Complex Inheritance & Pedigree Analysis in Biology

What is complete dominance?

A pattern where the heterozygote looks like the dominant homozygote.

What is incomplete dominance?

A pattern where the heterozygote shows a blended intermediate phenotype.

Give an example of incomplete dominance.

Red (RR) × White (rr) → ALL Pink (Rr).

What is codominance?

A pattern where both alleles are fully expressed simultaneously without blending.

Provide an example of codominance.

Black (FBFB) × White (FWFW) → Speckled (FBFW).

What are multiple alleles?

When three or more alleles exist for a gene, such as the ABO blood types.

What is the genotype for blood type A?

IAIA or IAi.

What is the genotype for blood type B?

IBIB or IBi.

What is the genotype for blood type AB?

IAIB.

What is the genotype for blood type O?

ii.

What is a pedigree?

A chart that shows the pattern of inheritance in a family for a specific trait.

What do filled shapes represent in a pedigree?

Affected individuals who show the trait.

What do empty shapes represent in a pedigree?

Unaffected individuals.

What does a half-filled shape indicate in a pedigree?

A carrier individual (heterozygous).

How can you identify if a trait is dominant or recessive in a pedigree?

Check if the trait skips generations (suggests recessive) or appears every generation (suggests dominant).

What is the significance of father-to-son transmission in a pedigree?

If present, the trait is NOT X-linked.

What is nondisjunction?

An error in meiosis where chromosomes fail to separate properly.

What are karyotypes used for?

To visualize and identify chromosomal abnormalities.

What is a common example of a sex-linked trait?

Hemophilia.

What is the probability of a male kitten being orange in a calico cross?

1/2.

What is the phenotype ratio for a dihybrid cross?

9:3:3:1.

What is the role of a probability calculator in genetics?

To predict the likelihood of certain genotypes and phenotypes in offspring.

What is the Rh factor?

An antigen that can be present (+) or absent (-) on red blood cells.

What is the universal donor blood type?

Type O (ii), as it has no antigens for the recipient's immune system to attack.

What is the universal recipient blood type?

Type AB (IAIB), as it has no antibodies to attack any blood type.

What does a diagonal line through a shape in a pedigree indicate?

That the individual is deceased.

What is the purpose of a pedigree detective?

To identify the inheritance pattern for each pedigree.

What is the inheritance pattern where only one copy of a gene is needed to express the trait?

Autosomal Dominant

What is the inheritance pattern where two copies of a gene are needed to express the trait?

Autosomal Recessive

What is the inheritance pattern where the gene is located on the X chromosome and typically affects males more than females?

X-Linked Recessive

In an Autosomal Dominant inheritance pattern, what is the likelihood of an affected child if one parent is affected?

50% chance

What is the genotype of an individual who is a carrier for an Autosomal Recessive trait?

Heterozygous (Aa)

What is the expected offspring ratio from two heterozygous parents (Aa) for an Autosomal Recessive trait?

25% affected, 50% carriers, 25% normal

What does a Punnett square for X-Linked Recessive inheritance show for a carrier mother and a normal father?

50% chance of affected sons, 0% chance of affected daughters

What is the term for when chromosomes fail to separate correctly during meiosis?

Nondisjunction

What is the result of nondisjunction during meiosis?

Aneuploidy (abnormal chromosome number)

Which trisomies are known to produce live births?

Trisomy 13 (Patau), Trisomy 18 (Edwards), Trisomy 21 (Down)

What is a karyotype?

A picture of all chromosomes from a single cell, arranged in matched homologous pairs.

What is the notation for a normal male karyotype?

46, XY

What is the genetic cause of Hemophilia?

X-Linked Recessive gene on the X chromosome

What are the key symptoms of Down Syndrome?

Distinct facial features, intellectual disability, heart defects

What is the inheritance pattern of Sickle Cell Anemia?

Autosomal Recessive with codominant expression

What does it mean if a trait skips generations in a pedigree?

It is likely a recessive trait.

What is the genotype of a color-blind male?

XcY (X with recessive color-blind allele and Y chromosome)

What is the expected outcome for two affected parents in a dominant inheritance pattern?

They can produce unaffected children if both are heterozygous.

What is the genetic notation for Turner Syndrome?

45, X (only one X chromosome)

What is the result of a deletion in a chromosome?

A piece of a chromosome is lost, potentially causing disorders like Cri-du-chat.

What is the genetic notation for Klinefelter's Syndrome?

47, XXY (extra X chromosome in males)

What is the expected offspring ratio from two heterozygous tasters (Tt) for the tasting trait?

25% non-taster (tt), 50% tasters (Tt), 25% homozygous taster (TT)

What is the significance of the gene notation 'Nn' in Autosomal Recessive inheritance?

N represents normal pigmentation (dominant), n represents albinism (recessive).

What is the expected outcome for two normal-vision parents having a color-blind son?

The son must be XcY, indicating the mother is a carrier (XCXc).

What type of inheritance is Sickle Cell Anemia?

Autosomal Recessive

What is the genetic expression type of Sickle Cell Anemia?

Codominant expression

What is a characteristic of Sickle Cell Anemia?

Misshapen red blood cells block vessels; carriers have some malaria resistance.

What is the karyotype for Turner Syndrome?

45, X (or 45, X0)

What are the symptoms of Turner Syndrome?

Short stature, sterile, webbed neck, no secondary sex traits at puberty.

What is the karyotype for Down Syndrome?

47, XX +21 / 47, XY +21

What are common features of Down Syndrome?

Facial features, intellectual disability, heart defects.

What is the karyotype for Edwards Syndrome?

47, +18

What are the characteristics of Edwards Syndrome?

Severe organ defects, low survival.

What is the karyotype for Patau Syndrome?

47, +13

What are the symptoms of Patau Syndrome?

Severe brain & heart defects.

What is the karyotype for Klinefelter Syndrome?

47, XXY

What are the characteristics of Klinefelter Syndrome?

Reduced fertility, less developed male traits.

What is the karyotype for Jacob's Syndrome?

47, XYY

What are the characteristics of Jacob's Syndrome?

Often tall, usually normal.

What is the karyotype for Triple X Syndrome?

47, XXX

What are the characteristics of Triple X Syndrome?

Often no major symptoms.

What is the karyotype for Cri-du-chat Syndrome?

46, XX or XY, 5p-

What are the symptoms of Cri-du-chat Syndrome?

High-pitched cat-like cry as infant, intellectual disability.

What type of inheritance is Hemophilia?

X-linked recessive

What is a characteristic of Hemophilia?

Blood doesn't clot, mostly affects males.

What type of inheritance is Color Blindness?

X-linked recessive

What is a characteristic of Color Blindness?

Can't distinguish colors (especially red/green), mostly affects males.

What type of inheritance is Huntington's Disease?

Autosomal dominant

What is a characteristic of Huntington's Disease?

Late-onset brain degeneration.

What type of inheritance is Cystic Fibrosis?

Autosomal recessive

What is a characteristic of Cystic Fibrosis?

Thick mucus in lungs and digestive tract.

What is the karyotype notation for a normal female?

46, XX

What is the karyotype notation for a normal male?

46, XY

What does the notation 47, +21 indicate?

47 total chromosomes with an extra copy of chromosome 21 (Down syndrome).

What does the notation 45, X indicate?

A female with only one X chromosome (Turner syndrome).

What does the notation 5p- indicate?

A deletion on the short arm (p) of chromosome 5 (Cri-du-chat).

What is a common misconception about X-linked recessive traits?

Males can't be carriers; they either have the trait or they don't.

What are the only viable trisomies in humans?

Trisomy 13, 18, and 21.

What is the only viable monosomy in humans?

Turner syndrome (45, X).