Section 5 Flashcards by Zach Silverman

A modified form of guanine nucleotide added onto the 5’ end of a pre-mRNA molecule

5’ cap

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One of a ribosome’s three binding sites for tRNA during translation, holds the tRNA carrying the next amino acid to be added to the polypeptide chain. (A stands for aminoacyl tRNA.)

A site

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Any of the alternative versions of agene that may produce distinguishable phenotypic effects

allele

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A type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the primary transcript, depending on which RNA segments are treated as exons and which as introns.

alternative RNA splicing

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An organic molecule possessing both a carboxyl and an amino group, serve as the monomers of polypeptides

amino acid

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An enzyme that joins each amino acid to the appropriate tRNA

aminoacyl-tRNA synthetase

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A nucleotide triplet at one end of a tRNA molecule that base-pairs with a particular complementary codon on an mRNA molecule

anticodon

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Referring to the arrangement of the sugar-phosphate backbones in a DNA double helix (they run in opposite 5′ S 3′ directions).

antiparallel

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The generation of offspring from a single parent that occurs without the fusion of gametes. In most cases, the offspring are genetically identical to the parent.

asexual reproduction

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A maternal effect gene that codes for a protein responsible for specifying the anterior end in Drosophila melanogaster.

bicoid

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Definition of a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring but do not produce viable, fertile offspring with members of other such groups.

biological species concept

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originally, the idea that information flows from DNA to RNA to protein, but not in the opposite direction

central dogma

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In a duplicated chromosome, the region on each sister chromatid where it is most closely attached to its sister chromatid

centromere

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The X-shaped, microscopically visible region where crossing over has occurred earlier in prophase I between homologous nonsister chromatids.

chiasma

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A cellular structure consisting of one DNA molecule and associated protein molecules.

chromosome

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A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.

codon

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The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.

crossing over

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A nucleic acid molecule, usually a double-stranded helix, in which each polynucleotide strand consists of nucleotide
monomers with a deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T); capable of being replicated and determining the inherited structure of a cell’s proteins.

deoxyribonucleic acid

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The sugar component of DNA nucleotides, having one fewer hydroxyl group than ribose, the sugar component of RNA nucleotides.

deoxyribose

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The events involved in an organism’s changing gradually from a simple to a more complex or specialized form.

development

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A cell containing two sets of chromosomes (2n), one set inherited from each parent.

diploid cell

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A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3′ end of one DNA fragment (such as an Okazaki fragment) to the 5′ end of another DNA fragment (such as a growing DNA chain).

DNA ligase

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The presence of methyl groups on the DNA bases (usually cytosine) of plants, animals, and fungi. (The term also refers to the process of adding methyl groups to DNA bases.)

DNA methylation

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An enzyme that catalyzes the elongation of new DNA (for example, at a replication fork) by the addition of nucleotides to the 3′ end of an existing chain.

DNA polymerase

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The process by which a DNA molecule is copied

DNA replication

An allele that is fully expressed in the phenotype of a heterozygote.

dominant allele

The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape.

double helix

One of a ribosome’s three binding sites for tRNA during translation. The E site is the place where discharged tRNAs leave the ribosome. (E stands for exit.)

E site

Describes effects on gene expression due to differences in DNA packaging, such as modifications in histones or chromatin structure.

epigenetic

A sequence within a primary transcript that remains in the RNA after RNA processing; also refers to the region of DNA from which this sequence was transcribed.

exon

A haploid reproductive cell, such as an egg or sperm, that is formed by meiosis or is the descendant of cells formed by meiosis

gamete

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).

gene

The process by which information encoded in DNA directs the synthesis of proteins or, in some cases, RNAs that are not translated into proteins and instead function as RNAs.

gene expression

A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next, most pronounced in small populations

genetic drift

The genetic makeup, or set of alleles, of an organism.76

genotype

A cell containing only one set of chromosomes (n).

haploid cell

An enzyme that untwists the double helix of DNA at replication forks, separating the two strands and making them available as template strands.

helicase

In a population, the proportion of the total variation in a trait that is due to genetic differences among individuals.

heritability

An organism that has two different alleles for a gene (encoding a character).

heterozygote

A small protein with a high proportion of positively charged amino acids that binds to the negatively charged DNA and plays a key role in chromatin structure.

histone

Any of the master regulatory genes that control placement and spatial organization of body parts in animals, plants, and fungi by controlling the developmental fate of groups of cells.

homeotic gene

A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism’s father, the other from the mother.

homologous chromosomes

Having two identical alleles for a given gene.

homozygous

Offspring that results from the mating of individuals from two different species or from two true-breeding varieties of the same species.

hybrid

A noncoding, intervening sequence within a primary transcript that is removed from the transcript during RNA processing; also refers to the region of DNA from which this sequence was transcribed.

intron

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5′→3′5′→3′ direction away from the replication fork.

lagging strand

Genes located close enough together on a chromosome that they tend to be inherited together.

linked genes

A gene that, when mutant in the mother, results in a mutant phenotype in the offspring, regardless of the offspring’s genotype, also called egg-polarity genes, were first identified in

maternal effect gene

A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. It results in cells with half the number of chromosome sets as the original cell.

meiosis

A type of RNA, synthesized using a DNA template, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.

messenger RNA

The cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides.

mismatch repair

A nucleotide-pair substitution that results in a codon that codes for a different amino acid.

missense mutation

A change in the nucleotide sequence of an organism’s DNA or in the DNA or RNA of a virus.

mutation

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

natural selection

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

nonsense mutation

A graphical depiction of the change in phenotype across a range of environments.

norm of reaction

The basic, bead-like unit of DNA packing in eukaryotes, consisting of a segment of DNA wound around a protein core composed of two copies of each of four types of histone.

nucleosome

The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one to three phosphate groups.

nucleotide

A short segment of DNA synthesized away from the replication fork on a template strand during DNA replication

Okazaki fragment

Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.

origin of replication

One of a ribosome’s three binding sites for tRNA during translation. This site holds the tRNA carrying the growing polypeptide chain. (P stands for peptidyl tRNA.)

P site

The observable physical and physiological traits of an organism, which are determined by its genetic makeup.

phenotype

A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms.

phylogenetic tree

The ability of a single gene to have multiple effects.

pleiotropy

A sequence of 50–250 adenine nucleotides added onto the 3′ end of a pre-mRNA molecule.

poly-A tail

A chromosomal alteration in which the organism possesses more than two complete chromosome sets. It is the result of an accident of cell division.

polyploidy

A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring.

population

A reproductive barrier that prevents hybrid zygotes produced by two different species from developing into viable, fertile adults.

postzygotic barrier

A reproductive barrier that impedes mating between species or hinders fertilization if interspecific mating is attempted.

prezygotic barrier

An enzyme that joins RNA nucleotides to make a primer during DNA replication, using the parental DNA strand as a template.

primase

A short polynucleotide with a free 3′ end, bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication.

primer

One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a five-membered ring. Adenine (A) and guanine (G)

purine

One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring. Cytosine (C), thymine (T), and uracil (U)

pyrimidine

On an mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis.

reading frame

An allele whose phenotypic effect is not observed in a heterozygote.

recessive allele

A Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are being synthesized.

replication fork

The existence of biological factors (barriers) that impede members of two species from producing viable, fertile offspring.

reproductive isolation

A type of nucleic acid consisting of a polynucleotide made up of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis, in gene regulation, and as the genome of some viruses.

ribonucleic acid

The sugar component of RNA nucleotides.

ribose

RNA molecules that, together with proteins, make up ribosomes; the most abundant type of RNA.

ribosomal RNA

A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit.

ribosome

An enzyme that links ribonucleotides into a growing RNA chain during transcription, based on complementary binding to nucleotides on a DNA template strand.

RNA polymerase

Type of DNA replication in which the replicated double helix consists of one old strand, derived from the parental molecule, and one newly made strand.

semiconservative model

Reproduction arising from fusion of two gametes.

sexual reproduction

A nucleotide-pair substitution that has no observable effect on the phenotype; for example, within a gene, a mutation that results in a codon that codes for the same amino acid.

silent mutation

Any cell in a multicellular organism except a sperm or egg or their precursors.

somatic cell

An evolutionary process in which one species diverges into two or more species.

speciation

A DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex.

TATA box

The tandemly repetitive DNA at the end of a eukaryotic chromosome’s DNA molecule.

telomere

The DNA strand that provides the pattern, or template, for ordering, by complementary base pairing, the sequence of nucleotides in an RNA transcript.

template strand

A protein that breaks, swivels, and rejoins DNA strands. During DNA replication, this helps to relieve strain in the double helix ahead of the replication fork.

topoisomerase

The synthesis of RNA using a DNA template.

transcription

A regulatory protein that binds to DNA and affects transcription of specific genes.

transcription factor

An RNA molecule that functions as a translator between nucleic acid and protein languages by picking up a specific amino acid and carrying it to the ribosome, where the tRNA recognizes the appropriate codon in the mRNA.

transfer RNA

The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of “language” from nucleotides to amino acids.

translation

The diploid cell produced by the union of haploid gametes during fertilization; a fertilized egg.

zygote

A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons.

spliceosome

Section 5 Flashcards

(97 cards)