Key Concepts in Genetics and Inheritance

Genetics

1.  study of inheritance patterns and variation

Heredity

the passing of genes from parents to offspring

Gene

A segment of DNA that codes for a specific protein (and therefore a trait).

Trait

A characteristic or feature determined by genetics (e.g., eye color).

Allele

A version of a gene. Each individual inherits two alleles per gene—one from each parent.

Inherited Traits

Passed down genetically. Controlled by DNA.

Acquired Traits

Learned or developed over life

Genotype

The actual genes (e.g., Aa, AA, aa).

Phenotype

Physical trait you see (e.g., brown eyes).

Homozygous Dominant

2 dominant alleles (AA).

Homozygous Recessive

2 recessive alleles (aa).

Heterozygous

1 dominant + 1 recessive (Aa).

Dominant

The trait/characteristic that is always seen if it is present.

Recessive

The trait that is only seen when the dominant gene is not present.

Law of Dominance

In heterozygous individuals, the dominant allele is expressed.

Law of Segregation

Each parent passes only one of their two alleles to offspring during meiosis

Law of Independent Assortment

Genes for different traits assort independently, if they're on different chromosomes so the inheritance of one trait does not influence the inheritance of another trait.

Codominance

When both alleles are equally expressed in a heterozygous individual

Incomplete Dominance (The genotype of an organism with incomplete dominance can be determined from its phenotype)

a blend of the two parent phenotypes rather than showing complete dominance.

(Ex: When a red flower (RR) is crossed with a white flower (WW), the offspring (RW) have a pink intermediate/blended color.)

Multiple Alleles

Some genes have more than just two alleles, meaning there are multiple versions of a gene that can influence a trait.

(ex.Blood types A, B, O)

Polygenic Traits

Traits that are controlled by multiple genes, each of which may have two or more alleles.

(ex. Skin color: Determined by multiple genes controlling the production of melanin. More dominant alleles = darker skin)

Why do X-linked traits affect males more?

Since males only have one X, if it's recessive then the ressecive trait will be seen

Effects of Environment on Phenotype

Genes set potential traits, but environmental factors can modify their expression.
(ex. A person with genes for tall height may not reach their full potential if they experience poor nutrition during childhood.)

What causes variation in siblings if same parents?

Independent assortment + random fertilization + crossing over = infinite combos!

Differce b/w codominance and incomplete dominance

Codominance = both show up, Incomplete Dominance = blended result

Sex-linked features

males only have 1 allele located on the X chromosome because they inherit only 1 X chromosome (XY)

Where do we get our genes from:

When the sperm and egg cells combine they form 1 cell with 46 single chromosomes (23 pairs).