8.7 Mutations

KEY CONCEPT Mutations are changes in DNA that may or may not affect phenotype.

8.7 Mutations

MutationsCaused by errors in• Replication, transcription, cell division, or by external

factorsGerm-cell mutation – occurs in a gamete• Does not affect the individual but may be passed on to

offspringSomatic mutation – occurs in a body cell• Will affect the individual but are not passed on to

offspring

8.7 Mutations

Lethal Mutations

• Cause death, often before birth

8.7 Mutations

Gene Mutations

1. point mutation – substitutes, adds or deletes a single nucleotide

mutatedbase

8.7 Mutations

Gene Mutations2. Frame Shift Mutation • Deletion & addition point mutation cause the remaining

codons to be incorrectly grouped

8.7 Mutations

8.7 Mutations

Chromosome Mutations

1. Deletion – loss of a piece of a chromosome due to chromosomal breakage

2. Inversion – chromosomal segment breaks off and then reattaches in reverse order to the same chromosome

3. Translocation – chromosome piece breaks off and reattaches to another non-homologous chromosome

8.7 Mutations

8.7 Mutations

4. Nondisjunction – failure of homologous chromosomes to separate properly during meiosisTwo possible outcomes:

1. One gamete - an extra chromosome • when fertilized - 3 copies of chromosome • trisomy

2. One gamete - one less chromosome • when fertilized - 1 copy of chromosome • monosomy

8.7 Mutations

KEY CONCEPT A combination of methods is used to study human genetics.

7.4 Human Genetics and Pedigrees

13.1 Ecologists Study Relationships

Pedigree – family record that shows how a trait is inherited over several generations

7.4 Human Genetics and Pedigrees

8.7 Mutations

Pedigrees

Circles Girls

Squares Boys

Carrier – individual with one copy of a recessive allele• Usually do not express the trait but can pass it along to

offspring• ½ colored in

• Ex: Autosomal Hh

Sex-linked XHXh

7.4 Human Genetics and Pedigrees

8.7 Mutations7.4 Human Genetics and Pedigrees

8.7 Mutations

• Karyotypes can show changes in chromosomes.

– deletion of part of a chromosome or loss of a chromosome

– Some translocation changes in chromosomes– extra chromosomes or duplication of part of a

chromosome

7.4 Human Genetics and Pedigrees

8.7 Mutations

Detecting Human Genetic Disorders• Genetic screening – examination of a person’s genetic

makeup• Genetic counseling – medical guidance that informs

about possible problems that could affect their offspring

Prenatal testing• Amniocentesis – removes a small amount of amniotic

fluid between the 14th

and 16th week of pregnancy

7.4 Human Genetics and Pedigrees

8.7 Mutations

Chorionic villi sampling

• physician obtains a sample of the chorionic villi • tissue that grows between the mothers uterus and the

placenta, between the 8th and 10th week of pregnancy

7.4 Human Genetics and Pedigrees

13.1 Ecologists Study Relationships

Cancer

Tumor – abnormal group of cells that result from uncontrolled,

abnormal cell division

5.3 Regulation of Cell Cycle

8.7 Mutations

cancer cellbloodstream

normal cell

– Benign - tumors remain clustered and can be removed.– Malignant - uncontrolled dividing cells invade and

destroy healthy tissues elsewhere in the body

– Metastasize - spread of cancer cells beyond their original site

5.3 Regulation of Cell Cycle

8.7 Mutations

Kinds of Cancer – based on types of tissue that affect

• Carcinomas – grow in the skin and tissues that line organs. Ex: lung cancer & breast cancer

• Sarcomas – grow in bone and muscle tissue• Lymphomas – solid tumors that grow in the tissues that

form blood cells– Leukemia – tumors that form in blood-forming tissue –

over production of white blood cells

5.3 Regulation of Cell Cycle

8.7 Mutations

Causes of Cancer

• Carcinogen – substance that increases the risk of developing cancer Ex: tobacco, asbestos, X-rays, or UV rays from sun

• Mutagen – cause mutations to occur within a cell that leads to cancer

5.3 Regulation of Cell Cycle

8.7 Mutations

• Standard cancer treatments typically kill both cancerous and healthy cells.

5.3 Regulation of Cell Cycle

8.7 Mutations

Oncogenes – gene that causes cancer

• Proto-oncogene – normal gene that control cell’s growth. When mutated oncogene

• Tumor-suppressor gene – code for proteins to prevent uncontrolled cell division. When mutated cancer

5.3 Regulation of Cell Cycle

8.7 Mutations

Viruses & Cancer

• Viruses can stimulate uncontrolled cell division• Cause mutations in proto-oncogenes & tumor suppressor

genes

5.3 Regulation of Cell Cycle

8.7 Mutations

Cancer Prevention

• Diet high in fiber and low in fat• Fruits & vegetables are high in fiber• Vitamins & minerals: carotenoids, vitamins A, C, and E,

and calcium• Daily exercise• And lowering exposure to carcinogens (tobacco, UV rays)

5.3 Regulation of Cell Cycle

8.7 Mutations

Extra Credit:

• Millions of dollars are spent each year on cancer research.

• Contact an oncologist in a cancer treatment center.• Conduct an interview, prepare a paper, and create a

visual to show the new treatments that have been developed in the past 10 years

5.3 Regulation of Cell Cycle