non- mendelian genetics
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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 - PowerPoint PPT PresentationTRANSCRIPT
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: