What is genetics?

• Every sex cell has one allele for each trait. • Genetics - the study of how traits are

inherited through the interactions of alleles is

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Punnett Squares

• How could you predict what the offspring would look like without actual mating?

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• Punnett square –

A tool used to show possible combinations of alleles

Alleles Determine Traits

• Most cells in your body have two alleles for every trait.

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• These alleles are located on chromosomes within the nucleus of cells.

Punnett Squares

• They show the genotype or genetic makeup, of an organism.

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• The way an organism looks and behaves as a result of its genotype is its phenotype

Alleles Determine Traits

• An organism with two alleles that are the same is called homozygous

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• An organism that has two different alleles for a trait is called heterozygous

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1.Draw box2.Put names on top and side3.Put genotypes4.Cross top5.Cross bottom6.List genotypes (1 hetero Xx,) 7.List phenotypes (1 albino bird)8.Calculate number out of 4 (1 of 4)9.Calculate percentages (25%)

Solving Punnet Squares

Making a Punnett Square 11

GeneticsGenetics

DdD d

D

d

Dd

DD

dd

Dd

Dd

Punnett Squares

• In a Punnett square, letters represent Dominant and recessive alleles.

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DdD d

D

d

Dd

DD

dd

Dd

Dd

Punnett Squares 11

GeneticsGenetics

DdD d

D

d

Dd

DD

dd

Dd

Dd

•An Uppercase (D) letter stands for a dominant allele. •A lowercase (d) letter stands for a recessive allele.

Incomplete Dominance

• When the offspring of two homozygous parents show an intermediate phenotype, this inheritance is called incomplete dominance.

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Genetics Since MendelGenetics Since Mendel

• Examples of incomplete dominance include the flower color of some plant breeds and the coat color of some horse breeds.

Multiple Alleles

• Traits controlled by multiple alleles produce more than three phenotypes of that trait.

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• Blood type in humans is an example of multiple alleles that produce only four phenotypes.

• The alleles for blood types are called A, B, and O.

Multiple Alleles • When a person inherits

one A allele and one B allele for blood type, both are expressedphenotype AB.

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• A person with phenotype A blood has the genetic makeup, or genotypeAA or AO.

Multiple Alleles

• Someone with phenotype B blood has the genotype BB or BO.

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• Finally, a person with phenotype O blood has the genotype OO.

Multiple Alleles 22

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Father type AB phenotype

A B

Mother type Bphenotype B

AB

Called AB

BB

Called B

B AB BB

Allele O is recessive A and B are dominant

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Genetics Since MendelGenetics Since Mendel

Father type A phenotype

A

Can only be Ao or AA

o

Mother type Bphenotype B

AB

Called AB

Bo

Called B

o Ao

Called Aoo

Allele O is recessive A and B are dominant

Multiple Alleles • When a person inherits

one A allele and one B allele for blood type, both are expressedphenotype AB.

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• A person with phenotype A blood has the genetic makeup, or genotypeAA or AO.

Multiple Alleles

• Someone with phenotype B blood has the genotype BB or BO.

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• Finally, a person with phenotype O blood has the genotype OO.

Multiple Alleles 22

Genetics Since MendelGenetics Since Mendel

Father type AB phenotype

A B

Mother type Bphenotype B

AB

Called AB

BB

Called B

B AB BB

Allele O is recessive A and B are dominant

Multiple Alleles 22

Genetics Since MendelGenetics Since Mendel

Father type A phenotype

A

Can only be Ao or AA

o

Mother type Bphenotype B

AB

Called AB

Bo

Called B

o Ao

Called Aoo

Allele O is recessive A and B are dominant

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Genetics Since MendelGenetics Since Mendel

Genotype Phenotype

Ao or AA A

Bo or BB B

AB AB

oo o

Note in blood typing there is only one recessive – type oThe A or B are dominant – which why it is called multiple alleles

Pedigrees Trace Traits

• A pedigree is a visual tool for following a trait through generations of a family.

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• Males are represented by squares and females by circles.

Child

Child

Note children and genetic/blood relatives are connected by the direct white line

Pedigrees Trace Traits • A completely filled circle or square shows

that the trait is seen in that person.

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• Half-colored circles or squares indicate carriers.

• People represented by empty circles or squares do not have the trait and are not carriers.

Using Pedigrees

• A pedigree is a useful tool for a geneticist.

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• When geneticists understand how a trait is inherited, they can predict the probability that a baby will be born with a specific trait.

Using Pedigrees • Pedigrees also are important in breeding

animals or plants.

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• These organisms are bred to increase theiryield and nutritional content.

Sex Determination

• Each egg produced by a female normally contains one X chromosome.

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• Males produce sperm that normally have either an X or a Y chromosome.

Sex Determination

• When a sperm with an X chromosome fertilizes an egg, the offspring is a female, XX.

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• A male offspring, XY is the result of a Y-containing sperm fertilizing an egg.

Chromosome Disorders

• If three copies ( an extra ) of chromosome 21 are produced in the fertilized human egg, Down’s syndrome results.

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Recessive Genetic Disorders

• Cystic fibrosis is the most common Recessive genetic disorder

• Can lead to death among Caucasian Americans.

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Impact of the Environment

• Your environment plays a role in how some of your genes are expressed or whether they are expressed at all.

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• Environmental influences can be internal or external.

• Genes determine many of your traits, you might be able to influence their expression by the decisions you make.

• Some genetically people at risk for skin cancer limit their exposure to the Sun and take care of their skin, they might never develop cancer.

Genetic Engineering • Through genetic engineering, scientists are experimenting

with biological and chemical methods to change the arrangement of DNA that makes up a gene.

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BiotechnologyBiotechnology

• Genetic engineering already is used to help produce large volumes of medicine.

Genetically Engineered Plants

• Genetic engineering can produce improvements in crop plants, such as corn, wheat, and rice.

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• One type of genetic engineering involves finding the genes that produce desired traits in one plant and then inserting those genes into a different plant.

BiotechnologyBiotechnology