Biology EXAM 3 Dr. MIKE

Centimorgan (cM)

The measurement unit for genetic maps

Short Tandem Repeats (STRs)

Repeating two to four DNA nucleotide bases that differ in number between individuals and serve as markers for genetic mapping.

Single-nucleotide polymorphisms (SNPs)

Differences in single bases of a gene locus occurring at low frequencies

Operon

In prokaryotes organized sets of genes involved in related metabolic pathways.

lac operon

A control system in prokaryotes containing genes for the digestion of lactose that is both positively and negatively controlled.

trp operon

A control system in prokaryotes that regulates the synthesis of tryptophan when it is not available in the environment.

Positive control

Transcription regulated by an activator protein such as the CAP activator promoting transcription when glucose is absent.

Negative control

Transcription regulated by a repressor protein such as the lac repressor inhibiting transcription when lactose is absent.

Induction

When a molecule in the environment stimulates transcription such as allolactose inducing the lac operon.

Repression

When a molecule in the environment inhibits transcription such as tryptophan repressing the trp operon.

General transcription factors

Proteins necessary for any transcription to occur in eukaryotes.

Specific transcription factors

Signal and gene-sensitive proteins that regulate targeted transcription in eukaryotes.

Enhancer region

Any region upstream where transcription factors bind to promote downstream transcription.

Methylation

The hiding or tightening of DNA around histones found in inactive regions of chromatin to prevent transcription.

Acetylation

The opening or loosening of DNA around histones found in active regions making DNA accessible for transcription.

Alternative splicing

A post-transcriptional process where introns are spliced out of pre-mRNAs to produce mature mRNA allowing the same gene to have different expression in different tissues.

miRNA and siRNA

Small double-stranded RNAs processed into single strands that bind to complementary mRNA transcripts causing them to be degraded to silence gene expression.

Proteasome

A cellular system that acts as protein quality control by degrading damaged misfolded or specific short-lived proteins.

Ubiquitin

A molecule used to mark specific proteins for destruction at the proteasome.

Binary fission

The process by which prokaryotes divide replicating their haploid genome without a sexual cycle.

Mitosis

A process for the complex DNA of eukaryotes to be bundled up and packaged into new cells replacing old cells with exact genetic replicas.

Growth phase (Interphase)

The phase where DNA codes for cell products through transcription and translation and includes G1 S and G2 phases.

Reproductive phase (M phase)

The phase where DNA replicates and cells divide through either mitosis or meiosis.

Somatic cells

Typical body cells that undergo mitosis to replace worn-out cells.

Sex cells (Gametes)

Haploid cells like eggs or sperm created through meiosis for sexual reproduction.

Gonads

The reproductive organs where sex cells are produced.

Diploid

Having a pair of each kind of chromosome (2n).

Haploid

Having only one set of chromosomes meaning one of each kind (1n).

Chromosome

A visible body of packaged DNA and histone proteins.

Chromatin

The complex of DNA and histone proteins that make up eukaryotic chromosomes.

Sister Chromatids

Two identical DNA molecules held together by cohesin proteins at the centromeric region after DNA replication.

Homologous pairs

Pairs of chromosomes one inherited from each parent that contain the same genes.

G1 Phase

The primary growth phase of the cell cycle and typically the longest phase.

S Phase

The synthesis phase of the cell cycle where DNA replicates.

G2 Phase

The phase where organelles replicate and microtubules organize prior to cell division.

Cytokinesis

The physical separation of the cell into two new daughter cells.

G0 Phase

A resting phase exhibited by cells like mature neurons that continue protein synthesis but do not divide.

Apoptosis

The programmed death of cells at specific times.

G1/S checkpoint

The primary point for external signal influence where the cell decides to divide.

G2/M checkpoint

The point that assesses the success of DNA replication before committing to mitosis utilizing the p53 protein.

Spindle checkpoint (APC)

The checkpoint in late metaphase that ensures all chromosomes are properly attached to the spindle.

Cancer

The unrestrained uncontrolled growth and reproduction of cells due to a failure of cell cycle control.

Proto-oncogenes

Genes that can cause uncontrolled cell division and tumors through a gain-of-function mutation such as the RAS protein.

Tumor-suppressor genes

Genes that normally repair DNA or suppress tumors but lead to cancer through a loss-of-function mutation such as the p53 or Rb proteins.

Meiosis

A reduction division related to the sexual life cycle that results in haploid daughter cells that are semi-different from the mother cell.

Synapsis

The pairing of homologous chromosomes during Prophase I to form a synaptonemal complex.

Crossing over

The exchange of genetic material between non-sister chromatids at the site of crossover (chiasmata) during Prophase I.

Independent assortment

The random alignment of paired homologous chromosomes on the metaphase plate during Metaphase I contributing to genetic variation.

Genotype

The genetic compliment or specific combination of alleles an organism possesses.

Phenotype

The physical expression of the genes or traits.

Homozygous

Having two of the same allele for a given gene.

Heterozygous

Having two different alleles for a given gene.

Principle of Segregation

Mendel's law stating that during gamete formation pairs of genes separate during meiosis when homologous chromosomes separate.

Principle of Independent Assortment

The law explaining how different genes independently separate from one another when reproductive cells develop.

Complete Dominance

An inheritance pattern where the dominant allele completely masks the expression of the recessive allele such as edible almonds or the white spirit bear.

Co-dominance

An inheritance pattern where more than one dominant allele exists and heterozygotes express aspects of both such as ABO blood type.

Incomplete Dominance

An inheritance pattern resulting in a blended phenotype that is distinct from complete dominance.

Epistasis

When the phenotype of one gene is modified or controlled by another gene such as Labrador retriever coat color or piebald spotting in dogs.

Multiple alleles

Traits controlled by more than two alleles in a population such as human height.

Environmental effects

When the environment influences phenotype such as temperature affecting pigment enzyme production in Himalayan rabbits Siamese cats and Arctic hares.

Monohybrid cross

A genetic cross tracking a single trait typically resulting in a 3:1 phenotypic and 1:2:1 genotypic ratio for heterozygous parents.

Dihybrid cross

A genetic cross tracking two distinct traits simultaneously to calculate the probability of different genotypes.

Autosomal genes

Genes located on any of the non-sex chromosomes.

Sex-linked genes

Genes located on the X or Y sex chromosomes such as the white eye mutation in Drosophila or hemophilia in humans.

Dosage compensation

An epigenetic mechanism ensuring equal expression of X chromosome genes by inactivating one X chromosome in XX individuals.

Barr body

The highly condensed inactivated X chromosome found in the cells of XX individuals.

Genomic imprinting

Epigenetic inheritance where chemical tags affect DNA expression and can be passed on to embryos such as damage from cigarette smoke.

Nondisjunction

An error in meiosis that changes the chromosome number leading to disorders like Trisomy 21 (Down syndrome) Klinefelter syndrome (XXY) or Turner syndrome (XO).

Recombination frequency

The percentage of recombinant progeny out of total progeny used to calculate the distance between linked genes.

Centimorgan (cM)

The measurement unit for genetic maps where 1 map unit equals a 1% recombination frequency.

Short Tandem Repeats (STRs)

Repeating two to four DNA nucleotide bases that differ in number between individuals and serve as markers for genetic mapping.

Single-nucleotide polymorphisms (SNPs)

Differences in single bases of a gene locus occurring at low frequencies used to map evolutionary history and most common type of genetic variation amoung people