Human genetics

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Questions and Answers

What is the inheritance pattern of Treacher Collins Syndrome (TCS) when it is autosomal dominant?

The likelihood of inheritance in children is 50%. (correct)

The syndrome cannot be inherited.

The likelihood of inheritance in children is 75%.

The likelihood of inheritance in children is 25%.

Which of the following craniofacial characteristics is NOT associated with Treacher Collins Syndrome?

Macrognathia (correct)

Coloboma of the lower eyelid

Down slanting palpebral fissures

Malar hypoplasia

What dental anomaly is most frequently observed in individuals with Treacher Collins Syndrome?

Hyperdontia

Periodontal disease

Congenitally missing teeth (correct)

Cleft palate

How does Down Syndrome primarily arise?

Trisomy for chromosome 21 Signup and view all the answers

What is a common dental feature associated with Down Syndrome?

Crowded teeth due to arch discrepancies Signup and view all the answers

What is a common clinical management challenge faced by pediatric patients with Down syndrome?

Increased risk of infections Signup and view all the answers

Which statement correctly describes the prevalence of Treacher Collins Syndrome?

It has a prevalence of 1:10,000 to 1:50,000. Signup and view all the answers

Which syndrome is known to co-occur with Treacher Collins syndrome?

Down syndrome Signup and view all the answers

Which feature is typically NOT a consequence of Treacher Collins Syndrome in terms of dental occlusion?

Mesial drift of molars Signup and view all the answers

What differentiates the dental formation in the maxilla compared to the mandible in patients with Treacher Collins Syndrome?

Maxillary teeth form earlier than mandibular teeth. Signup and view all the answers

What craniofacial feature is commonly observed in individuals with Down syndrome?

Flat facial profile Signup and view all the answers

Which of the following inheritance patterns does Treacher Collins syndrome primarily follow?

Autosomal dominant inheritance Signup and view all the answers

What is a general challenge in the dental treatment of patients with Treacher Collins syndrome?

Limited mouth opening Signup and view all the answers

In managing oral health in pediatric patients with both Down syndrome and Treacher Collins syndrome, which factor is most crucial?

Addressing behavioral management issues Signup and view all the answers

What craniofacial characteristic might you expect in a patient with Treacher Collins syndrome?

Underdeveloped jaw Signup and view all the answers

Which of the following parameters is commonly monitored in managing pediatric patients with compromised oral health under general anesthesia?

Blood chemistry parameters Signup and view all the answers

What type of inheritance pattern is evident in the case of Treacher-Collins syndrome as described?

Autosomal dominant Signup and view all the answers

Which of the following craniofacial characteristics is specifically associated with Treacher-Collins syndrome?

Reduced cranial base Signup and view all the answers

What was a significant clinical management challenge faced in the case?

Managing the patient’s difficult behavior Signup and view all the answers

What common misconception might arise regarding the co-occurrence of Treacher-Collins syndrome and Down syndrome?

The co-occurrence is equally likely across all families. Signup and view all the answers

In cases considered isolated, what was noted about the occurrence of Treacher-Collins syndrome?

It can appear in the absence of family history. Signup and view all the answers

Which characteristic was identified as more indicative of Treacher-Collins syndrome compared to Down syndrome in the patient?

Craniofacial anomalies Signup and view all the answers

Why was general anesthesia deemed necessary in this patient's treatment?

Because of the child's difficult behavior Signup and view all the answers

What craniofacial characteristics were found to be reduced in individuals with Down syndrome compared to healthy individuals?

Posterior and anterior facial heights Signup and view all the answers

What is the main function of mRNA in protein synthesis?

To carry genetic instructions from the nucleus to the cytoplasm Signup and view all the answers

What are codons in the context of translation?

Triplets of nucleotides on the mRNA Signup and view all the answers

How does selective gene expression occur in different cell types?

Regulatory substances control which genes are 'switched on' or 'off' Signup and view all the answers

What is a characteristic of mitosis?

Results in two identical diploid daughter cells Signup and view all the answers

What is the primary role of meiosis in organisms?

To produce haploid gametes for reproduction Signup and view all the answers

What defines a homozygous individual?

An individual with two identical forms of a gene Signup and view all the answers

What does co-dominance imply in genetics?

Both alleles are expressed equally in the phenotype Signup and view all the answers

What is the significance of DNA replication in cell division?

It ensures genetic information is passed on to daughter cells Signup and view all the answers

What is the primary effect of cumulative exposure to potential mutagens on cellular DNA?

It leads to mutations due to impaired DNA repair. Signup and view all the answers

How does the genetic basis of cancer primarily manifest?

Via mutation of cellular DNA. Signup and view all the answers

Which of the following conditions results from chromosomal abnormalities?

Down's syndrome Signup and view all the answers

What occurs during cell senescence in relation to cell division?

Cells are unable to divide after about 50 to 60 divisions. Signup and view all the answers

What is the consequence of a faulty gene responsible for producing phenylalanine hydroxylase?

Accumulation of phenylalanine leading to potential brain damage. Signup and view all the answers

What distinguishes homologous chromosomes from other chromosomes?

They come in pairs from both parents. Signup and view all the answers

Which of the following correctly describes a lethal mutation?

It disrupts an essential cellular function leading to cell death. Signup and view all the answers

What is the primary role of DNA in an organism?

To store genetic information and transmit it across generations. Signup and view all the answers

Which of the following statements about genes is accurate?

Genes are responsible for transmitting hereditary information. Signup and view all the answers

What characteristic is true of diploid cells?

They have two complete sets of chromosomes. Signup and view all the answers

What is a common outcome of non-lethal mutations?

They can alter the function of the cell, such as leading to tumor development. Signup and view all the answers

Which structure contains the genetic material of a cell that is important for its division?

Chromatin. Signup and view all the answers

What is a karyotype?

The complete set of chromosomes in a cell. Signup and view all the answers

Study Notes

Treacher Collins Syndrome

A hereditary disorder characterized by craniofacial anomalies like external ear abnormalities, down slanting palpebral fissures, malar hypoplasia, coloboma of the lateral portion of the lower eyelid, and micrognathia.
Prevalence is approximately 1:10,000–1:50,000 people.
Can be inherited in an autosomal dominant or autosomal recessive manner.
If inheritance is autosomal dominant, the likelihood of a child inheriting the condition when either parent has the syndrome is 50%.
In addition to facial deformities, often causes oral and dental anomalies, such as cleft palate, missing or hypoplastic teeth.
Malocclusion is related to a high incidence of tooth/arch discrepancies, resulting in crowded teeth; transverse maxillary hypoplasia and cross bites; anterior open bite; and Class II molar relationship with mandibular retrognathism.

Down Syndrome

One of the most common genetic abnormalities in the world, with a prevalence of 1:600–1:800 live births.
The prevalence increases with maternal age.
It is caused by trisomy for chromosome 21.
Has a highly variable prognosis and associated features.
May compromise a person's physical and intellectual abilities.

Co-Occurence

Treacher Collins and Down syndrome can co-occur in individuals.
The case report discussed a patient who exhibited characteristics of both disorders.
The patient’s craniofacial characteristics were more indicative of Treacher Collins syndrome than Down syndrome.
In this case, the use of general anesthesia (GA) was necessary due to the child’s difficult behavior.

Protein Synthesis

mRNA carries genetic instructions from the nucleus to the cytoplasm.
Transcription is the process of DNA to mRNA synthesis.
Translation is the synthesis of protein using information carried on mRNA.

Gene Expression

Cells only use genes related to their function, controlled by regulatory substances.

Cell Division

Mitosis produces two identical daughter cells for growth and repair.
Meiosis produces haploid daughter cells with half the chromosome number.

DNA Replication

DNA is the only molecule capable of self-replication.
Mistakes during replication can lead to tumor development.

The Genetic Basis of Inheritance

Autosomal inheritance involves genes for the same traits on homologous chromosomes.
Homozygous individuals have two identical alleles for a gene.
Heterozygous individuals have one dominant and one recessive allele.
Punnett squares show all possible combinations of genes.
Co-dominance involves multiple alleles, where more than one can be dominant.
Sex-linked inheritance occurs on the X and Y chromosomes.

Chromosomes, Genes, and DNA

Chromatin is the diffuse genetic material in the nucleus, becoming visible as chromosomes during division.
Humans have 23 pairs of chromosomes, one from each parent.
Diploid cells have 23 pairs, while haploid gametes have 23 chromosomes.
Homologous chromosomes are pairs with the same genetic material.
Autosomes are the first 22 pairs, while sex chromosomes (pair 23) determine gender.
A karyotype is the complete set of chromosomes from a cell.
Genes are DNA sequences that code for proteins.
DNA is a double-stranded molecule with bases forming rungs of a ladder.
Mitochondrial DNA is present in each cell and passed through the ovum.

Mutation

A heritable change in a cell's genetic makeup.
Lethal mutations disrupt essential cellular function, resulting in cell death.
Non-lethal mutations alter cell function, potentially leading to tumor development.

Ageing and Genetics

Cumulative exposure to mutagens leads to impaired DNA repair and mutations.
Cell senescence is progressive impairment of cell function.

Genetic Basis of Disease

Cancer is caused by mutations in cellular DNA.
Inherited diseases are passed through faulty genes.
Chromosomal abnormalities are often caused by abnormal gametes.
Down's syndrome results from three copies of chromosome 21.
Cri-du-chat syndrome involves a missing portion of chromosome 5.
Abnormalities of sex chromosomes occur when they fail to separate properly.

Review and Revise

Phenylketonuria is caused by a faulty gene for the enzyme phenylalanine hydroxylase, leading to brain damage.
Mitochondrial abnormalities can cause inherited disorders.

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Description

Explore the genetic conditions of Treacher Collins Syndrome and Down Syndrome in this quiz. Learn about their characteristics, prevalence, inheritance patterns, and associated oral anomalies. Test your knowledge on these important genetic disorders and their implications.