Week 13 Epigenetics, Linkage and Extranuclear Inheritance

What are the three rules of Mendelian inheritance?

1. Genes are passed unaltered from cell to cell and generation to generation. 2. Genes obey Mendel's law of segregation. 3. Crosses with more than two genes obey Mendel's law of independent assortment.

What is epigenetics?

Epigenetics refers to stable changes in gene expression that do not involve changes in the DNA sequence.

How can DNA mutations affect phenotype?

DNA mutations can alter the RNA or protein produced, affecting the phenotype.

What is gene regulation?

Transient increases or decreases in gene expression due to environmental signals.

What is an example of epigenetic modification in honeybees?

Female honeybee larvae fed royal jelly develop into queen bees, while those not fed it become worker bees.

How do muscle cells exhibit epigenetic changes?

Muscle cells express high levels of actin and myosin due to epigenetic changes that turn these genes ON during development.

What is vernalization in plants?

Vernalization is the process where cold temperatures are required for flowering, involving epigenetic silencing of the FLC gene.

What are the main epigenetic mechanisms?

DNA methylation, histone modification, and regulation by non-coding RNAs.

Why is epigenetics important in medicine?

It plays a significant role in drug resistance in diseases like cancer and bacterial infections by altering gene expression.

What is epigenetic inheritance?

Epigenetic inheritance refers to the passing of epigenetic changes from parent to offspring via sperm or egg cells.

What is X inactivation?

In female mammals, one X chromosome is randomly inactivated in all somatic cells, leading to a Barr body.

What is the Lyon Hypothesis?

It states that in female mammals, one of the two X chromosomes is randomly inactivated early in embryonic development for dosage compensation.

What is cytoplasmic inheritance?

Cytoplasmic inheritance refers to the transmission of genes located outside the cell nucleus, such as those in mitochondria and chloroplasts.

How are organelle genomes inherited?

Organelle genomes are typically inherited maternally, as the egg cell provides most of the cytoplasm.

What is an example of a mutation in the chloroplast genome?

Mutations can affect chlorophyll synthesis, leading to green, white, or variegated leaf colors.

What is the mitochondrial genome responsible for?

The mitochondrial genome encodes tRNAs, rRNA, and proteins necessary for oxidative phosphorylation.

What is Leber's hereditary optic neuropathy (LHON)?

LHON is an inherited form of vision loss caused by mutations in mitochondrial genes, affecting ATP production.

What is gene linkage?

Gene linkage occurs when different genes are close together on the same chromosome and tend to be inherited together.

Who first studied gene linkage?

Bateson and Punnett conducted the first study showing linkage between two different genes in 1911.

What did Morgan's experiments with fruit flies demonstrate?

Morgan showed that genes located on the same chromosome are more likely to be inherited together and that crossing over can create new allele combinations.

What are nonrecombinants?

Nonrecombinants are offspring with the same combination of traits as the parental generation, indicating no crossing over occurred.

What are recombinants?

Recombinants are offspring with a different combination of traits from the parental generation, indicating that crossing over occurred.

How is genetic mapping achieved?

Genetic mapping is achieved using recombination frequencies to estimate the arrangement and distances between linked genes.

What is the significance of a genetic map?

A genetic map shows the linear order of genes along a chromosome and helps in understanding gene linkage.

What does a recombination frequency of 1% represent?

A recombination frequency of 1% corresponds to 1 map unit (mu) or centiMorgan (cM).

How do you calculate recombination frequency?

Recombination frequency = (Number of recombinant offspring / total offspring) * 100.

What is the outcome of a testcross between body color and wing shape in Drosophila?

The testcross produced 270 recombinants out of 1000, leading to a recombination frequency of 27%.