AP Biology:: Heredity

What is MEIOSIS, at a general level, and how does its purpose differ from mitosis?

- **A)** A type of cell division that produces FOUR genetically-unique daughter cells, each with HALF the number of chromosomes as the original cell (haploid), specifically for producing GAMETES (sex cells) -- unlike mitosis, which produces two identical, full-chromosome-number (diploid) daughter cells for growth/repair
- **B)** Meiosis always produces daughter cells with MORE chromosomes than the original cell, rather than fewer
- **C)** This process has no actual relationship to producing sex cells (gametes)
- **D)** Meiosis is simply another name for mitosis, with no actual distinction between the two processes

What does it mean for a cell to be DIPLOID versus HAPLOID?

- **A)** A DIPLOID cell has TWO complete sets of chromosomes (one from each parent), while a HAPLOID cell has only ONE complete set -- gametes (sperm and egg) are haploid, while most other body cells are diploid
- **B)** This distinction has no actual relationship to the number of chromosome sets present in a cell
- **C)** Diploid and haploid cells always contain the exact same identical number of chromosome sets, with no distinction
- **D)** A haploid cell always has MORE chromosome sets than a diploid cell, rather than fewer

Why is it important that gametes (sperm and egg) are HAPLOID rather than diploid, in the context of sexual reproduction?

- **A)** If gametes were diploid rather than haploid, FERTILIZATION (combining a sperm and egg) would produce an offspring with DOUBLE the normal chromosome number each generation -- haploid gametes ensure that combining two of them restores the correct, normal diploid chromosome number in the offspring
- **B)** Gamete ploidy has no actual relationship to the chromosome number of resulting offspring
- **C)** Fertilization always occurs between two diploid cells, never involving haploid gametes at all
- **D)** Haploid gametes would result in offspring with HALF the normal chromosome number, rather than the correct amount

What are HOMOLOGOUS CHROMOSOMES?

- **A)** Homologous chromosomes always come from the SAME single parent, never one from each parent
- **B)** This term refers only to sister chromatids produced during DNA replication, not to chromosomes inherited from different parents
- **C)** Homologous chromosomes are always genetically IDENTICAL copies of each other, with no possibility of carrying different alleles
- **D)** A pair of chromosomes (one inherited from each parent) that are the SAME SIZE, carry genes for the SAME TRAITS at the same locations (loci), but may carry DIFFERENT versions (alleles) of those genes

What is CROSSING OVER (recombination), and during which stage of meiosis does it typically occur?

- **A)** Crossing over has no actual relationship to increasing genetic variation among offspring
- **B)** Crossing over refers to sister chromatids separating from each other, not to genetic exchange between homologous chromosomes
- **C)** This process always results in exactly IDENTICAL chromosomes, with no new allele combinations produced
- **D)** The physical EXCHANGE of genetic material between HOMOLOGOUS chromosomes (specifically their non-sister chromatids), typically occurring during PROPHASE I of meiosis, creating NEW combinations of alleles not present in either original parental chromosome

What is INDEPENDENT ASSORTMENT, another source of genetic variation during meiosis?

- **A)** Independent assortment refers to the physical exchange of genetic material between homologous chromosomes (this actually describes crossing over, not independent assortment)
- **B)** This process always results in every gamete receiving the exact same predetermined combination of maternal and paternal chromosomes
- **C)** The RANDOM orientation and separation of EACH pair of homologous chromosomes during meiosis I, independent of how any other pair separates -- meaning the specific combination of maternal and paternal chromosomes ending up in a given gamete is essentially random
- **D)** Independent assortment has no actual relationship to generating genetic variation among gametes

What are the TWO major divisions of meiosis, and what is the key distinguishing event of EACH?

- **A)** Meiosis II always occurs BEFORE meiosis I, rather than after it
- **B)** Sister chromatids separate during meiosis I, while homologous chromosomes separate during meiosis II (the reverse of the actual sequence)
- **C)** Meiosis consists of only a single, undivided division, with no distinguishable stages
- **D)** MEIOSIS I (homologous chromosomes separate from each other, reducing chromosome number from diploid to haploid) and MEIOSIS II (sister chromatids separate from each other, similar to mitosis, but starting from haploid cells)

What is a GENOTYPE, and how does it differ from a PHENOTYPE?

- **A)** This distinction has no actual relationship to how an organism's genes relate to its observable traits
- **B)** A phenotype refers only to an organism's genetic makeup, while a genotype refers to its observable traits (the reverse of the actual definitions)
- **C)** A GENOTYPE is an organism's actual genetic makeup (the specific alleles it carries for a gene), while a PHENOTYPE is the observable physical or biochemical TRAIT that results from that genotype (often also influenced by environment)
- **D)** Genotype and phenotype are always exactly the same thing, with no meaningful distinction between them