Biology Test - Melanin, Genetics, Protein Synthesis, and Evolution

Work Cited Zhang, Michael. ““It’s Test Time Again” (Melanin Test).” Google Docs, Bergen County Academies, 25 Mar. 2026, docs.google.com/document/d/1SE7iX0RAkWfy7Ix1e9ZK_KP-x5kv8KGnkwKMufkDkPU/edit?tab=t.424l8898onwj#heading=h.ck5ezwhcvnm. Accessed 25 Mar. 2026.

DNA

deoxyribonucleic acid, is in the nucleus and contains genetic information in chromosomes

Gene

A segment of DNA on a chromosome that codes for a specific trait

Chromosome

a threadlike structure of DNA, containing genetic information

Incomplete Dominance

Both alleles are blended, resulting in offspring with a mix of their parents' traits (Ex: White flower + Red flower = Pink flower)

Codominance

Both alleles are expressed (Ex: Brown Cow + White Cow = Brown cow with some white)

Multiple Alleles

Multiple alleles coding for the same gene, each with varying levels of dominance (Ex: Black > Chinchilla > Himalayan > Albino fur colors in rabbits)

Dihybrid Crosses

4x4 punnet square, checks for two traits rather than 1

Polygenic inheritance

Multiple genes affect a single trait, usually resulting in a spectrum of traits rather than a set (Ex: Skin color)

Law of Independent Assortment

Mendel's law, states that allele pairs separate from one another during gamete formation

Epistasis

One gene masks another (Ex: In dog coats, the A allele can be affected if the dog contains the B allele)

Albinism Inheritance

Autosomal recessive trait that causes one from a dark skinned family to have light skin

Mutation

An error made when replicating a gene that changes the codon sequence, changing the amino acid sequence and the trait expressed

Insertion

The addition of nucleotides to a codon, causing the rest of the sequence to frameshift down (AGC GCA -> ACG CGC)

Deletion

The removal of nucleotides in a codon, causing the rest of the sequence to frameshift up (AGC GCA -> ACG CAG)

Substitution

The replacement of a single codon (AGC GCA -> GCA GCA)

Frameshift

Inserting or deleting nucleotides (not a multiple of 3) that cause the reading frame of the sequence to shift

Missense

One singular base is swapped for another, resulting in a different amino acid

Nonsense

A genetic mutation resulting in a stop codon, ending the amino acid sequence early

Silent

A genetic mutation that changes a codon but does not alter the amino acid sequence

Transcription

The process occurring in the nucleus where RNA polymerase copies a DNA sequence into mRNA with a complementary sequence, replacing thymine with uracil

Translation

mRNA is released into the cytoplasm and reaches the ribosome (rRNA). tRNA with complementary codons then match with each codon, and each codon maps to a specific amino acid.

mRNA

messenger RNA; carries instructions for amino acid structure

rRNA

ribosomal RNA; catalyzes the forming of peptide bonds between amino acids

tRNA

transfer RNA; brings the amino acid correlating to the codon on the mRNA, matches based on its complementary anticodon

Cell Nucleus

The location of DNA

Codon

Bases on mRNA grouped in threes

Anticodon

Found on tRNA, is complementary to the codon

Amino Acid

Monomer of protein

Protein Synthesis

the formation of proteins by using information contained in DNA and carried by mRNA (transcription + translation)

Protein Shape

Determined by the amino acid sequence, results in different traits

Protein Function

Structure, enzymes, cell signaling

Melanin

A pigment that gives the skin its color

Pheomelanin

Melanin that causes lighter skin color. Is more common further from the equator

Eumelanin

Melanin that causes darker skin color. Is more common closer to the equator

Effect of UV Radiation

UVB required for the body to synthesize Vitamin D, UV rays destroy folate

Vitamin D

Deficiencies of vitamin D can cause rickets and other bone diseases

Folate

Prevents certain events that can harm pregnancy

Consequences of Light Skin close to the Equator

Folate destroyed

Consequences of Dark Skin far from the Equator

Little vitamin D is synthesized

Selective Advantage

A trait within an organism that gives it a higher chance of reproduction

Selective Pressure

The environment pushing against or towards the passing down of specific traits

Fitness

Ability of an organism to survive and reproduce in its environment

Pedigree

A chart or "family tree" that tracks which members of a family have a particular trait

Karyotype

The complete set of chromosomes within an individual

Punnet Square

A chart that shows all the possible combinations of alleles that can result from a genetic cross

Genotype

The genetic makeup of an organism (Ex: Bb)

Phenotype

An observable trait of an organism (Ex: Red in color)

Stabilizing Selection

Selects for average traits (Ex: Robins lay four eggs because too little eggs result in little offspring and too many eggs result in malnourishment)

Directional Selection

Selects for an extreme trait (Ex: Dark mice develop on dark rock pockets because light mice are more easily caught by predators)

Diversifying Selection

Selects for traits away from the average one, occasionally causing different species (Ex: Gray and Himalayan rabbits are hard to spot, while white rabbits are easy to prey on)

Related Species

Have a recent common ancestor

Divergent Evolution

Related species adapt with different traits

Artificial Selection

Humans select traits they want to see in offspring, developing new species

Adaptive Radiation

A group of organisms quickly diverges into new species because of environmental stresses

Convergent Evolution

Unrelated species evolve to become more similar because they live in similar habitats

Analogous Structures

Found in convergent evolution; different structures with the same function

Gradualism

Continuous change at a constant pace (gradually)

Punctuated Equilibrium

Rapid bursts of evolution followed by long periods of stability (equilibrium)

Coevolution

A species evolves in response to another (Ex: As newts produce more toxins, snakes that consume them gain more resistance)

Allopatric Speciation

New species are formed when physically separated or occupying different geographical areas (often due to a change in environment)

Sympatric Speciation

New species are formed when occupying the same area and separated by reproductive or behavioral differences

Prezygotic Isolation

A barrier to breeding that occurs before fertilization

Postzygotic Isolation

A barrier to breeding that occurs after fertilization

Temporal Isolation

prezygotic barrier: two species mate at a different time of year

Ecological Isolation

prezygotic barrier: two species inhabit similar regions but occupy different habitats

Behavioral Isolation

prezygotic barrier: two species respond to different specific courtship patterns

Mechanical Isolation

prezygotic barrier: genital differences prevent two species from being physically capable of mating

Hybrid Inviability

postzygotic barrier: hybrids are produced but fail to develop to reproductive maturity

Hybrid Infertility

postzygotic barrier: hybrids fail to produce functional gametes

Hybrid Breakdown

F1 hybrids are fertile but the F2 generation either fails to develop or is infertile

Hardy Weinberg Equation

p + q = 1, p^2 +2pq + q^2 = 1

Frequency of allele

The total amount of instances of a specific allele in a population divided by the total amount of alleles in a population

Frequency of a genotype

The total amount of instances of a specific genotype in a population divided by the total amount of genotypes

p

Frequency of the dominant allele

q

Frequency of the recessive allele

p^2

Frequency of the homozygous dominant genotype

2pq

Frequency of the heterozygous genotype

q^2

Frequency of the homozygous recessive genotype

Product Rule

Used when the probability of two or more events happening simultaneously is being tracked (and), probability of each individual event is multiplied

Sum Rule

Used when the probability of two or more mutually exclusive events are being tracked (or), probability of each individual event is added

Gene Flow

Movement of alleles from one population to another

Genetic Drift

A random change in the allele frequency of a population

True Breeding

Organisms that produce offspring identical to themselves if allowed to self-pollinate (homozygous)

Hybrids

A cross between different varieties of organisms

P generation

The true-breeding parents

F1 generation

Hybrid offspring of the P generation

F2 generation

Offspring of the F1 generation

Law of Segregation

A gamete only contains one chromosome from each pair

Locus

Location of a gene on a chromosome

Testcross

The mating of an individual with an unknown genotype and an individual with a homozygous recessive genotype

Carriers

Heterozygous individuals who carry the recessive allele, but display the dominant trait

Type A Blood

AA or Ai: contains A antigens and anti-B antibodies, can receive A and O blood

Type B Blood

BB or Bi: contains B antigens and anti-A antibodies, can receive B and O blood

Type AB Blood

AB: contains A and B antigens and no antibodies, can receive any blood

Type O Blood

ii: contains no antigens and A and B antibodies, cannot receive any blood

What happens when an individual receives the wrong blood?

Antibodies attack the antigens and cause clotting

Autosomal Chromosomes

Non sex chromosomes, 22 pairs found in humans

Sex Chromosomes

XX codes for a female, XY codes for a male. Only 1 pair of sex chromosomes in a human

Sex-linked genes

Gene located on a sex chromosome. X linked recessive traits are more common in males because they only have one X chromosome, and the trait cannot be masked

Pleiotropy

A single gene influences multiple traits