Epigenetics, Linkage, and Extranuclear Inheritance

This set of flashcards covers key concepts from the lecture on epigenetics, linkage, and extranuclear inheritance, helping to reinforce understanding for exam preparation.

What is epigenetics?

The study of stable changes in gene expression that do not involve a change in the DNA sequence.

What does gene expression follow?

DNA → RNA → Protein.

What are the three rules of Mendelian inheritance?

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

What are transient increases or decreases in gene expression due to environmental signals called?

Gene regulation.

What is epigenetic gene regulation?

Stable changes in gene expression that are passed from cell to cell and are reversible.

What ensures stable gene expression patterns in the adult?

Epigenetic changes established in the developing embryo.

What is vernalization in flowering plants?

The process in which cold temperatures are required to flower.

How does flowering require the expression of the FLC gene?

Flowering requires low levels of FLC gene expression.

What happens to FLC expression during winter?

Cold temperatures induce epigenetic silencing of FLC.

What is epigenetic inheritance?

Inheritance of an epigenetic state from parents via sperm or egg cells.

Can an affected male pass on a mitochondrial disease to his offspring?

No, males cannot transmit mitochondrial diseases to their offspring.

What is a Barr body?

A condensed X chromosome that is silenced and prevents gene expression.

Why are calico cats' fur patterns an example of X inactivation?

One of the two X chromosomes in female cats is randomly inactivated, resulting in patches of different colors.

Define gene linkage.

When different genes are close together on the same chromosome and tend to be transmitted as a unit.

Who first demonstrated the concept of gene linkage?

Bateson and Punnett.

What is a linkage group?

A group of genes that usually stay together during meiosis.

What is the recombination frequency?

The percentage of recombinant offspring produced during genetic crossing.

What is the significance of crossing over during meiosis?

It can create new combinations of alleles between linked genes.

What does the term 'mosaic' refer to in genetics?

An individual with somatic cells that are genetically different from each other.

What is the role of maternal inheritance in extrachromosomal genetics?

Maternal inheritance refers to genes passed down through the mother, especially in mitochondria and chloroplasts.

What do mitochondria and chloroplasts contain?

Their own genomes separate from the nuclear genome.

What is the result of mutations in the mitochondrial DNA?

Can cause rare diseases affecting high ATP-consuming organs.

What is the primary function of tRNA and rRNA encoded by mitochondrial genes?

Needed for translation inside mitochondria.

What does gene expression regulation often involve in development?

Turning genes ON or OFF depending on the cell type.

What is the overall purpose of X inactivation?

To achieve dosage compensation for X-linked genes between genders.

What does the term 'cis-acting elements' refer to in genetics?

Regulatory sequences located on the same DNA molecule as the genes they regulate.

What can induce epigenetic changes in lung cells?

Exposure to cigarette smoke.

What is meant by 'organellar genomes'?

Genomes located in organelles, such as mitochondria and chloroplasts.

What is genetic mapping?

A method for estimating the arrangement and relative distances between linked genes based on recombination frequencies.

What does a genetic map show?

The linear order of genes along a chromosome.

How does recombination frequency relate to mapping distance?

1% recombination frequency equals 1 map unit (mu) or centiMorgan (cM).

What does epigenetic silencing mean in terms of gene expression?

Turning OFF specific genes in a cell type through epigenetic changes.

What is the ultimate source of variability in phenotypes among organisms?

Changes in gene expression due to environmental factors or mutations.

When are high levels of FLC expression found in flowering plants?

In the new seedlings before exposure to cold temperatures.

What is a testcross?

A cross between an individual of unknown genotype and a homozygous recessive individual.

How do you calculate recombination frequency?

Recombination frequency = Number of recombinant offspring / Total offspring * 100.

What happens to genes separated by greater distances on a chromosome?

They are more likely to assort independently due to crossing over.

Define 'extrachromosomal DNA.'

DNA located outside the cell nucleus, such as in mitochondria and chloroplasts.

How do mutations affect leaf color in plants?

Mutations can lead to changes in chlorophyll synthesis, affecting pigmentation.

What do recombinants refer to in genetic terms?

Offspring that have a different combination of traits from the parental generation.

What is the relationship between gene linkage and independent assortment?

Linked genes do not follow the law of independent assortment.

What was Morgan's observation with Drosophila?

Deviation from expected phenotypic ratios suggested gene linkage.

What major concepts did Morgan propose regarding genes on the same chromosome?

Traits determined by these genes are more likely inherited together.

What can cause chronic degenerative disorders involving mitochondrial function?

Mutations in mitochondrial genes.

What are parental types in genetics?

Offspring's combinations of traits that have not changed from parental generations.

Why is a testcross important in genetics?

It helps to determine the genotype of an individual exhibiting a dominant phenotype.

What did Bateson and Punnett observe during their experiments?

Surprisingly more parental phenotypes than expected in F2 generation.

Define epigenetic silencing in development.

The process through which some genes are turned OFF in specific cell types.

How can organelle genomes be inherited?

Typically maternally, since the egg cell provides most of the cytoplasm.

What does the term 'plant vernalization' refer to?

The need for a period of cold temperatures to promote flowering.

What do mutations in human mitochondrial genes often lead to?

A variety of rare diseases, particularly in high ATP-requiring organs.

What aspect of epigenetics allows for reversible gene expression changes?

Epigenetic modifications such as DNA methylation and histone modification.