GeneticsThe study of inherited traits

Jennifer and Homer Simpson If the two of them were to get married, would

their children look like this?

Definitions1. Heredity – the passing of traits from parents to

offspring2. Gregor Mendel – the father of genetics3. Self-pollination – all traits are received from the

one parent4. Cross-pollination – seeds are produced as

offspring from two different plants5. Purebred – offspring are bred for specific traits

by mating identical parents

6. Traits – an organism’s characteristics passed on by the biological parents

7. Hybrids – offspring created by crossing parents with different characteristics

8. Genes – segments of DNA that code for traits

9. Alleles – letters that are used to express the frequency of traits

10.Dominance – individual traits that are more likely to be expressed in a population, capital letters

11.Recessive – traits less likely to be visible in a population , lower case letter.

12.Segregation – separation of alleles during meiosis

13.Punnett Square – a probability chart used to determine possible outcomes for the inheritance of traits

14.Phenotype – a description of an organism’s physical appearance, what it looks like.

15.Genotype – a two letter code using alleles that expresses the dominance of an individual, what genes/letter are there.

16.Probability – the % chance of a specific trait or set of traits being inherited

17.Homozygous – the two alleles that represent a trait are exactly the same, ex. HH, hh

18.Heterozygous – the two alleles that represent a trait are different, ex. Hh

19.One-Factor Cross – only one allele is used in a Punnett Square, ex. Hair color

20.Two-Factor Cross – two sets of alleles are used to determine probability of having two linked traits, ex. Hair and eye color

What is Genetics?

Genetics is the study of traits and how they are chemically passed from one generation to their offspring by meiosis and fertilization

Where did Genetics get its Start?

Gregor Mendel (a Biology Teacher and a Catholic Priest) made some observations while working in the monastery gardens

He hypothesized that each organism had its own unique set of traits that could be transferred from one organism to the next.

He used pea plants to test and support his hypothesis.First:  peas exhibit a number of contrasting traits that Mendel could easily studySecond:  pea plants can easily be cross pollinatedThird:  a relatively large number of seeds are produced

The Start of Genetics cont.

Mendel's first observations showed that peas self pollinate.

Each pea plant had its own egg and sperm.He exchanged male and female pollen from two different

plants to force cross-pollination. (hybrid)The plants that weren’t switched were purebreds.

Gregor Mendel1822 - 1884

Genes and DominanceEvery organism has

certain characteristics called traits.

Each trait is expressed by a two letter code (alleles)

Some alleles are stronger than others (dominant) and others are weaker (recessive)

Number your paper from 1 to 3Do Not skip a space!

1. Each trait is expressed by a _________?

2. What are stronger traits called?

3. What are weaker traits called?

1. Two letter code (alleles)

2. Dominant

3. Recessive

Alleles Each trait is controlled by two genes (1 from each biological parent) Genes can be represented by letters An uppercase letter denotes the wild type (usual, dominant)

form of the gene A lowercase letter denotes the mutant (unusual, recessive)

form of the gene There are three distinct combinations; e.g. TT,Tt, and tt If a dominant gene is paired with a recessive gene, the

dominant's trait will usually out power the recessive, but not always

Questions 4, 5, & 6

4. How many genes control one trait?

5. What are genes represented by?

6. If a dominant and recessive gene are paired together, which trait is seen?

4. Two

5. Letters

6. Dominant

Punnett Squares• To set up a Punnett square, draw a large square,

and then divide it into 4 equal sections. It should look something like this:

Punnett Squares cont.

Now you need two parents to mate with a known genotype. For example, a red flower (genotype Rr) and a white flower (genotype rr). Place one of the parents on top, and one on the left. You should get a something similar to this:

Punnett Squares cont…

• Take each letter in each column and combine it with each letter from each row in the corresponding square. You should now have a picture close to this:

Punnett Squares cont….Each punnett square is equal to 100% of the possible

genotypes.Therefore each box in our punnett square is equal to 25%

probability

• We can then look at the results of our Punnett Square and determine the probability of traits.

• 50% of the squares are Rr; 50% are rr• We can assume there is a 50% chance the flowers will be

red or 50% chance of them being white.

Questions 7 & 87. What is each punnett square worth in percentage?

8. If there are 10 boxes in a Punnett Square, what would each individual box represent in percentage?

7. 100%

8. 10%

Try your own Punnett Square

• Find out the probability of having a tall or short plant using these two genotypes.

• TT and tt (T = Tall t = short)

Genotype and PhenotypeGenotype is the genetic code (alleles) for an organism.Phenotype is the actual physical appearance.

Blonde Hair = BBGreen Hair = bbBrown eyes = AAYellow eyes = aa

Figure out probability of this problem.Write down each of their traits for hair and eye color

The Information

The Grinch

Phenotype: Green Hair

Yellow Eyes

Genotype: bb (green hair)

aa (yellow eyes)

Britney Spears

Phenotype: Blonde HairBrown Eyes

Genotype: BB(blonde hair)AA

(brown eyes)

Try again!

This time, come up with your own set of alleles for hair color and skin color.

Is this what their kids would look like?