GeneticsGeneticsDef: the study of reproduction and the results of

the combination of chromosomes.Gregor Mendel – (1822 – 1884)Austrian Monk who is considered

“Father of Genetics”

Mendel’s LawsMendel’s Laws1. Law of Segregation -

Chromosomes separate (segregate) into different gametes during meiosis.2. Law of Independent

AssortmentAll Chromosomes segregate independent of each other. None are connected to each other

Example of Independent Assortment

Mendel talked about traits and called the genes for those traits alleles.Allele -Allele - the

different genes for a traitThe traits that you got

when sperm and egg came together was

NOTHINGNOTHING but probability.

A roll of the dice or a flip of a

coin

Mendel also gave us the genetics terms Dominant and Recessive

Dominant - A trait that will ALWAYS show up if it is in the genesRecessive - A trait that will ONLY

show up if there are no dominant genes presentExample: Example: Your Mom gives you the gene for having a Your Mom gives you the gene for having a

Unibrow (recessive) and Unibrow (recessive) and your father gives you the gene your father gives you the gene for having two eye brows (dominant)for having two eye brows (dominant)What are

you?

Mom Dad

Let’s look at some traits

DOMINANT Black color

Recessive lighter color

This dog’s genetics could be two waysWe show it like this:“B” from one parent, “B” from the

other parent

“BB” is Homozygous for the trait.

“B” from one parent, “b” from the other parent

OROR

“Bb” is Heterozygous for the trait.

This dog’s genetics CAN ONLY be shown one way:

“b” from one parent, “b” from the other parentRecessive traits are ALWAYSALWAYS homozygous; thus it would be “bb”

OK, now for a problem:

If I have a heterozygous black male and a golden female that mate,

X what is the chances of having golden puppies in the litter?

B b b b50% black

50% golden100% golden

You can make a Punnett square

b b

B

b

Bb Bb

bb bb

50%

What do we do if we want to predict the offspring with two traits?

• Dihybrid Cross: tool used to predict the offspring of parents with TWO traits

• Ex:

Definitions to know:

GenotypeGenotype: what the genes say (heterozygous or

homozygous).PhenotypePhenotype: physical appearance of the organism (black or golden).P GenerationP Generation: the parents in the problemFF11 Generation Generation: the first “filial” – child, first generation after the parents.FF22 Generation Generation: the second generation after the parents.

Everything is not always clear cut:Incomplete

Dominance:One allele can not completely dominate the other.

Codominance:When both dominant alleles show in the offspring.

Red White

RoanRoan offspring

Multiple Allele Multiple Allele TraitsTraits::Traits having more than one allele that can be found in the population.

Example:

Human hair color

Black, Brown BlondeBlonde & & RedRed

Human Blood Types

Type A, Type B, Type AB, Type

O

Polygenic TraitsPolygenic Traits::

Traits that are controlled by several genes at the same time.

Four distinctly different types

Four major colors blended through more than a dozen different allele groups.

Example:

Genetic Engineering

Definition: manipulating the genes of an organism due to selective breeding or microbiological processesSelective Breeding:Selective Breeding:

selecting certain selecting certain individuals to be the individuals to be the parents of the future parents of the future generations.generations.

All of these

things are products

of selective breeding

Hybridization:Crossing two Crossing two “wild” species to “wild” species to try to get a try to get a hybrid with the hybrid with the best traits of the best traits of the parent species. parent species.

Hybrid VigorHybrid Vigor:Having an offspring Having an offspring species that is species that is better in many better in many ways than either of ways than either of the parent speciesthe parent species

ChromosomesYou have two for each “pair”.

Mom

One from Mom, and one from Dad

But what happens if there are three for a “pair”?The situation is called

Trisomy: Having three chromosomes for a pair of chromosomes.

Dad

Some Trisomy situations:

Trisomy 21 (Down syndrome)

Trisomy 18 (Edwards syndrome)

Trisomy 13 (Patau syndrome)

Trisomy 8 (Warkany syndrome 2)

Of these, Trisomy 21 and 18 are the most common. Both cause delayed growth, mental issues, and physical limitations. How can a Doctor know if a person has a

specific Trisomy situation?

Karyotyping:This involves catching the chromosomes when they are compacted ready for cell division. Then they must be paired up with their “match”When all the chromosomes in the human genetic makeup are paired, it looks like this:For simplicity, geneticist only use one half of each of the Chromosome to do the matching. Each half is a Chromatid

Genetic Manipulation:

The process of manipulating a gene by taking genes from one organism and moving them to another.

Step 1 – Isolation of target gene.

Lets say that there is a gene in this corn that is drought resistant.

Researchers use enzymes to isolate and cut the gene out (excise) from the original corn.

enzymes

Target Gene

Recombinant DNA:

Step 2 - Copy the geneUsing a machine called a PCR (polymerase chain reaction), the geneticist make thousands of copies of the gene

Step 3 – Insertion of geneUsing enzymes again, the geneticist inserts the gene into the genetic code of the target plant.

Step 4 – Testing of resultsField Biologists set out

plots to test the drought resistance of the new plants.

Organisms that have the genes of other organisms are called: TransgenicTransgenic organismsExamples:

Transgenic Yeast Transgenic Yeast cellscellsProduces human insulin

Drought-resistant Drought-resistant BarleyBarleyCan live in little water

and some in salty water environments

Herbicide resistant and Herbicide resistant and Pest Resistant CornPest Resistant Corn

Plants that will not die when weeds around them are sprayed, and some species that pests do not want to eat

CloningCloningProcess:

Take a cell from your organism and an egg from a donor female.Take the nucleus from the donor egg.

Fuse the two cells by electro-shock. Introduce the right hormones to begin division becoming an embryo.Implant the embryo into the donor female.

The cloned organism is born.

Target sheep

Donor sheep

nucleus

Embryo

Review for Genetics TestReview for Genetics TestDefine:Define:1.1. GeneticsGenetics 2. Gregor Mendel2. Gregor Mendel 3. Allele3. Allele

4. Dominant4. Dominant 5. Recessive5. Recessive 6. Homozygous 6. Homozygous pairspairs

7. Heterozygous pairs7. Heterozygous pairs 8. Genotype8. Genotype 9. 9. PhenotypePhenotype

10. P Generation10. P Generation 11. F11. F22 Generation Generation 12. 12. FF1 1 GenerationGeneration

13. Incomplete Dominance13. Incomplete Dominance 14. Co-dominance14. Co-dominance

15. Multiple Allele Trait15. Multiple Allele Trait 16. Polygenic Trait16. Polygenic Trait 17. 17. MonosomyMonosomy

18 Polysomy18 Polysomy 19. Hybrid vigor19. Hybrid vigor 20 Genetic 20 Genetic engineeringengineering

21. Hybridization21. Hybridization 22. cloning22. cloning 23. recombinant DNA23. recombinant DNA

Questions:Questions:

1.1. What are the two “laws” that are attributed What are the two “laws” that are attributed to Mendel?to Mendel?

2.2. How do they affect genetics?How do they affect genetics?