Patterns of Inheritance - Chapter 10

This set of flashcards covers the vocabulary and core concepts of Mendelian genetics and inheritance patterns from Chapter 10.

Diploid ($2n$)

Organisms or cells containing two sets of chromosomes; in humans, this corresponds to $23$ pairs or $46$ chromosomes.

Haploid ($n$)

Cells, such as gametes (sperm and eggs), that contain only one set of chromosomes.

Crossing over

Also known as recombination, this is the process where two homologous chromosomes randomly exchange genetic information during prophase I, giving rise to new allele combinations.

Random assortment

Also known as independent assortment, this is the process where homologous chromosomes randomly assemble at the metaphase plate during metaphase I, changing the alleles a daughter cell can receive.

Random fertilization

A mechanism of genetic diversity where any sperm can fuse with any egg, resulting in approximately $1$ in $70$ trillion possible combinations of chromosomes.

Law of dominance

One of Mendel's three core laws of genetics stating that certain traits (dominant) can mask other traits (recessive).

Law of segregation

The law stating that the two alleles of a gene end up in different gametes, meaning each gamete receives only one copy of the gene.

Law of independent assortment

The law stating that genes on different chromosomes are inherited independently of one another.

Alleles

Variants of a gene that can determine specific traits.

Dominant trait

A trait that masks another trait; represented by capital letters in genotypes.

Recessive trait

The 'weak' trait that is masked by a dominant allele; only expressed when the genotype is homozygous recessive.

Genotype

The specific allele combination of an organism (e.g., $DD$, $Dd$, or $dd$).

Phenotype

The observable trait or physical characteristic of an organism.

Homozygous

A genotype consisting of two identical alleles, which can be either dominant ($DD$) or recessive ($dd$).

Heterozygous

A genotype consisting of two different alleles ($Dd$).

True-breeding

Also known as self-fertilization, this process always produces offspring with the same trait/seed color as the parent plant.

Test cross

A method used to predict an unknown genotype by crossing the individual with a homozygous recessive individual.

Complete dominance

A pattern of inheritance where the dominant allele completely masks the recessive allele.

Codominance

A pattern of inheritance where multiple dominant alleles are expressed simultaneously, such as in the ABO blood type gene.

Incomplete dominance

A pattern of inheritance where an intermediate phenotype is expressed between the dominant and recessive alleles, such as pink flowers resulting from red and white parents.

Monohybrid cross

A genetic cross tracking one gene; if both parents are heterozygous, the offspring follow a approximately $3:1$ phenotypic ratio.

Dihybrid cross

A genetic cross tracking two traits (two genes); the offspring of true-breeding parents for two traits follow a $9:3:3:1$ phenotypic ratio.

Nondisjunction

A violation of Mendel's Law of Segregation that results in abnormal gametes ($n + 1$ or $n - 1$).

Genetic linkage

A violation of the law of independent assortment occurring when genes located closely together on the same chromosome tend to be inherited together.