Polymorphisms & Genes

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Questions and Answers

What is a single base change in DNA called?

  • Chromosomal variation
  • Genetic drift
  • Single nucleotide polymorphism (SNP) (correct)
  • Short tandem repeat polymorphism (STR)

How much of your DNA do you share with other humans?

  • 99.0%
  • 97.5%
  • 98.5%
  • 99.5% (correct)

Which of the following describes short tandem repeat polymorphisms (STR)?

  • They involve substitutions of entire genes.
  • They are variations involving a single base pair.
  • They are long sections of DNA over 100 base pairs.
  • They are short sections of DNA that are repeated multiple times. (correct)

What percentage of DNA do humans share with chimpanzees?

<p>98.5% (C)</p> Signup and view all the answers

What structure within cells contains the majority of human genes?

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

What type of variations are commonly found in intron sequences among humans?

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

How many chromosomes do humans typically have?

<p>46 (D)</p> Signup and view all the answers

What is the total number of base pairs in the human genome?

<p>3 billion (B)</p> Signup and view all the answers

What are gene regulators responsible for?

<p>Turning different genes on and off (B)</p> Signup and view all the answers

What is a common characteristic of most single nucleotide polymorphisms (SNPs)?

<p>They account for many genetic differences among people. (A)</p> Signup and view all the answers

What percentage of the human genome is made up of exons that encode proteins?

<p>1% (B)</p> Signup and view all the answers

What are polymorphisms primarily associated with?

<p>Inherited non-coding DNA variations (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of introns?

<p>Introns are mostly responsible for genetic diseases. (A)</p> Signup and view all the answers

What is the main risk associated with mutations occurring in exons?

<p>They may result in genetic diseases. (B)</p> Signup and view all the answers

How do mutations in introns affect an individual?

<p>They usually have no effect on function. (B)</p> Signup and view all the answers

What was the early perception of noncoding DNA often referred to as?

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

What is the main reason mutations in exons are less likely to be passed on compared to those in introns?

<p>Exon mutations often lead to a decrease in reproductive success. (D)</p> Signup and view all the answers

Which genetic diseases are primarily caused by mutations in exons?

<p>Cystic fibrosis and sickle cell disease (C)</p> Signup and view all the answers

Which factor contributes to the uniqueness of individuals in the population?

<p>Differences in noncoding DNA (B)</p> Signup and view all the answers

What is the role of introns in the gene structure?

<p>They contribute to chromosome structure. (D)</p> Signup and view all the answers

The portion of Eukaryotic DNA that encodes proteins comprises about 50% of the genome.

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

Introns are responsible for the majority of known genetic diseases due to mutations.

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

Polymorphisms are variations found in non-coding DNA that can act as genetic fingerprints.

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

Mutations in introns have a higher likelihood of being passed down through generations than mutations in exons.

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

Scientists originally viewed noncoding DNA as having significant functional roles within the cell.

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

Random mutations are more likely to occur in exons since they are crucial for protein function.

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

Mutations occurring in an exon can lead to serious health issues in an individual.

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

Introns are considered filler DNA that may contribute to the structural integrity of chromosomes.

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

The differences passed down through generations due to random mutations in exons often lead to genetic variation between individuals.

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

The majority of human genetic variation arises from mutations in coding regions of DNA.

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

Polymorphisms specifically refer to variations in the exon sequences of DNA.

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

Single nucleotide polymorphisms (SNPs) are the most common type of genetic variation.

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

Humans typically possess 23 pairs of chromosomes.

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

The human genome consists of approximately 3 million base pairs.

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

Most SNPs have observable differences that can affect an individual’s appearance or health.

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

You share 98.5% of your DNA with chimpanzees.

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

Introns are primarily responsible for coding proteins in genes.

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

Gene regulators are proteins that help to express the appropriate traits in an organism.

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

Short tandem repeat polymorphisms (STRs) consist of longer sections of DNA than SNPs.

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

The majority of your genes are located in your mitochondria.

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

Flashcards

Polymorphism

Variations in intron sequences between humans.

Single Nucleotide Polymorphism (SNP)

A change in a single base pair in DNA.

Short Tandem Repeat Polymorphism (STR)

Short DNA sequences repeated multiple times.

Genome

Complete set of DNA in an organism.

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Gene

Part of DNA that codes for a protein.

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Chromosome

Organized pieces of DNA, containing genes.

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DNA

The genetic material in cells.

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Genetic code

The way the sequence of bases in DNA determines traits.

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Protein

Large molecules built from amino acids, carrying out many functions in the body

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human genome

The complete DNA instructions or recipe for all the genes in the body.

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Exon

A segment of DNA that codes for a protein.

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Intron

A segment of DNA that does not code for a protein.

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Junk DNA

Term for non-coding regions, but now seen as having possible functions.

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Genetic Disease

Disease caused by a mutation in a gene (exon).

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Exon Mutation

Mutation in a region of DNA that codes for protein.

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Intron Mutation

Mutation in a region of DNA that doesn't code for protein.

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Random Mutation

A change in DNA sequence that occurs randomly.

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What is the majority of our DNA?

About 99% of human DNA does not code for proteins and is considered non-coding DNA. This DNA was initially called 'junk DNA' because its function was unknown but now we know it plays a role in regulating genes.

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What are introns?

Introns are segments of non-coding DNA found within genes. They are spliced out of the RNA transcript before protein synthesis.

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Exons vs. Introns

Exons are coding regions of DNA that are translated into proteins. Introns are non-coding regions that are removed from the RNA transcript before translation.

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What is a polymorphism?

Polymorphisms are variations in non-coding DNA sequences that are inherited from both parents. These variations contribute to individual differences.

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Why are intron mutations less likely to cause issues?

Intron mutations typically do not affect protein synthesis or cell function. They can be passed on to offspring without causing harm.

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Why do mutations in exons often harm cells?

Exons code for proteins. Mutations in these regions can alter protein structure and function, leading to cellular dysfunction.

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How are mutations passed on?

Mutations can be passed on from parents to offspring through gametes (sperm and egg cells).

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Do mutations always cause disease?

No, most mutations are neutral or even beneficial. However, harmful mutations can lead to genetic disorders.

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What are genetic diseases caused by?

Genetic diseases are caused by mutations in exons that alter the protein's function, leading to cellular dysfunction and disease.

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What is the main difference between exons and introns?

Exons are coding regions of DNA that are translated into proteins, while introns are non-coding regions that are removed from the RNA transcript before translation.

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What are polymorphisms?

Variations in intron sequences between individuals. These are differences in DNA that don't affect protein function but reveal ancestry.

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What is a SNP?

A single nucleotide polymorphism (SNP) occurs when a single base pair in DNA is changed. This is the most common type of polymorphism.

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What's an STR polymorphism?

A short tandem repeat polymorphism (STR) involves short sections of DNA (2-5 base pairs) repeated multiple times. The number of repeats varies between individuals.

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What's a genome?

The entire set of chromosomes in an organism - all the DNA in a cell.

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How many chromosomes do humans have?

Humans typically have 46 chromosomes, organized in 23 pairs. Each parent contributes one set of 23 chromosomes.

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What makes us different from each other?

Differences in our DNA sequences, including SNPs, contribute to individual variations like appearance and disease susceptibility.

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What is a gene regulator?

Gene regulators are like switches that turn genes on and off in different cells, controlling cell function.

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What is the genetic code?

The sequence of bases in DNA spells out the genetic code, determining everything from hair color to protein production.

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What are genes?

Genes are sections of DNA that provide the instructions for making specific proteins.

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How does DNA affect traits?

Genes contain the information for making proteins that influence traits, like eye color or the type of hair you inherit.

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Study Notes

Human Genes and DNA

  • Humans have approximately 20,000-25,000 genes.
  • Only about 1% of DNA codes for proteins (exons).
  • Introns are non-coding DNA regions interspersed with exons; not used for protein synthesis, but may affect chromosome structure.
  • Originally, non-coding regions were called "junk DNA," but evidence shows some have important functions like gene regulation.
  • Human genetic differences are mainly found in non-coding regions.

Polymorphisms

  • Polymorphisms are inherited segments of non-coding DNA, acting as genetic fingerprints.
  • Population variations form the basis of polymorphisms.
  • Non-coding DNA mutations are more likely to be passed down due to no direct effect on protein function.
  • Polymorphisms can involve single base changes (SNPs) or repeated sections (STRs).

Mutations and Genetic Diseases

  • Random mutations can occur anywhere in the genome.
  • Exon mutations are often harmful, causing genetic diseases (e.g., cystic fibrosis, sickle cell disease, Huntington's disease).
  • Exon mutations negatively impact cell function and are less likely to be passed on.
  • Intron mutations generally have no effect on cell function and are easily inherited.
  • Exons responsible for nearly identical sequences between humans, while introns show variation among individuals.

Relatedness and DNA

  • Humans share around 99.9% of their genes.
  • Variations in introns (polymorphisms) provide insights into shared ancestry.
  • Single nucleotide polymorphisms (SNPs) are the most common type, involving single base-pair changes.
  • Short tandem repeat polymorphisms (STRPs) involve repeated short DNA sequences.

DNA Structure and Function

  • DNA is a double-stranded molecule composed of sugar, phosphate, and four bases (adenine, thymine, cytosine, guanine).
  • The order of these bases determines genetic traits.
  • Genes are recipes for making proteins, and these recipes are inherited.
  • Genes function through protein production; cells express specific traits using genes.
  • A cell's function is orchestrated by Gene Regulators turning on or off specific genes based on the need.
  • The full set of 23 human chromosomes constitutes a human genome.
  • Variation in a single base pair is a single nucleotide polymorphism (SNP).

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