non- mendelian genetics

NON-MENDELIAN GENETICS

Complexity of Genetics: In most cases,

genetics are not as simple as presented in school

There many factors and genes that contribute to the traits we see

Incomplete Dominance: A heterozygous

phenotype that is somewhere between the two homozygous phenotypes

R = Red, r = white

RR = red, rr = white, Rr = pink

R Rr Rr Rrr Rr Rr

Codominance When two different

alleles for the same gene are both expressed and cannot mask the expression of the other

Red Cows and White Cows, can combine to make an offspring called Roan, where both the Red and White show through

Multiple Alleles When three or

more alleles exist for a single gene or trait

Polygenic Inheritance When more than

one gene contribute to a trait

High blood pressure, obesity, etc.

Blood Type Considered an example

of both codominance and multiple alleles

Two dominant traits, iA and iB

One recessive trait, i Leads to the following

blood types: iAiA or iAi = A iBiB or iBi = B iAiB = AB ii = O

O is the universal donor

Sex Linked Traits: Two types of

chromosomes Autosomes – all

homologous chromosomes (#1-#22)

Sex Chromosomes – The two unmatched chromosomes that determine the sex of the individual

Sex Chromosomes Male genotype is

xy Female genotype

is xx The chromosome

is much larger and can carry more genetic information

Sex Linked Traits: Controlled by the

genes on the x-chromosomes

Examples: Hemophilia – “Bleeders

Disease” Muscular Dystrophy –

gradual destruction of muscle cells

Color Blindness – unable to perceive different colors

Male Pattern Baldness

Sex Linked Traits:1. Females can carry both the

dominant and recessive traits on the x-chromosomes at the same time (a carrier for the recessive trait)

2. Males can only carry either the dominant or the recessive (only one x chromosomes)

3. Whatever is on the x chromosome for a male will be expressed (can never be a carrier)

Practice #1: In Snapdragons, the color Red

(R) and White (W) only show through when they are homozygous. When they are heterozygous (RW) they are pink. Predict the genotype and phenotype ratios for a cross between two pink flowers. Include a Punnett square

Genotype: RR:RW:WW, 1:2:1 Phenotype: Red:Pink:White,

1:2:1

R W

R RR RW

W RW WW

Practice #2: A person with Type AB blood

and a person with Type O blood have a child. What are the possible outcomes for blood type? What is the possibility that the child has Type AB blood?

Type A or Type B blood type

No chance for AB blood

iA iB

i iAi iBi

i iAi iBi

Practice #3: Identify as many genotypes as

possible for color blindness. Squares are men, blue means the presence of the gene: