Hair HAIR

Nose-

Eye Color

Face Shape

Patterns of Heredity

During sexual reproduction a cell containing genetic information from the mother and a cell containing genetic information from the father combine into a completely new cell, which becomes the offspring.

In Humans, the 23rd pair of chromosomes are the sex chromosomes. A human female has two X-Chromosomes and the male has one X-chromosome and one Y-chromosome.

So what is Heredity?

Heredity is the biological process whereby genetic factors are transmitted from one generation to the next. Traits are passed from parents to offspring.

Inherited traits Vs. Acquired traits

A sun burn is an acquired trait…you are not born with one. Scars are also acquired.

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What determines the traits you inherit from your parents?

A gene is a unit of heredity that occupies a specific location on a chromosome and codes for a particular trait. Individuals inherit their genes from their parents. These genes code for hair color, eye color, detached ear lobes etc.

* Each chromosome consists of a thread of DNA coiled up tightly.

*DNA contains genetic information called genes.

*Alleles are various forms of the same gene.

The gene at the bottom of this image codes for height. The capital H is for regular height and the lower case h is for short height.

The Genotype is the name for the genes an organism has. Sometimes your genes contain information the is not expressed physically. This is your complete heritable

genetic identity.

*An organism’s phenotype describes the actual characteristics that can be

observed. (Brown eyes, red hair, widows peak, dimples, height,

diseases)

The Phenotype is the gene that is expressed and observable.

*Widows Peak Detached Earlobes

Rolling tongue

Red Hair

So how do I end up with certain phenotypes?

Some genes are dominant

And others are recessive

A dominant allele is one that is expressed in the phenotype even if only one copy is present in the genotype.

A recessive allele is one that is expressed in the phenotype only when two copies of it are present.

For example…..

E = Unattached earlobe

e = Attached earlobe

****Capital letter= dominant

Lower case= recessive

Detached Earlobes are a dominant trait:

EE or Ee

* Remember that you get these genes (E or e) from your parents

Attached earlobes are recessive:

ee

Gregor Mendel and his Pea Plants

Mendel was a monk who lived in Austria during the mid 1800s. Before he became a monk, he attended university and received training in science and mathematics. Mendel is well-known for his experiments in genetics with pea plants.

Crossing a true-breeding regular pea plant with a true-breeding dwarf pea plant produces all regular pea plants in the first generation.

Allowing the first generation pea plants to self-pollinate resulted in about three-fourths regular pea plants and one-fourth dwarf pea plants.

Mendel also experimented with different traits in the plants like flower and pod position, seed shape, seed color and flower color. His experiments showed similar patterns of heredity.

Gregor Mendel realized that each plant must have two “factors” for each possible trait. Those things called “factors” are what we now call genes and alleles.