Genetics Overview and Inheritance Patterns

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Questions and Answers

Which components make up nucleotides in DNA?

Fatty acids, nitrogenous base, and glycerol

Sugar, phosphate, and nitrogenous base (correct)

Carbohydrates, water, and amino acids

Amino acids, phosphate, and ribose

What is the consequence of mitochondrial DNA mutations?

Inherited differently than genes on chromosomes (correct)

Transmitted from parent to child

Inherited like chromosomes

Not related to hereditary diseases

What is TRUE regarding gene therapy?

Involves replacing a whole chromosome

Inserts a normal gene into a defective cell (correct)

Only treats environmental mutations

Does not involve recombinant DNA technology

Which of the following best describes Trisomy 21?

Results from non-disjunction during meiosis Signup and view all the answers

What accounts for many early abortions in relation to genetics?

Chromosomal disorders related to abnormalities Signup and view all the answers

Which one of the following is NOT a characteristic of Down's Syndrome?

All individuals have fatal congenital heart defects Signup and view all the answers

What are the patterns of inheritance observed in the context of genetics?

Homozygous, dominant, recessive, and heterozygous Signup and view all the answers

What percentage of Down's Syndrome patients develop Alzheimer's by age 50?

50% Signup and view all the answers

What type of disorders are predominantly transmitted from an affected parent to offspring regardless of gender?

Autosomal dominant disorders Signup and view all the answers

Which diagnostic method is used for confirming Marfan syndrome?

Skin biopsy for fibrillin Signup and view all the answers

Which of the following is a common feature of multiple neurofibromatosis type 1?

Café-au-lait spots Signup and view all the answers

What is the primary cause of Tay-Sachs disease?

Deficiency of hexosaminidase A Signup and view all the answers

What is a typical consequence if Phenylketonuria (PKU) is left untreated?

Severe intellectual disability Signup and view all the answers

Which chromosome is associated with the mutation in Marfan syndrome?

Chromosome 15 Signup and view all the answers

What type of therapy is recommended for managing PKU?

Enzyme therapy Signup and view all the answers

What is the inheritance pattern of Tay-Sachs disease?

Autosomal recessive Signup and view all the answers

In autosomal dominant disorders, which statement is true regarding unaffected individuals?

They do not pass on the disorder Signup and view all the answers

Which of the following is a characteristic sign of multiple neurofibromatosis type 2?

Tumors of the acoustic nerve Signup and view all the answers

What is a common manifestation of Fragile X syndrome?

Long face with large mandible Signup and view all the answers

Which of the following disorders involves the deletion of all or part of an X chromosome?

Turner syndrome Signup and view all the answers

What is one of the primary treatments for Turner syndrome?

Estrogen and growth hormones Signup and view all the answers

Which of the following is NOT a usual manifestation of Klinefelter syndrome?

Gonadal streaks Signup and view all the answers

What is one known risk factor for the development of cleft lip and palate?

Maternal diabetes Signup and view all the answers

Which conditions are typically associated with Klinefelter syndrome?

Learning disabilities and behavioral problems Signup and view all the answers

What would be a diagnostic approach for Fragile X syndrome?

Physical examination and genetic testing Signup and view all the answers

Females have a chance of being carriers of which condition?

Fragile X syndrome Signup and view all the answers

What type of genetic inheritance is associated with multifactorial inheritance disorders?

An interaction between environmental and genetic factors Signup and view all the answers

What is the hallmark presentation of Turner syndrome?

Short stature and webbed neck Signup and view all the answers

Study Notes

Chromosomes

Contain genetic information in the form of DNA and RNA
23 pairs of chromosomes, including one pair of sex chromosomes
Composed of a double helix of nucleotides, each with 3 components: sugar, phosphate, and nitrogenous base
DNA contains four bases: adenine (A), guanine (G), cytosine (C), and thymine (T).
RNA contains four bases: adenine (A), guanine (G), cytosine (C), and uracil (U).
A codon is a three-base pair code for protein synthesis.

Patterns of Inheritance

Homozygous: Having two identical alleles for a trait
Heterozygous: Having two different alleles for a trait
Dominant: An allele that masks the expression of another allele
Recessive: An allele that is only expressed when two copies are present
Genotype: The genetic makeup of an individual
Phenotype: The observable characteristics of an individual

Mitochondrial Genes and Inheritance

Mitochondria contain small amounts of DNA, which are inherited differently than genes on chromosomes.
Mitochondrial genes are not transmitted from parents to children like chromosomes.
Hereditary diseases resulting from mitochondrial DNA mutations are inherited differently from genetic mutations carried on chromosomes.

Gene Therapy

An extension of recombinant DNA technology.
A normal gene is inserted into a defective cell lacking the enzyme or structural protein to compensate for the missing or dysfunctional gene.

CRISPR

Stands for Clustered Regularly Interspaced Short Palindromic Repeats
A powerful gene editing tool.

Genetic and Congenital Disorders

Caused by mutations, which can be multifactorial, or involve transcription mistakes in mRNA.
Over 6000 single gene defects are recognized.
Characterized by patterns of transmission.

Chromosomal Disorders

Can involve abnormality in chromosome number and/or structure, often occurring during meiosis.
Account for most early abortions.
Over 60 syndromes documented.

Trisomy 21 (Down's Syndrome)

Risk increases with maternal age.
Caused by nondisjunction during meiosis.
Common manifestations include small square head, upward slant of eyes, small low-set ears, a fat pad on the back of the neck, open mouth with protruding tongue, simian crease, varying degrees of mental retardation, and behavioral issues.
Also associated with congenital heart defects, ocular issues, leukemia, respiratory complications, gastrointestinal complications, and hypothyroidism.
Diagnosis can be made through parental screening including amniocentesis, hormone levels, and 4D ultrasound.
Treatment is symptomatic and supportive.

Autosomal Dominant Disorders

Transmitted from an affected parent to offspring, regardless of gender.
50% chance of transmission.
Unaffected individuals do not pass on the disorder.
Delayed onset is possible.
Examples include Marfan syndrome, multiple neurofibromatosis, and achondroplasia.

Marfan Syndrome

Disorder of connective tissue.
Mutation on chromosome 15 (FBN1).
Affects the eyes, skeleton, and cardiovascular system.
Diagnosis combines history taking, physical examination, skin biopsy (presence of fibrillin), and genetic testing.
Treatment involves surgical intervention for cardiac complications and glasses/surgical intervention for vision correction.

Multiple Neurofibromatosis

Characterized by neurogenic tumors.
Two forms:
- Type 1: Defect on chromosome 17 (NF1); includes subcutaneous lesions, café-au-lait spots (at least 6 at birth), freckles, scoliosis, erosive bone defects, and nervous system tumors.
- Type 2: Defect on chromosome 22 (NF2); includes tumors of the acoustic nerve.
Treatment involves palliative removal of tumors.

Autosomal Recessive Disorders

Rare.
Both members of the gene pair are affected.
Affects both genders.
Usually caused by a deficient enzyme.
Examples include PKU and Tay-Sachs.

PKU (Phenylketonuria)

Mutation on chromosome 12 (PAH gene).
Error in converting phenylalanine to tyrosine.
Appears normal at birth but fails to meet milestones later.
Progressive neurological decline if untreated.
Can lead to severe intellectual disability.
Diagnosis involves serum phenylalanine levels at 3 days old.
Treatment includes avoiding high protein foods, pharmacologic interventions, and enzyme therapy.

Tay-Sachs

Progressive disorder due to mutation of hexosaminidase A, an enzyme necessary to metabolize certain lipids.
Accumulation of lipids destroys and demyelinates nerve cells.
Nerve cell destruction leads to a progressive mental and motor deterioration.
Most affected individuals are of Jewish descent.
Appears normal at birth but then the infant begins to miss developmental milestones.
Progresses to seizures, muscular rigidity, and blindness.
Usually fatal by 3-4 years of age.
Diagnosis involves a combination of history taking, physical examination, and low serum and amniotic hexosaminidase A levels.
There is no cure, but genetic counseling is suggested.

Sex-Linked Disorders

Almost always X-linked.
Males have a 50% chance of getting the disorder from their mother.
Females have a 50% chance of being carriers.
All daughters of affected males will be carriers, but none of their sons.
Examples include Fragile X syndrome, Turner syndrome, and Klinefelter syndrome.

Fragile X Syndrome

Associated with a trinucleotide gene (FMR1) sequence on the X chromosome, which is repeated more than 200 times.
Plays a role in synapse development.
Manifestations include a long face with a large mandible, large ears, large testicles, mental retardation, learning disabilities, speech delays, connective tissue disorders, behavioral issues, and autism spectrum disorder.
Diagnosis involves a combination of history taking, physical examination, and genetic testing.
Treatment is supportive.

Monosomy X (Turner's Syndrome)

Deletion of all or part of an X chromosome, occurring spontaneously.
Specific gene(s) associated are unknown.
No Y chromosome, so only females are affected.
Manifestations include gonadal streaks instead of ovaries, short stature, neck webbing, small lower jaw, drooping eyelids, small fingernails, and widely spaced nipples.
Also associated with coarctation of the aorta, vision issues, hearing loss, renal and skeletal abnormalities, infertility, and increased risk for infections.
No mental retardation is present.
Diagnosis relies on history taking, physical examination, chromosomal testing, and serum hormone levels.
Treatment includes estrogen and growth hormones.

Trisomy X (Klinefelter's Syndrome)

One or more extra X chromosomes with the presence of the Y chromosome, leading to a male appearance.
Often undetected.
Manifestations include gynecomastia, small testes and penis, tall stature, increased weight, and sparse body hair.
Also associated with learning disabilities, behavioral problems, sexual dysfunction, pulmonary disease, varicose veins, osteoporosis, and breast cancer.
Treatment involves testosterone therapy.

Multifactorial Inheritance Disorders

Result from interaction between environmental and genetic factors.
Less predictable.
Extremely common.
May be expressed at birth or later.
Examples include cleft lip/palate, clubfoot, congenital dislocation of hips, congenital heart defects, pyloric stenosis, urinary tract malformations, diabetes mellitus, hypertension, cancer, and psychiatric disorders.

Cleft Lip and Palate

Improper formation of soft tissues of the mouth and lips.
Unilateral or bilateral deformities leading to feeding and nutritional issues.
Maternal smoking, diabetes, and seizure medication use (first trimester) are important risk factors.
Diagnosis can be made through prenatal ultrasound.
Treatment includes surgery and speech therapy.

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Description

This quiz covers the essential concepts of chromosomes, patterns of inheritance, and mitochondrial genes. Learn about genetic information, allele types, and how traits are passed down through generations. Test your understanding of DNA, RNA, and key genetic terms.