Mendelian Genetics and Chromosomal Basis of Inheritance Flashcards

Vocabulary flashcards based on lecture notes covering Mendelian genetics, meiosis, and chromosomal inheritance.

Gametes

Reproductive cells (sperm and ova) that transmit genes from one generation to the next.

Locus

The location of a gene on a chromosome.

Clone

A group of genetically identical individuals derived from a single parent through asexual reproduction.

Karyotype

A picture of an organism's complete set of chromosomes, arranged in homologous pairs from largest to smallest.

Homologous Chromosomes

Chromosomes that carry genes controlling the same inherited characteristics.

Autosomes

Non-sex chromosomes; all chromosomes except X and Y.

Haploid Cells

Cells containing half the number of chromosomes of somatic cells (n).

Fertilization

The combination of a sperm cell and an egg cell.

Zygote

A fertilized egg that is diploid (2n).

Synapsis

The joining of homologous chromosomes along their length during prophase I of meiosis.

Tetrad

The structure formed during synapsis that precisely aligns homologous chromosomes gene by gene.

Crossing Over

The exchange of DNA between homologous chromosomes during prophase I of meiosis.

Chiasmata

Crisscrossed regions where crossing over has occurred that hold the homologs together until anaphase I.

Cytokinesis

Division of the cytoplasm that occurs during telophase.

P (Parental) Generation

True-breeding parents in a genetic cross.

F1 (First Filial) Generation

The offspring of the P generation.

F2 (Second Filial) Generation

The offspring of the F1 generation.

Alleles

Alternative versions of a gene.

Law of Segregation

Mendel's law stating that the two alleles for each character separate during gamete production.

Law of Independent Assortment

Mendel's law stating that each pair of alleles segregates independently during gamete formation.

Homozygous

Organisms with two identical alleles for a trait.

Heterozygous

Organisms with two different alleles for a trait.

Phenotype

An organism's expressed physical traits.

Genotype

An organism's genetic makeup.

Testcross

A cross done to determine if an individual showing a dominant trait is homozygous or heterozygous; always done with a homozygous recessive individual.

Monohybrid Cross

A cross involving the study of only one character.

Dihybrid Cross

A cross involving the study of two characters.

Rule of Multiplication

The rule stating that the probability of two or more independent events occurring together is the product of their individual probabilities.

Rule of Addition

The rule stating that the probability of any of two or more mutually exclusive events occurring is the sum of their individual probabilities.

Complete Dominance

Dominance in which the heterozygote and the homozygote for the dominant allele are indistinguishable.

Codominance

Condition in which two alleles are dominant and affect the phenotype in two different but equal ways.

Incomplete Dominance

Condition in which the F1 hybrids have an appearance that is in between that of the two parents.

Multiple Alleles

Condition when a gene has more than two alleles.

Pleiotropy

The property of a gene that causes it to have multiple phenotypic effects.

Epistasis

A gene at one locus alters the effects of a gene at another locus.

Polygenic Inheritance

Two or more genes have an additive effect on a single character in the phenotype.

Pedigree

A diagram showing the relationship between parents and offspring across two or more generations.

Pedigree

A diagram showing the relationship between parents and offspring across two or more generations.

Chromosome Theory of Inheritance

The idea stating that genes have specific locations on chromosomes and that chromosomes segregate and assort independently.

Sex-Linked Gene

A gene located on a sex chromosome (X or Y in humans).

Barr Body

The inactive X chromosome in females that condenses and lies along the inside of the nuclear envelope.

Linked Genes

Genes located on the same chromosome that tend to be inherited together during cell division.

Genetic Recombination

The production of offspring with a new combination of genes inherited from the parents due to crossing over.

Parental Types

Offspring with the same phenotype as one of the parents.

Recombinants

Offspring with phenotypes different from either parent.

Linkage Map

A genetic map based on the percentage of crossover events.

Map Unit

A unit equal to a 1% recombination frequency used to express relative distances along the chromosome.

Nondisjunction

Occurs when members of a pair of homologous chromosomes do not separate properly during meiosis I, or sister chromatids don't separate properly during meiosis II.

Aneuploidy

A condition in which offspring have an incorrect chromosome number due to nondisjunction.

Trisomic

Fertilized eggs that have received three copies of a chromosome.

Monosomic

Fertilized eggs that have received just one copy of a chromosome.

Polyploidy

The condition of having more than two complete sets of chromosomes (3n or 4n).

Deletion

A chromosomal fragment is lost, resulting in a chromosome with missing genes.

Duplication

A chromosomal segment is repeated.

Inversion

A chromosomal fragment breaks off and reattaches to its original position but backward.

Translocation

The deleted chromosome fragment joins a nonhomologous chromosome.

Genomic Imprinting

The phenotypic effect of a gene may depend on which allele is inherited from which parent.