Biology: Genotype, Phenotype, and Inheritance

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Questions and Answers

What is the primary function of the resolvase enzyme in recombination?

To synthesize new DNA strands

To exchange genetic material between non-homologous chromosome pairs

To cleave homologous chromosomes at Holiday Junctions (correct)

To replicate DNA during meiosis

What is the unit of measurement used to express the relative distance between two loci during recombination?

Megabase pair (Mbps)

Kilobase pair (kb)

Centimorgan (cM) (correct)

Micrometer (μm)

What is a key characteristic of autosomal dominant inheritance?

Only affected females can transmit the trait

The trait is only expressed in males

Skipped generations are common

Each affected individual has at least one affected parent (correct)

What is the term for the exchange of genetic material between homologous chromosome pairs?

Recombination Signup and view all the answers

What is the formula to calculate recombination frequency?

Number of recombinants / total number of meiosis Signup and view all the answers

What is Mendelian inheritance?

A set of primary rules relating to the transmission of hereditary characteristics Signup and view all the answers

What is the result of recombination?

Shuffling of genetic material Signup and view all the answers

What is the purpose of genetic pedigrees?

To study the inheritance patterns of traits Signup and view all the answers

What is the main cause of Marfan Syndrome?

Mutation in the FBN1 gene Signup and view all the answers

What is a characteristic of Autosomal Recessive Inheritance?

Both copies of the gene have to be mutated for expression of the abnormal phenotype Signup and view all the answers

What increases the risk of recessive disease?

Both parents coming from a high-risk population Signup and view all the answers

What is a characteristic of X-Linked Recessive Inheritance?

One mutant copy of the gene on the X-chromosome is sufficient to manifest the phenotype in males Signup and view all the answers

What is a characteristic of X-Linked Dominant Inheritance?

Either sex can be affected, but usually at least one parent is affected Signup and view all the answers

What is a characteristic of Y-Linked Inheritance?

All sons of an affected father are affected Signup and view all the answers

What is the term for when a dominant allele does not completely mask the effects of a recessive allele?

Incomplete dominance Signup and view all the answers

What is the term for when some mutation carriers may not show disorder features?

Incomplete penetrance Signup and view all the answers

What is the term for the phenomenon where people with the same genotype exhibit different symptom severities?

Variable Expression Signup and view all the answers

In mitochondrial inheritance, why do only offspring of a female with a mitochondrial trait inherit the trait?

Because the mitochondrial DNA is only inherited from the mother Signup and view all the answers

What is the definition of heteroplasmy?

A mixture of normal and abnormal mitochondria within each cell Signup and view all the answers

What is the purpose of mitochondrial DNA replacement therapy?

To prevent the passing of mitochondrial diseases from mother to child Signup and view all the answers

What is a characteristic of mitochondrial inheritance?

Only one allele is present in each individual Signup and view all the answers

What is the term for the phenomenon where symptoms of a genetic disorder appear at a younger age in each new generation, often with increased severity?

Anticipation Signup and view all the answers

What is the outcome of mitochondrial DNA replacement therapy?

The child has functioning mitochondria Signup and view all the answers

What is the term for the phenomenon where mitochondria within a cell are all the same, either all normal or all mutant?

Homoplasmy Signup and view all the answers

Study Notes

Mendelian Inheritance and Mitochondrial Genetics

Mendelian inheritance is a set of primary rules relating to the transmission of hereditary characteristics from parent organisms to the offspring.

Recombination

Recombination is the exchange of genetic material between homologous chromosome pairs, strands, or cross-over.
Segments of DNA exchanged result in shuffling of genetic material.
Resolvase enzyme function: cleaves homologous chromosomes at Holiday Junctions to separate DNA strands.

Calculating Recombination Frequency

Recombination frequency is calculated as: number of recombinants / total number of meiosis.
1 cM (centiMorgan) is approximately equal to 1Mb (megabase).

Autosomal Dominant Inheritance

Characteristics of Autosomal dominant inheritance (AD):
- Each affected individual has at least one affected parent.
- No skipping of generations.
- Transmitted by either sex equally.
- Examples: Huntington's disease, Marfan syndrome.
Marfan Syndrome: a connective tissue disorder, caused by mutations in FBN1 gene, characterized by patients being very tall.

Autosomal Recessive Inheritance

Characteristics of Autosomal recessive inheritance (AR):
- Both males and females can be affected.
- If both parents are affected, usually all children are affected as well.
- Affected individuals with normal partners have normal children.
- Both copies of the gene have to be mutated for expression of the abnormal phenotype.
Two factors that increase the risk of recessive disease:
- Both parents come from a high-risk population.
- Consanguinity (partners share an ancestor).

X-Linked Recessive Inheritance

Characteristics of X-Linked Recessive Inheritance:
- Mainly males are affected since one mutant copy of the gene on the X-chromosome is sufficient to manifest the phenotype in males.
- No male-to-male disease transmission.

X-Linked Dominant Inheritance

Characteristics of X-Linked Dominant Inheritance:
- Either sex can be affected.
- Usually at least one parent is affected.
- For an affected male, all of his daughters, but none of his sons are affected.

Y-Linked Inheritance

Characteristics of Y-Linked Inheritance:
- Only males are affected.
- All sons of an affected father are affected.

Incomplete Dominance and Non-Penetrance

Incomplete Dominance: dominant allele does not completely mask the effects of a recessive allele, causing a mix.
Incomplete/Non-Penetrance: some mutation carriers may not show disorder features.
Variable Expression: people with the same genotype can exhibit different symptom severities.
Anticipation: symptoms of a genetic disorder appear at a younger age in each new generation, often with increased severity.

Mitochondrial Inheritance

Mitochondrial inheritance is only inherited from the mother because only the head of the sperm is involved in the fusion with the oocyte.
If a female has a mitochondrial trait, all her offspring inherit it.
If a male has a mitochondrial trait, no offspring inherit it.
Only 1 allele is present in each individual, so dominance is not an issue.

Heteroplasmy and Homoplasmy

Heteroplasmy: a mixture of normal and abnormal mitochondria within each cell.
Homoplasmy: mitochondria within a cell are the same, all normal or all mutant.

Mitochondrial DNA Replacement Therapy

A method to prevent the passing of mitochondrial diseases from a mother to her child.
It involves replacing faulty mitochondrial DNA in the mother's egg with healthy mitochondrial DNA from a donor.
This way, the child inherits genetic material from three individuals, ensuring the child has functioning mitochondria.

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Description

This quiz covers the basics of Mendelian inheritance, genetic terminology, and the principles of recombination. It's a great resource for students of biology and genetics.