bio test rn brochacho (copy)
🧬 Complex Genetics Vocabulary
Codominance – A condition in which both alleles in a heterozygous organism are fully expressed (e.g. AB blood type).
Incomplete dominance – A form of inheritance where the heterozygous phenotype is a blend between both alleles (e.g. red + white = pink flower).
Multiple alleles – When more than two alleles exist for a trait, even though each individual can only carry two (e.g. blood type alleles: A, B, O).
Sex-Linked traits – Traits carried on the X or Y chromosome, usually the X.
Sex chromosome – The 23rd pair of chromosomes that determines sex (XX = female, XY = male).
Polygenic trait – A trait controlled by two or more genes, often showing a range of phenotypes (e.g. height, skin color).
Carrier – An individual who is heterozygous for a recessive disorder but does not show symptoms.
Pedigree – A diagram used to trace the inheritance of traits through generations.
Recessive genetic disorder – A disorder that appears only when an individual is homozygous recessive.
Dominant genetic disorder – A disorder that appears when an individual has at least one dominant allele.
🧬 Vocabulary You Should Already Know
Dominant allele – The allele that expresses itself over another allele.
Recessive allele – The allele that is masked by a dominant one unless both alleles are recessive.
Homozygous – Having two identical alleles for a gene (AA or aa).
Heterozygous – Having two different alleles for a gene (Aa).
Genotype – The genetic makeup of an organism (e.g., AA, Aa, aa).
Phenotype – The physical expression of the genotype.
Autosome – Any chromosome that is not a sex chromosome.
🧪 Incomplete Dominance & Codominance
(Chap 11, sec 2, p302-303)
Q: How can you tell the inheritance pattern based on the phenotype of a heterozygous individual?
A:
Mendelian: One allele is dominant, the other recessive (heterozygote shows dominant trait).
Codominance: Both traits are visible.
Incomplete dominance: Heterozygote shows a blended trait.
🧬 Sickle Cell Anemia (Codominant Disorder)
Q: What do RBCs look like in people with each genotype?
A:
Homozygous normal (SS) – Normal-shaped RBCs.
Heterozygous (Ss) – Both normal and sickle-shaped RBCs (codominant).
Homozygous sickle (ss) – All RBCs are sickle-shaped.
🩸 Multiple Alleles (Blood Types)
(Chap 11, sec 2, p304)
Q: How many alleles are there for blood type?
A: Three – A, B, O.
Q: Which are codominant and which is recessive?
A: A and B are codominant. O is recessive.
Q: What are the genotypes and phenotypes for blood types?
A:
Type A: AA or AO
Type B: BB or BO
Type AB: AB
Type O: OO
🧬 Sex-Linked Traits
(Chap 11, sec 2, p307-308)
Q: What sex chromosomes do females have? Males?
A: Females = XX, Males = XY
Q: Are sex-linked traits usually dominant or recessive?
A: Recessive
Q: Is there an allele for sex-linked traits on the Y chromosome?
A: No, usually only the X chromosome carries the allele.
Q: Why do males get sex-linked traits more often?
A: Males have only one X, so one recessive allele is enough to show the trait.
Q: Is a carrier homozygous or heterozygous?
A: Heterozygous
Q: Can males be carriers for sex-linked traits? Why or why not?
A: No, because they only have one X chromosome. They either have the trait or they don't.
Q: Can males be carriers for autosomal traits?
A: Yes, because autosomes are not sex-linked and both sexes have two copies.
Q: Can females be carriers for sex-linked traits? Autosomal traits?
A: Yes, they can be carriers for both.
🌈 Polygenic Traits & Environmental Influence
(Chap 11, sec 2, p309)
Q: What is a polygenic trait?
A: A trait influenced by multiple genes.
Q: Examples of polygenic traits?
A: Height, skin color, eye color.
Q: How is phenotype determined in polygenic traits?
A: By the additive effect of all the genes involved.
Q: What does "additive" mean in polygenic traits?
A: Each allele adds to the expression of the trait.
Q: Which genotype gives darker skin: AABbCc or aabbCC?
A: AABbCc, because more dominant alleles contribute to more pigment.
Q: What genotype gives mid-tone skin?
A: A mix like AaBbCc.
Q: Environmental influence examples?
A: Sun exposure (skin), nutrition (height), temperature (fur color in animals), chemicals (gene expression).
Q: Can environment change genotype?
A: No, only phenotype can be influenced.
🧬 Pedigrees
(Chap 11, sec 1, p299-301)
Q: Why use pedigrees?
A: To track inheritance of traits through generations.
Q: Symbols?
A: Squares = males, Circles = females. Shaded = has trait. Horizontal line = marriage. Vertical line = offspring.
Q: How to tell a trait is recessive?
A: Trait skips generations; unaffected parents can have affected children.
Q: Can you determine relatedness in a pedigree?
A: Yes—use the layout, generations, and connecting lines.
🧬 Recessive & Dominant Genetic Disorders
(Chap 11, sec 1, p296-298)
Match the disorder to the description:
Albinism – Recessive; lack of melanin pigment in skin, hair, eyes.
Huntington’s – Dominant; causes progressive brain deterioration, symptoms appear later in life.
Galactosemia – Recessive; cannot break down galactose, leads to liver damage and intellectual disability.
Tay-Sachs – Recessive; lipid accumulation in brain cells, leads to early death.
Cystic Fibrosis – Recessive; thick mucus in lungs and organs, breathing and digestion issues.
Achondroplasia – Dominant; a form of dwarfism, affects bone growth.