Introduction to Genetics

Genetics = the study of heredity

Objectives:E2 - Summarize Mendel’s principle of dominance, identify where the genes that control traits are located, & explain how geneticists use the principles of probabilityE3 - Predict possible outcomes of various genetic combinations such as monohybrid … inheritance

•Gregor Mendel•The Father of Genetics•carried out important studies of heredity•Heredity—the passing on of traits from parents to offspring

• Trait- a specific characteristic that is controlled by genes•Exp. Eye color, hair color,

height

•Chromosomes•Tightly coiled DNA where your genes are carried

•Genes• Sections of DNA

that control your traits

•Homologous Chromosomes•Chromosomes that are the same size and shape and carry the same genes. You get one from your mother and one from your father that match up.

Short pea plant Tall pea plant

All tall pea plants

3 tall: 1 short

P1

F1

F2

•Alleles•The different forms a gene can take.

(Letters)•2 Types of Alleles:

•1. Dominant - Represented by a capital letter (Exp. A)

•2. Recessive - Represented by a lower-case letter (Exp. a)

•Genotype•The combination of two alleles (letters) that represent the genetic make-up of an individual. (AA, Aa, aa)

•Phenotype•The observable physical characteristic of an individual that are the result of its genotype.

(Long eyelashes, Blue or Brown eyes)

3 Types of Genotypes:

• 1. Homozygous Dominant•2 identical alleles that are capitalized

(AA, TT)

• 2. Heterozygous•2 different alleles (Aa, Tt)

• 3. Homozygous Recessive•2 identical alleles that are lower-case

(aa, tt)

Principle of Dominance • An organism with a recessive

allele for a particular trait will exhibit that form only when the dominant allele for the trait is not present.

• Organisms with a heterozygous genotype (Aa) will never exhibit the recessive trait because it is hidden (masked) by a dominant allele.

• You try this one:

A A

A

a

Etymology

• Homozygous: homo- (same) + -zygous (joined)

• Heterozygous: hetero- (other) + -zygous (joined)

Question 1The passing on of characteristics from parents to offspring is __________.

D. allelic frequency

C. pollination

B. heredity

A. genetics

Question 2

What are traits?

Answer

A specific characteristic that is controlled by genes. Height, hair color and eye color are examples of traits in humans.

Question 3Gametes are __________.

D. fertilized cells that develop into adult organisms

C. both male and female sex cells

B. female sex cells

A. male sex cells

Question 4

Which of the following genotypes represents a animal that is homozygous dominant for a trait?

a. KK

b. Kk

c. kk

Question 5Which of the following genotypes represents a plant that is homozygous recessive for height?

C. tt

B. Tt

A. TT