1. Chromosomes
strands of DNA in pairs

2. Chromosomes Vehicle of trait inheritance.
Each chromosome in a pair is from one parent.
Each pair = homologous chromosomes.

3. DNA
GENE: sequence of DNA on a
chromosome that codes for a
protein.

4. galaxy
Solar system
North America
Columbia, MO?

5. Alleles and loci
ALLELES: two alternate forms of a gene on a pair of homologous chromosomes.
LOCUS (plural ‘loci’): position of the allele on the chromosome.

6. Alleles
Alleles work in pairs (each allele is in one of two homologous chromosomes).
Dominant alleles: always expressed.
Recessive alleles: only expressed in absence of a dominant allele.

7. Alleles TT (Homozygous dominant) tt (Homozygous recessive)
Tt (Heterozygous)

8. Trait expression Genotype: genetic make-up for a trait (eg. Tt).
Phenotype: genotype + environment, or the expression of a trait. (Eg. Tall plant, brown eyes etc).

9. A monk played with peas…
Gregor Mendel is considered the father of modern genetics. He was an Austrian monk who worked with pea plants.
Replaced Blending Theory with Particulate Theory of Inheritance.

10. …and discovered the meaning of sex!
Genetic recombination: process by which combination of genes in offspring is different from that in either parent.

11. Genetic recombination has two laws… Law of Equal Segregation
Either allele from either homologous
chromosome has equal probability of
ending up in the gamete.

12. Law of Independent Assortment
Genes on different chromosomes assort
independently of each other.

13. Monhybrid Cross (one trait)
P TT X tt
F1 Tt X Tt F2
Can you fill in this Punnett square? T t
PUNNETT square: table used to determine all possible genotypes in the next generation.

14. Dihybrid cross (two traits)
P RRSS X rrss
F1 RrSs X RrSs F2 RS Rs rS rs
RrSS
How about this one?

15. Polygenic traits Most traits not influenced by only one gene.
Multiple genes may interact to influence a trait.
e.g.: Multiple genes interact to influence human height.

16. Polygenic variation
Polygenic traits tend to have normal distributions. (This is a histogram.)
Frequency