Human traits and gene therapy

A pedigree is a graphic way to look at a trait between ancestors. It shows how a trait is passed between each direct member

of the family. It can be used to see where a trait came from or if you have a chance for a disease.

Simple recessive traits

Most genetic human disorders are caused from recessive traits. We have removed them from the gene pool. Cystic fibrosis- caused by a defective protein in the plasma

membrane.

Tay-Sachs disorder- causes damage to the central nervous system because an enzyme is not produced and can not break down certain lipids in the cell

Phenylketonuria- can cause mental retardation and damage central nervous system because of a missing enzyme

Simple dominant traits

Widows peak, cleft chin, earlobe attachment: attached earlobes are recessive. Hitchhikers thumb, almond eyes, and hairy knuckles are dominant traits.

Remember that it can be homozygous or heterozygous for a dominant trait.

Huntington's disease- a deadly disease that causes brain breakdown between ages 30 and 50. This is why it is passed on, the individual does not know they carry it until it is to late.

Traits are not so simple

Incomplete dominance- when an individual has the middle between dominant and recessive. Neither allele is expressed, but a middle ground is. Red flower and white flower makes a pink flower

Codominance of traits Both alleles are expressed.

If a homozygote recessive and homozygote dominant mate then the offspring will be heterozygous for both traits, both are expressed

White chicken mates with black chicken and makes a black and white chicken.

Multiple alleles- this means that the trait (gene) is controlled by more than 2 alleles, but the cell is still diploid. To have a certain color you have to have the correct alleles.

A, b, and c are possible alleles:

A -could be red-dominant

Ab -could be green

aac -could be brown

a- could be black-recessive

Sex determination

There are 22 pairs of homologues

1 pair that look different-sex chromosomes X and y

XX is female

XY is male Male determines gender

Sex linked traits- genes for a trait that are located on the X or Y chromosome If it is Y linked, it will only affect males

X linked could be either male or female

Any recessive x link passed to a male will not be over powered by a dominant trait because there is not another x.

You write the chromosome then the trait Eye color in flies is sex linked

XRY XRXR

Polygenic inheritance-many genes control the trait, the genes can be on different chromosomes.

Height of humans, skin color, height of plants are polygenic Since a trait is on different genes there will be many alleles.

Height ABC alleles

Tall is AABBCC

Short is aabbcc

then there is a whole range in between

Environmental influences- This can control whether a trait is expressed or how much it is expressed External influences

Temperature, light, chemical, and infections can all cause changes to gene expression

Changing fur color in winter, or leaf color in fall

Internal influences

Hormones, age, body structure

Males have bright feathers females do not

Men bald as they get older

Complex Inheritance

Sickle cell anemia (homozygous recessive)- Caused by defective translation into protein hemoglobin-

oxygen carrier

Slows down blood flow and can block blood vessels

Reduces oxygen movement through body

Causes pain

Codominance in humans- both normal and sickle cells are made Fewer problems but they still exist

Multiple allele Blood type in humans, controlled by 3 genes

IA, IB, ii

Determine the molecule on the outside of red blood cells

Must make sure to get the right blood type because unlike blood types will clump and cause death

Rh factor of positive and negative blood Discovered in the Rhesus monkeys, a blood protein that is

attached to the blood type

Positive means you carry the protein

Negative means you don't

Must be compatible or can cause major issues for expectant mothers

Sex linked human traits Color blindness

Caused by X-linked recessive traits

Causes problems with the color receptors of the eye

Hemophilia

Blood does not clot and can cause death

X linked recessive allele carried by women

10,000 to 1 men

100,000,000 to 1 women

Since there is not a Y linked dominant allele the only thing it can do is be expressed as recessive

Polygenetic in humans Multiple allele representation

Get a range in phenotype

Eye color

Skin color

Height

Genetic Technology

Selective breeding- increases the frequency of a desired allele When humans chose what organisms breed together

Used to get the most desired traits from an animal

stronger faster horse

bigger eggs from a chicken

Faster growing corn plants

Rose color

Anything that a human could benefit from

Inbreeding- breeding between closely related animals Used to get only desired traits and to rid the population of

negative traits

Can bring out harmful recessive traits because of how close gene would match

Also called a pure breed

Horses and dogs are 2 good examples of pure breeds

Hybrid organisms- a cross between 2 organisms Are usually bigger and healthier than the original

Cross fast growth corn with drought resistant corn

2 pure breeds can make an even stronger organism

Use a test cross to determine the genotypes of possible unknown parents

Recombinant DNA Technology

Genetic engineering- taking DNA from one organism and adding it to another to get specific gene qualities Plants that glow

Plants with qualities of 2 different plants

How is this done?

1. the DNA fragment that is to be removed must be isolated using a restriction enzyme Restriction enzyme is a bacterial protein that will cut both sides of the

DNA strand at the exact same nucleotide sequence.

The cut DNA can have 2 flat ends, or ends that hang over

These will join easily with new DNA

To get the fragment of DNA into the new cell it must be fixed to a vector A vector is the way a DNA sequence from one organism can be carried

to another

Can be mechanical or biological

Plasmid- small ring of Bacterial DNA This is a biological way to fix the new DNA

Viral- DNA is transported by a virus to the new cell

Mechanical The use of very small tools to insert the new DNA sequence into the

cell

Micropipette

Gene cloning- the process of making genetically identical copies of DNA Bacteria is often used because it replicates or doubles so many times

faster than other organisms

Insert a plasmid and the bacteria will replicate the plasmid DNA separate from its own

Scientists can make proteins and mutations to study how they react to certain stimuli

Dolly the sheep- an animal clone Very tricky to replicate so many different genes at once

Could benefit farmers and ranchers with limitless supply of perfect plants and animals

What are some of the consequences?

What if you want to replicate DNA outside of the cell? There is an app for that!!! Hahahaha

Or you could use PCR- polymerase chain reactions: http://www.youtube.com/watch?v=2KoLnIwoZKU&feature=related

Use this to replicate DNA over and over again without needing cells or getting DNA mixed up

Can make millions of copies in a day

Used for sequencing genes, investigating crimes, and studying diseases.

Only needs a small amount of DNA to make lots of copies

Why is this good?

Gene sequencing : http://www.youtube.com/watch?v=6ldtdWjDwes&feature=related http://www.youtube.com/watch?v=aPN8LP4YxPo&feature=related

Used to identify the sequence or correct order of DNA. Great for finding mutations. Use PCR to make lots of copies

Then the copies are separated using gel electrophoresis: http://www.youtube.com/watch?v=QEG8dz7cbnY&feature=player_embedded#!

Like separating chlorophyll, the larger strands do not move as far as shorter strands

Then UV light can be used to see how far the bands moved

Electrophoresis mechanism

Uses of DNA technology- let bacteria make a lot of copies of certain chemicals and proteins Indigo for blue jeans, sewage treatment options, cheese and laundry

applications

Medicines like insulin for diabetics can be made from bacteria, hemophilia medications

Super plants that are infestation resistant, or do not cause allergic reactions like peanuts

Human genome project- map out and sequence the genes of humans 3,000,000,000 base pairs

35,000-40,000 genes

46 chromosomes

Uses for this information Determination of a genetic disorder

Once scientists know what a sequence should look like they can determine any abnormalities for a disorder.

Gene therapy- for those that have a genetic disorder

Insert normal DNA into cells to correct the disorder

Take bad cells from person, use a virus to insert the new good DNA, and then inject the cells back into the person

DNA fingerprinting- catch the bad guy by matching up DNA from a person and from the crime scene

Sequence it with gel electrophoresis