Mendel's Law of Segregation states what?

Genes occur in pairs,

separate into gametes

(with each gamete receiving

one copy of the gene)

What is a phenotype?

The appearance of a trait,

such as the color of a flower

What is genotype?

The actual genes inherited

(RR, Rr, rr)

What does homozygous mean?

The two inherited genes are the same

(RR or rr, not Rr)

What does heterozygous mean?

The two inherited genes are different

(Rr)

What is an allele?

The alternative form of a gene

(purple flower vs white)

What is a locus?

The location of a gene

on the chromosome.

What is a monohybrid cross?

Following the inheritance of one trait

What is a dihybrid cross?

The inheritance of two traits

(flower is purple and tall)

What is a test cross?

An experimental cross to determine

the genotype having a dominant trait

but unknown parents

What is Mendel's Law of

Independent Assortment?

Genes on separate homologous

 chromosomes line up and separate

independently of each other.

What is incomplete dominance?

A blending of two traits

(red flower x white flower = pink flower)

What is codominance?

Both alleles in a heterozygous pair

completely express their traits.

What is epitasis?

When one gene completely blocks another

(such as in albinos)

What is pleiotropy?

One gene affects more than one trait

(such as poor eyesight in albinos)

Why are some genetic diseases

found mostly in male offspring?

Their syndrome disease is

on an x-linked gene.

What is autosomal linkage?

When two genes are linked

on the same chromosome

What is nondisjunction?

Faulty separation of chromosomes

Turner Syndrome is an

example of nondisjunction.

Describe it.

A child lacking a second sex chromosome

(XO instead of XX or XY).

Short, sterile, female, no breasts,

may have flap of skin on neck.

Klinefelter's Syndrome

is an example of nondisjunction.

Describe it.

A child with an extra set of chromosomes

(XXXY or XXY)

Sterile male, small testes, perhaps small breasts, high voice, often mental retardation.

What is Jacob's syndrome?

XYY baby (supermale)

Tall, possibly impulsive and agressive,

acne, otherwise normal.

What is a metafemale?

XXX baby

Very petite and feminine,

may have mentrual and fertility problems.

Otherwise normal.

Cystic Fibrosis is an autosomal recessive disorder,

caused by a faulty ion channel.

Describe it.

Thick mucous in respiratory tract

and digestive pathways.

Destroys lung tissue.

Tay-Sachs is an autosomal recessive disorder

 affecting 1 in 3600 Jewish babies.

Describe it.

They lack an enzyme, fatty wastes

accumulate and damage neurons.

Death is usually by age 5.

Huntington's Disease is an

autosomal dominant disorder.

Describe it.

Loss of voluntary muscle control,

onset after age 30,

caused by repeated CAG sequence.

What are Barr Bodies?

Normal inactivated x chromosomes

in all mammalian females.

What is the Rh factor in blood typing?

The presence or absence of D protein

on the red blood cell membrane.

What causes fetal hemoltyic disease?

When a mother is Rh- and the baby is Rh+,

treated with medication during pregnancy.

What is it called when a

blood sample is taken,

white blood cells removed,

freeze in cell division,

and then examine chromosomes?

Karyotyping

This prenatal procedure is performed at 16-18 weeks, some of the fluid surrounding fetus is removed, and various tests can be done on that fluid (karyotype, DNA test, etc.)

Amniocentisis

This prenatal procedure

is done at 6-8 weeks,

and some of the chorion is

removed for testing.

Chorionic Villi Sampling (CVS)

How are gene markers

used to find disease genes?

Bits of DNA often inherited

along with the disease genes.