Different Types of Inheritance
description
Transcript of Different Types of Inheritance
Different Types of Inheritance
SEX LINKED TRAITS
First Type of Inheritance
Sex Determination
In humans and many other organisms, sex is determined by the X and Y chromosomes.
Females: XX
Males: XY
Sex Determination
Sons get their X chromosome from their mothers only.
Fathers must pass their X chromosomes to their daughters.
Sex Linked Traits
Genes that are found on the X chromosome follow a have a special pattern of inheritance:
X linked traits are only passed to sons from the mother
Males are much more likely to be affected than females. If trait is recessive, daughters have a second X
chromosome so they can be heterozygous. Sons only have one X chromosome
Sex Linked Traits
Daughters can be carriers and pass the trait onto their son.
Examples
Baldness
Example: Colorblindness
Sex Linked Problem
A woman is not colorblind but her husband is. Construct a punnett square to determine what is the chance that their children will be colorblind.
Xb
Y
XBXb XBXb
XBY XBY
XB XB 0%- what about % of being carrier
50%
Sex Linked Example
A woman who is a carrier for hemophilia marries an unaffected male. What is the % chance that their children will be affected?
XH Xh
XH
Y
XH XH XH Xh
XH Y Xh Y
25% affected- how many carriers?
25%
INCOMPLETE DOMINANCE
Second Type of Inheritance:
Incomplete Dominance
Inheritance that occurs when one trait is not completely dominant over another
Results in the heterozygous form being blended together
Solving an Incomplete Dominance Problem
Perform a regular monohybrid punnett square
Only difference is the heterozygous offspring will be mixture of two traits (i.e. if black and white than gray)
Example
Red carnations are not completely dominant to white carnations- perform a punnett square mating a red and white carnation
r r
R
R
Rr
Rr
Rr
Rr
Results
Genotype: 4/4 RrPhenotype 4/4 Pink
Example: Black fur (B) is dominant over white fur (b) in guinea pigs. Cross a grey guinea pig with a white guinea. What do we get?
Answer: ½ Bb (grey) and ½ bb (white)
CODOMINANCE
Third Type of Inheritance
Codominance
When two different alleles are present and both are expressed
Codominance Example
Red flowers and white flowers are codominant.
What color will the heterozygote be?
Cross a red flower with a white flower and report the phenotype and genotype.
Example: Blood Types
Red blood cells are coated with different markers.
Each person contains either A, B, A and B
or neither protein.
Blood Types are: A, B, AB, O
Blood Type Key
Genotype PhenotypeIAIA, IAIO A BloodIBIB, IBIO B BloodIAIB AB BloodIOIO O Blood
Example: Blood Type
Susan (blood type AB) and Bryan (blood type O) have a son that has blood type B? Since neither Susan nor Bryan have this blood type, was their a mistake in the hospital?
Construct punnett square on next slide
Example: Blood Types
IA IB
IO
IO
IA IO IBIO
IAIO IBIO
Results: ½ A blood type or ½ blood type B
Yes he is their son!
DIHYBRID CROSSES
Fourth Type of Inheritance:
Dihybrid Crosses
Cross that involves two traits
Concludes with 16 offspring
Steps for Solve for Dihybrid Cross
Make a key for the two traits that you are crossing Black Hair (B) vs Brown Hair (b) Curly Hair (S) vs Straight Hair (s)
Write out the different genotypes of the parents Mother is heterozygous for both traits BbSs Father is heterozygous for hair color but has straight hair
BbssFigure out the possible gametes (similar to FOIL)
there are four for each parent and each gamete must have one allele from each trait Mother: BbSs BS; Bs; bS; bs Father: Bbss Bs; Bs; bs;bs
Steps for Solve for Dihybrid Cross
Set up your punnett squareBS Bs bS bs
bs
bs
Bs
Bs
BbSs
BbSs
BBSs
BBSs
Bbss
Bbss
BBss
BBss
bbSs
bbSs
BbSs
BbSs
bbss
bbss
Bbss
Bbss
Steps for Solve for Dihybrid Cross
Count up the possible genotypes and phenotypes that you have from your punnett square Genotypes: Phenotypes:
BbSs:4/16 Black/Curly: 6/16 BBSs:2/16 Black/Straight: 6/16 Bbss:4/16 Brown/ Straight:2/16 BBss: 2/16 Brown/Curly: 2/16 bbSs: 2/16 bbss:2/16