Genetic Disorders and DNA Structure Quiz
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Questions and Answers

What are genetic disorders and how do they arise?

Genetic disorders are illnesses caused by abnormalities in the genome, arising from heritable mutations or new defects in DNA.

How does DNA relate to chromosomes?

DNA is packaged into chromosomes, which are structures composed of DNA and associated proteins.

What percentage of the human genome is made up of genes?

Genes form only about 1.5% of the human genome.

What role do exons and introns play in gene structure?

<p>Exons contain the coding information for proteins, while introns are non-coding sequences that are typically removed during mRNA processing.</p> Signup and view all the answers

Define genotype and phenotype.

<p>Genotype refers to the alleles present in an individual, while phenotype is the visible or clinically apparent expression of those alleles.</p> Signup and view all the answers

What does genetic heterogeneity mean?

<p>Genetic heterogeneity refers to a common phenotype that can arise from different genotypes.</p> Signup and view all the answers

What constitutes a mutation in genetic terms?

<p>A mutation is an alteration in the DNA sequence that deviates from the normal genetic code.</p> Signup and view all the answers

How does one type of cancer illustrate the complexity of genetic disorders?

<p>Certain cancers can arise from inherited genetic conditions, new mutations, or non-genetic causes.</p> Signup and view all the answers

What is a proto-oncogene and how can it become an oncogene?

<p>A proto-oncogene is a normal gene that regulates cell growth and can become an oncogene due to mutations.</p> Signup and view all the answers

List at least two examples of proto-oncogenes.

<p>Examples of proto-oncogenes include RAS and MYC.</p> Signup and view all the answers

What are the two mechanisms by which proto-oncogenes can convert into oncogenes?

<p>The two mechanisms are quantitative, involving an increase in protein products, and qualitative, involving changes in nucleotide sequences.</p> Signup and view all the answers

Explain the difference between a missense mutation and a nonsense mutation.

<p>A missense mutation results in a change of a single amino acid, while a nonsense mutation changes a codon to a stop codon.</p> Signup and view all the answers

How do recessive mutations in enzyme coding genes typically manifest?

<p>They appear as recessive traits because one normal copy of the gene can produce enough enzyme for normal function.</p> Signup and view all the answers

What type of mutation involves the gain of a single base pair?

<p>An insertion mutation involves the gain of a single base pair.</p> Signup and view all the answers

Describe the structure and composition of human chromosomes.

<p>Human chromosomes are composed of DNA packaged with proteins and consist of 23 pairs, including 22 autosomes and one pair of sex chromosomes.</p> Signup and view all the answers

What does haploid mean in the context of human cells?

<p>Haploid refers to a cell that contains a single set of chromosomes, which is the case for human gametes.</p> Signup and view all the answers

What type of mutation leads to the substitution of valine for glutamic acid in the beta globin chain?

<p>A missense mutation.</p> Signup and view all the answers

Explain the term 'dominant negative' effect in the context of autosomal dominant mutations.

<p>A 'dominant negative' effect occurs when a mutated gene product interferes with the normal protein's function, disrupting complex protein structures.</p> Signup and view all the answers

What are some factors that influence the development of non-insulin dependent diabetes mellitus?

<p>Family history, dietary influence, smoking, and obesity are key factors.</p> Signup and view all the answers

What significant discovery did James Watson and Francis Crick make in 1953?

<p>They deduced the double helical structure of DNA.</p> Signup and view all the answers

What gene mutation is associated with Marfan syndrome?

<p>A mutation in the fibrillin gene.</p> Signup and view all the answers

Describe the phenotypic effects seen in individuals with Marfan syndrome.

<p>Affected individuals are typically tall with long fingers, loose joints, and may have ocular issues and a risk of aortic rupture.</p> Signup and view all the answers

What are restriction enzymes used for in molecular biology?

<p>Restriction enzymes are used to cut DNA into reproducible pieces for gene cloning.</p> Signup and view all the answers

What did Phillip Sharp and Richard Roberts demonstrate about pre-mRNA?

<p>They demonstrated that pre-mRNA is processed by excising introns and splicing together exons.</p> Signup and view all the answers

How does X-inactivation affect the expression of X-linked recessive conditions in females?

<p>X-inactivation can lead to some genes being non-functional while others remain active, often causing females to be carriers without showing symptoms.</p> Signup and view all the answers

What role does factor VIII play in hemophilia A, and how does it impact disease severity?

<p>Factor VIII is a blood clotting protein, and its activity levels determine the severity of hemophilia A, varying from mild to severe.</p> Signup and view all the answers

What was announced in 1986 that significantly advanced genomic research?

<p>The Human Genome Initiative was announced.</p> Signup and view all the answers

When was the first draft of the human genome sequence published?

<p>The first draft was published in 2001.</p> Signup and view all the answers

What does reduced penetrance imply in genetic inheritance?

<p>Reduced penetrance means the gene is present but does not always manifest as a phenotype in the parent, potentially skipping generations.</p> Signup and view all the answers

Define multifactorial inheritance in genetics.

<p>Multifactorial inheritance refers to traits that result from the interaction of multiple genes and environmental factors.</p> Signup and view all the answers

What was completed in April 2003 as part of genomic research?

<p>The Human Genome Project was completed.</p> Signup and view all the answers

Who developed the automated sequencing mechanism in 1986?

<p>Leroy Hood developed the automated sequencing mechanism.</p> Signup and view all the answers

What are the main types of chromosomal disorders, and how do they differ?

<p>The main types of chromosomal disorders are numerical and structural disorders. Numerical disorders involve changes in the number of chromosomes, while structural disorders involve changes in the structure of chromosomes.</p> Signup and view all the answers

Define Down syndrome and explain its chromosomal basis.

<p>Down syndrome, or trisomy 21, is caused by an extra copy of chromosome 21, resulting in a total of 47 chromosomes. It is characterized by distinctive facial features, short stature, and varying degrees of intellectual disability.</p> Signup and view all the answers

What is the recurrence risk of autosomal recessive conditions, and why?

<p>The standard recurrence risk for autosomal recessive conditions is 25%. This is because both parents must be carriers of the mutated gene for there to be a chance of having an affected child.</p> Signup and view all the answers

What is sickle cell anemia, and how is it related to mutations?

<p>Sickle cell anemia is an autosomal recessive condition caused by a point mutation in the beta globin gene. This mutation leads to the production of an abnormal beta globin chain, causing red blood cells to deform into a sickle shape under low oxygen conditions.</p> Signup and view all the answers

What are some common chromosomal abnormalities associated with syndromes?

<p>Common chromosomal abnormalities include trisomy 13 (Patau syndrome), trisomy 18 (Edwards syndrome), and complex abnormalities like Klinefelter syndrome (47 XXY). Each of these conditions is characterized by specific physical and health-related traits.</p> Signup and view all the answers

What are the characteristic features of Prader-Willi syndrome?

<p>Prader-Willi syndrome is characterized by hyperphagia (compulsive overeating), mild to moderate mental retardation, short stature, small external genitalia, and hypotonia. It results from a deletion at chromosome 15.</p> Signup and view all the answers

How do Mendelian inheritance patterns manifest in chromosomal disorders?

<p>Mendelian inheritance patterns in chromosomal disorders manifest as autosomal recessive, autosomal dominant, or X-linked conditions. Each pattern affects the likelihood of offspring inheriting certain traits or disorders based on parental genotype.</p> Signup and view all the answers

Explain what is meant by aneuploidy and give an example.

<p>Aneuploidy refers to the presence of an abnormal number of chromosomes, such as monosomy or trisomy. An example is Down syndrome, which is the result of trisomy 21, where there is an extra chromosome.</p> Signup and view all the answers

What role do nucleic acid probes play in detecting pathogens like TB?

<p>Nucleic acid probes are used to detect genetic information of a pathogen in a sample, thereby identifying diseases like TB.</p> Signup and view all the answers

How are nucleic acid hybridization assays useful in diagnosing neoplastic conditions such as leukemia?

<p>These assays help detect surface markers that may be absent or present in small amounts, indicating the presence of leukemia.</p> Signup and view all the answers

What is the significance of the Philadelphia chromosome in genetic diseases?

<p>The Philadelphia chromosome indicates the genetic abnormality t(9;22), which can be detected using specific probes for the c-abl-bcr gene rearrangement.</p> Signup and view all the answers

What techniques are included in the realm of pathologists for genetic analysis?

<p>Techniques include IHC, FISH, CISH, PCR, genetic mapping, and DNA typing.</p> Signup and view all the answers

Describe one application of therapeutic cloning in gene therapy.

<p>Therapeutic cloning involves extracting stem cells from embryos to treat various ailments.</p> Signup and view all the answers

What is gene splicing, and how is it utilized in biotechnology?

<p>Gene splicing involves cutting DNA from one organism and inserting a gene, which is useful for recombinant technology to produce insulin and vaccines.</p> Signup and view all the answers

How is DNA analysis applied in forensics, particularly in paternity testing?

<p>DNA analysis, such as paternity testing, compares genetic markers between individuals to determine biological relationships.</p> Signup and view all the answers

What challenges do forensic scientists face when identifying decomposed remains?

<p>Identifying decomposed remains is challenging due to the degradation of DNA and tissue artifacts that may impede accurate matches.</p> Signup and view all the answers

Flashcards

Mutation

A change in the DNA sequence from its usual state.

Gene

A unit of DNA that codes for a specific protein. It is made up of exons and introns.

Genotype

The actual genetic makeup of an individual, represented by the alleles they possess.

Phenotype

The observable characteristics of an individual, resulting from the interaction between their genotype and the environment.

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Locus

The location of a specific gene on a chromosome.

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Genetic Heterogeneity

The presence of multiple different genotypes that can lead to the same phenotype.

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Chromatin

The combination of DNA and associated proteins that make up a chromosome.

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Genetic Disorder

Illness caused by abnormalities in an individual's genome. Some are inherited, while others are caused by new mutations or defects in DNA.

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Proto-oncogene

A normal gene that can become an oncogene due to mutations. They regulate cell growth and differentiation.

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Oncogene

A gene that, when mutated, can contribute to cancer development.

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Quantitative mechanism of oncogene activation

Increases in the quantity or activity of proto-oncogene products can lead to cancer.

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Qualitative mechanism of oncogene activation

Changes in the DNA sequence of a proto-oncogene can make it a cancer-causing oncogene.

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Missense mutation

A change in a single amino acid in a protein.

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Nonsense mutation

A change in a DNA sequence that results in a premature stop codon.

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Frameshift mutation

A change in the DNA sequence that results in abnormal protein production or lack of protein. This can be caused by insertions or deletions.

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Chromosome packaging

The process of packaging DNA with proteins to form chromosomes.

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Down Syndrome

A condition where an individual has an extra copy of chromosome 21.

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Aneuploidy

A condition where an individual has one less or one extra chromosome, caused by a non-disjunction event during meiosis.

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Euploidy

A condition where an individual has a multiple of the haploid number of chromosomes.

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Translocation

A type of chromosomal mutation where a segment of a chromosome is moved to a different position.

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Deletion

A type of chromosomal mutation where a segment of a chromosome is deleted.

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Inversion

A type of chromosomal mutation where a segment of a chromosome is flipped, resulting in a reversed sequence.

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Duplication

A type of chromosomal mutation where a segment of a chromosome is duplicated.

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Autosomal Recessive Disorder

A genetic disorder that is inherited through an autosomal recessive pattern, meaning two copies of the faulty gene are needed to express the disorder.

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Reduced Penetrance

A condition where a gene is present and can be passed down, but doesn't always cause the related phenotype in the parent, leading to seemingly skipped generations in family trees.

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Autosomal Dominant

A pattern of inheritance where a mutation affects a gene that creates a structural protein, causing the protein to have an abnormal shape or function.

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Variable Expression

Describes the variation in the severity of a disease even though the same gene is mutated. It's like turning up or down the volume on a gene's expression.

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Dominant Negative Effect

A condition where one mutated gene interferes with the formation of normal protein structures.

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Gain Of Function Mutation

A change in the DNA sequence that leads to the production of a protein with an abnormal function.

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Hemophilia A

An X-linked recessive condition where mutations in the gene for factor VIII, a protein needed for blood clotting, cause a bleeding disorder.

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X-Linked Recessive

A pattern of inheritance where the faulty gene is found on the X chromosome and females are typically carriers, while males are often affected.

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Multifactorial Inheritance

A pattern of inheritance where traits are influenced by multiple genes and the environment.

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Genetics

The study of genes and heredity, including their structure, function, and inheritance.

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Transcription

The process of copying a DNA sequence into an RNA sequence.

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Restriction Enzyme

A specific type of endonuclease that cuts DNA at a specific sequence.

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Gene Cloning

The process of inserting a gene into a vector (e.g., a bacterial plasmid) which can then be introduced to a host cell.

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RNA Splicing

The process of removing introns and joining exons together to form a mature mRNA molecule.

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DNA Probe

A technique that uses specific sequences of DNA to identify and locate genes or other DNA sequences.

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Nucleic Acid Probe

A short, identifiable sequence of DNA used to search for complementary sequences in a sample. It's like a detective looking for a specific type of DNA using a tiny 'fingerprint' to find matches.

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In Situ Hybridization (ISH)

A technique that uses nucleic acid probes to detect specific DNA or RNA sequences in cells or tissues. It's like using a special light to highlight certain areas in a cell.

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Fluorescence In Situ Hybridization (FISH)

A type of ISH that uses fluorescent probes to detect specific DNA or RNA sequences in cells. It's like using a special light to highlight DNA in a cell.

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Chromogenic In Situ Hybridization (CISH)

A technique that uses probes to detect specific DNA or RNA sequences in a tissue sample. It's like using a special stain to reveal specific DNA sequences in a tissue.

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Polymerase Chain Reaction (PCR)

A technique that allows for the amplification of specific DNA sequences, making them easier to detect. It's like making copies of a specific book chapter to make it easier to read.

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Chromosomal Microarray Analysis

A technique that uses fluorescent probes to detect specific DNA sequences in chromosome spreads. It's like using a special light to find specific parts on a chromosome.

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Gene Therapy

The process of altering the genetic makeup of an organism, including replacing, adding, or removing genes. It's like editing a book to change its story.

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Gene Silencing

A technique used to deactivate or silence the expression of a specific gene. It's like turning off a switch to stop a gene from working.

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Study Notes

Genetic Basis of Disease and Disorders

  • Genetic disorders are illnesses caused by abnormalities in the genome.
  • Some are inherited from parents, while others are caused by new DNA mutations.
  • Heritability depends on whether the mutation affects germ (sex) cells.
  • Diseases like cancer may have inherited or non-genetic causes.

Chromosomes

  • DNA is packaged into chromosomes along with proteins.
  • Chromatin: DNA + associated proteins.
  • Prokaryotes: have a single circular chromosome.
  • Eukaryotes: have a species-specific number of linear chromosomes.
  • Humans: have 23 pairs of chromosomes (22 autosomes and 1 pair of sex chromosomes).
  • Humans have 46 chromosomes (23 pairs).
  • Haploid cells: have one set of chromosomes (gametes).
  • Diploid cells: have two sets of chromosomes (most human cells).

DNA

  • DNA is the "blueprint" for an organism.
  • Composed of nucleotides with four bases (A, C, G, T).
  • DNA is a polymer of nucleotides.
  • DNA is considered digital information.
  • A single strand of DNA is a string of A, C, G, T.
  • Genes form 1.5% of the human genome.
  • ~3.2 billion base pairs in every human cell.
  • Gene: a segment of DNA encoding a protein.

Genes

  • Genes are units of DNA coding for specific proteins.
  • Consist of exons (protein-coding segments) and introns (non-coding segments).
  • Introns are removed from mRNA before it leaves the nucleus.
  • Locus: location of a gene on a chromosome.

Genotype and Phenotype

  • Genotype: the combination of alleles present in an individual.
  • Phenotype: the observable characteristics resulting from the expression of the genotype.
  • Genetic heterogeneity: the same phenotype can arise from several different genotypes.
  • Mutation: alteration from normal.

Proto-oncogenes

  • Proto-oncogenes are normal genes that can become oncogenes (cancer-causing genes) due to mutations.
  • Code for proteins regulating cell growth and differentiation.
  • Often involved in signal transduction.
  • Activation converts proto-oncogene to oncogene.
  • Examples of proto-oncogenes include RAS, WNT, MYC, ERK, and TRK.
  • Proto-oncogenes can be converted to oncogenes through quantitative or qualitative changes.

Mutations

  • Mutations can affect autosomes or sex chromosomes.
  • Effect of mutations depends on the function of the affected region of DNA.
  • Mutation in an enzyme gene: appears as a recessive trait.
  • The effect in the heterozygote, enough enzyme to function.
  • Mutation in a structural protein gene: appears as a dominant trait.

Single Gene Mutations

  • Missense: Change in a single amino acid.
  • Nonsense: Change in a stop codon.
  • Deletion: Loss of a base pair (frameshift).
  • Insertion: Gain of a base pair (frameshift).
  • Duplication: An extra gene (more protein production).
  • Splice site: Abnormalities at the intron-exon boundary.
  • Triple repeats: Increased tandem repeats.

Chromosomal Disorders

  • DNA packaged into chromosomes.
  • Humans have 23 pairs: 22 autosomes, 1 pair of sex chromosomes.
  • Haploid: one set of chromosomes.
  • Diploid: two sets of chromosomes.
  • Numerical disorders: involve variations in the total number of chromosomes (euploid vs aneuploid).
  • Structural disorders: involve changes in the structure of chromosomes.
  • Common disorders: Down syndrome (trisomy 21), Fragile X syndrome.

Patterns of Inheritance

  • Mendelian disorders typically involve whole chromosomes.
  • Autosomal recessive, autosomal dominant, X-linked recessive, X-linked dominant.

Autosomal Recessive

  • Mutation in gene coding for an enzyme, resulting in loss of function.
  • Heterozygotes often have enough gene product to function.
  • Homozygotes typically have too little gene product.
  • Recurrence risk = 25%.
  • Sickle cell anemia: a prominent example.

Autosomal Dominant

  • Mutation involving a structural gene generally results in a dominant negative effect.
  • The product may interfere with the complex protein functions.
  • May lead to abnormal features.
  • Marfan syndrome: an example.

X-linked Recessive

  • Females are typically carriers, owing to X inactivation.
  • Males are more likely to show the phenotype.
  • Hemophilia A: an example.

X-linked Dominant

  • Theoretically, both males and females would be affected.
  • A "double dose" of abnormal gene product can be lethal in utero.

Penetrance and Variable Expression

  • Penetrance: the percentage of individuals with a particular genotype who express the associated phenotype.
  • Reduced penetrance means no phenotype in some who carry the gene.
  • Variable expression: severity of the phenotype is variable.

Multifactorial Inheritance

  • Multiple genes and environmental factors interact to produce a phenotype.
  • Recurrence risk above average, but not precisely calculable.
  • Non-insulin dependent diabetes mellitus: an example.

Major Events in Molecular Biology

  • Key dates and discoveries in the field, including the structure of DNA, discovery of restriction enzymes, and the Human Genome Project.

Clinical Applications

  • Use of genetic information in disease diagnosis, treatment.
  • Identifying pathogens and cancers.
  • DNA testing for various purposes.

Gene Therapy

  • Cloning technologies (reproductive, DNA, therapeutic).
  • Gene splicing and silencing.

Forensics

  • DNA testing in criminal investigations (paternity testing, crime scene evidence).

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Genetic Diseases and Disorders PDF

Description

Test your knowledge on genetic disorders, DNA, and chromosomes with this comprehensive quiz. Explore key concepts including mutations, gene structure, and the roles of proto-oncogenes in cancer. Challenge yourself to understand the complexities of genetics today!

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