Bio - Matching Quiz on Friday

Things to know

• why were pea plants a good choice for Mendel?
• many dominant and recessive traits
• large number of offspring produced quickly
• monohybrid
• An organism that is heterozygous for one of its characters (Tt for example)
• dihybrid
• An organism that is heterozygous for two of its characters (TtBb for example)
• monohybrid cross ratios
• The ratios when two monohybrid organisms mate
• 1:2:1 genotype ratio
• 3:1 phenotype ratio
• dihybrid cross ratios
• The ratios when two dihybrid organisms mate
• 9:3:3:1 phenotype ratio
• don't memorize the genotype ratio
• allele
• An alternate form of a gene
• carrier
• An organism that is heterozygous for a recessive disorder
• codominance
• Two different alleles that have equal effect on an organism's phenotype
• Example
• BB = blue flowers
• BW = blue and white flowers
• WW = white flowers
• complete dominance
• When one form of the gene determines the phenotype
• Example
• RR = red flowers
• Rr = red flowers
• rr = white flowers
• incomplete dominance
• When the recessive allele can contribute to the phenotype
• Example
• NN = big nose
• Nn = medium nose
• nn = little nose

• cystic fibrosis
• Disease caused by the presence of 2 recessive alleles
• Chloride channel in the lung cells is defective
• Mucus builds up in lungs leading to infections
• dominant allele
• The version of a gene that affects the phenotype of the heterozygous organism
• epistasis (when a pair of genes modifies the effects of another pair of genes)
• Example: Coat color in dogs
• CC or Cc = color in fur
• cc = no color in fur
• BB, Bb = black color
• bb = chocolate color
• Yellow lab (ccBB, ccBb, ccbb)
• Black lab (CcBb, CcBB, CCBb, CCBB)
• Chocolate lab (Ccbb, CCbb)
• F1 generation
• In a breeding program the offspring of the parent generation
• If the parents were true-breeding (pure-bred) the F1 generation are all hybrid
• If the characters considered are controlled by complete dominance the F1 generation shows the dominant trait
• Recessive traits will tend to "skip a generation"
• F2 generation
• In a breeding program the offspring of the F1 generation
• In the example above, organisms showing the dominant trait in the F1 generation are hybrids. The F2 generation will have a ratio of dominant to recessive offspring.
• genotype
• The combination of alleles that exist in an organism
• heterozygous
• The genotype in which an organism contains two different alleles for a character
• homozygous
• The genotype in which an organism contains two of the same alleles for a character
• Huntington’s disease (HD)
• Inherited disease in which a dominant allele leads to the disorder
• Brain cells deteriorate due to the disease
• Currently, there is no treatment and the disease is lethal
• If a parent has HD, then the children have a 50% chance of inheriting the disease
• There are over 100 different alleles that can cause the disease
• Severity of the disease depends on which allele you have inherited
• law of independent assortment
• Mendel's law of how traits are passed from parent to offspring
• How it works:
• In organisms with many different characteristics (flower color, seed shape, height, etc.)
• Each character may have more than one form (trait)
• The gametes will have all possible combinations of the alleles

	Characters
	Flower color		Seed shape		Plant height
Traits	Blue	White	Round	Wrinkled	Tall	Short
Allele symbol	B	b	R	r	T	t

Gametes will have the following 8 combinations:

BRT

BRt

BrT

Brt

bRT

bRt

brT

brt

• law of segregation
• Mendel's law stating that organisms only inherit ONE allele for each trait from each parent

• multifactorial
• A genetic character that is controlled by genes and our environment
• Example:
• Musical ability seems to be genetic, but practice is also needed.
• On the other hand, blood type seems to be determined only by ones genes.
• P generation
• Breeding organisms that are pure-bred. Used to start a breeding experiment.
• pedigree
A diagram showing the relationships between organisms.
• phenotype

The inherited traits an organism posses.

• pleiotropy (one gene - changes more than one characteristic)
When one gene can lead to multiple changes in an organism.
Example: PKU
Reduced hair and skin pigmentation
Can not convert phenylalanine to tyrosine
• polygenic inheritance (one characteristic - controlled by two or more genes)
Similar to epistasis
One trait is controlled by two or more genes
(In epistasis one gene's ability to function is controlled by another gene.)
• Punnett square
A data table-like diagram that is used to help solve genetics questions
• quantitative character
A character such as skin color in which there are many forms from one extreme to the other
• recessive allele
The form of a gene that only affects an organism if the organism inherits two copies.
• sickle-cell disease
A disease caused by a pair of recessive alleles. The recessive alleles lead to the body producing misshapen hemoglobin molecules.
• Tay-Sachs disease
A disease caused by a pair of recessive alleles. The disease leads to the destruction of nerve cells in the brain and spinal chord.
• testcross
A procedure in which an organism with a dominant phenotype is mated with one that has a recessive phenotype. If any of the offspring show the recessive phenotype, then we know that the dominant parent was heterozygous.
• trait versus character (think trait: BLUE; think character: EYE COLOR)
• Character = category
• Trait = specific detail that fits the category
• true-breeding
An organism that is homozygous for a given character. This results in the parent's ability to only produce like offspring.