key concept mutations are changes in dna that may or may not affect phenotype

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