Ayache Genetics

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

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

State the 3 generations

P: parent generation
F1: Offspring of P
F2: Offspring of F1

allele

Form of a gene

Form of a gene

allele

When do alleles separate?

Meiosis

Autosome

A non sex chromosome. Chromosomes pairs 1-22

A non sex chromosome. Chromosomes pairs 1-22

Autosome

Incomplete dominance (Definition + Examples explained)

When the heterozygous phenotype is an intermediate (in between) of the dominant and recessive phenotypes. Neither allele is dominant or recessive over the other. Snapdragon flower (WW white, RR red, WR pink) and Sickle cell anemia (AA normal RBC, SS sickle shaped RBC/sickle cell anemia, AS both normal and sickle shaped RBC/sickle cell trait).

When the heterozygous phenotype is an intermediate (in between) of the dominant and recessive phenotypes. Neither allele is dominant or recessive over the other.

Incomplete dominance

Co-dominance (Definition + Examples explained)

When both alleles are dominant and expressed in the phenotype. Roan Cattle (has red and white fur), Speckled Chickens (has black and white feathers), and blood type (blood type A and B are co-dominant, resulting in a AB blood type).

When both alleles are dominant and expressed in the phenotype.

Co-dominance

Multiple alleles (definition + examples explained)

When there are more than 2 different alleles coding for one trait, but only 2 alleles are inherited. Human blood types (I^a, I^b, and i alleles).

When there are more than 2 different alleles coding for one trait, but only 2 alleles are inherited.

Multiple alleles

DEFINITIONS:
Polygenic
Polygenic trait
Polygenic Inheritance

3 Examples of polygenic traits

2 or more genes affecting a trait
Traits that are controlled by 2 or more genes
Type of inheritance where a single trait is controlled by 2 or more genes (with 2 alleles per gene)

Skin color, height, eye color

When a single trait is controlled by 2 or more genes (with 2 alleles per gene)

Polygenic inheritance

X linked inheritance (Definition + 2 examples)

Inheritance where the gene is carried on the X chromosomes. Colorblindness and Hemophilia

Inheritance where the gene is carried on the X chromosomes

X linked inheritance

Is X linked recessive traits/disorders more likely to happen to men or women? Why?

Men, because they would only need to have one allele for the disorder to have the disorder (XY), while women need to have two alleles for the disorder to have it (XX) since it is recessive.

Carrier

People (women in x linked recessive disorders) that have an allele for the disorder, but do not show symptoms of the disorder.

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

Stabilizing selection (Definition + 1 example)

Type of natural selection where an intermediate (in between) phenotype is the most preferred given the environmental conditions. The size of babies being born.

Directional Selection (Definition + 1 example)

Type of natural selection where one extreme end of the phenotype is the most preferred given the environmental conditions. Giraffe neck size.

Disruptive selection (Definition + 1 example)

Type of natural selection where both extreme ends of the phenotype are the most preferred given the environmental conditions. The feather brightness of birds (bright feathers attract mates, duller feathers avoid predators).

Type of natural selection where both extreme ends of the phenotype are the most preferred given the environmental conditions

Disruptive Selection

Type of natural selection where one extreme end of the phenotype is the most preferred given the environmental conditions.

Directional selection

Type of natural selection where an intermediate (in between) phenotype is the most preferred given the environmental conditions.

Stabilizing selection

Freckles are dominant over no freckles, Dimples are dominant over no dimples.
A male homozygous dominant with both freckles and dimples mates with a female with no dimples and no freckles. State the possible phenotypes of their offspring.

All offspring will have freckles and dimples

Freckles are dominant over no freckles, Dimples are dominant over no dimples.
A male heterozygous for both freckles and dimples mates with a female heterozygous for both freckles and dimples. State the possible phenotypes of the offspring and draw a test cross.

1 will have no freckles and dimples, 3 will have freckles but no dimples, 3 will have dimples but no freckles, and 9 will have both freckles and dimples.

Another word for a two trait cross

Dihybrid cross

Charles Darwin

Proposed the theory of evolution with natural selection, nicknamed “survival of the fittest”. Believed in natural selection (genetic variation, organisms with the the fitter trait pass it on to their offspring while the organisms with the less fit trait don’t, leading to more of the fitter trait in the population over time). Evolution would happen in many generations.

Jean-Baptiste Lamarck

Proposed the inheritance of acquired characteristics. Believed that offspring inherited acquired traits. No genetic variation. Believed that the physical changes the organism made in its life time (giraffes stretching their necks or cutting off a finger) could pass on to their offspring. Evolution would happen in a few generations.

Fitness

The ability of an individual to survive and reproduce in its specific environment

Natural selection

The process where individuals with traits that are better suited to their environment survive and reproduce more successfully, passing down their traits to their offspring. Proposed by Darwin.

Acquired traits

Characteristics that an organism develops during its lifetime due to its behavior and environment. Proposed by Lamarck.

Homologous structures
Analogous structures

Structures that are anatomically similar and inherited from a common ancestor.
Structures that are anatomically different (but serve the same function) and originated independently without a common ancestor.

Structures that are anatomically different (but serve the same function) and originated independently without a common ancestor.

Analogous structures

Structures that are anatomically similar and inherited from a common ancestor.

Homologous structures

Vestigial structures (Definition + 1 example)

Structures that used to function and serve a purpose in an ancestor but have since lost most or all of their function. Human appendix.

Structures that used to function and serve a purpose in an ancestor but have since lost most or all of their function.

Vestigial structure

Definition and who said it:
“Survival of the Fittest”
“Descent with Modification”

Phrase that describes the concept of natural selection (process where individuals better suited to survive do and pass on their trait)
Phrase that describes the concept of evolution (each species descended with changes over time from other species).
Charles darwin

Phrase that describes the concept of natural selection (process where individuals better suited to survive do and pass on their trait)

Survival of the fittest

Phrase that describes the concept of evolution (each species descended with changes over time from other species).

Descent with modification

Definition and 1 example:
Convergent evolution
Divergent evolution

Phenomenon where two unrelated species evolve similar traits as a result of exposure to similar environments. Shark and dolphin fins.
Phenomenon where two related species evolve different traits as a result of exposure to different environments. Galapagos finches beaks.

Phenomenon where two unrelated species evolve similar traits as a result of exposure to similar environments.

Convergent evolution

Phenomenon where two related species evolve different traits as a result of exposure to different environments. Galapagos finches beaks.

Divergent evolution

sex linked trait

a trait present on the sex chromosomes

test cross

A cross that tests whether an individual with a dominant phenotype has a homozygous dominant or heterozygous genotype by crossing it with a homozygous recessive individual. (H? x hh).

DEFINE:
phenotype
genotype

A physical characteristic displayed in an organism
The alleles that determine the a trait’s phenotype.

IDENTIFY THE GENETIC DISORDER

Hemophilia
Muscular dystrophy
Baldness
Huntington’s disease
Cystic Fibrosis
Retts syndrome
Phenylketonuria
Color Blindness
Tay-Sachs disease

Sex linked recessive
Sex linked recessive
Sex linked polygenic
Autosomal dominant
Autosomal recessive
Sex linked dominant
Autosomal recessive
Sex linked recessive
Autosomal recessive

Which gender is more likely to be affected by a sex linked dominant disorder? Why?

Females, because they have 2 X chromosomes, meaning they have 2 chances of inheriting the disorder while males have only 1 X chromosome (1 chance).

Simple dominance

When one dominant allele completely masks the other recessive allele

When one dominant allele completely masks the other recessive allele

Simple dominance

Dihybrid traits

Traits from a dihybrid cross. Two traits with two pairs of alleles with one pair of alleles per trait.

Monohybrid trait

Trait from a monohybrid cross. A trait with a pair of alleles, one dominant and one recessive.

Monohybrid cross
Dihybrid cross

A cross for one trait with a pair of alleles involved
A cross for two traits with 2 pairs of alleles involved.