Genetics and Karyotype Analysis

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Questions and Answers

What is the main reason for X-chromosome inactivation in females?

  • To prevent the accumulation of harmful mutations on the X-chromosome.
  • To allow for greater genetic diversity in females.
  • To ensure equal gene expression between males and females. (correct)
  • To reduce the energy requirements of the cell by silencing one X-chromosome.

Which of the following is a characteristic of SSRs (Simple Sequence Repeats)?

  • They are less variable than VNTRs.
  • They consist of di, tri, or tetra nucleotides repeated tandemly. (correct)
  • They are found in only a few places in the genome.
  • They are typically larger than 1000 base pairs.

Which type of repeat is described as 'quite large' and found in only a few places in the genome?

  • SSR (Simple Sequence Repeat)
  • VNTR (Variable Number Tandem Repeat)
  • LCR (Low Copy Repeat) (correct)
  • None of the above

What is the relationship between the length of a repeat sequence and its variability?

<p>Shorter repeat sequences are generally more variable. (C)</p> Signup and view all the answers

Which of the following statements accurately describes the process of X-chromosome inactivation?

<p>One X-chromosome is randomly chosen in each cell and completely silenced. (D)</p> Signup and view all the answers

Based on the DNA analysis presented, which individual has the highest probability of being the father?

<p>Jerry (B)</p> Signup and view all the answers

What type of DNA polymorphism is primarily being analyzed in the DNA fingerprint provided?

<p>Single Nucleotide Polymorphism (SNP) (C)</p> Signup and view all the answers

Why are SSR polymorphisms useful for paternity testing?

<p>They are highly variable, allowing for clear distinction between individuals. (D)</p> Signup and view all the answers

What is the correct interpretation of the DNA analysis regarding the father?

<p>Jerry is the most likely father of the child. (D)</p> Signup and view all the answers

What is the significance of the 'polymorphic 14 bp tandem repeat' mentioned in the context of the genetic disorder?

<p>It is linked to a gene potentially involved in the disorder. (C)</p> Signup and view all the answers

Which of the following best describes a 'Copy Number Variant (CNV)'?

<p>A variation in the number of copies of a specific DNA segment. (B)</p> Signup and view all the answers

Which of the following best describes a 'VNTR'?

<p>A tandem repeat of a short DNA sequence. (D)</p> Signup and view all the answers

What is the primary function of LINEs (Long Interspersed Nuclear Elements) in the genome?

<p>To create their own reverse transcriptase for replication. (C)</p> Signup and view all the answers

Which genetic abnormality can be best diagnosed using standard G-banded karyotype analysis?

<p>Trisomy (A)</p> Signup and view all the answers

What is a key feature of a human acrocentric chromosome?

<p>It possesses repetitive rRNA sequences on one end. (B)</p> Signup and view all the answers

Which regulatory element is likely removed by a mutation that deletes the 100 nucleotides before transcription start in β-globin genes?

<p>CAAT &amp; TATA boxes (A)</p> Signup and view all the answers

What is the most descriptive karyotype for a patient with Down syndrome?

<p>47,XX (D)</p> Signup and view all the answers

What is the name of the site where mitotic spindle fibers attach to chromosomes?

<p>Centromere (A)</p> Signup and view all the answers

Which part of the nuclear gene POLG is not transcribed during gene expression?

<p>Introns (B)</p> Signup and view all the answers

What type of mutation was identified in the genetic testing of a 7-year-old boy with distal tubule acidosis?

<p>A pathogenic mutation affecting splicing (C)</p> Signup and view all the answers

Which of the following definitions best matches a frameshift mutation?

<p>An insertion or deletion of nucleotides that alters the reading frame. (A)</p> Signup and view all the answers

What would most likely cause an aberration if the mRNA for a gene is larger than normal?

<p>Mutation of splice donor site of intron 1 (B), Mutation of the splice acceptor site of exon 2 (D)</p> Signup and view all the answers

What best describes a 14 bp tandem repeat located near a gene involved in a genetic disorder?

<p>VNTR (A)</p> Signup and view all the answers

To maintain balanced gene expression between sexes, what happens to one of the X-chromosomes in females?

<p>One X-chromosome is deactivated (A)</p> Signup and view all the answers

What facilitates the export of RNA to the cytoplasm after it is processed in the nucleus?

<p>Nuclear pores (A)</p> Signup and view all the answers

Which genetic abnormality is best established through standard G-banded karyotype analysis?

<p>Trisomy (D)</p> Signup and view all the answers

What is the primary function of the specific amino acid sequence in mitochondrial proteins?

<p>To direct the protein to the mitochondria (D)</p> Signup and view all the answers

Which of the following mutations would have the least impact on mRNA size?

<p>A non-sense mutation within exon 1 (D)</p> Signup and view all the answers

What could be the consequence of a splice site mutation?

<p>Alteration of mRNA size (A)</p> Signup and view all the answers

Which mutation is most likely to cause an increased size of the mRNA transcript?

<p>Mutation of splice donor site of an intron (A)</p> Signup and view all the answers

What effect would a non-sense mutation within an exon likely have on mRNA?

<p>No effect on mRNA length (C)</p> Signup and view all the answers

Which type of mutation is characterized by a change in a single nucleotide that may lead to a premature stop codon?

<p>Non-sense mutation (B)</p> Signup and view all the answers

Which of the following would most likely cause a complete loss of mRNA function?

<p>Frame-shift mutation (C)</p> Signup and view all the answers

When discussing splicing, what does the term 'splice acceptor site' refer to?

<p>Position correlating to the preceding exon (C)</p> Signup and view all the answers

In the context of molecular biology, what term is used to describe the process of directing proteins to their specific cellular locations?

<p>Protein trafficking (C)</p> Signup and view all the answers

Which choice would most likely lead to a smaller mRNA being produced?

<p>Mutation of the splice acceptor site of an exon (A)</p> Signup and view all the answers

What is the minimum size of a chromosomal abnormality detectable by G-band karyotype?

<p>5 – 10 Mb (C)</p> Signup and view all the answers

Which type of mutation typically creates a stop codon by chance?

<p>Frameshift mutation (A)</p> Signup and view all the answers

Which characteristic is true of acrocentric chromosomes?

<p>They have very short p arms and long q arms (C)</p> Signup and view all the answers

What is a dicentric chromosome?

<p>A chromosome with two centromeres (C)</p> Signup and view all the answers

What happens to a chromosome that lacks a centromere?

<p>It is acentric and not stable (A)</p> Signup and view all the answers

How are the repetitive rRNA sequences associated with acrocentric chromosomes?

<p>They are found on the q arm, adjacent to the centromere (B)</p> Signup and view all the answers

What describes the arm lengths of a submetacentric chromosome?

<p>Both arms are of different lengths (C)</p> Signup and view all the answers

Which of the following mutations is detectable by G-band karyotyping?

<p>Trisomy (B)</p> Signup and view all the answers

Flashcards

G-banded karyotype analysis

A prenatal test that helps identify chromosomal abnormalities such as trisomy.

Acrocentric chromosome

A chromosome with the centromere located near one end, creating unequal arm lengths.

β-thalassemia mutation

A genetic condition resulting from mutations in β-globin genes, affecting hemoglobin production.

Down syndrome karyotype

A chromosomal condition characterized by an extra chromosome 21, represented as 47,XX.

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Mitotic spindle fibers attachment

The site where spindle fibers attach to chromosomes during cell division, located at the centromere.

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NON-transcribed gene part

Portions of a gene that are not translated into protein, including introns and promoters.

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Pathogenic mutation

A genetic change that has been proved or predicted to adversely affect an organism's function.

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Splicing mutation prediction

A genetic change affecting the proper splicing of RNA, potentially leading to dysfunctional proteins.

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G-band karyotype

A laboratory technique that stains chromosomes to reveal banding patterns for identification of abnormalities.

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Chromosomal deletion

The loss of a segment of DNA from a chromosome, affecting the banding pattern if over 5 Mb.

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Trisomy

A genetic condition where an individual has three copies of a chromosome instead of two.

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Substitution mutation

A type of mutation involving the replacement of one base pair with another.

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Frameshift mutation

A mutation resulting from the insertion or deletion of bases, changing the reading frame.

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Gene duplication

A mutation that results in a gene being copied, potentially visible on a karyotype in some cases.

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Metacentric chromosome

A chromosome with the centromere located in the middle, leading to arms of equal length.

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Gene expression

The process by which genes are turned on to produce RNA and proteins.

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Protein trafficking

The process of directing proteins to their specific cellular locations, like mitochondria.

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Mitochondrial zip code

A specific amino acid sequence in proteins that targets them to mitochondria.

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Aberrant mRNA

mRNA that has an abnormal size or sequence due to mutation or splicing errors.

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Splice donor site

The sequence at the start of an intron that signals where splicing begins.

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Splice acceptor site

The sequence at the end of an intron that indicates where splicing ends.

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RNA editing

The process of modifying RNA molecules after they are transcribed, altering their function.

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Aberration in mRNA

An abnormal size of mRNA transcript due to genetic mutations.

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Splice donor site mutation

A change at the beginning of an intron that affects mRNA splicing.

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DNA fingerprinting

A method used to analyze an individual's DNA characteristics.

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Paternity analysis

Studying DNA to determine the potential father of a child.

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Tandem repeat sequence

A short DNA sequence repeated multiple times in a row.

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X-chromosome inactivation

Process where one X-chromosome in females is turned off.

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Simple Sequence Repeat (SSR)

Highly polymorphic sequences of di, tri or tetra nucleotides repeated in tandem.

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Variable Number Tandem Repeat (VNTR)

Tandem repeats larger than SSR, consisting of repeat sequences up to several hundreds of nucleotides.

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Low Copy Repeat (LCR)

Large, highly similar repetitive sequences found in few places in the genome.

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Gene Dosage Compensation

Mechanism ensuring equal gene expression levels from X-chromosomes in males and females.

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DNA Fingerprint

A pattern of DNA bands that can identify individuals based on their unique genetic makeup.

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SSR Polymorphisms

Short Sequence Repeats that are inherited and can be tracked through co-dominance.

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Paternity Probability

The likelihood that an individual is the biological father based on DNA markers.

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Polymorphic Loci

Locations on DNA that contain variations, allowing for analysis of genetic diversity.

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SNP

Single Nucleotide Polymorphism, a common variation at a single nucleotide position in DNA.

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CNV

Copy Number Variant, indicating variations in the number of copies of a particular gene.

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VNTR

Variable Number Tandem Repeats, sequences in DNA where a short nucleotide motif is repeated multiple times.

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Interspersed Nuclear Elements

DNA sequences (LINE and SINE) that are repeated and scattered throughout the genome.

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Study Notes

Question 1

  • A pregnant 39-year-old woman is offered standard G-banded karyotype analysis.
  • This analysis is most helpful for diagnosing trisomy.
  • A 500,000 bp deletion is not visible on a G-band karyotype.
  • Gene substitutions and frameshift mutations are not easily diagnosed through G-banded karyotypes.
  • Gene duplications may or may not be visible.

Question 2

  • An acrocentric chromosome has a centromere located near one end.
  • Repetitive rRNA sequences are found on one end.
  • The long and short arms are of different lengths.
  • A chromosome with two centromeres is called dicentric.

Question 3

  • A teenage female with beta-thalassemia has a mutation removing 100 nucleotides before the start of transcription.
  • The CAAT and TATA boxes are most likely removed by this deletion.
  • These boxes are regulatory elements crucial for transcription initiation.

Question 4

  • A 2-year-old female patient with Down syndrome has a karyotype of 47,XX+21.
  • This indicates an extra copy of chromosome 21.

Question 5

  • The attachment site for mitotic spindle fibers on chromosomes is the centromere.

Question 6

  • The POLG gene replicates the mitochondrial genome.
  • The 5' UTR (untranslated region) is transcribed.
  • The 3' UTR, exons, and introns are transcribed.

Question 7

  • A 7-year-old boy with renal distal tubule acidosis has a splicing mutation.
  • The mutation results in a larger-than-normal mRNA.
  • A mutation in the splice donor site of intron 1 is the most likely cause.

Question 8

  • Jessica gave birth to a baby boy, Billy.
  • Several men claim paternity.
  • A DNA analysis of multiple marker loci.
  • Jerry has the highest probability of being the father.

Question 9

  • Linkage analysis is used to place a 14-bp tandem repeat.
  • The sequence is a variable number tandem repeat (VNTR).

Question 10

  • The human X-chromosome has many protein-coding genes.
  • The Y-chromosome has fewer genes.
  • One X-chromosome is deactivated in females to balance gene expression.

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