1. Genetics

2. Genetics: the study of heredity

3. Heredity: the passing on of characteristics from the parent to the offspring

4. Background (not in notes)
Gregor Mendel: first lab in the garden
Studied garden peas
Performed cross-breeding with different types of pea plants
- yellow peas x green peas
- wrinkled peas x non wrinkled plants
Determined that the inheritance of traits followed laws and that determined the ratios of how often those traits would be seen in the offspring of subsequent generations

5. For Example Gregor Mendel crossed pea plants: Green X Yellow
Then he crossed the offspring
Green (75%) Yellow (25%)
HMMM… Interesting

6. So before we go any further: Important Genetics Vocab!!!!
Genes – a segment of a chromosome which codes for something specific
Ex: seed colour

7. Alleles: different forms of a gene (variations)
Each cell will have two allele
Remember that each cell has homologous chromosomes
Eg: The gene is for seed colour but the alleles are for yellow and green
The homologous chromosomes will have the gene for seed colour…
Each chromosome will have a variation of that gene… green colour and yellow colour

8. Dominant: an allele that shows over the other allele of the gene.
The dominant allele is written in uppercase.
Green colour is dominant = G
If present, it always shows! (it wins!)
Recessive: an allele that does not up over the dominant allele.
It only shows up when the other allele is recessive
Yellow colour is recessive = g
Need to have 2 recessives together for this to show! (otherwise it hides)

9. Green X Yellow (GG) Dominant (gg) Recessive Green (100%) (Gg)

10. Homozygous – an individual with copies of the same type of allele
Eg: GG (green peas) x gg (yellow peas)
Two copies of green Two copies of yellow
Heterozygous – an individual with copies of two DIFFERENT alleles
Eg: Gg – (green peas)
One copy of the dominant green seed allele and one copy of the recessive allele (yellow)
Dominant allele wins… therefore the peas show as green even though they have a the yellow recessive allele

11. Genotype: The particular combination of alleles an organism has
Eg: GG or Gg or gg
Phenotype: The physical appearance of the organism.
Green seed colour is the phenotype (GG or Gg genotype)
Yellow seed colour (gg is the genotype)

12. Hybrid – crossing of the two forms of a trait.
Pure bred- an individual with only one type of allele
F1 offspring (F1 generation) – the offspring of two pure bred individuals
F2 offspring (F2 generation)- the offspring of the F1 individuals bred with each other

13. For Example Gregor Mendel crossed pea plants: Green X Yellow
Then he crossed the offspring
Green (75%) Yellow (25%)
HMMM… Interesting
Pure bred individuals
F1 Offspring
F2 Offspring

14. Genetics and Probability
Probability is the chance or likelihood of something occuring
Does not tell you what it will be but what is possible
Ex. 50% chance a baby is a boy or girl
Ex. Chance of tossing two heads in a roll is:
½ x ½ = ¼

15. So:
During meiosis different alleles can go into different cells

16. A plant that is heterozygous for the seed colour Gg can give a G allele or a g allele
A Punnett square is one way to show all the possible genotypes of offspring
ANIMATION G g

17. Cross between 2 pure breds (homozygous)Gg
Genotype results: Gg
Phenotype results: 100% Green peas
Cross between 2 individuals from F1 generation
(heterozygous) G g GG Gg gg
Genotype results: GG, Gg, gg
Phenotype results: 75% Green peas
25% Yellow peas

18. Sex Determination in Humans
Humans have 22 numbered chromosomes and a 23rd pair that is labeled XX or XY
A pair of XX produces a female
A pair of XY produces a male
The male parent determines the sex of the offspring

20. Sex Linked Genes Some genes are located only on the X or Y chromosome
Eg: colourblindness is a recessive gene found on the X chromosome
A male with the recessive X gene will have colourblindness
A female with the recessive X gene may have another copy that is dominant and therefore is only a carrier for colourblindness

21. Sex linked traits are usually exhibited by males rather than females because males have only one copy of the X chromosome (XX vs. XY)
If the X chromosome carries the recessive allele, only the male will be affected
Females are often carriers because the second copy of the X chromosome is dominant and the recessive trait is oppressed.

22. Hemophelia XH Xh XHXH XHXh Y XHY XhY
A body’s inability to clot blood properly XH
(Normal allele) Xh
(hemophelia allele)
XHXH
XHXh Y
XHY
XhY