sex-linked and non trad modes of inheritance

How many chromosomes do humans typically have in their somatic cells?

46

What are the first 22 pairs of human chromosomes known as?

Autosomes

What is a characteristic of autosomal inheritance?

Males and females are equally affected.

What is a key difference between X-linked and autosomal inheritance?

X-linked conditions often show a discrepancy in disease incidence between males and females.

From whom do males receive their X chromosome?

Mother

What is the primary purpose of X-inactivation in females?

Equalize gene dosage between sexes.

Which gene on the X chromosome is responsible for initiating X-inactivation?

XIST

What is the condensed, inactive X chromosome in females called?

Barr body

A female who is a carrier for an X-linked recessive condition but displays mild symptoms is referred to as a

Manifesting heterozygote

What does skewed X-inactivation mean?

There is a disproportionate inactivation of one X chromosome over the other.

Approximately what percentage of genes on the X chromosome escape X-inactivation?

15%

A female with a 45,X karyotype can manifest symptoms of an X-linked recessive condition primarily because

She has only one X chromosome, similar to a male.

What is a hallmark feature of X-linked dominant inheritance?

No male-to-male transmission.

For a female carrier of an X-linked recessive condition, what is the chance of having an unaffected son who is not a carrier?

1 in 4 (25% chance)

In gene structure, the coding regions that contain instructions for protein synthesis are called

Exons

A deletion in a gene that causes the downstream genetic message to become "jibberish" due to a shift in the reading frame is known as an

out-of-frame deletion

A deletion that removes a section of a gene but keeps the reading frame intact, potentially resulting in a shorter but partially functional protein, is called an

In-frame deletion

The therapeutic strategy of exon skipping aims to

Block a specific exon to convert an out-of-frame deletion into an in-frame deletion.

Antisense oligonucleotides (AONs) are a key tool used in which therapeutic approach?

Exon skipping

What is Y-linked inheritance characterized by?

Exclusive male-to-male transmission.

A condition where a gene on an autosomal chromosome primarily manifests in one sex (e.g., hereditary cancer syndromes like BRCA1/BRCA2 in females) is described as

Sex-limited

What is male pattern baldness an example of?

Sex-influenced trait

Which tissue is most likely affected by mitochondrial disorders?

Skeletal muscle

How is mitochondrial DNA inherited?

Exclusively from the mother.

What is the risk of a male with a mitochondrial disorder passing the condition to his children?

0% for all children.

The term heteroplasmy in mitochondrial disorders refers to

The presence of both mutated and non-mutated mitochondrial DNA within the same cell.

For a female with homoplasmy in a mitochondrial disorder, the recurrence risk for her children is

100%

If a female has heteroplasmy for a mitochondrial mutation, her recurrence risk for her children is typically described as

Up to 100% (variable).

Genomic imprinting primarily involves the regulation of gene expression through

epigenetic factors like methylation based on parental origin

Where is methylation often found in a gene to inhibit its expression?

Promoter regions

How many of the 22,000 human genes are affected by genomic imprinting?

About 200 genes

If a disorder results from the absence of functional genes that are normally provided by the paternal chromosome, this is an example of a problem with:

Genomic imprinting

A key feature of trinucleotide repeat expansion disorders is that the repeat sequence can increase in size over successive generations. This is known as a:

Dynamic mutation

What does the phenomenon of anticipation in trinucleotide repeat disorders refer to?

Symptoms appearing at an earlier age and worsening in successive generations.

What is a 'premutation' in a trinucleotide repeat disorder?

A repeat size that is of intermediate size, not causing symptoms but unstable for future generations.

What influences the stability of a trinucleotide repeat expansion?

The sex of the transmitting parent.

What does vertical transmission in a pedigree mean?

The condition appears in every generation.

In a pedigree, if a condition appears in every generation, affects males and females equally, and shows male-to-male transmission, the mode of inheritance is most likely:

Autosomal dominant

A pedigree showing primarily affected males, no male-to-male transmission, and an apparent "skipping of generations" (through carrier females) suggests which mode of inheritance?

X-linked recessive inheritance

If a pedigree demonstrates that affected mothers pass a condition to ALL of their children, but affected fathers pass it to NONE of their children, the mode of inheritance is:

Mitochondrial inheritance

What does a double line connecting parents in a pedigree indicate?

Consanguinity (related by blood).

What does a pedigree showing only males affected with transmission exclusively from father to son indicate?

Y-linked inheritance

In a pedigree, if an affected mother has unaffected children, this immediately rules out which mode of inheritance?

Mitochondrial inheritance

A key epigenetic factor that can turn genes on or off without altering the DNA sequence.

methylation

What concept is fundamental to understanding genomic imprinting and X-inactivation?

Dosage of genetic information.

What is the primary goal of genetic counselors using Punnett squares or pedigrees?

To provide non-directive information to inform parents.

A condition where a single gene not working correctly can affect many body systems (e.g., due to its role in multiple copper-dependent enzymes) illustrates the concept that

Genes often interact and have systemic effects.

What is the fundamental difference between nuclear-encoded mitochondrial genes and mitochondrial DNA-encoded genes?

One is inherited maternally (Mitochondrial DNA-encoded), the other is autosomal/sex-linked (Nuclear-encoded)

What is the term 'dynamic mutation' most commonly associated with?

trinucleotide repeat expansions.