Campbell Unit 3: Genetics

Genes

Genes

The hereditary units that parents endow offspring with, which contain coded information.

Heredity

The transmission of traits from one generation to the next.

Variation

The occurrence of differences in traits alongside inherited similarities.

Genetics

The study of both heredity and variation.

Gametes

The vehicles that transmit genes from one generation to the next.

Somatic Cells

All body cells other than gametes and their precursors.

Locus

The specific location of a gene along the length of a chromosome.

Asexual Reproduction

When a single individual is the sole parent, passing on all of its genes to the offspring without fusing gametes.

Clone

An organism that is genetically identical to its parent, resulting from asexual reproduction.

Sexual Reproduction

When parents give rise to offspring with unique combinations of genes inherited from both parents.

Life Cycle

The generation-to-generation sequence of stages in the reproductive history of an organism, including conception and the production of offspring.

Karotype

Images of chromosomes arranged in pairs, starting with the longest.

Homologous Chromosomes (Homologs)

Chromosomes with the same length, centromere position, and staining patterns.

Sex Chromosomes

The X and Y chromosomes that determine an individual's sex.

Autosomes

The other chromosomes that are not sex chromosomes.

Diploid Cell

A cell with two sets of chromosomes (2n).

Haploid Cell

A cell with a single set of chromosomes (n), such as gametes.

Fertilization

The union of gametes, resulting in the fusion of their nuclei.

Zygote

The resulting fertilized egg, which is diploid.

Meiosis

The cell division process that leads to the formation of gametes.

Genomic Imprinting

When the allele inherited depending on which parent (male or female) changes the phenotype

Mitochondrial Inheritance

Inheritance of traits controlled by genes present in mitochondria and plastids depend solely on the material parent

DNA

The genetic material that carries the instructions for the synthesis of proteins

Transformation

A change in genotype and phenotype due to assimilation of external DNA by a cell

Nucleotide

The building blocks of DNA, consisting of a nitrogenous base, a deoxyribose sugar, and a phosphate group

Chargaff's Rules

DNA base composition varies between species, but for every species, the % of A and T are equal, same with C and G

Double Helix

The structure of DNA, consisting of two polynucleotide strands wound around each other in a spiral shape

RNA

Ribonucleic acid, a molecule involved in protein synthesis that carries the genetic message from DNA to the ribosomes

Transcription

The synthesis of RNA using information from the DNA

Translation

The synthesis of a polypeptide using the information from mRNA

Promoter

A DNA sequence where RNA polymerase attaches and begins transcription

RNA Processing

Enzymes in eukaryotic nucleus modify pre-mRNA before it is dispatched to the cytoplasm

RNA Splicing

The removal of introns and joining of exons in the RNA molecule

Transfer RNA (tRNA)

A type of RNA that carries amino acids to the ribosome during translation

Ribosome

The site of translation, where amino acids are added to the growing polypeptide chain

Point Mutation

A change in a single nucleotide pair of a gene, which can affect protein structure and function

Missense Mutation

A substitution that changes one amino acid into another.

Nonsense Mutation

A mutation where the codon for an amino acid is changed into a stop codon, resulting in a shorter polypeptide.

Insertion

The addition of nucleotide pairs in a gene.

Deletion

The loss of nucleotide pairs in a gene.

Frameshift Mutation

A mutation where the number of nucleotides inserted or deleted is not a multiple of three.

Mutagens

Physical and chemical agents that cause mutations in DNA.

Gene Editing

The alteration of genes in a specific and predictable way.

CRISPR-Cas9 System

A new technique for gene editing that utilizes the Cas9 protein.

Cas9

A bacterial protein that helps defend bacteria against viruses.

Operon

DNA required for enzyme production and the tryptophan pathway, including the operator and promoter.

Operator

A segment of DNA that acts as an on-off switch for transcription units.

Repressor

Binds to the operator to prevent RNA polymerase from transcribing genes, acting as the "off switch" of an operator.

Regulatory Gene

Encodes the repressor protein and is expressed continually in bacteria.

Corepressor

A small molecule that cooperates with the repressor to turn an operon off.

Inducer

Binds to the operator and inactivates the repressor.

Cyclic AMP (cAMP)

A small organic molecule that stimulates transcription by interacting with an allosteric regulatory protein.

Activator

A protein that binds to DNA and stimulates transcription.

Differential Gene Expression

The expression of different genes by cells with the same genome, leading to differences between cell types.

Histone Acetylation

The addition of an acetyl group to an amino acid in a histone tail, promoting transcription by opening up chromatin structure.

DNA Methylation

The methylation of DNA on certain bases, usually cytosine.

Epigenetics

The study of inheritance of traits transmitted by mechanisms not involving the nucleotide sequence itself.

Control Elements

Segments of noncoding DNA that serve as binding sites for proteins, such as transcription factors, which regulate transcription.

Enhancers

Groupings of distal control elements that may be located thousands of nucleotides up or downstream of a gene or within an intron.

Alternative RNA Splicing

The production of different mRNA molecules from the same primary transcript, depending on which parts are considered exons.

MicroRNAs (miRNAs)

Small, single-stranded RNA molecules capable of binding to complementary sequences in mRNA molecules.

Small Interfering RNAs (siRNAs)

Small noncoding RNAs similar in size and function to miRNAs.

RNA Interference (RNAi)

The blocking of gene expression by siRNAs.

Long Noncoding RNAs (lncRNAs)

Long and noncoding strings of RNA.

Differentiation

The process by which cells become specialized in structure and function.

Morphogenesis

The development of the form of an organism and its structures.

Cytoplasmic Determinants

Maternal substances in the egg that influence the course of early development.

Induction

Signals conveyed to an embryonic cell from other embryonic cells in the vicinity that cause changes in target cells.

Determination

The point at which an embryonic cell is irreversibly committed to becoming a particular cell type.

Pattern Formation

The spatial organization of tissues and organs in an organism, involving cytoplasmic determinants and inductive signals.

Positional Information

Molecular cues that control pattern formation.

Homeotic Genes

Regulatory genes that control pattern formation.

Embryonic Lethals

Mutations with phenotypes causing death at the embryonic or larval stage.

Maternal Effect Gene

A gene that, when mutant in the mother, results in a mutant phenotype in the offspring.

Morphogens

Gradients of substances that establish an embryo's axes and other features of its form.

Oncogenes

Cancer-causing genes found in certain types of viruses.

Proto-Oncogenes

Normal versions of oncogenes.

Tumor Suppressor Genes

Genes whose products inhibit cell division.

Ras Gene

A G protein that relays a signal from a growth factor receptor to a cascade of protein kinases.

p53 Gene

A tumor suppressor gene named for the molecular weight of its protein product.

Virus

An infectious particle consisting of nucleic acid surrounded by a protein coat.

Capsid

The protein shell enclosing the viral genome.

Viral

Pseudogenes

Former genes that have accumulated mutations over time and no longer produce functional proteins, unique noncoding DNA.

Repetitive DNA

Sequences that are present in multiple copies in the genome.

Transposable Elements

Stretches of DNA that can move from one location to another within the genome. In eukaryotes, two types:transposons and retrotransposons.

Transposons

Move within a genome using a DNA intermediate. Can use either a "copy and paste" or "cut and paste" method using transposase.

Retrotransposons

Move by means of an RNA intermediate, leaving a copy at the original site.

Simple Sequence DNA

Stretches of DNA that contain many copies of tandemly repeated short sequences.

Short Tandem Repeat (STR)

Series of repeats in a unit.

Multigene Families

Collections of 2+ identical or very similar genes. Can be clustered tandemly or encode different globin proteins.

Duplication, rearrangement, and mutation of DNA contribute to genome evolution.

Polyploidy

Errors in cell division lead to extra copies of all or part of entire chromosome sets, contributing to speciation.

Chromosomal organization of genomes can be compared among species to provide information about evolutionary relationships.

Genes encoding various related but different globin proteins evolved from one common ancestral globin gene through duplication and divergence.

Rearrangement of exons within and between genes during evolution has led to genes containing multiple copies of similar or different exons.

Movement of transposable elements or recombination between copies of the same element generates new sequence combinations, which can be beneficial to the organism.

Comparing genome sequences provides clues to evolution and development.

Evo-Devo

Evolutionary developmental biology.

Homeobox

A 180 nucleotide sequence that codes for a homeodomain (amino acid) in the encoded proteins.