetic information.

CRISPR

A revolutionary tool for editing genes, allowing scientists to precisely modify DNA in various organisms.

Excretion

The process by which living organisms eliminate waste products and toxins from their bodies.

Excretory system

The organ system responsible for removing waste from the body, including the kidneys, ureters, bladder, and urethra.

Kidney

The organs that filter blood to remove waste products and excess substances, producing urine in the process.

Filtration

The process of separating solid particles from liquids or gases using a filter.