summer - bio 190 - ch 15

15.1

mendels laws of inheritance

inheritance

The acquisition of traits by their transmission from parent to offspring

trait

binary

identifiable characteristic of an organism

white or purple flower, nothing inbbetween

Pea plants are normally

self-fertilizing

mendel began with true breeding plants

Monitor the change of one single trait

mated true breeding plants

P generation

TT tt

F1 generation

monohybrid - heterozygous, which all show the dominant trait

all tall

Tt

F2 generation

TT Tt tt

genotype ratio: 1:2:1

phenotype ratio: 3:1

dominant trait

displayed by F1 generation

recessice trait

masked in F1 reappeared in F2

AA

homozygous dominant

bb

homozygous recessive

Cc

heterozygous

mendelian

dominant masks recessive

incomplete dominance

one copy of “normal“ allele does NOT produce enough protein to achieve dominant phenotype

dominant TT = purple

Tt = light purple

mendel’s laws of segregation

the two alleles of a gene separate (segregate) from each other during meiosis so that every gamete receives only one allele

meiosis

after gametes are made, they unite in fertilization

Depending on the gamete genotypes, there will be different possible genotypes of the offspring

genotype

genetic compisition of an individual

phenotype

physical or behavioral characteristics that are the result of gene expression

Mendel asked, Does the separation of alleles at one gene locus have any influence on the separation of alleles at a second locus?

There is a 25% chance each of transmitting allele cobos b+c, b+c+, bc, and bc+ to offspring. This is what independent assortment of the alleles of two gene loci means

Punnett square with 4 gametes from each parent has 16 possible offspring genotypes - dyhybrid

phenotype ratio

9:3:3:1

15.2

chromosome theory of inheritance

sister chromatids connected during

S phase

identical chromosomes

homogolous chromosomes

not connected

similar DNA sequences but different

same genes in the same order

15.3

pedigree analysis of human traits

pedigree analysis

allows us to determine whether a mutant allele is dominant or recessive and to predict the likelihood of an individual being affected

wild-type allele vs mutant allele

common vs rare

Most genes display

autosomal inheritance patterns

15.4

variations in inheritance patterns and molecular basis

simple mendelian inheritance

the alleles are dominant or recessive

incomplete dominance

occurs when one copy of the “wildtype allele“ does not produce enough protein to achieve the dominant phenotype

norm of reaction

the phenotype range that individuals with a particular genotype exhibit under differing enviornmental conditions

15.5

sex chromosomes and X-linked inheritance patterns

male mammals are hemizygous

for X-linked genes they have only one copy of genes on the X chromosome