Introduction to Genetics “the study of heredity”

Gregor Mendel The Father of Genetics carried out important studies of heredity, used pea plants 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

All of our “traits” are coded into the DNA that makes up our chromosomes.

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 3 tall: 1 short P1P1 F1F1 F2F2

Karyotype A picture of all the chromosomes contained within a single cell. Contains 22 pairs of autosomes and one pair of allosomes (sex chromosomes)

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 (purebred) 2 identical alleles that are capitalized (AA, TT) 2. Heterozygous (hybrid) 2 different alleles (Aa, Tt) 3. Homozygous Recessive 2 identical alleles that are lower-case (aa, tt)

Principle of Dominance If a dominant allele is present that phenotype is visible An organism that is recessive for a particular trait will exhibit that form only when the dominant allele is not present. Organisms with a heterozygous genotype (Aa) will never exhibit the recessive trait because it is hidden (masked) by the dominant allele.

Mendel’s Principles Law of Segregation -- the two alleles for a characteristic are packaged into separate gametes Law of Independent Assortment -- each pair of alleles segregates into gametes independently

The Tall (T) allele in snapdragons is dominant to the short (t) allele. If two heterozygous tall (Tt) snapdragons are crossed, what will be the ratio of short to tall plants?

You try this one: AA A a

Section 1 Check Question 1 The passing on of characteristics from parents to offspring is __________. D. allelic frequency C. pollination B. heredity A. genetics

The answer is B. Genetics is the branch of biology that studies heredity.

Section 1 Check 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.

Section 1 Check Question 3 Gametes are __________. D. fertilized cells that develop into adult organisms C. both male and female sex cells B. female sex cells A. male sex cells

Section 1 Check The answer is C. Organisms that reproduce sexually produce male and female sex cells, called gametes.

Section 1 Check Question 4 Which of the following genotypes represents a animal that is homozygous dominant for a trait? a. KK b. Kk c. kk

Section 1 Check Question 5 Which of the following genotypes represents a plant that is homozygous recessive for height? C. tt B. Tt A. TT