Chapter 10: Patterns of Inheritance — Vocabulary Flashcards

Vocabulary flashcards summarizing essential terms from Chapter 10, including Mendelian genetics, non-Mendelian inheritance patterns, human genetic analysis, chromosomal abnormalities, and prenatal diagnostic techniques.

Cystic fibrosis

The most common fatal genetic disorder in the United States; caused by a deletion in the CFTR gene and expressed only in individuals homozygous for the mutant allele.

CFTR gene

Gene whose deletion mutation leads to cystic fibrosis by disrupting chloride-ion transport and causing thick mucus.

Gregor Mendel

Nineteenth-century monk whose pea-plant experiments founded modern genetics and revealed basic inheritance principles.

Homozygous

Having two identical alleles of the same gene (e.g., AA or aa).

Heterozygous

Having two different alleles of the same gene (e.g., Aa).

Genotype

The specific combination of alleles carried by an individual.

Phenotype

An individual’s observable traits resulting from genotype and environmental influences.

Dominant allele

Allele whose effect masks that of its recessive partner in heterozygotes.

Recessive allele

Allele whose effect is masked by a dominant partner; expressed only when homozygous.

Monohybrid cross

Genetic cross tracking one gene; typically yields a 3:1 phenotype ratio when alleles show dominance.

Dihybrid cross

Cross that follows two genes simultaneously; classic phenotype ratio is 9:3:3:1 and demonstrates independent assortment.

Independent assortment

Principle stating that each gene is distributed to gametes independently of other genes if located on different chromosomes or far apart.

Punnett square

Grid used to predict genotype and phenotype ratios of offspring from a genetic cross.

Testcross

Cross between an individual with a dominant phenotype and one homozygous recessive to reveal the unknown genotype.

Incomplete dominance

Inheritance in which the heterozygote phenotype is intermediate between the two homozygotes (e.g., red × white → pink flowers).

Codominance

Condition in which both alleles are fully expressed in heterozygotes (e.g., human AB blood type).

Pleiotropy

Single gene influences multiple traits; mutations can cause disorders such as sickle-cell anemia or Marfan syndrome.

Epistasis

Interaction in which multiple genes together affect one trait, as in Labrador retriever coat color.

Polygenic trait

Characteristic influenced by many genes, producing a wide range of phenotypes (e.g., human skin color).

Nature versus nurture

Phrase describing how both genetic factors (nature) and environmental factors (nurture) shape phenotype.

Continuous variation

Range of small, incremental phenotypic differences governed by multiple genes and environmental factors.

Bell curve

Normal distribution curve produced when frequencies of a continuous trait are plotted in a population.

Short tandem repeats (STRs)

Sequences of 2–6 nucleotides repeated many times in DNA; contribute to variability in continuous traits.

Pedigree

Standardized chart showing family phenotypes and genetic connections; used to analyze inheritance patterns in humans.

Genetic abnormality

Uncommon heritable trait that does not cause medical problems (e.g., polydactyly).

Genetic disorder

Heritable condition that results in mild or severe medical problems (e.g., cystic fibrosis).

Autosomal dominant inheritance

Pattern where a dominant allele on an autosome is expressed in both homozygotes and heterozygotes.

Autosomal recessive inheritance

Pattern where a recessive allele on an autosome is expressed only in homozygous individuals.

X-linked recessive inheritance

Recessive allele located on the X chromosome; more common in males because they possess only one X.

Polyploidy

Having three or more complete sets of chromosomes; common in flowering plants.

Aneuploidy

Having too many or too few copies of a single chromosome rather than complete sets.

Nondisjunction

Failure of chromosomes to separate properly during meiosis or mitosis, producing abnormal chromosome numbers.

Trisomy 21 (Down syndrome)

Aneuploid condition with three copies of chromosome 21; only autosomal trisomy allowing survival to adulthood.

Turner syndrome

XO female sex-chromosome abnormality associated with short stature and developmental issues.

Klinefelter syndrome

XXY male sex-chromosome abnormality linked to learning difficulties and infertility.

Amniocentesis

Prenatal test sampling amniotic fluid to obtain fetal cells; carries a small risk of miscarriage.

Chorionic villi sampling (CVS)

Prenatal diagnostic method collecting placental tissue; allows early detection but carries a higher risk than amniocentesis.

Fetoscopy

Invasive prenatal procedure using a fiber-optic scope to view the fetus; carries risk of miscarriage.