chapter 14: mendel and the gene idea

character

a heritable feature of an organism

trait

different variations of a character

P generation

parental generation, original generation, true-breeding

F1 generation

offspring of P generation

F2 generation

self-pollinated offspring of F1 generation

hybridization

cross genetically different organisms

locus

the specific location of an allele on a chromosome

homozygous

an organism having a genotype with the same alleles for a gene

heterozygous

an organism having a genotype with different allels for a gene

pleiotropy

a genotype with multiple phenotypic effects

epistatis

one gene on a locus affecting the expression of a different gene on a different locus

norm of reaction

the range of phenotype expression for a genotype

allele

alternative versions of a gene

how many alleles does an offspring get from each parent for one character?

one allele from each parent

dominant allele

overrules other alleles

recessive allele

can be ruled over by different alleles

phenotype vs genotype

• phenotype is what is seen or expressed

• genotype is the actual genetic code

testcross and why it’s used

• used to determine the genotype of an unknown organism with a dominant appearance with a homozygous recessive organism

mendel’s law of segregation

2 alleles are going to segregate into 2 different gametes

genotypic and phenotypic ratio of monohybrid cross

• genotype= 1:2:1 (1 homo dom, 2 hetero, 1 homo rec)

• phenotype= 3:1 (3 dom, 1 rec)

mendel’s rule of independent assortment

each pair of alleles separating into different gametes is unaffected by other pairs of alleles

physical basis of mendel’s laws of inheritance

first meiosis division

probability multiplication rule

probability of 2+ independent event occurring together

probability addition rule

probability of 1-2 mutually exclusive events occurring together

incomplete dominance

the phenotype of the offspring is somewhere between the parental phenotypes

codominance

2 dominant traits are seen in separate, distinguishable ways

quantitative character and polygenic inheritance

• the phenotype of trait is on a scale

• usually indicate polygenic inheritance

environment effect on phenotypes

• even if the genotype is the same between organisms, the organism’s phenotype can still be changed/adjust based on the environment

• e.g. flower color changing based on soil acidity

cystic fibrosis

• most common lethal genetic disorder

• makes chloride transport channels ineffective or absent

• causes buildup of mucus in different organs

sickle-cell disease

• 1 amino acid substituted

• changes red-blood cell shape

Huntington’s disease

• degenerative disease of nervous system

• doesn’t appear until 30s-40s

multifactorial disorder

• disorder that has genetic and environmental factos

• e.g. smoking increases lung cancer risk