real key terms

Heritability

the ability of a trait to be passed down from one generation to the next

Laws of Mendel

law of dominance, law of segregation and law of independent assortment

Genotype

genetic makeup of an organism

Phenotype

An organism's physical appearance, or visible traits.

wildtype

the most common genotype/phenotype observed in a population

heterozygote

organism that inherits two different alleles for a given gene

homozygote

organism that inherits two alleles of the same type for a given gene

punnet square

a chart that show all the possible genotypes for the offspring of a genetic cross

genome

the complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes

gene

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

allele

Different forms of a gene

Diploid

an organism or cell having two sets of chromosomes or twice the haploid number

Haploid

An organism or cell having only one complete set of chromosomes.

Gamete

sex cell

Soma

cell body

sex chromosomes

Chromosomes that determine the sex of an individual, XY or XX

autosome

Any chromosome that is not a sex chromosome

Mitosis

part of eukaryotic cell division during which the cell nucleus divides

Meiosis

Cell division that produces reproductive cells in sexually reproducing organisms

Co-dominance

both alleles of a gene contribute to the phenotype of the organism( spotted flower)

intermediate dominance

Neither allele is dominant so the heterozygotes have a phenotype that is intermediate between the phenotypes of the two homozygotes ("blending")

incomplete dominance

Situation in which one allele is not completely dominant over another allele

epistasis

A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited.

X-linked (sex-linked)

gene found on the X chromosomes; traits more common in males since males only have one copy of the gene.

Rett Syndrome

Neurodevelopment of child (girl, as boys die in utero) fails between age 1-4, with poor head growth

additive traits

alleles combine to create a combo phenotype (codominance)

bell shaped curve

a graph of a normal distribution,

continuous traits

determined by multiple genes (polygenic), such as height or hair color

Quantative traits

a measurable phenotype that depends on the cumulative actions of many genes and the environment

Variance

standard deviation squared

Chromosomes

threadlike structures made of DNA molecules that contain the genes

Chromatid

one of two identical "sister" parts of a duplicated chromosome

Chromatin

Clusters of DNA, RNA, and proteins in the nucleus of a cell

Nucleotides

Basic units of DNA molecule, composed of a sugar, a phosphate, and one of 4 DNA bases

Nucleosomes

Bead-like structures formed by histones and DNA

Histones

protein molecules around which DNA is tightly coiled in chromatin

base pairing

principle that bonds in DNA can form only between adenine and thymine and between guanine and cytosine

double helix

Shape of DNA

DNA

A complex molecule containing the genetic information that makes up the chromosomes.

mRNA

type of RNA that carries instructions from DNA in the nucleus to the ribosome

Exons

Coding segments of eukaryotic DNA.

intorns

This portion of a DNA segment does not code for a protein.

Replication

process of copying DNA prior to cell division

genetic code

the ordering of nucleotides in DNA molecules that carries the genetic information in living cells

redundant

repetitive

Mutation

A change in a gene or chromosome.

non-synonymous substitution

Substitutions that alter the amino acid sequence of a protein. They can affect the phenotype and are therefore more subject to selection.

synonymous substitution

a substitution that does not change the encoded amino acid

transversion mutation

A point mutation in which a pyrimidine is substitued for a purine, or vice versa.

DNA repair

The removal and replacement of damaged DNA by the correct sequence

Helicase

An enzyme that untwists the double helix of DNA at the replication forks.

Polymerase

an enzyme that brings about the formation of a particular polymer, especially DNA or RNA.

Transcription

the organic process where the DNA sequence in a gene is copied into mRNA

Nucleus

A part of the cell containing DNA and RNA and responsible for growth and reproduction

alternative splicing

a cellular process in which exons from the same gene are joined in different combinations, leading to different, but related, mRNA transcripts.

Translation

Process by which mRNA is decoded and a protein is produced

Ribosome

Cytoplasmic organelles at which proteins are synthesized.

rRNA

ribosomal RNA; type of RNA that makes up part of the ribosome

tRNA

transfer RNA; type of RNA that carries amino acids to the ribosome

post-translational modification

Changes to the new protein that may be critical to its final function, like folding, phosphorylating glycosylating, or lipidating

amino acids

building blocks of proteins

Protein

An organic compound that is made of one or more chains of amino acids and that is a principal component of all cells

Polypeptide

long chain of amino acids that makes proteins

Central Dogma

DNA -> RNA -> Protein

RNA viruses

Usually single stranded, may be double stranded, may be segmented into separate RNA pieces

Transposons

segments of DNA that can move from one region of DNA to another

Epigenetics

the study of environmental influences on gene expression that occur without a DNA change

DNA methylation

The addition of methyl groups to bases of DNA after DNA synthesis; may serve as a long-term control of gene expression.

histone modification

changes in the structure of histones that make it more or less likely that a segment of DNA will be transcribed

non-coding RNA (ncRNA)

a form of RNA that does not encode for protein but has functions of its own

modern sythesis

describes how evolutionary processes, such as natural selection, can affect a populations genetic makeup and how this results in evolution

population genetics

Study of allele frequency distribution and change under the influence of evolutionary processes.

natural selection

the process whereby organisms better adapted to their environment tend to survive and produce more offspring

allele frequency

Number of times that an allele occurs in a gene pool compared with the number of alleles in that pool for the same gene

Fitness

Ability of an organism to survive and reproduce in its environment

relative fitness

the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

disruptive selection

favors individuals at both extremes of the phenotypic range

directional selection

occurs when natural selection favors one of the extreme variations of a trait

Pleiotropy

A single gene having multiple effects on an individuals phenotype

Hardy-Weinberg equilibrium

condition that occurs when the frequency of alleles in a particular gene pool remain constant over time

heterozygote advantage

individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygotes

mutation-selection balance

equilibrium in the frequency of an allele that occurs because new copies of the allele are created by mutation at exactly the same rate that old copies of the allele are eliminated by natural selection

cystic fibrosis

A genetic disorder that occurs in people with two copies of a certain recessive allele; characterized by an excessive secretion of mucus and consequent vulnerability to infection; fatal if untreated.

bottleneck effect

A change in allele frequency following a dramatic reduction in the size of a population

Tay-Sachs disease

A human genetic disease caused by a recessive allele that leads to the accumulation of certain lipids in the brain. Seizures, blindness, and degeneration of motor and mental performance usually become manifest a few months after birth.

abiotic evolution

the process of life arising from nonliving matter

RNA-first hypothesis

suggests that only the macromolecule RNA was needed to progress toward formation of the first cell or cells

Chronocyte Hypothesis

chronocyte lineage evolved a cytoskeleton and the ability to eat other microbes by phagocytosis. A chronocyte then ate an archaean that resisted digestion and became an endosymbiont. This endosymbiont eventually evolved into an organelle, the nucleus

Endosymbiosis

A theorized process in which early eukaryotic cells were formed from simpler prokaryotes.

Mitochondria

Powerhouse of the cell

uniparental inheritance

inheritance pattern in which the progeny have the genotype and phenotype of one parent only, for example, inheritance of mitochondrial genomes

Prokaryote

A unicellular organism that lacks a nucleus and membrane bound organelles

Eukaryote

A cell that contains a nucleus and membrane bound organelles

cell wall

A rigid layer of nonliving material that surrounds the cells of plants and some other organisms.

membrane

thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ

Cytoskeleton

network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement

Phagocytosis

Cell eating

Multicellularity

The state of being composed of many cells that adhere to each other and do not all express the same genes with the result that some cells have specialized functions.