Introduction to Genetics

Ch. 11

Write the information on the slides that

show this symbol or that is this color.

Genetics

• The scientific study of heredity

Gregor Mendel

• Father of modern genetics

• Combined plant breeding, statistics, careful record keeping

Mendel studied pea plants traits (characteristics)

Genetic Information

• Gene – basic unit of genetic information

Allele – one form of a gene

Principle of Dominance

• Some alleles are dominant and others are recessive

Dominant vs. Recessive

•Dominant alleles express a trait. (capital letter)

•Recessive alleles are only visible when paired with another recessive allele. (lower case letter)

Segregation

Gamete

Separation of alleles during gamete formation

Sex cells

Punnett Square

• Diagram used to predict and compare variations resulting from a genetic cross

Homozygous vs. Heterozygous

• Homozygous - having two dominant or two recessive alleles. (BB or bb)

•Heterozygous - having both a dominant and recessive allele. (Bb)

http://en.wikipedia.org/wiki/Image:Stop_sign_MUTCD.svg

Genotypes Phenotypes

• Genotype - genetic make up

• Phenotype – physical characteristics

Genotypes Phenotypes (example)

genotypes

phenotypes

Hybrid• Offspring of crosses between parents with

different traits

Principle of Independent Assortment

• Genes for different traits can segregate independently during the formation of gametes.

• Example: genes for seed shape segregate independently of those for seed color

Incomplete Dominance

• One allele is not completely dominant over another

Incomplete Dominance

• A flower has genes for white petals (w) and red petals (r).  When you mix white flowers with red flowers you get pink flowers.  How is this possible?  The w gene does not dominate over the r gene and vice versa. Both genes express themselves equally so you get a pink color in the petals. 

w w

r wr wr

r wr wr

Codominance

• Both alleles contribute to the phenotype

Polygenetic Traits

• Traits controlled by two or more genes

Meiosis

• reproduction of gametes

(Similar to mitosis, but there are 2 divisions, ending with ½ the number of chromosomes of the parent cell.)

Diploid vs. Haploid

• Diploid – contains both sets of homologous chromosomes

• Haploid – contains a single set of chromosomes

Crossing-over is the process in which homologous chromosomes exchange portions of their chromatids during

meiosis.

Gene Map

• Diagram showing the relative locations of each known gene on a particular chromosome