Genetics Fundamentals and Chromosomal Inheritance

Comprehensive question-and-answer flashcards covering key topics in introductory genetics, including Mendelian inheritance, cell cycle and meiosis, sex determination, gene interactions, pedigree analysis, and gene mapping.

What role did albinism play in the culture of Hopi Native Americans, and how did it affect its frequency?

Albinism was culturally accepted, which reduced selection against it and contributed to a higher frequency of the condition within the tribe.

What are the three major divisions of genetics and what does each study?

Transmission genetics studies heredity from parent to offspring; molecular genetics studies DNA, RNA, and proteins; and population genetics studies genetic variation within populations.

How do pangenesis, germ-plasm theory, and preformationism differ in their explanations of heredity?

Pangenesis proposes that body parts send hereditary info to gametes; germ-plasm theory states heredity passes only through reproductive cells; preformationism suggests a miniature fully formed organism exists inside the sperm or egg.

What are the key cellular differences between eukaryotes and prokaryotes?

Eukaryotic cells contain a nucleus and linear chromosomes, whereas prokaryotic cells lack a nucleus and typically possess circular DNA.

What are the three functional elements of a eukaryotic chromosome and their functions?

Origins of replication initiate DNA synthesis; centromeres facilitate chromosome segregation during cell division; and telomeres protect the ends of linear chromosomes.

How do DNA content and chromosome number change during the eukaryotic cell cycle?

DNA quantity doubles during the S phase of interphase, whereas chromosome numbers stay constant until sister chromatids separate in mitosis or meiosis.

How does the genetic basis of blond hair in Solomon Islanders compare to that in Europeans?

Blond hair in Solomon Islanders is caused by a specific variant in the $TYRP1$ gene, whereas European blond hair involves different genetic variants.

What formula is used to calculate the chi-square goodness-of-fit value in genetic crosses?

$\chi^2 = \sum \frac{(O - E)^2}{E}$, where $O$ represents the observed number of progeny and $E$ represents the expected number.

How is sex determined in XX-XO, XX-XY, and ZZ-ZW chromosomal systems?

In XX-XO, females are XX and males are XO; in XX-XY, females are XX and males are XY; in ZZ-ZW, males are ZZ and females are ZW.

How is the biological sex of Drosophila determined based on the X:A ratio?

An X:A ratio of $1.0$ produces a female fly, whereas an X:A ratio of $0.5$ produces a male fly.

What is the formula to predict the number of Barr bodies in a human somatic cell?

$$\text{Barr bodies} = \text{number of X chromosomes} - 1$$

What role does XIST RNA play in dosage compensation in mammals?

XIST RNA coats one of the X chromosomes in female somatic cells, promoting its random condensation and inactivation into a Barr body.

What is the difference between incomplete penetrance and variable expressivity?

Incomplete penetrance occurs when an individual with a specific genotype does not express the expected phenotype; variable expressivity refers to the degree or intensity to which the phenotype is expressed.

How do epistatic and hypostatic genes interact in genic interactions?

An epistatic gene masks or overrides the expression of a gene at a different locus; the gene whose phenotype is masked is the hypostatic gene.

What distinguishes polygeny, pleiotropy, and phenocopy?

Polygeny refers to multiple genes influencing a single trait; pleiotropy refers to one gene affecting multiple traits; phenocopy is an environmentally induced phenotype that mimics a genetically produced trait.

What gene mutation is responsible for the genetic condition adermatoglyphia?

Adermatoglyphia is caused by a specific mutation in the $SMARCAD1$ gene.

How is the recombination frequency (RF) between two linked genes calculated?

$$\text{RF} = \frac{\text{number of recombinant progeny}}{\text{total number of progeny}} \times 100\%$$

What is the difference between cis and trans arrangements of linked alleles?

In cis (coupling) configuration ($AB/ab$), wild-type alleles are on one chromosome and mutant alleles on the other; in trans (repulsion) configuration ($Ab/aB$), each chromosome carries one wild-type and one mutant allele.

How did Creighton and McClintock experimentally confirm the chromosome theory of inheritance?

They showed that genetic recombination of linked genes directly correlates with physical exchange between homologous chromosomes.

What are the main principles of somatic cell hybridization, deletion mapping, and FISH in physical gene mapping?

Somatic cell hybridization assigns genes to specific chromosomes by human-rodent cell fusion; deletion mapping locates genes by looking for loss of wild-type allele function in deleted regions; FISH uses fluorescent probes to hybridize directly to specific chromosome locations.