Genetics

#1 #2

#3 What is

happening here? These are

called ______ _________

#4

#5 Diploid or Haploid ?

#6 Diploid or Haploid?

Completely Random!!!!!!

• Genes – determine the characteristics of an organism.

• Alleles – alternate forms of genes– Ex. Gene = seed color

Green or Yellow Alleles

*Remember*Only 1 allele for each trait is passed on to

the offspring from each parent!

The Terms…• Genotype – genetic make-up of an individual– Ex. T T = genotype (letter combination)

Each letter is inherited from different parents.Dad Mom T T

Genotype Possibilities

• Homozygous (purebred) – An organism with genes that are alike.

• Ex. BB or bb

• Heterozygous (hybrid)

– An organism with genes that are different• Ex. Bb

DOMINANT TRAITS!!!• Homozygous Dominant Genotype

-Both alleles are the same.

-Both are capital letters.

Ex. TT• Heterozygous Genotype

-Different alleles.

Ex. Tt

Recessive Traits • recessive genotype– Both alleles are the same

– Both represented by lower case letters

•Example = tt

**For an organism to show a recessive phenotype, the genotype must be homozygous recessive.• Example: tt = short

Mendel’s 1st Law• Law of Segregation

A) Hereditary characteristics are determined by factors called genes.

B) For each characteristic, an offspring gets 2 genes, one from each parent.

C) The 2 genes of each pair segregate from each other and end up in separate gametes.

Genotype and Phenotype• Letters represent traits– Capital letter = dominant trait– Lower case = recessive trait

• Ex. HEIGHT• Tall = T (dominant)• Short = t (recessive)

TT, Tt Tall tt short

Gene Expression

• Phenotype– Expression of an individual’s genes…what it

looks like.• Ex. Tall = phenotype (physical appearance)

Ww 2 wings

Solving Genetics ProblemsIf you know the genotype of the parents, it is

possible to predict the likelihood of an offspring inheriting a particular phenotype.

- Probability – the chance that a given event will occur

- Punnett Square – named for R.C. Punnett, British biologist and mathematician

- Probability is shown through monohybrid crosses – genetic cross involving only 1 trait of the parents.

Examples• Homozygous tall plant (TT) with

homozygous short plant (tt).

100% Tt 100% Tall heterozygous tall

Examples…• Heterozygous long hair female with

homozygous short hair male (long is dominant). L l x l l

50% Ll = long hair 50% ll = short hair 1 : 1 ratio (1Ll to 1ll)