AP®︎ Biology: Unit 5 Flashcards
Master key terms and definitions for Unit 5 of AP Biology – Heredity to help you prep for quizzes and the AP exam.
Meiosis
A two-division process that produces four haploid gametes from one diploid cell.
A two-division process that produces four haploid gametes from one diploid cell.
The pairing of homologous chromosomes during prophase I of meiosis.
Visible crossover points where nonsister chromatids of homologs exchange DNA.
Homologous chromosome pairs line up together at the cell's equator.
Homologous chromosomes separate to opposite poles while sister chromatids remain joined.
Chromosomes reach poles, nuclei may reform, and two haploid cells are produced.
A spindle forms in each haploid cell, and chromosomes attach for the second division.
Individual chromosomes align at the metaphase plate in each haploid cell.
Centromeres split and sister chromatids separate toward opposite poles.
Nuclei reform, chromosomes decondense, and four haploid cells with unduplicated chromosomes form.
Homologs are matching maternal and paternal chromosomes; sister chromatids are identical copies of one chromosome.
A microtubule structure that attaches to chromosomes and moves them during cell division.
A protein structure at the centromere where spindle microtubules attach.
Meiosis has two divisions and makes four unique haploid cells; mitosis makes two identical diploid cells.
Fusion of two haploid gametes restores the diploid chromosome number in offspring.
Variation arises from crossing over, independent assortment in metaphase I, and random fertilization.
Division of the cytoplasm that physically separates daughter cells after nuclear division.
The first meiotic stage when homologous chromosomes pair by synapsis, crossing over occurs, the spindle forms, and the nuclear envelope breaks down.
Homologous chromosome pairs align randomly in meiosis, producing different maternal-paternal chromosome combinations in gametes.
In meiosis I all four gametes are abnormal; in meiosis II only two are abnormal.
The number of chromosome combinations in gametes equals 2^n, where n is haploid number.
Correct meiosis produces haploid gametes containing one chromosome from each homologous pair.
Failure of chromosome separation in meiosis produces gametes with extra or missing chromosomes.
An abnormal chromosome number caused by chromosome gain or loss, including trisomy or monosomy.
Crossing over, independent assortment, and random fertilization increase genetic variation in offspring.
Exchange of corresponding DNA segments between nonsister chromatids of homologous chromosomes during prophase I, creating new allele combinations.
A maternal and paternal chromosome pair with the same genes at corresponding loci.
Meiosis I separates homologous chromosomes and halves chromosome number; meiosis II separates sister chromatids.
The two alleles for a gene separate during gamete formation, one per gamete.
Alleles of different genes assort independently into gametes when the genes are on different chromosomes.
Fusion of two haploid gametes that restores diploidy and combines parental alleles.
A grid used to predict possible offspring genotypes and phenotypes from parental alleles.
Cross an individual showing a dominant phenotype with a homozygous recessive to reveal its genotype.
Use addition for mutually exclusive events and multiplication for independent events.
Using family inheritance charts to infer genotypes and identify inheritance patterns.
Inheritance of a gene located on a non-sex chromosome.
Inheritance of a gene located on a sex chromosome, usually the X chromosome.
An organism’s alleles make up its genotype, while its observable traits are its phenotype.
Identical or different allele pairs affect whether dominant or recessive traits are expressed.
A one-gene cross that often produces 1:2:1 genotypic and 3:1 phenotypic ratios.
A two-gene cross that can produce a 9:3:3:1 phenotypic ratio.
A haploid sex cell that carries one allele for each gene.
A diploid cell formed when two haploid gametes fuse during fertilization.
Haploid cells have one chromosome set; diploid cells have two chromosome sets.
Inheritance patterns that do not match classic Mendelian dominant-recessive ratios.
Compares observed offspring ratios to expected ratios to test whether differences are due to chance.
A gene has more than two possible allelic forms in a population.
Neither allele fully masks the other, so heterozygotes show an intermediate blended phenotype.
Both alleles are fully expressed in a heterozygote, producing a phenotype distinct from either homozygote.
Incomplete dominance shows blending; codominance shows both alleles expressed side by side.
Use family inheritance patterns to infer whether a trait is X-linked or Y-linked.
Examples include XY, ZW, and haplodiploidy, which determine sex by different chromosome systems.
One gene influences multiple distinct phenotypic traits or effects.
Uses recombinant offspring percentages to estimate distances between linked genes on chromosomes.
Traits on sex chromosomes, with X-linked recessive alleles expressed more often in XY individuals.
Traits encoded by mitochondrial or chloroplast DNA usually show maternal inheritance patterns.
Genes on the same chromosome tend to be inherited together unless crossing over separates them.
Temperature, light, nutrition, hormones, chemicals, and social cues can activate or silence genes.
Nutrition and lifestyle affect growth and body mass, modifying genetically influenced trait expression.
Soil acidity or alkalinity changes pigment-related chemistry, producing different flower colors.
Seasonal cues such as day length trigger coat color changes without altering genotype.
Incubation temperature determines sex in some reptiles instead of sex chromosomes.
Increased ultraviolet radiation stimulates melanin synthesis, causing darker skin pigmentation.
Detection of the opposite mating type activates genes for pheromone production.
Environmental conditions alter gene expression, allowing one genotype to produce different phenotypes.
