COMPLEX INHERITANCE and COMMON GENETIC DISORDERS

COMPLEX INHERITANCE and COMMON GENETIC DISORDERS

Fill-in-blank Notes Use your text to read and learn about each topic, filling in the blanks below. Add pictures, examples, page numbers, or additional notes as needed.

p. 296-298 Recessive Disorders: most human disorders are recessive, so individuals must have two recessive alleles to show the disorder. Examples of Recessive disorders:

Cystic fibrosis –

Albinism

Tay-Sach’s disease –

Galactosemia

PKU (phenylketonuria) - inability to breakdown phenylalanine in blood;

tested with foot prick test shortly after birth. Can cause mental

impairment and lack of normal skin pigmentation. Babies and children

with it must maintain a strict diet low in this amino acid.

Discuss some dangers of inbreeding –

p. 298-Dominant disorders: some human disorders due to dominant alleles,

some non-lethal. Just because a gene is dominant does NOT mean that

there is more of it in a population. In fact, lethal dominant genes are

much less common than lethal recessive genes because it affects anyone

who gets it, so offspring may not survive long enough to reproduce. In

this way it reduces the number of lethal genes in the population.

Examples:

Huntington’s disease –

Achondroplasia –

Polydactyly – extra fingers or toes – usually underdeveloped appendages

p. 299-301 Pedigrees – family trees used to trace the inheritance of particular

traits over generations

Carriers – people who carry one copy of the recessive allele for a disorder

but do not exhibit symptoms

What do the symbols seen in a pedigree illustrate? Draw and describe the codes as listed on p. 299.

How are pedigrees used to infer genotypes?

How are pedigrees used to predict disorders?

What are some limitations of using pedigrees to predict disorders?

Codominant Disorders (p 302-303) See previous notes provided. Contrast Incomplete dominance and codominance below:

Sickle cell disease (codominant disorder)

Malaria Connection (describe how it is associated with sickle cell anemia)

p. 304-305 Multiple Alleles

See previous notes, and list some examples of characteristics determined by multiple alleles from text and notes below.

p. 305 Epistasis

Describe and give example.

p. 305-306 Sex Chromosomes

X-Y system in humans

What are some systems to determine sex which exist in other organisms?

Monoecious –

Hermaphroditic -

P 306 What does it mean for an X chromosome to be inactivated? How does this occur, and what may it impact?

p. 309 Polygenic Traits

Explain why your book shows the skin color example under a bell curve:

p. 309 -310 Environmental Influences

Describe how the environment may influence expression of certain traits:

Twin studies – How do twin studies help us determine environmental influences?

p. 314-315 Fetal testing to detect genetic disorders:

Amniocentesis –

Chorionic villus sampling (CVS) –

Fetal Blood Sampling -

Ultrasound –

Fetoscopy -

Genetic screening – testing of prospective parents for alleles associated

with a particular genetic disorder in order to assess, discuss, and weigh any

risks prior to pregnancy; is combined with education and genetic counseling

Linked genes – genes located close together on same chromosome so

they are usually inherited together

Crossing over produces new allele combinations and results in some

unexpected results and percentages from crosses of known genotypes

Recombination frequency – percentage of recombinants shows the

occurrence of crossing over

Mapping genes – recombination data helps scientists determine gene

locations on a chromosome and their distances from one another; mapping

is done with advanced DNA technology today

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