1. Genetics
Chapter 11

2. Genetics Genetics is the study of heredity
Every living thing- plant or animal, microbe or human being- has a set of characteristics inherited from its parent or parents.

3. Gregor Mendel “Father” of genetics Austrian monk, mid-1800s
Researched pea plant inheritance
Easy to grow, fast reproduction
Studied plant height, pea shape/color, pod color, etc.

5. Pea Plant Fertilization
Self-pollination
Male gametes (pollen) fertilize egg of same flower
Produces pure-bred offspring, meaning that all characteristics are received from a single parent or plant
True-breeding: produce offspring identical to parent when self-pollinated

6. Pea Plant Fertilization
Cross-pollination
Pollen from one plant fertilizes egg of another plant
Mendel had to prevent self-pollination in order to cross-pollinate.
He did this by cutting away the pollen-bearing male parts and dusting pollen from another plant into eggs of the flower.
Offspring have two parents

7. Mendel’s Experiments P = Parent generation
F1 = First filial generation
Filius = Latin for “sons” and “daughter”
F2 = Second filial generation (F1 X F1)
P Pure Green X Pure Yellow
F1 All Green
F2 3 Green:1 Yellow

9. Mendel’s Conclusions
Law of Dominance – one allele (form of a gene) is dominant, one is recessive
Recessive trait was hidden in F1 generation
Green = dominant
Yellow = recessive

10. Mendel’s Conclusions
Law of Segregation: alleles for a gene separate (segregate) when gametes (sex cells) form (meiosis I)
Each F1 plant produces two types of gametes, in the Mendel’s pea pod case one allele for tallness and one for shortness

11. Punnett Squares First must determine possible gametes
Heterozygous tall plant = Tt
Half of gametes will get ‘T’, other half will get ‘t’
Homozygous tall plant = TT
All gametes will get ‘T’

12. Punnett Squares Monohybrid cross Gametes go on the top and side
Tt X Tt
Monohybrid cross
Cross involving one trait
Gametes go on the top and side
Combine gametes to find possible offspring

13. Punnett Squares Genotype (genetic make-up) ratio 1TT: 2Tt: 1tt
Tt X Tt
Genotype (genetic make-up) ratio
1TT: 2Tt: 1tt
Phenotype (physical characteristics) ratio
3 tall: 1 short

14. Probability
Punnett squares are used to predict the probability of certain traits in offspring of genetic crosses
Tt X Tt
½ chance of getting ‘t’ from mom, ½ chance of getting ‘t’ from dad
½ X ½ = ¼ tt in offspring

15. Dihybrid Cross Mendel looked at the inheritance patterns of two traits
Seed shape and seed color
Found that the traits were inherited independently of each other
Law of Independent Assortment
Genes on separate chromosomes are inherited at random