INCOMPLETE INCOMPLETE DOMINANCEDOMINANCE

With incomplete dominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype that is a blending of the parental traits.

INCOMPLETE INCOMPLETE DOMINANCEDOMINANCE

When the phenotype of the heterozygous is intermediate between the two homozygous

Neither allele is dominant/recessive over the other. Neither allele will express itself---therefore NO capital or lower case letters

INCOMPLETE INCOMPLETE DOMINANCEDOMINANCE

EX: Snapdragon flowers.

Red flowers White flowers Pink Flowers

When working these problems it becomes essential to make a key

Red (RR) White (WW) Pink (RW)

INCOMPLETE INCOMPLETE DOMINANCEDOMINANCE

Cross a Red Snapdragon flower with a White Snapdragon flower.

Set up the Punnett Square and give me both pheno and geno Ratios.

INCOMPLETE INCOMPLETE DOMINANCEDOMINANCE

INCOMPLETE INCOMPLETE DOMINANCEDOMINANCE

Phenotypic Ratio

100% Pink

Genotypic Ratio

100% RW

INCOMPLETE INCOMPLETE DOMINANCEDOMINANCE

You cross two pink flowers and give me both phenotypic and genotypic ratios.

CO-DOMINANT ALLELESCO-DOMINANT ALLELES Where both alleles express

themselves fully. With Co-dominance, a cross

between organisms with two different phenotypes produces offspring with a third phenotype. This third phenotype has BOTH parental traits expressed.

CO-DOMINANT ALLELESCO-DOMINANT ALLELES This is most commonly seen in

chickens. Cross a black chicken with a white chicken you get what is called a speckled chicken

NOT GRAY…but both alleles (black and white) fully express themselves so the chicken has both types of feathers.

                                                                                                             

CO-DOMINANT ALLELESCO-DOMINANT ALLELES

White cow crossed with a Red Bull

CO-DOMINANT ALLELESCO-DOMINANT ALLELES

Roan Cow…. Roan refers to cows that have red coats with white blotches.

CO-DOMINANT ALLELESCO-DOMINANT ALLELES

A white horse crossed with a black stallion

CO-DOMINANT ALLELESCO-DOMINANT ALLELES

A gray horse…but upon closer inspection it has hairs that are both black and hairs

that are white.

POLYGENIC TRAITSPOLYGENIC TRAITS More than one allele pair

controls a single trait— Ex: Skin Color—Several

different allele pairs attribute to the overall phenotype—Tone, distribution, etc

MULTIPLE ALLELESMULTIPLE ALLELES A population might have more than

two alleles for a given gene. In this case you have to think of a

gene as a segment of your DNA that controls a trait.

You have more than 2 choices for an allele for each trait.

Even if more than two alleles exist in a population, any given individual can have no more than two of them.

MULTIPLE ALLELESMULTIPLE ALLELES Ex: Blood type, Rabbit Fur,

Labrador Retriever Coat Color

MULTIPLE ALLELESMULTIPLE ALLELES In Labs, coat color is determined

by one gene with four different alleles. Five different colors result from a combination of these alleles.

Phenotype Possible Genotypes

          

BBEE BbEE BBEe BbEe

                       

bbEEbbEe

                       

BBeeBbeebbee

Multiple Alleles- Blood Type

Blood Type of Recipient

Preferred Blood Type of Donor

Permissible Blood Type

of Donor

A A A, O

B B B, O

AB AB AB, A, B, O

O O O

Multiple Alleles- Blood Type

Multiple Alleles-Rabbit Fur Coat color in

rabbits is determined by a single allele pair that has at least four different alleles.

Full(C), Chinchilla (Ch), Himalayan (h),

Albino (c)

SEX CHROMOSOMESSEX CHROMOSOMES We already

know that each human has 46 chromosomes which means they have 23 homologous pairs.

The 23rd Pair is different. It determines the sex of the individual.

SEX CHROMOSOMESSEX CHROMOSOMES Homologous

Pairs1-22 are called Autosomes

The 23 pair often called the Sex Chromosome.

FEMALE SEX FEMALE SEX CHROMSOMESCHROMSOMES

Female 23rd Chromosome is represented by XX.

MALE SEX MALE SEX CHROMSOMESCHROMSOMES

The 23 Chromosome on the male is represented with a XY.

SEX-LINKED TRAITSSEX-LINKED TRAITS

Genes that are carried by either sex chromosome are said to be Sex-linked Traits.

SEX-LINKED TRAITSSEX-LINKED TRAITS Scientist discovered this

linkage when studying fruit flies (Drosophilia). Through many experiments scientist soon concluded eye color of these flies were determined by the sex chromosome.

SEX-LINKED TRAITSSEX-LINKED TRAITS Often an

allele for a trait can be found on the X but not on the Y chromosome.

The Y chromosome on the male carries little or NO genetic information.

SEX-LINKED TRAITSSEX-LINKED TRAITS WHEN WORKING ANY SEX-

LINKED TRAIT YOU MUST ALWAYS WRITE IT OUT……

XX x XY You still have dominant and

recessive alleles.

SEX-LINKED TRAITSSEX-LINKED TRAITS Eye color in fruit flies is a sex-

linked trait where Red eyes is dominant over White eyes. (This trait is carried on the X chromosome)

Cross a heterozygous Red eyed female with a red eyed male.

SEX-LINKED TRAITSSEX-LINKED TRAITS Practice Problems

Cross a heterozygous Red eyed female with a red eyed male.

Cross a homozygous Red eyed female with a white eyed male.

Allow the F1 generation male/female to cross.

Show me Cross, Punnett Square, and Phenotypic and Genotypic Ratio

SEX-LINKED TRAITSSEX-LINKED TRAITS Most sex-linked

traits are carried on the X chromosome. Therefore the female will carry two and the male will only carry one.

However, some sex-linked traits are carried on the Y…but only a few!!

Sex chromosomes can carry other genes

Y-LINKED GENES:Genes carried on Y chromosome

EX:Hairy pinna

_________genes only show up in _______Y linked males.

SEX-LINKED TRAITSSEX-LINKED TRAITS Colorblindness Hemophilia Duchenne Muscular Dystrophy Fragile X Syndrom

Sex chromosomes can carry other genes

X-LINKED GENES: Genes carried on the X chromosome

EX: __________________________

_________________________

HemophiliaColorblindness Duchenne Muscular Dystrophy

                                             

SEX-INFLUENCED TRAITS

(NOT located on X or Y chromosome)- found in both sexes but expressed differently.

Baldness-caused by autosomal allele that is dominant in men due to the presence of testosterone. It is recessive trait in women.

Index finger length- Dom/fem Rec/Mal

SEX-LIMITED TRAITSSEX-LIMITED TRAITS Sex-limited traits are

autosomal traits that are expressed in only one sex (In normal conditions)

Ex: Breast, Beards, Breast milk.

TESTCROSSTESTCROSS Testcross- one way to

determine the genotype of an unknown genotype is to cross it with a known genotype (usually recessive)

TESTCROSSTESTCROSS A breeder is

considering using this dog to produce offspring. However the owner is unsure if the dog is a possible carrier of a common hearing problem. She knows that he has normal hearing. What can she do?

CarrierCarrier A carrier is a

heterozygous individual. They do NOT have the trait but do have the possibility to pass it to their offspring.

Dd

TESTCROSSTESTCROSS When

performing a test cross you would cross the unknown genotype with a known…usually a homozygous recessive.

Many breeders will rely on a testcross to determine if they are dealing with a pure breed or a hybrid.

How are genes passed on over generations?

PEDIGREEPEDIGREE

A graphic representation of an individuals family tree.

PEDIGREE CHART

Males = Females =

Has trait = Carrier =

KAROTYPEKAROTYPE A photograph that shows an

individuals chromosomes in homologous pairs.

Usually done by collecting white blood cells-stimulating mitosis and capture the information.

Karotype can be used to find any chromosomal abnormality.

KAROTYPEKAROTYPE Most abnormalities are called by

Nondisjuction- the failure of one or more chromosomes pairs to separate during meiosis.

Down Syndrome Klinefelter Syndrome Turner Syndrome