The Patterns of Inheritance

What is a gene?

A segment of DNA that codes for a trait

What is an allele?

Different forms of a gene (ex: A or a)

What is a trait?

A characteristic (eye color, height)

What is genotype?

Genetic makeup (AA, Aa, aa)

What is phenotype?

Physical appearance (brown eyes, blue eyes)

What is a dominant allele?

An allele that shows its effect even if only one copy is present

What is a recessive allele?

An allele that only shows if both copies are recessive

What does homozygous mean?

Two same alleles (AA or aa)

What does heterozygous mean?

Two different alleles (Aa)

Who is the father of genetics?

Gregor Mendel

What is the Law of Segregation?

Alleles separate during gamete formation; each organism has two alleles for each trait

What is the Law of Independent Assortment?

Genes for different traits are inherited independently (if not linked)

What is a Punnett square used for?

To predict the probability of offspring traits

What is the genotype ratio of Aa × Aa?

1 AA : 2 Aa : 1 aa

What is the phenotype ratio of Aa × Aa?

3 dominant : 1 recessive

What is complete dominance?

One allele completely masks the other

What is incomplete dominance?

Blending of traits (red + white = pink)

What is codominance?

Both alleles are fully expressed

What are multiple alleles?

More than two allele options exist (ex: A, B, O blood types)

What are polygenic traits?

Traits controlled by multiple genes (ex: skin color, height)

What are sex-linked traits?

Traits carried on sex chromosomes (usually X), more common in males

What is the difference between genotype and phenotype?

Genotype = genetic makeup; Phenotype = physical appearance

What is probability?

The chance of an event occurring

Does probability guarantee outcomes in genetics?

No, it only predicts outcomes

What is a pedigree?

A chart used to track inheritance in families

What does a square represent in a pedigree?

Male

What does a circle represent in a pedigree?

Female

What does shading mean in a pedigree?

Individual has the trait

What should you identify first in genetics problems?

Dominant vs recessive alleles

What is a common mistake in genetics?

Mixing up genotype and phenotype

Why do recessive traits sometimes not appear?

They require two recessive alleles

What is the main idea of inheritance?

Traits are passed from parents through genes and expressed based on allele combinations

Huntingtons Disease

Autosomal Dominant, degenaration of the nervous system

Polydactyly

autosomal dominant, extra toes or fingers

Progeria

Autosomal dominant, premature aging

Albinism

autosomal reccessive, absence of pigmentation

Sickle cell anemia

autosomal reccessive, anemia, pain, swelling, frequent infections

Cystic Fibrosis

Autosomal reccessive, chronic lung infections, difficulty breathing

red-green colorblindness

x-linked reccessive, inability to distinguish red from green

Hemophilia

x-linked reccessive, impaired blood clotting

Muscular Dystrophy

x-linked recessive, progressive loss of muscle function

Down syndrome

extra chromosome 21, metal impairment, heart defects

Klinefelter syndrome

XXY(1 in 500 males), sterility, mental impairment, overweight and tall

XXX Syndrome

XXX(1 in 1000 females), minimal changes, sometimes mild mental impairment