Genetics and Inheritance Principles

Vocabulary flashcards covering Mendelian and non-Mendelian genetics, chromosome organization, Punnett squares, blood typing, polygenic inheritance, and sex-linked traits.

Gregor Mendel

Known as the Father of Genetics, who described fundamental principles of inheritance.

Principle of Independent Assortment

The genetic principle stating that the inheritance of one trait has no effect on the inheritance of another trait.

Genetics

The study of how traits are passed from parent to offspring.

Gene

A segment of DNA on a chromosome that determines a trait.

Homologous pairs

Matching pairs of chromosomes and genes, where one chromosome comes from the female parent and one from the male parent.

Human chromosome count

Humans have $46$ chromosomes or $23$ pairs, receiving $23$ chromosomes in sperm from dad and $23$ in egg from mom.

Alleles

Different genes or possibilities for the same trait, such as blue eyes or brown eyes.

Dominant gene

A gene that prevents the other gene from showing, represented by an upper case letter.

Recessive gene

A gene that does not show even though it is present, represented by a lower case letter.

Recessive trait expression

The condition where an organism must possess $2$ recessive alleles for a recessive trait to show.

Homozygous

Having both genes of a pair be the same, such as $TT$ or $tt$.

Purebred

An organism with two identical alleles for a trait, synonymous with homozygous.

Heterozygous

Having one dominant gene and one recessive gene in a pair, such as $Tt$.

Hybrid

An organism possessing one dominant and one recessive gene for a trait, synonymous with heterozygous.

Genotype

The combination of genes an organism has, representing its actual gene makeup.

Phenotype

The physical appearance resulting from an organism's gene makeup.

Punnett Square

A tool used to predict the possible gene makeup of offspring.

Autosomes

The $22$ pairs of homologous chromosomes in humans that look alike and determine body traits.

Sex chromosomes

The $1$ pair of chromosomes that determines the sex of an organism.

Female sex chromosomes

Homologous sex chromosomes that look alike, labeled $XX$.

Male sex chromosomes

Sex chromosomes that are different from each other, labeled $XY$.

Mendelian Genetics

Inheritance patterns based on complete dominance or recessiveness resulting in only two possible phenotypes.

Complete Dominance

An inheritance pattern where a heterozygous individual expresses only the dominant phenotype, masking the recessive phenotype.

Incomplete Inheritance

A non-Mendelian inheritance pattern where neither trait is completely dominant, resulting in a hybrid offspring with a third, blending phenotype.

Codominance

A non-Mendelian inheritance pattern where both traits are dominant and both show up together in the phenotype.

Meaning of Co

In genetics, 'Co' means 'together,' indicating co-expression of both alleles.

Intermediate inheritance

A type of inheritance where heterozygous offspring express a phenotype that is intermediate between two parental traits.

Multiple Alleles

A pattern of inheritance occurring when more than $2$ varieties or alleles exist for a single trait.

Carbohydrate allele $I$

The dominant allele in human blood typing that codes for the presence of a carbohydrate on red blood cell surfaces.

Recessive allele $i$

The blood type allele that codes for the absence of cell surface carbohydrates.

Alleles $I^A$ and $I^B$

Codominant alleles coding for cell surface carbohydrates A and B, respectively.

Type A blood genotypes

The genotypes $I^A i$ and $I^A I^A$, which result in A carbohydrates on red blood cells.

Type B blood genotypes

The genotypes $I^B i$ and $I^B I^B$, which result in B carbohydrates on red blood cells.

Type AB blood genotype

The genotype $I^A I^B$, resulting in both A and B carbohydrates on red blood cells due to codominance.

Type O blood genotype

The genotype $ii$, resulting in no carbohydrates on red blood cells.

Polygenic Traits

Traits that require more than one gene (allele) to determine.

Polygenic inheritance of skin tone

Human skin tone determination governed by $4$ to $6$ genes, involving up to six different chromosomes.

Sex-linked Inheritance

The inheritance pattern for traits whose genes are located on the sex chromosomes ($X$ or $Y$).

Carrier female

A heterozygous female ($X X^c$) who carries a recessive sex-linked gene without displaying the trait.

Sex-linked traits in males

Males with an affected X chromosome ($X^c Y$) express the trait because they lack a second X chromosome to counterbalance the gene.

Color blindness

A sex-linked recessive trait where the gene is inherited through the X chromosome.