BIOL 300 Exam 2 (Modules 5-8)

What is a gene?

A section of DNA that contains the instructions for building a particular protein. Genes reside at specific locations on chromosomes.

What is a chromosome?

A coiled structure of DNA and proteins that contains genetic information. Humans have 46 chromosomes arranged in 23 pairs within the nucleus of their cells. Chromosomes carry multiple genes.

What is a genome?

The complete set of genetic material present in an organism or a cell. The human genome, for instance, is mapped and contains approximately 20,000-25,000 genes.

What is a genotype?

The specific genetic makeup of an individual, referring to the combination of alleles they possess for a particular gene or set of genes. It represents the genetic code.

What is a phenotype?

The observable physical and behavioral traits of an organism, which result from the interaction between its genotype and the environment.

What is gene expression?

The process by which the information encoded in a gene is used to direct the synthesis of a functional gene product, such as a protein or RNA. A gene is considered 'on' when it is actively transcribed and translated.

What is the nature vs. nurture debate?

This explores the relative contributions of genetic inheritance (nature) and environmental factors (nurture) to the development of traits and behaviors. Phenotype is generally considered a product of the genotype interacting with the environment.

What is epigenetics?

A system of controls that determines whether specific genes are turned 'on' or 'off' without altering the underlying DNA sequence. Epigenetic modifications, influenced by environmental factors, play a crucial role in cell differentiation, development, and can sometimes be inherited across generations.

What is an allele?

A particular version or variant of a gene. For many genes, there can be multiple alleles within a population, leading to different phenotypes.

What does homozygous mean?

Having two identical alleles for a particular gene (e.g., FF or ff).

What does heterozygous mean?

Having two different alleles for a particular gene (e.g., Ff).

What are dominant-recessive allele interactions?

Some alleles exhibit a relationship where one allele can mask the effect of another.

What is a dominant allele?

An allele whose phenotypic effect is fully expressed in a heterozygote, masking the effect of the recessive allele (e.g., F).

What is a recessive allele?

An allele whose phenotypic effect is masked in a heterozygote by the presence of a dominant allele and is only expressed in a homozygous recessive individual (e.g., f).

How does the freckle example illustrate Mendelian genetics?

In the freckle example: FF (homozygous dominant) = Freckles, ff (homozygous recessive) = No freckles, Ff (heterozygous) = Freckles (dominant allele masks recessive allele).

What assumptions are made in simple Mendelian genetics?

These patterns often assume no environmental influence on the phenotype and complete dominance.

What is a Punnett square?

A diagram used to predict the possible genotypes and phenotypes of offspring from a cross between two parents.

What do the top and side of a Punnett square represent?

The top and side represent the possible gametes (sperm or egg cells) produced by each parent.

What does each square within a Punnett square represent?

Each square represents a possible combination of parental gametes, showing the potential genotypes of the offspring.

What is the significance of the resulting genotypes in a Punnett square?

Each resulting genotype has a specific probability of occurring in the offspring.

How are Punnett squares used in practice?

Punnett squares are used for single-gene crosses involving dominant and recessive alleles to calculate the probabilities of different genotypes and phenotypes (e.g., for freckles).

What is cystic fibrosis?

Cystic fibrosis is a recessive genetic disorder where individuals with two copies of a non-functional CFTR gene (ff) will have the disease. Carriers (Ff) have one normal and one non-functional allele but do not exhibit symptoms.

What is a pedigree?

A diagram that shows the inheritance pattern of a particular trait or genetic disorder through multiple generations of a family, with circles for females and squares for males.

What do filled shapes in a pedigree represent?

Filled shapes indicate individuals expressing the trait or genetic disorder.

How can pedigrees be useful in genetics?

Pedigrees can help predict the likelihood of offspring inheriting certain genetic conditions through family inheritance patterns.

What is codominance?

A pattern of inheritance where both alleles in a heterozygote are fully and equally expressed, resulting in a phenotype that shows the effects of both alleles (e.g., red and white petals in flowers).

What is incomplete dominance?

A pattern of inheritance where the phenotype of a heterozygote is intermediate between the phenotypes of the two homozygotes (e.g., red and white flowers producing pink flowers).

What are multiple alleles?

When a gene has more than two allelic forms within a population, although an individual still inherits only two alleles for that gene (e.g., human blood type determined by I^A, I^B, and i alleles).

How do I^A and I^B alleles relate to blood type inheritance?

I^A and I^B alleles are codominant, while i is recessive to both, leading to four possible blood types: A, B, AB, and O.

What are polygenic traits?

Traits determined by the interaction of multiple genes, often exhibiting a continuous range of variation (e.g., eye color and skin color).

What are sex-linked traits?

Traits determined by genes located on the sex chromosomes (X and Y) in humans.

What is a Y-linked trait?

A trait determined by genes located on the Y chromosome, inherited only by males and passed from father to son.

What is an X-linked trait?

A trait determined by genes on the X chromosome, with differing inheritance patterns between males and females due to the presence of only one X chromosome in males, making recessive X-linked traits more commonly expressed in males.

What is genetic diversity?

The variety of genes within a species, which is crucial for the adaptability and survival of populations.

How does sexual reproduction contribute to genetic diversity?

It combines genetic material from two parents through meiosis and random fertilization, creating unique combinations of alleles in offspring.

What is meiosis?

The process of cell division that produces gametes (sperm and egg cells) with half the number of chromosomes as the parent cell, increasing genetic variation through crossing over and independent assortment.

What is crossing over in meiosis?

The exchange of genetic material between homologous chromosomes

What is independent assortment?

The random segregation of chromosomes during meiosis that contributes to genetic variation in offspring.

What are mutations?

Random changes in the DNA sequence that can introduce new alleles into a population, affecting genetic diversity.

Can mutations be beneficial?

Yes, while many mutations are neutral or harmful, some can confer advantages in certain environments, contributing to evolution.