Genetics Ch 1, 2, 7

agarose

An inert material derived from agar that is mixed with buffer and used to form gels for gel electrophoresis.

allele

An alternative form of a gene.

anticodon

The nucleotide triplet sequence of transfer RNA that pairs with an mRNA codon sequence in translation.

artificial cross

cutting the immature male pollen-producing parts of the plant and manually fertilizing it with pollen from another plant

clamp loader

A multisubunit protein complex (like the $\gamma$ complex in bacteria) that uses ATP to lock open and load the sliding clamp onto DNA at the primer

coding strand

The nontemplate strand of DNA that has the same polarity as its transcript and the same sequence, except for T in DNA and U in RNA.

codon

The nucleotide triplet of mRNA that encodes a single amino acid.

conditional probability

A probability prediction that is dependent on another previous event having taken place.

consensus sequence

A nucleotide sequence in a DNA segment derived by comparing sequences of similar segments from other genes or organisms. The most commonly occurring nucleotides at each position comprise the sequence.

conservative DNA replication

A disproven model of DNA replication positing that one duplex produced by replication contained the two original strands and the other two daughter strands.

controlled genetic cross

Genetic crosses controlled by an investigator who usually knows the genotypes and/or phenotypes of the organisms being crossed.

cytoplasmic inheritance

Transmission of genes outside of the nucleus, e.g., in the mitochondrial or chloroplast genome.

daughter strand

A newly synthesized strand of DNA that is complementary to a template strand.

deoxynucleotide monophosphate (dNMP)

Monophosphate forms of deoxynucleotides.

deoxynucleotide triphosphate (dNTP)

Triphosphate forms of deoxynucleotides.

dihybrid cross

A cross between organisms that are heterozygous for two loci.

diploid number

The characteristic number of chromosomes (2n) in somatic cell nuclei during the diploid phase of the eukaryotic life cycle. Equal to twice the haploid (n) number of chromosomes found in the nuclei of gametes of sexually reproducing diploid species.

dispersive DNA replication

A disproven model of DNA replication positing that each strand of daughter duplexes is composed of segments of original DNA and segments of newly synthesized DNA.

DNA ligase

An enzyme active in DNA replication that joins together segments of a DNA strand by catalyzing formation of a phosphodiester bond.

DNA polymerase I

An enzyme that removes RNA primers and replaces them with DNA nucleotides, utilizing a unique 5'-to-3' exonuclease activity.

DNA polymerase III

The primary enzyme complex responsible for elongating the leading and lagging strands by adding nucleotides in the 5'

DNA proofreading

The capacity of many types of DNA polymerase to utilize a 3'-to-5' exonuclease activity to remove and replace mismatched or damaged nucleotides during replication.

DNA topoisomerase

Enzyme that relaxes DNA supercoiling by controlled strand nicking and rejoining.

DnaA (Initiator protein)

The specific protein that binds to the origin of replication (oriC) and destabilizes the double helix to initiate the opening of the replication bubble.

ethidium bromide (EtBr)

A compound used to stain DNA and RNA in electrophoresis gels.

exon

the part of the mRNA sequence that gets translated (the TV show)

exonuclease activity

An enzymatic activity of DNA- or RNA-digesting enzymes (nucleases) that cleaves nucleotides one by one from the exposed end of a nucleic acid chain. This digestion progresses linearly in either a 3'-to-5' or 5'-to-3' direction, distinct from endonucleases which cut within the middle of a strand.

gene

The physical unit of heredity, composed of a DNA sequence that is transcribed and encodes a polypeptide or another functional molecule.

genetic code

The universal set of correspondences of mRNA codons to amino acids. Used in translation to synthesize polypeptides.

genome

The entire complement of DNA sequences in a chromosome set of an organism.

genotype

(1) The genetic composition of an organism or a cell (i.e., all the alleles of all the genes). (2) The alleles of a single gene or a specified set of genes in a cell or organism.

genotypic ratio (1:2:1 ratio)

(1) A ratio or set of relative proportions between organisms with different genotypes. (2) The ratio of 1/4 : 1/2 : 1/4 observed among the homozygous and heterozygous progeny of a monohybrid cross.

Hayflick limit

The name given to the observation that normal human cells in cell culture usually experience a limited number of cycles of cell division before they die.

helicase

In DNA replication, the enzyme responsible for breaking hydrogen bonds between complementary nucleotides of a DNA duplex. Unwinding of the strands occurs ahead of the advancing replication fork.

homologous chromosomes (homologous pair)

Chromosomes that synapse (pair) during meiosis. Chromosomes with the same genes in the same order. Also known as homologs.

homologs

Homologous chromosomes or genes that have the same genes and structure and pair with one another during meiosis.

homology

Evolutionarily related, having descended from a common ancestor.

homoplasmy

The presence of only one allelic version of DNA in the organellar genomes of a cell.

hybridization

In an electrophoresis gel or in gel blotting, the binding of a single-stranded nucleic acid probe to a single-stranded target nucleic acid by complementary base pairing. In other contexts, the formation of a double-stranded nucleic acid molecule by the base pairing of two wholly or largely complementary single-stranded molecules.

intron

Intervening sequences between the exons of many eukaryotic genes. Present in DNA and pre

law of independent assortment (Mendel’s second law)

The random distribution of alleles of unlinked genes into gametes.

law of segregation (Mendel’s first law)

The separation of alleles of a gene during gamete formation.

leading strand

In DNA replication, the continuously synthesized strand. Compare with lagging strand.

LUCA

An acronym for the last universal common ancestor, meaning the last ancestor from which all living organisms are descended.

major groove

The larger of two grooves formed in the DNA sugar

megabase (Mb)

Equal to 1,000,000 nucleotide bases. Refers to DNA or to RNA molecules or fragments.

metabolomics

The study of proteins, processes, and interactions involved in the metabolism of organisms.

minor groove

The smaller of two grooves formed in the sugar

modern synthesis of evolution

Referring to the broad

molecular genetics

The subfield of genetics that studies hereditary transmission, variation, mutation, and evolution through the analysis of nucleic acids and proteins.

monophyletic group

A group of organisms with a single common ancestor.

multiplication rule

See product rule.

next

generation sequencing (NGS)

northern blotting

A method for transferring mRNA from an electrophoresis gel to a permanent membrane or filter.

nucleoid

The region of bacterial and archaeal cells (or mitochondria or chloroplasts) where the main chromosome resides.

Okazaki fragment

A short segment of newly synthesized DNA that is part of a lagging strand and is ligated to other Okazaki fragments to complete lagging strand synthesis.

origin of migration

The starting point of nucleic acid or protein migration in gel electrophoresis.

origin of replication

The specific sequence at which DNA replication begins.

outgroup

A species related to members of a clade but outside the clade; used to root the clade.

parental generation (P generation)

The parents of progeny. In controlled genetic crosses, the parents are pure

parental strand

The DNA strand acting as a template to direct the synthesis of a new (“daughter”) strand of DNA.

particulate inheritance

Mendel’s theory that genetic information is transmitted from one generation to the next as discrete units or elements of heredity.

Pascal’s triangle

A diagram listing the coefficients of a given binomial expansion in which the binomial expression is expanded n number of times.

pedigree

A family tree composed of standard symbols that depicts relationships in successive generations and often displays individual phenotypes.

peptide bond

A type of covalent bond that joins amino acids in polypeptide chains. Formed between the amino end of one amino acid and the carboxyl end of the adjoining amino acid.

phenotype

(1) The observable physical characteristics or traits of an organism. (2) The physical manifestation of a specific genotype.

phenotypic ratio

A ratio or set of relative proportions between organisms with different phenotypes—for example, the ratio of progeny produced by a monohybrid cross (3:1) or a dihybrid cross (9:3:3:1).

phosphodiester bond

A type of covalent bond formed between two nucleotides in a nucleic acid strain. Formed between the phosphate group of one nucleotide and the OH of the adjacent nucleotide.

phylogenetic tree

A diagram of evolutionary relationships among organisms or genes based on morphological or molecular characteristics.

polyacrylamide

A synthetic compound mixed with buffer and used to form electrophoresis gels.

polymerase activity

DNA synthesizing activity of DNA polymerases that progresses in the 5'

polymerase chain reaction (PCR)

A laboratory method for controlled replication of a specific target sequence of DNA in successive cycles. Using two short single

polypeptide

A chain of amino acids joined by peptide bonds. Formed at ribosomes during translation.

polyploidy

The presence of more than two complete sets of chromosomes in a genome. See also allopolyploidy and autopolyploidy.

primase (DnaG)

The specialized RNA polymerase that synthesizes the RNA primer during DNA replication.

prior probability

A statistical prediction of an outcome before the event. In genetics, the prediction of the possible outcomes of a genetic cross based on Mendelian genetics.

probability value (P value)

In the chi square test, the likelihood that a repeat experiment will produce a result as deviant or more deviant than expected in comparison with the experimental result being tested.

product rule

The probability of an event requiring the sequential or simultaneous occurrence of two or more contributing events. The probabilities of contributing events are multiplied, and their product is the event in question.

promoter

A regulatory sequence of DNA near the 5' end of a gene that acts as the binding location of RNA polymerase and directs RNA polymerase to the start of transcription.

protein

A string of amino acids encoded during translation of mRNA and linked together by peptide bonds. See also polypeptide.

proteome

Set of the proteins in a cell, tissue, or organism.

proteomics

The study of all the proteins, collectively known as the proteome, within a cell, tissue, or organism.

pure

breeding strains

recessive allele

An allele that can only be expressed in a phenotype if two copies of the allele make up the genotype.

recessive phenotype

The phenotype observed in an organism that is homozygous for the recessive allele. Compare with dominant phenotype.

reciprocal cross

Paired crosses involving distinct parental phenotypes in which the sexes are switched (i.e., if one cross is ♂ phenotype A × ♀ phenotype B, the reciprocal cross is ♂ phenotype B × ♀ phenotype A).

replication bubble

A region of active bidirectional DNA replication containing replication forks on each end, an origin of replication in the middle, and leading and lagging strands in each half of the bubble.

replication fork

In DNA replication, the site of the replisome structure, and the site of synthesis of leading strand and lagging strand DNA.

replicate cross

Repeated crosses involving parents with the same genotypes and phenotypes.

replisome

The large molecular machine located at the replication fork that coordinates multiple reaction steps during DNA replication.

reverse transcription

The process of DNA synthesis from an RNA template by the enzyme reverse transcriptase.

ribonucleic acid (RNA)

A family of polynucleotides that are transcribed from DNA. RNAs are composed of nucleotides containing the sugar ribose, one or more phosphate atoms, and one of four nitrogenous bases (A, G, C, and U).

ribosomal RNA (rRNA)

A group of RNA molecules that compose part of the structure of ribosomes.

ribosome

Ribonucleoprotein particles, composed of rRNAs and numerous proteins, at which translation takes place.

RNase H

An endonuclease enzyme that specifically degrades the RNA strand of RNA

RNA primer

In DNA replication, the short, single

self

fertilization

semiconservative DNA replication

The established method of DNA replication in which each strand of a parental duplex acts as a template for daughter strand synthesis and each daughter duplex is composed of one parental strand and a complementary daughter strand.

sex chromosome

Homologous chromosomes that differ between the sexes. Designated X and Y in species in which females are XX and males XY. Designated Z and W in species in which females are ZW and males are ZZ.

shared derived characteristics

Characteristics or traits of organisms that evolve from more ancestral characteristics or traits found in ancestral organisms.