Epigenetics
What is epigenetics?
The study of changes in gene expression that do not involve alterations to the underlying DNA sequence.
What is a dihybrid cross?
A cross that examines the inheritance of two different traits.
What is nondisjunction?
The failure of homologous chromosomes or sister chromatids to separate properly during cell division.
What is independent assortment?
The principle that alleles for different traits are distributed to gametes independently of one another.
What is crossing over?
The exchange of genetic material between homologous chromosomes during meiosis.
Name one factor that can cause epigenetic changes
Environmental factors such as diet, stress, or exposure to toxins.
If a plant with genotype RrYy is crossed with RrYy, what is the expected phenotypic ratio?
9:3:3:1
What condition can result from nondisjunction during meiosis?
Down syndrome (trisomy 21).
Who is credited with the law of independent assortment?
Gregor Mendel
When does crossing over occur?
During prophase I of meiosis.
How can epigenetics affect an organism’s phenotype?
Epigenetic changes can modify gene expression, leading to different traits without changing the DNA sequence.
What do the letters in a dihybrid cross represent?
The alleles for two different genes (e.g., R for round seeds, r for wrinkled seeds; Y for yellow color, y for green color).
How can nondisjunction affect gametes?
It can lead to gametes with an abnormal number of chromosomes, resulting in genetic disorders.
How does independent assortment contribute to genetic variation?
It allows for new combinations of alleles to be formed in offspring.
How does crossing over contribute to genetic diversity?
It creates new allele combinations, leading to increased variation in offspring.
What is DNA methylation?
A process by which methyl groups are added to DNA, often affecting gene expression.
Explain the significance of the Punnett square in dihybrid crosses.
It visually represents all possible allele combinations from parental gametes, predicting offspring ratios.
Describe the difference between primary and secondary nondisjunction.
Primary nondisjunction occurs during meiosis I, while secondary nondisjunction occurs during meiosis II.
Explain how independent assortment is observed in a dihybrid cross.
Alleles for one trait segregate independently of alleles for another trait during gamete formation.
What are chiasmata?
The points where crossing over occurs between homologous chromosomes.
Describe how epigenetic changes can be inherited.
Epigenetic modifications can be passed from one generation to another, influencing traits in offspring without altering the genetic code.
What is the difference between dominant and recessive traits in a dihybrid cross?
Dominant traits are expressed when at least one dominant allele is present, while recessive traits are expressed only when two recessive alleles are present.
What are the implications of nondisjunction in human development?
Nondisjunction can lead to various chromosomal disorders, affecting health and development.
What is the role of meiosis in independent assortment?
Meiosis facilitates the random distribution of chromosomes to gametes, leading to independent assortment.
Describe how crossing over can affect inheritance patterns.
It can lead to recombinant chromosomes, altering the expected ratios of traits in offspring.