Genetic Processes and Principles

These flashcards cover key concepts in genetic processes, including meiosis, mitosis, genetic diversity, and sex-linked traits, providing a comprehensive review for exam preparation.

What is meiosis often described as?

A shuffling of our genes for genetic diversity.

What is the outcome of meiosis in terms of chromosome numbers?

Starts with 92 chromosomes, ends with four cells having 23 chromosomes each.

How does crossing over contribute to genetic diversity?

It mixes genes between homologous chromosomes during prophase I.

What is the phenotypic ratio in a typical monohybrid cross?

3:1 ratio of dominant to recessive traits.

What is a test cross used for in genetics?

To determine the genotype of an organism with a dominant phenotype by crossing it with a homozygous recessive.

What does a carrier of a recessive genetic disorder possess?

One normal allele and one mutated allele.

What is the expected chance for male offspring in a carrier female for a sex-linked disorder?

50% chance of being affected.

For a dominant trait, what will the genotype typically consist of?

Homozygous dominant (AA) or heterozygous (Aa).

What results from an X-linked recessive trait in sons and daughters if their mother is a carrier?

Sons have a 50% chance of being affected; daughters have a 50% chance of being carriers and 0% chance of being affected.

What is the probability of two linked genes crossing over when they are further apart?

The further apart two genes are, the more likely they will show recombination.

What does nondisjunction refer to in cell division?

The failure of chromosomes to separate properly during cell division.

What percentage of offspring do affected males contribute to their daughters for an X-linked trait?

100% of the daughters will be carriers if the father is affected.

What kind of genetic cross would reveal whether a dominant phenotype is homozygous or heterozygous?

A test cross with a homozygous recessive partner.

What is a typical phenotypic outcome of a cross between two homozygous plants, one dominant and one recessive?

All offspring will exhibit the dominant trait.

Why is Trisomy 21 more frequently observed in individuals born to older mothers?

Older eggs have undergone more divisions, increasing the likelihood of chromosomal errors.

What is the primary purpose of mitosis versus meiosis in eukaryotes?

Mitosis is utilized for somatic cell division, producing two identical diploid cells for growth and repair. Meiosis produces four genetically diverse haploid gametes for sexual reproduction.

What are the typical chromosome numbers for somatic cells and gametes in humans?

Somatic cells are diploid (2n = 46 chromosomes), while gametes are haploid (n = 23 chromosomes).

Besides crossing over, what other key event during meiosis contributes to genetic diversity?

Independent assortment of homologous chromosomes during metaphase I, which allows for different combinations of maternal and paternal alleles in the gametes.

What is the main practical application of a Punnett square?

To predict the genotypes and phenotypes of offspring resulting from a genetic cross and to visualize their probabilities.

Distinguish between an organism's genotype and phenotype.

Genotype is the genetic makeup (set of alleles) that determines traits, while phenotype is the observable physical or biochemical characteristics expressed by the genotype.

In genetics, what does it mean for an organism to be "true breeding"?

An organism that, when self-fertilized or crossed with another true-breeding organism of the same type, consistently produces offspring with the same traits over many generations, indicating homozygosity.

Why are males more susceptible to expressing X-linked recessive disorders than females?

Males only possess one X chromosome (inherited from their mother) and a Y chromosome. Therefore, inheriting a single recessive allele on the X chromosome will result in the expression of the disorder because there is no second X to mask it.

What is the standard unit for measuring the distance between linked genes on a chromosome during genetic mapping?

The centimorgan (cM) or map unit, which represents a 1% chance of recombination (crossing over) occurring between two genes.

What is a karyotype and what is its primary use in genetics?

A karyotype is an organized profile of an individual's complete set of chromosomes, arranged by size, shape, and banding patterns, primarily used to detect chromosomal abnormalities.