Heredity

Outline• What are genes?• Gregor Mendel• Where can we find our genes?• What do our genes do?• Our Genes• Genetic Trait Tree• Where do we get our genes from?• Inheritance• Predicting Inheritance• Modern uses of DNA technology

What are genes?• Heredity: the passing of

genes from parents to offspring (children)

• Gene: a specific part of DNA that controls a hereditary trait– Hereditary traits are

characteristics that can be passed from parents to their offspring

Inherited vs. Acquired Characteristics

• Inherited characteristics: characteristics that are controlled by genes/DNA passed from parents to their offspring– Examples -> height, natural hair color, eye

color

• Acquired characteristics: characteristics that can be developed or altered during a person’s lifetime– Examples -> tattoo, learning to play a sport,

learning to play a musical instrument

Gregor Mendel• Austrian monk• Considered to be the

father of modern Genetics

• Used pea plants to demonstrate how certain characteristics were passed through generations– Seed shape, seed color,

flower color, pod shape, pod color, and stem height

Mendel’s Work

Where can we find our genes?

• We have 1000’s of genes and each one is found at a specific location on a specific chromosome– What does that mean?

• All genes have a certain part (location) of a chromosome where they are found

• Everyone has different combinations of traits, but…– The genes for those traits are on the same

parts (locations) of chromosomes in everyone.

Human Genome Project

• Major science project that mapped out all of the genes on the human chromosomes– Identified the location of our genes

Our Genes

• How many genes do humans have?

http://web.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/

What do our genes do?

• Genes determine the traits that we have– We are most familiar with

physical traits– So basically our genes

determine what we look like

• Physical traits are observable characteristics– Things that we can see– examples: hair color, eye

color, tongue rolling, ear lobes, hairline

Our Genes

• We have 2 copies of each gene.

• Each gene has 2 or more variations for what we see– We can inherit the same

or different variations– examples:

• Hair color – brown, black, red, blonde

• Tongue rolling – can do it, can’t do it

Genetic Trait Tree

• We are going to be creating a Genetic Trait Tree to examine certain characteristics (traits) within our class

• For this activity we will be examining 3 traits– Free or attached ear

lobes– Widow’s peak– Tongue rolling

Where do we get our genes from?

• ½ comes from mother– 23 single chromosomes in

the egg cell

• ½ comes from father– 23 single chromosomes in

sperm cell

• When the sperm and egg cell combine they form 1 cell with 46 single chromosomes (23 pairs).– All humans have started

as 1 cell just like that

Inheritance• The characteristics seen in us depend on 2

things.1. the combination of gene variations we get from our parents2. how those gene variations interact with each other

• The different variations of genes are called alleles

• 2 basic alleles (gene variations)– Dominant: the trait/characteristic that is always seen or

observed if it is present– Recessive: the trait/characteristic that is only seen or

observed when the dominant variation is not present

Dominant and Recessive Traits

• Example of dominant and recessive alleles– A person can have a

widow’s peak (dominant) or a straight hairline (recessive)

– 2 dominant alleles = a person with a widow’s peak

– 1 dominant and 1 recessive allele = a person with a widow’s peak

– 2 recessive alleles = a person with a straight hairline

Inheritance Terms

• Homozygous Dominant: 2 dominant genes

• Homozygous Recessive: 2 recessive genes

• Heterozygous: 1 dominant and 1 recessive gene

Predicting Inheritance• Punnett Square: a tool

to predict the characteristics a child can inherit from its parents– Use the alleles each

parent has to determine the possible combinations that can be passed to offspring

– Capital letters represent dominant allele

– Lowercase letters represent recessive allele

W = dominant

w = recessive

Punnett Square Example• Example using hairline

– Mother has the following combination – Ww

– Father has the following combination – ww

– They each pass 1 variation (letter) on to their offspring

• Draw a Punnett Square• Label sides• Add parent variations• Fill in the square

MOTHER

FATHER

W w

w

w

W w

W w

w w

w w

Punnett Square Example• What does this show us?

– Ww would have a widow’s peak

– ww would have straight hairline

– Genotype: genetic makeup

• 2 of 4 children have Ww and 2 have ww

– Phenotype: physical appearance

• 50% chance of having a child with a widow’s peak

• 50% chance of having a child with straight hairline

MOTHER

FATHER

W w

w

w

W w

W w

w w

w w

Modern uses of DNA Technology

• Selective Breeding– Breeding plants or animals for specific

traits– Has been used to create all of the different

breeds of dogs that we currently have• Bred to make them better hunters, or nicer

temper, or better for protection

Modern uses of DNA Technology

• Forensic Science– DNA Fingerprinting: identifying people

based on their DNA– What shows on TV have you seen that use

this?

Forensic Science Pictures

Forensic Science Pictures

Modern uses of DNA Technology

• Genetic engineering– Changing the DNA of an organism to alter it

in some way– Has been used to alter plants and vegetables

• Grow bigger, faster, in tougher conditions, and resistant to insects

– Transgenic organism: an organism that has had it’s DNA altered by genetic engineering.

Modern uses of DNA Technology

• Gene Therapy– A type of genetic engineering in which

damaged genes are replaced by normal genes

Genetic Engineering Movies

Modern Uses of DNA Technology

• Cloning– Creating an exact copy of an existing

organism– Dolly (a sheep) was the first cloned

animal to survive the process• Happened in 1997

– How is it done?– There are problems with it though

Cloning

Cloning Movies

Cloning Movies

Cloning Movies

Modern uses of DNA Technology

• Stem Cell Research– Taking an undifferentiated cell (one that

hasn’t changed into a specific type of cell) and making it turn into the type of cell you want it to

– Can be used for:• Creating new organs to replace damaged ones • Replace damaged nerve cells in a spinal cord • Replace damaged brain cells

Stem Cells