CH 8 Genetics II

Genetic Disorders

-Caused by the DNA becoming mutated and no longer functioning as it should

-multiple ways that DNA can become mutated

DNA Polymerase

-Protein that helps makes new DNA strands

-often makes mistakes during this process

How many bases do humans have?

-3 million on average

-1 in 10,000 are incorrectly placed by DNA polymerase when it is first copying

How does DNA polymerase help reduce errors?

It will proofread itself

Editing feature of DNA polymerase

-Catches most errors but not all

-with editing there is an error rate of 1 out of 2,000,000 bases

-cancerous cells can form

Apoptosis (programmed cell death)

-Occurs if a cell cannot fix a mistake or starts to go under mitosis too rapidly

-normal healthy cells have this regulation to

Tumors

-masses formed by super dividing cells

-DNA can become so damaged or mutated where the cells lose their ability to run checkpoints or undergo apoptosis during cell cycle

Tumor Supressor Genes

Genes in our DNA that code for

-Proteins that regulate and check mitosis in cells

-proteins that signal cells that are dividing too rapidly to undergo apoptosis

-can become cancerous

TP53 gene

-Encodes p53 protein

-if protein can no longer be made then the odds of a cell detecting DNA damage decrease

-why its called one of the tumor suppressing genes

P53 protein

-Crucial transcription factor that acts as a “guardian of the genome” by regulating cell cycle, DNA repair, and apoptosis

Rapid Cell division

-Can be very bad due to how many nutrients it takes to make a new cell

-will start to steal nutrients from surrounding cells and tissues, often killing

-both G1 and G2 are stages when the cell is gathering nutrients and growing in size

Benign tumors

-sometimes mutated cells are so bad that it can no longer undergo mitosis

-cells do not spread to other parts of the body

-usually just lumps of cells that may eventually go away on their own

Malignant tumors

-formed if nothing stops the cancerous cells and continue to grow

Mestastasize

when cells spread and destroy healthy tissue in other parts of the body as they search for more nutrients

Cancerous cell is a term for any cell that:

-undergoes mitosis without regulation

-steals nutrients from surrounding tissues

-no longer functions as it should

-continues to develop more mutations

-moves around the body searching for more nutrients

Stage 0 Cancer

Cancer cells found in their earliest form

Stage 1 Cancer

A small tumor that hasn’t spread

Stage 2 Cancer

Cancer that has grown more deeply into nearby tissue

Stage 3 Cancer

Cancer that has spread to lymph nodes or nearby tissue

Stage 4 Cancer

Cancer that has spread to distant parts of the body

Is cancer just 1 disease?

no it is many diseases, over 100 different types

What can get cancer?

Any living thing that lives long enough can have their cells become cancerous

How common is cancer?

-not that common

-in most cases cells must sustain multiple cases of DNA damage

Hereditary Cancer

-some are considered hereditary

-passed down from generation to generation

-not directly passed down

What is passed down through “hereditary” cancer

-Mutations that make the likelihood you will get cancer in the same type of cell very high

How can cancer be diagnosed

compare the normal rate of mitosis in tissues to the cancerous rate

Mitotic index

-a measure of how rapidly a sample of cells are undergo mitosis

-a sample of tissue is taken from the body and the humber of cells undergoing any stage of mitosis and is compared to the number of cells in interphase

3 main ways to treat patients who have cancerous

1) Surgery

2) Radiation Therapy

3) Chemotherapy

Surgery for cancer

if the cancer cells have not metastasized they can physically remove the cancer

Radiation theraphy for cancer

-therapy using ionizing radiation, generally as part of cancer treatment to control or kill malignant cells

-kills cells in a very small location

Chemotherapy for cancer

-a chemical cocktail that targets all cells that have a high mitotic index as cancer cells do

-can workout throughout your body and can also affect some fast-growing healthy cells

How do DNA mutations occur?

-DNA replication errors

-Radiation

-Chemical Mutagens

-Viruses

Ultraviolet radiation from sun

-leads to DNA mutations in our skin

-both UVA and UVB rays damage our skins

-over time can lead to formation of skin cancer

How does sunscreen prevent cancer?

-blocks out UV rays for a period of times

Skin cancer

-can be detected early before it has the chance to spread

Marks that can be skin cancer

-Asymmetrical

-Growing in size

-Changing in color

Ionizing radiation

-damage and mutations can occur if cells are exposed

-causes single and/or double stranded DNA breaks in the sugar phosphate backbone

-lead to point or frameshift mutationswhen cell attempts to repair damage

Fission

-nuclear power plants use this process to break down the nucleus of large atoms which releases large amounts of energy

-can produce gamma radiation

Chemical Mutagens or Carcinogens

Chemicals that can cause our DNA to become mutated

Viruses

-replicate by inserting their own DNA into DNA of host tricking the host to replicate the body

-sometimes alter the hosts DNA and causes cells to become cancerous

HPV (human papilloma virus)

-very likely to mutate cells and cause them to become cancerous

-targets cervical cells of a woman’s reproductive system

Mutations

Changes to the original sequence of DNA

Genetic diseases

-are inherited and cannot be prevented

Genome

-all our bases pairs together

-contains aprox 3 billion pairs which reside in the 23 pairs of chromosomes

Purposes of the Human genome project

1) determine the nucleotide sequence of the entire human genome

2) map the location of every gene on each chromosome

3) improve diagnoses, treatments, and cures for genetic diseases

Restriction enzymes

-very specific enzymes allowed scientists to cut DNA at a very accurate sequence

-bacteria made enzymes highly specific and could only be used in a handful of cases

-are preset to cut DNA in a very specific location based on previous viruses that attacked the bacteria

CAS 9

-in 1990s a new type of restriction enzymes was discovered while studying E. Coli

-bacteria could produce unique structure that was a unique type of restriction enzyme

• a protein that can be instructed, or programmed, to cut any particular sequence of DNA

CRISPR

-Clustered Regularly Interspaced Short Palindromic Repeats

-the guide RNA (gRNA) of the CRISPR is used to find a particular segment of a genome and direct the Cas9 to cut