Unit 5: Genetics

Learning Goal 5: Examine problems that arise from miscoded DNA and chromosome conditions.

Mutation

A Mutation occurs when

a DNA gene is damaged

or changed in such a way as to alter the genetic message carried by that gene.

A Mutagen is an agent of substance that can bring about a permanent alteration to the physical composition of a DNA gene such that the genetic message is changed.

Types of Mutations

Types of Mutations

Point Mutation: Gene mutations involving changes in one or a few nucleotides. Substitution: One base is changed to

another. • This only affects one amino acid.

Frameshift Mutations: Changes that shift the “reading frame” of the genetic message.

• This may change every amino acid after that point.

• This occurs if a nucleotide is added or deleted.

Types of Mutations

Types of Mutations

Types of Mutations

Chromosomal Mutations

Changes in the number or structure of chromosomes.

Chromosomal Mutations Deletion: Involves the loss of

all or part of the chromosome. Duplication: produce extra

copies of parts of the chromosomes.

Inversion: Reverse the direction of parts of the chromosomes.

Translocation: Occurs when part of one chromosome breaks off and attaches to another.

Significance of Mutations

Most mutations are neutral. Meaning that they have little or no effect on the

expression of genes or the function of the proteins for which they code.

Mutations that cause dramatic change in the protein structure are usually harmful. Some are beneficial. They lead to variations in populations

Karyotype A picture of chromosomes grouped in order

of pairs.

Cystic Fibrosis Cystic fibrosis is a

genetic disorder that affects the respiratory and digestive systems.

Sickle Cell Disease Sickle cell disease is a

disorder that affects the red blood cells, which use a protein called hemoglobin to transport oxygen from the lungs to the rest of the body.

Huntington’s Disease

Huntington's Disease (HD) is a brain disorder that affects a person's ability to think, talk, and move.

Alzheimer’s Disease

Alzheimer's is a disease that causes dementia, or loss of brain function. It affects the parts of the brain that deal with memory, thought, and language.

What Are BRCA1 And BRCA2 Genes?

In the 1990s, mutations in two genes, BRCA1 (BReast CAncer 1) and BRCA2 (BReast CAncer 2), were shown to be involved in inherited breast cancer. It is estimated that 40 percent to 90 percent of families with an inherited form of breast cancer have a defective copy of the BRCA1 or BRCA2 gene.

BRCA1 and BRCA2 are called "tumor suppressor genes" because they make proteins that help prevent the cells from forming tumors. If one of these genes is changed through a mutation, the protein may not do its job, making it easier for a tumor to develop. Women who inherit a mutated copy of either the BRCA1 or BRCA2 gene have an

increased chance of developing

breast cancer. In addition, there

may be an increased risk for other

cancers.

Hemophilia

Hemophilia is an inherited bleeding, or coagulation, disorder. Persons with hemophilia

lack the ability to stop bleeding because of the low levels, or complete absence, of specific proteins, called “factors,” in their blood that are necessary for clotting.

Hemophilia

Turner Syndrome Turner syndrome is

caused by a missing orincomplete X chromosome.

People who have Turner syndrome develop as females.

The genes affected are involved in growth and sexual development. sex organs don't mature at adolescence sterility short stature

Down Syndrome Down syndrome is a

developmental disorder caused by an extra copy of chromosome 21 (which is why the disorder is also called "trisomy 21").

Having an extra copy of thischromosome means that each gene may be producing more protein product than normal.

Children with Down Syndrome develop slower, may have heart and stomach illnesses and vary greatly in their degree of intelligence

Klinefelter Syndrome Klinefelter syndrome is a

disorder that affects only males. Males normally have an X chromosome and

a Y chromosome (XY). Males who have

Klinefelter syndrome have an extra X chromosome XXY, XXYY, XXXY Sterility Breast enlargement

XYY Syndrome “super male”

This condition occurs in about 1 in 1,000 newborn

boys. Five to 10 boys with 47,XYY syndrome are

born in the United States each day. Most males with 47,XYY syndrome have normal sexual

development and are able to father children. 47,XYY syndrome is associated with an increased risk of

learning disabilities and delayed development of speech and language skills.

Delayed development of motor skills (such as sitting and walking), weak muscle tone (hypotonia), hand tremors or other involuntary movements (motor tics), and behavioral and emotional difficulties are also possible.

These characteristics vary widely among affected boys and men.

XYY Syndrome “super male”•Normal male traits•Often tall and thin•Associated with antisocial and behavioral problems

Triple X syndrome also called trisomy X or 47,XXX,

characterized by the presence of an additional X chromosome in each of a female's cells.

This condition occurs in about 1 in 1,000 newborn girls. Five to 10 girls with triple X syndrome are born in the United States each day.

Triple X syndrome

Physical Symptoms-Taller than average

-Increased width between eyes

-Skin fold at inner eyelid

-Smaller head size

-Porportionatly tinier chin

Developmental Symptoms:-Learning disabilities-Speech & language delays-Poor coordination-Awkwardness-Clumsiness

Trisomy 18Edwards Syndrome

Caused by extra chromosome at chromosome 18.

It is three times more common in girls than boys.

Fifty percent of infants with this

condition do not survive beyond

the first week of life. Some children

have survived to the teenage years,

but with serious medical and developmental problems.

Trisomy 18Edwards Syndrome

Symptoms Clenched hands Crossed legs (preferred position) Feet with a rounded bottom (rocker-bottom feet) Low birth weight Low-set ears Mental deficiency Small head Small jaw Underdeveloped fingernails Undescended testicles Unusual shaped chest

Trisomy 13Patau Syndrome

Trisomy 13 occurs when extra DNA from chromosome 13 appears in some or all of the body's cells. The extra material interferes with normal development.

Trisomy 13 occurs in about 1 out of every 10,000 newborns. Most cases are not passed down through families (inherited). Instead, the events that lead to Trisomy 13 occur in either the sperm or the egg that forms the fetus.

The syndrome involves multiple

abnormalities, many of which are

not compatible with life. More than

80% of children with trisomy 13 die

in the first month.

Trisomy 13Patau SyndromeSymptoms

Cleft lip or palate Clenched hands (with outer fingers on top of the inner fingers) Close-set eyes -- eyes may actually fuse together into one Decreased muscle tone Extra fingers or toes Hole, split, or cleft in the iris Low-set ears Mental Retardation,severe Scalp defects (missing skin) Small eyes Small head Small lower jaw