Genetics, Evolution, and Taxonomy Overview

Gregor Mendel

Gregor Mendel is known as the father of genetics; he studied inheritance in pea plants.

Traits

Traits are controlled by genes, which are segments of DNA.

Phenotype

Physical appearance.

Genotype

Genetic makeup (e.g., Bb).

Dominant trait

A dominant trait is expressed if at least one dominant allele is present.

Recessive trait

A recessive trait is only expressed when both alleles are recessive.

Law of Segregation

Alleles for a trait separate during gamete formation.

Principle of Dominance

Some alleles are dominant and mask the effect of recessive alleles.

Homozygous dominant

AA.

Homozygous recessive

aa.

Heterozygous

Aa.

Law of Independent Assortment

Genes for different traits can segregate independently during gamete formation.

Punnett squares

Punnett squares are used to predict the probability of inheriting traits.

Incomplete dominance

Blend of traits (red + white = pink).

Codominance

Both traits are expressed equally (e.g., black + white = speckled).

Multiple alleles

More than two allele forms for a gene (e.g., blood types: A, B, O).

Punnett squares

A diagram used to predict the outcome of a genetic cross.

Polygenic traits

Traits controlled by multiple genes (e.g., skin color, height).

Sex-linked traits

Traits found on sex chromosomes (usually the X); more common in males.

Meiosis

A process that produces gametes (sperm/egg) for sexual reproduction.

Meiosis I

The phase of meiosis where homologous chromosomes separate.

Meiosis II

The phase of meiosis where sister chromatids separate.

Meiosis I result

2 haploid cells.

Meiosis II result

4 haploid cells (gametes).

Genetic diversity

Created by crossing over, independent assortment, and random fertilization.

Hydrogen bonds

Hold DNA strands together (between bases).

Watson and Crick

Discovered DNA's double helix structure.

DNA replication

Occurs during the S phase of interphase.

Helicase

Enzyme that unwinds the DNA double helix.

Semi-conservative

Each new DNA molecule has one old strand and one new strand.

DNA polymerase

Adds complementary nucleotides during DNA replication.

DNA ligase

Joins Okazaki fragments on the lagging strand.

Okazaki fragments

Short DNA fragments made on the lagging strand.

mRNA

Carries the genetic code from DNA to ribosomes.

Transcription

Occurs in the nucleus of eukaryotic cells.

tRNA

Carries amino acids to the ribosome during translation.

Ribosome

Assembles amino acids into proteins using mRNA.

Translation

Converts mRNA into amino acids (protein).

Codon

A three-base sequence on mRNA that codes for an amino acid.

Mutation

A change in DNA sequence.

Point mutation

One base change in the DNA sequence.

Frameshift mutation

Insertion or deletion changes the reading frame.

Evolution

Change in a species over time.

Natural selection

Survival and reproduction of organisms best suited to the environment.

Homologous structures

Similar structure, different function (e.g., arm and wing).

Vestigial structures

Structures no longer used (e.g., appendix).

Artificial selection

Human-controlled breeding; natural selection occurs in nature.

Speciation

Formation of a new species due to isolation and genetic changes.

Taxonomy order

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Eukaryotic kingdoms

Four kingdoms: Protista, Fungi, Plantae, Animalia.

Prokaryotic domains

Bacteria and Archaea; they lack a nucleus.

Viruses

Made of DNA or RNA in a protein coat.

Lytic cycle

Virus replicates and bursts the host cell.

Lysogenic cycle

Virus DNA integrates and stays dormant.

Bacteria reproduction

Occurs through binary fission (asexual).

Gram-positive

Bacteria with thick peptidoglycan, purple stain.

Gram-negative

Bacteria with a thin wall, pink stain.

Malaria

Caused by Plasmodium, a protist.

Protists movement

Move using cilia, flagella, or pseudopodia.

Fungi

Heterotrophs that absorb food.

Lichen

Symbiosis between fungi and algae.

Mycorrhizae

Fungi associated with plant roots.

Fungi reproduction

Occurs by spores (asexual or sexual).

Hyphae

Thread-like cells that make up fungi.

Mycelium

Network of hyphae.

Fruiting body

Reproductive structure (e.g., mushroom).

Mollusks

Have soft bodies, often with shells, and a muscular foot.

Frogs

Belong to Phylum Chordata (they have a backbone).

Earthworms

Belong to Phylum Annelida and have segmented bodies.

Gastropods

Snails that have a coiled shell, muscular foot, and radula (tongue-like organ).