1. Genetics Terms

2. Genes - Segments of Dna which code for proteins There are different forms of genes. Each “form” of the same gene is called an allele.

3. Gene- segment of DNA that codes for a certain protein/trait
Allele- different forms of the same gene (ex: white or purple)

4. Examples: Gene for Hitchhiker's Thumb: Gene for earlobe shape:
Allele for Hitchhiker’s Thumb
Allele for Non-Hitchhiker’s
Gene for earlobe shape:
Allele for attached earlobes
Allele for detached earlobes

5. Each organism receives 2 alleles for each gene: 1 from mom 1 from dad

6. Complete dominance
When a trait exhibits complete dominance, one allele is dominant over the other. The non-dominant trait is called the recessive allele.
NOTE  Dominant does NOT mean more common. Dwarfism is a dominant trait and is not more common.
We represent dominant alleles with capital letters.
We represent recessive alleles with lower case letters.
Example:
E = Widow’s peak
e = Straight hair-line

7. How many dominant alleles do you need for the dominant trait to be shown? How many recessive alleles do you need for the recessive allele to be shown?

8. Rules of inheritance
Dominant traits only need 1 dominant allele to be visible.
EE = widow’s peak
Ee = widow’s peak (only need 1 capital E)
Recessive traits need 2 recessive alleles to be visible.
ee = straight hairline

9. How would you define heterozygous and homozygous?

10. Homozygous= 2 of the same allele; either 2 dominant or 2 recessive
Terms to know
Homozygous= 2 of the same allele; either 2 dominant or 2 recessive
Also called purebred
Examples: TT cc dd YY
Heterozygous = 2 different alleles
Examples: Bb Hh Ll Rr
Also called hybrid

11. Purebred
Homozygous BB bb

12. HYBRID Bb Ff Gg

13. Homozygous or heterozygous?
Purebred -when the same traits are seen generation after generation
Hybrid- when the traits seen in the offspring are different than the parent generation
Homozygous or heterozygous?

14. Homozygous or heterozygous?
Mom
Dad
Homozygous or heterozygous?
Child

15. How would you define genotype & phenotype?

16. Phenotype- physical or visible characteristics Genotype- genetic composition of alleles

17. Definitions
Genotype = organism’s allele combinations (always 2 letters)
Examples: GG, Tt, bb
Phenotype = organism’s physical appearance
Think PHENO = PHYSICAL
Examples: Tall, short, round peas, wrinkled peas

18. Phenotype or Genotype? Green eyes Widow’s Peak Aa Tail length Attached earlobes GG Ff tt

19. GENOTYPE PHENOTYPE BB Bb White fur
In one species of wild cat, black fur is dominant to white fur. Fill in the chart in your notes.
GENOTYPE
PHENOTYPE BB Bb
White fur

20. Mendel’s Experiment
Gregor Mendel crossed (bred) pea plants to study how traits are passed to offspring.
Cross Terms
P – parent generation
F1 – offspring of P generation
F2- offspring of F1 generation

21. Mendel’s Laws
1. The Law of Dominance: In a cross between contrasting homozygous individuals, only one form of the trait will appear in the F1 generation - this trait is the dominant trait.

22. 2. The Law of Segregation: during the formation of gametes, alleles responsible for a trait separate; one allele is receive from each parent (in gametes).

24. 3. The Law of Independent Assortment:
- alleles responsible for different traits are distributed to gametes (and thus the offspring) independently of each other

26. 21. Lupe grows pea plants in her garden
21. Lupe grows pea plants in her garden. The pea plants have flowers that can be either purple or white, with purple color being dominant to white color. The peas produced by Lupe's pea plants can also be either round or wrinkled, with round peas being dominant to wrinkled peas. Lupe crosses two pea plants that are heterozygous for both traits. If a gamete from this cross receives a dominant allele for flower color, how does this influence the probability of the gamete receiving a dominant allele for pea shape? (Assume that the genes for flower color and pea shape follow the law of independent assortment.)
        

27. Decreases probability Gamete can’t receive the allele
Lupe crosses two pea plants that are heterozygous for both traits. If a gamete from this cross receives a dominant allele for flower color, how does this influence the probability of the gamete receiving a dominant allele for pea shape?
No effect
Decreases probability
Gamete can’t receive the allele
Increases probability

28. A. No effect! Because the alleles sort independently into gametes, they do not affect the reception of the second allele.

29. A Punnett Square is a tool used to predict the offspring from a cross.
Uses the laws of probability
Probability- describes how likely it is that an event will occur
Each outcome is equally likely to occur despite previous outcomes
Each allele combination is equally likely to occur because the alleles sort independently

30. When crossing 2 heterozygotes with complete dominance, you get the following ratios always:
1:2:1 Genotypic
1 Homozygous dominant (25%)
2 Heterozygous (50%)
1 homozygous recessive (25%)
3:1 Phenotypic
3 dominant phenotype (75%)
1 recessive phenotype (25%)
Mendelian Ratios B b BB Bb bb

31. Test Cross
We use a test cross when we have an organism with an unknown genotype and we cross it with a homozygous recessive organism.

32. - Blue = dominant - Yellow = rec
- Blue = dominant - Yellow = rec. Results from testcross: 50% blue 50% yellow

33. Heterozygous Homozygousb B Bb bb b B Bb

34. Monohybrid Crosses Looks at only 1 characteristics/gene
Basically, all the problems we’ve been doing b B Bb bb