bio genetics

Draw the one-trait cross and phenotype

Draw the two-trait cross and phenotype

Phenotypic ratio (monohybrid and dihybrid)

Monohybrid: (dominant trait) : (recessive trait)

Dihybrid (heterozygous): 9 (dominant both traits) : 3 (dominant #1, recessive #2) : 3 (dominant #2, recessive #1) : 1 (recessive both traits)

Genotypic ratio (monohybrid and dihybrid (both heterozygous))

Monohybrid: (homozygous dominant) : (heterozygous) : (homozygous recessive)

Dihybrid: 1 AABB : 2 AABb : 1 AAbb : 2 AaBB : 4 AaBb : 2 Aabb : 1 aaBB : 2 aaBb : 1 aabb

Monohybrid trait

Trait that uses one pair of alleles from recessive or dominant,

dihybrid traits

Traits that uses two pairs of alleles from recessive or dominant. One pair per trait.

Incomplete dominance

Where one allele does not fully dominate the other, leading to an intermediate phenotype when it is heterozygous

Example of incomplete dominance

The cross between red and white snapdragons producing pink snapdragons for heterozygous.

Multiple alleles

Traits which are expressed by more than two alleles resulting in a variety of phenotypes

Example of multiple alleles

The ABO blood group system in humans, which includes three alleles: $I^A$, $I^B$, and $i$, producing four possible blood types: A, B, AB, and O

Co-dominance

Where multiple dominant alleles express themselves simultaneously

Example of codominance

Roan cattle exhibiting both red and white hairs, resulting in a speckled coat pattern.

Polygenetic traits

Traits produced by multiple genes (each containing two alleles (unless see note)) which together can produce a continuous range of phenotypes. A polygenetic trait can also be influenced by genes with multiple alleles.

Example of polygenetic traits

Skin color, as it has a continuous range of shades due to using several genes, where each gene has an additive effect on the phenotype.

X-linked traits

Traits associated with genes found on the X chromosome, often displaying different patterns of inheritance in males and females.

Example of X-linked trait

Color blindness (recessive), which frequently affects males due to the lack of a redundant X chromosome

Draw X-linked disorder Punnett Square for hemophilia

Carrier (in the context of X-linked traits)

Female who carries the gene but does not have it due to X redundancy

Test cross

Cross between homozygous recessive and a test subject with a dominant phenotype to determine if they are homozygous or heterozygous for that trait

Simple dominance (Mendelian) v. Incomplete dominance

• Simple dominance has the dominant allele completely mask a recessive one

• Incomplete dominance results in a blending of traits in the heterozygous condition

phenotype v. genotype

• Phenotype: physical characteristic

• Genotype: how this is encoded into their genes/genetic makeup

allele

An alternative form/type/version of a gene that can produce differing effects

recessive

An allele which is masked by the presence of a dominant allele in a heterozygous individual. They are only fully expressed if there are two recessive genes together.

sex-linked

Where genes for traits are located on the sex chromosomes, which can affect both genders unequally

Autosome

Any chromosome which is not a sex chromosome (chromosomes 1-22)

autosomal dominant v. autosomal recessive

Autosomal dominant + recessive are methods of inheritance which only occurs in non-sex chromosomes.

In dominant, one copy of a dominant allele is sufficient to express the trait, while autosomal recessive requires two copies for expression.

Independent assortment (Definition, Impact, Who discovered it?)

The random distribution of alleles during gamete formation. Contributes to genetic variation in offspring. Gregor Mendel.

When do alleles separate?

Meiosis

A carrier for hemophilia and a person without hemophilia cross. What percent of their offspring will have hemophilia. Create a test cross and state the genotypes of the cross.

25%, X^HX^h x X^H Y

Name 3 genetic disorders

Cystic fibrosis, hemophili, color-blindness

Hemophilia pattern of inheritance

Sex-linked recessive

Color-blindness pattern of inheritance

Sex-linked recessive

Cystic fibrosis pattern of inheritance

Autosomal recessive