genetics intermediate traits. traits most traits are controlled by more than 1 gene most traits have...

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Genetics Intermediate Traits

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GeneticsIntermediate Traits

TraitsMost traits are controlled by

more than 1 geneMost traits have multiple alleles

Incomplete dominanceFor some

traits, neither allele is dominant

Blending occurs

Ex. Snapdragons◦Cross a red

flower with a white flower and get pink flowered offspring

ProblemA true breeding red

snapdragon is crossbred with a true breeding white snapdragon. Red and white colors are considered to be incompletely dominant. What will the phenotypic ratio of their offspring be?

Codominance Both alleles are expressed in the

same organismEx. Chicken feathers

◦Black feathered rooster + a white feathered hen = offspring with some white feathers and some black feathers

ProblemIn a certain type of

rabbit, black fur is codominant with brown fur resulting in an agouti color. If a true breeding black fur rabbit and an agouti rabbit are bred, what will the phenotypic ratio of the offspring be?

Multple AllelesEach organism

has only 2 possible alleles for a trait

Multiple alleles for the trait may exist in the entire population

Ex. Human Blood types◦A, B, AB, O

Blood TypesA and B are CODOMINANTA and B are DOMINANT over OWritten as IA, IB, and I

◦IA IA produce A blood type◦IA i produce A blood type◦IB IB produce B blood type◦IB i produce B blood type◦ii proudces O blood type

What type of parents can produce offspring with any blood type?

ProblemA man with type O

blood marries a woman with type A blood. They have a son with type O blood. Several years later they get a divorce and the wife is suing the husband for child support. Is it possible that he should have to pay?

ProblemA man with type O

blood marries a woman with type A blood. They have a son with type B blood. Several years later they get a divorce and the wife is suing the husband for child support. Is it possible that he should have to pay?

Polygenetic TraitsSome traits are controlled by

more than one gene◦Ex. In humans

Height Eye color Skin color

Intermediate Patterns of Inheritance

Pattern of Inheritance

Description Example

Incomplete Dominance

One allele is not completely dominant over another

Snapdragons: Red flowered plant and white flowered plant crossed make pink flowered plants

Codominance Both alleles contribute to the phenotype

Chicken variety: black feathered chicken X with a white feathered chicken = white and black feathered chicken

Multiple alleles A gene has more than 2 alleles possible

Human blood type: IA and IB (codominant) and i

Polygenetic Traits

Traits are controlled by more than 1 gene

Human skin color: wide range of colors due to several different genes

Chromosomes2 types Autosomes are any

type of chromosome other than a sex chromosome

Sex chromosomes are X and Y

Females XX – always donate an X

Males XY – determines gender of offspring

Sex – Linked TraitsDetermined by alleles

located on the sex chromosomes (X and Y chromosomes)

Males have 1 X chromosome meaning they are more likely to show a sex linked recessive trait

Ex. Albinism, hemophilia, blindness, muscular dystrophy are sex linked

KaryotypesVisual display of all the

chromosomes in an organismIndicate chromosomal

abnormalities◦Broken, missing, or extra◦Down’s syndrome

Down’s syndromeResults from an extra 21st

chromosome

Turner’s syndromeOnly 1 X chromosome and no YAlways FemaleUsually develop normally but

may result in shorter stature

Triple XGoes undiagnosed most of the

timeEstimated 1 out of 10 girls are

XXX

XYY syndromeExtra Y chromosomeOnly in Males

Klinefelter syndromeMalesTendency to develop female-like

characteristics