big guns exam 4

Heredity

The passing of traits from parents to offspring.

Genetics

The branch of biology that studies heredity and variation in organisms.

Genetic variation

Differences in the genetic makeup among individuals within a population.

Phenotype

The observable physical and physiological traits of an organism, determined by its genotype.

Genotype

The genetic constitution of an organism.

Gregor Mendel

The father of genetics known for his work on pea plants and the principles of inheritance.

Hybrid

An organism that has two different alleles for a trait.

True-breeding

Organisms that, when reproducing, create offspring identical to themselves.

Parental generation (P)

The first individuals crossed in a breeding experiment.

F1 generation

The first generation of offspring from a breeding cross.

F2 generation

The second generation of offspring from a breeding cross.

Blending inheritance

An outdated theory that offspring inherit a smooth blend of parental traits.

Gene

A segment of DNA that codes for a specific trait.

Allele

Different forms of a gene.

Dominant

An allele that expresses its phenotype even in the presence of a recessive allele.

Recessive

An allele that is only expressed in the phenotype if two copies are present.

Principle of segregation

Mendel's principle stating that the two alleles for each trait separate during gamete formation.

Punnett square

A diagram used to predict the outcome of genetic crosses.

Locus (pl. loci)

The specific location of a gene on a chromosome.

Homozygous

Having two identical alleles for a specific trait.

Heterozygous

Having two different alleles for a specific trait.

Monohybrid cross

A genetic cross that involves one trait.

Phenotypic ratio

The ratio of different phenotypes in the offspring of a genetic cross.

Dihybrid cross

A genetic cross that involves two traits.

Principle of independent assortment

Mendel's principle that genes for different traits can segregate independently during the formation of gametes.

Genetic recombination

The process of combining different DNA sequences to create genetic diversity.

Linked genes

Genes that are located close together on the same chromosome and tend to be inherited together.

Sex-linked genes

Genes located on sex chromosomes, often exhibiting unique inheritance patterns.

Sex chromosomes

Chromosomes that determine the sex of an individual (X and Y in humans).

Autosomes

Non-sex chromosomes that contain genes for traits unrelated to gender.

Incomplete dominance

A genetic situation where one allele does not completely dominate another, resulting in a mixed phenotype.

Codominance

A situation in which both alleles are expressed equally in the phenotype.

Multiple alleles

More than two possible alleles exist for a single trait.

Polygenic inheritance

Inheritance of traits that are controlled by multiple genes.

DNA

The molecule that carries the genetic instructions for life.

Gene

A segment of DNA that contains the instructions for the synthesis of proteins.

Chromosome

A structure formed by condensed chromatin that contains genetic information.

Histone

A protein that helps package DNA into a compact structure called chromatin.

Nucleosome

A unit of DNA wrapped around a core of histone proteins.

Cell Cycle

The series of events that lead to cell division and duplication.

Interphase

The phase of the cell cycle where the cell spends most of its life, including G1, S, and G2 phases.

Mitosis

The process of cell division that results in two identical daughter cells.

Cytokinesis

The process that divides the cytoplasm of a parental cell into two daughter cells.

Sister Chromatids

Identical copies of a chromosome, connected by a centromere.

Centromere

The region of the chromosome that holds the two sister chromatids together.

Asexual Reproduction

Reproduction that does not involve the fusion of gametes, resulting in clones.

Homologous Chromosomes

Chromosome pairs, one from each parent, that are similar in shape, size, and genetic content.

Diploid

A cell that contains two complete sets of chromosomes.

Haploid

A cell that contains only one complete set of chromosomes.

Meiosis

A type of cell division that produces gametes with half the number of chromosomes.

Crossing-over

The exchange of genetic material between homologous chromosomes during meiosis.

Genetic Recombination

The process of forming new combinations of alleles in offspring.

Cleavage Furrow

The indentation that begins the process of cytokinesis in animal cells.

Cell Plate

The structure that forms during cytokinesis in plant cells.

Tetrad

A structure containing four chromatids formed during meiosis.

Chiasma

The point at which paired chromosomes remain in contact during the crossing-over process.

Interkinesis

The short resting period between the first and second meiotic divisions.

DNA

Deoxyribonucleic acid, the molecule that carries genetic information.

Double Helix

The structure of DNA, consisting of two strands wound around each other.

Nucleotide

The basic structural unit of DNA, composed of a sugar, a phosphate group, and a nitrogenous base.

Deoxyribose

The sugar component of DNA nucleotides.

Purine

A type of nitrogenous base with a two-ring structure; includes adenine and guanine.

Pyrimidine

A type of nitrogenous base with a single-ring structure; includes thymine and cytosine.

Antiparallel

Describes the opposite orientation of the two strands of DNA.

5’ end

The end of a DNA strand that has a phosphate group attached to the fifth carbon of the sugar.

3’ end

The end of a DNA strand that has a hydroxyl group attached to the third carbon of the sugar.

Chargaff’s rules

The observation that in DNA, the amount of adenine equals thymine and the amount of guanine equals cytosine.

Semiconservative replication

The mode of DNA replication where each new DNA molecule consists of one old strand and one new strand.

Origin of replication

The specific sequence of DNA where replication begins.

Replication fork

The region where the DNA is split into two strands during replication.

RNA (Ribonucleic acid)

A molecule involved in protein synthesis and sometimes in the replication process.

RNA primer

A short strand of RNA that provides a starting point for DNA synthesis.

Leading strand

The strand of DNA that is synthesized continuously in the same direction as the replication fork.

Lagging strand

The strand of DNA that is synthesized discontinuously, in the opposite direction to the replication fork.

Okazaki fragment

Short sequences of DNA synthesized on the lagging strand during DNA replication.

Telomere

The protective end of a linear chromosome that prevents degradation.

Helicase

An enzyme that unwinds the DNA double helix during replication.

Primase

An enzyme that synthesizes RNA primers for DNA replication.

DNA polymerase

An enzyme responsible for synthesizing new strands of DNA.

Ligase

An enzyme that joins Okazaki fragments on the lagging strand.

Telomerase

An enzyme that extends the telomeres of chromosomes.

Transcription

The process of copying a segment of DNA into messenger RNA (mRNA).

Translation

The process of converting the information in messenger RNA into a sequence of amino acids in a protein.

Ribonucleic Acid (RNA)

A nucleic acid that plays a central role in the synthesis of proteins.

Ribose

A sugar molecule that forms the backbone of RNA.

Uracil

A nitrogenous base found in RNA that pairs with adenine.

Messenger RNA (mRNA)

The type of RNA that carries the genetic information from DNA to the ribosome for protein synthesis.

Transfer RNA (tRNA)

The type of RNA that transports specific amino acids to the ribosome during protein synthesis.

Ribosomal RNA (rRNA)

A component of ribosomes that helps to catalyze protein synthesis.

Promoter

A DNA sequence that initiates transcription of a particular gene.

Template Strand

The strand of DNA that serves as the template for RNA synthesis.

Antiparallel

Refers to the opposite orientation of the two strands of DNA or RNA.

Codon

A sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule.

Anticodon

A three-nucleotide sequence in tRNA that is complementary to a codon in mRNA.

Ribosome

A cell structure that synthesizes proteins by translating mRNA into amino acids.

A site

The site on the ribosome where the tRNA carrying the next amino acid binds.

P site

The site on the ribosome where the tRNA holding the growing polypeptide chain is located.

E site

The exit site on the ribosome where discharged tRNAs leave the ribosome.

Peptide Bond

The chemical bond that links amino acids together in a protein.

Mutation

A change in the nucleotide sequence of an organism's DNA.