Biology Chapter on Genes and Chromatin

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Questions and Answers

How does the structure of chromatin affect gene expression?

  • Closed chromatin promotes gene expression, while open chromatin restricts it.
  • Open chromatin promotes gene expression, while closed chromatin restricts it. (correct)
  • Chromatin structure has no effect on gene expression.
  • Chromatin structure only affects gene expression in specific cell types.

What is the role of histone modifications in regulating gene expression?

  • Histone modifications can alter the structure of chromatin, making DNA more or less accessible for transcription. (correct)
  • Histone modifications directly code for specific proteins.
  • Histone modifications are not important for gene expression.
  • Histone modifications are only involved in DNA replication.

What is the primary function of transcription factors in gene expression?

  • Transcription factors are involved in the transportation of mRNA from the nucleus to the cytoplasm.
  • Transcription factors directly replicate DNA.
  • Transcription factors bind to specific DNA sequences to initiate gene transcription. (correct)
  • Transcription factors modify histones to regulate chromatin structure.

What is the significance of the centromere in a chromosome?

<p>The centromere is the site of attachment for spindle fibers during cell division. (A)</p> Signup and view all the answers

What is the primary role of DNA replication in the cell cycle?

<p>To ensure each new cell receives an identical copy of the genetic material before cell division. (D)</p> Signup and view all the answers

What are the potential consequences of errors in DNA replication?

<p>Errors in DNA replication can lead to mutations, which may result in genetic disorders or cell abnormalities. (C)</p> Signup and view all the answers

What is the primary function of checkpoints in the cell cycle?

<p>Checkpoints ensure the proper sequencing of events in the cell cycle. (B)</p> Signup and view all the answers

What is the role of cyclin-dependent kinases (CDKs) in the cell cycle?

<p>CDKs are proteins that control the transitions between different phases of the cell cycle. (B)</p> Signup and view all the answers

Which of the following is NOT a characteristic of incomplete dominance?

<p>One allele completely masks the other. (B)</p> Signup and view all the answers

What does the term 'penetrance' refer to in genetics?

<p>The likelihood that a specific genetic mutation will exhibit its associated trait. (D)</p> Signup and view all the answers

What is the primary function of nucleosomes?

<p>To compact and organize DNA within the nucleus. (B)</p> Signup and view all the answers

What is a karyotype?

<p>A visual representation of an individual's chromosomes arranged by size and banding patterns. (C)</p> Signup and view all the answers

Which of the following is NOT a direct outcome of the Human Genome Project?

<p>Development of a cure for all genetic diseases. (B)</p> Signup and view all the answers

In a homozygote, which of the following is TRUE?

<p>The individual possesses two identical alleles at the same gene locus. (A)</p> Signup and view all the answers

Which of the following scenarios would result in increased homozygosity in a population?

<p>Inbreeding. (C)</p> Signup and view all the answers

What determines an individual's biological sex?

<p>The presence or absence of the Y chromosome. (C)</p> Signup and view all the answers

Which of the following accurately describes a phenotype?

<p>The observable physical traits of an individual. (C)</p> Signup and view all the answers

What is the primary purpose of karyotyping?

<p>To identify chromosomal abnormalities. (A)</p> Signup and view all the answers

Which of these is NOT a characteristic of a dominant mutation?

<p>Always causes a severe phenotype (B)</p> Signup and view all the answers

What is the main goal of the ENCODE project?

<p>To create a comprehensive map of all functional elements in the human genome (D)</p> Signup and view all the answers

What is chromatin remodeling?

<p>Alterations in the structure of chromatin to allow or restrict access to specific regions of DNA (B)</p> Signup and view all the answers

What is the difference between euchromatin and heterochromatin?

<p>Euchromatin is transcriptionally active, while heterochromatin is transcriptionally inactive (C)</p> Signup and view all the answers

What are alleles?

<p>Different versions of a gene (C)</p> Signup and view all the answers

Which of the following is NOT a characteristic of autosomes?

<p>Contain genes related to sex determination (D)</p> Signup and view all the answers

In codominance, how are the two different alleles expressed in the offspring?

<p>Both alleles are fully expressed, leading to a mix of traits (A)</p> Signup and view all the answers

What are the two main components of chromatin?

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

What is the function of regulatory regions in the human genome?

<p>Controlling gene expression (D)</p> Signup and view all the answers

What is the function of a centromere in a chromosome?

<p>It joins the two sister chromatids together (A)</p> Signup and view all the answers

What is the difference between genotype and phenotype?

<p>Genotype refers to the genetic makeup, while phenotype refers to the physical appearance (D)</p> Signup and view all the answers

Why is understanding gene expression and inheritance patterns important in studying genetic disorders?

<p>It provides insights into the mechanisms behind disease development and potential treatment strategies (D)</p> Signup and view all the answers

What is the difference between incomplete dominance and codominance?

<p>In incomplete dominance, the offspring exhibits a blend of both traits, while in codominance, both alleles are expressed fully (D)</p> Signup and view all the answers

What is the main difference between mitosis and meiosis?

<p>Mitosis produces diploid cells, while meiosis produces haploid cells (C)</p> Signup and view all the answers

What is the role of non-coding DNA in the human genome?

<p>It plays a role in regulating gene expression and other cellular processes (C)</p> Signup and view all the answers

What is the difference between duplicate epistasis and complementary epistasis?

<p>Duplicate epistasis requires either of two genes to produce the same phenotype, while complementary epistasis requires both to be present (C)</p> Signup and view all the answers

Which of the following is NOT a characteristic of euchromatin?

<p>It is darkly stained under a microscope. (B)</p> Signup and view all the answers

What is the difference between a haploid and a diploid cell?

<p>A haploid cell contains half the number of chromosomes as a diploid cell. (B)</p> Signup and view all the answers

Which of the following is NOT a type of histone modification?

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

What is the role of heterochromatin in gene regulation?

<p>Heterochromatin represses gene expression. (C)</p> Signup and view all the answers

Which of the following is a characteristic of recessive epistasis?

<p>A recessive allele masks the expression of another gene. (B)</p> Signup and view all the answers

What is the significance of studying haplotypes?

<p>All of the above. (D)</p> Signup and view all the answers

Which of the following is NOT a true statement about expressivity?

<p>Expressivity can be predicted with complete accuracy for individuals with the same genotype. (C)</p> Signup and view all the answers

Which of the following is a defining characteristic of eukaryotes?

<p>The presence of a nucleus. (B)</p> Signup and view all the answers

What is the relationship between genes and genomes?

<p>A gene is a segment of a genome. (D)</p> Signup and view all the answers

What is the primary function of a gene?

<p>To synthesize proteins. (C)</p> Signup and view all the answers

Which of the following statements accurately describes a heterozygote?

<p>A heterozygote has two different alleles for a gene. (D)</p> Signup and view all the answers

The term "homologues" can refer to which of the following?

<p>All of the above. (D)</p> Signup and view all the answers

Which of the following is a key difference between eukaryotic and prokaryotic cells?

<p>Eukaryotes have a nucleus, while prokaryotes do not. (C)</p> Signup and view all the answers

Why is understanding expressivity important in managing genetic conditions?

<p>Expressivity determines the severity of a genetic condition, but not the likelihood of developing it. (B)</p> Signup and view all the answers

Flashcards

Genetics

The study of heredity and variation. It explains how characteristics are passed from parents to offspring.

Genes

Units of heredity found on chromosomes. They carry instructions for specific traits.

Alleles

Different forms of a gene. They create variations in a trait.

Chromosomes

Thread-like structures containing genetic material (DNA). They come in pairs: one from mom, one from dad.

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Chromatin structure

The way DNA is packed inside the nucleus, affecting how genes are used.

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DNA replication

The process by which a cell makes an exact copy of its DNA before dividing.

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Cell cycle

A series of steps a cell goes through, including DNA replication and division.

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Cyclin-dependent kinases (CDKs)

Proteins that regulate the cell cycle, ensuring proper timing of each step.

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What is a homozygote?

In a homozygote, an individual possesses two identical alleles at a specific gene locus, leading to the expression of a single trait. Homozygotes can have two dominant or two recessive alleles.

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What was the Human Genome Project?

The Human Genome Project aimed to map and understand all the genes in the human genome, providing insight into genetic variations and links to diseases.

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What is incomplete dominance?

Incomplete dominance occurs when the heterozygous phenotype is an intermediate blend of the homozygous phenotypes, rather than one dominant over the other. This blending results from both alleles contributing equally to the phenotype.

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What is a karyotype?

A karyotype is a visual representation of an individual's chromosomes, arranged and displayed according to size, banding patterns, and the position of the centromere.

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What is a nucleosome?

A nucleosome is a structural unit of DNA consisting of DNA wrapped around histone proteins, forming a bead-like structure that helps in DNA compaction.

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What is penetrance?

Penetrance refers to the likelihood that a particular genetic mutation will result in the observable trait or disorder in individuals possessing the mutation.

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What is a phenotype?

Phenotype refers to the observable physical traits or characteristics of an organism, which are the result of the interaction between their genes and their environment.

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What are sex chromosomes?

Sex chromosomes determine an individual's biological sex. In humans, females typically have two X chromosomes, while males have one X and one Y chromosome.

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What is euchromatin?

A loosely packed form of chromatin (DNA) that allows for gene expression. It appears lighter under a microscope compared to heterochromatin.

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What is heterochromatin?

A tightly packed form of chromatin (DNA) that is usually inactive and involved in gene silencing.

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What is expressivity?

The variation in the extent or severity of a genetic trait among individuals with the same genotype.

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What is a gene?

A segment of DNA containing instructions for making a specific protein, responsible for traits.

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What is a genome?

The complete set of an organism's genetic material, including all genes and non-coding sequences.

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What is a heterozygote?

An individual with two different alleles for a particular gene, resulting in a mix of contrasting traits.

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What is a haploid cell?

A cell containing a single set of chromosomes, half the number found in diploid cells.

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What is a haplotype?

A group of genes inherited from a single parent, located close together on the same chromosome.

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What are histone modifications?

Chemical modifications to the proteins (histones) around which DNA is wrapped, impacting gene expression.

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What are homologues?

Similar structures in different organisms, indicating a shared evolutionary origin.

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What is recessive epistasis?

The presence of a homozygous recessive genotype masking the expression of another gene.

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What is a eukaryote?

Organisms with complex cell structures, including membrane-bound organelles and a nucleus.

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What is recessive epistasis?

A condition where a recessive allele prevents the expression of another allele, even if that allele is dominant.

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Autosomes

Chromosomes carrying genes for traits other than sex determination.

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Chromatid

One half of a duplicated chromosome, joined at the centromere, each containing a DNA molecule.

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Chromatin

A complex of DNA and proteins within the nucleus, responsible for organizing and packaging DNA.

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Codominance

Expression of two different alleles for a gene, resulting in a blended or mixed phenotype.

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Diploid

Cells containing two complete sets of chromosomes, one from each parent.

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Dominant mutations

Variations in a gene that only require one copy to be expressed, affecting the corresponding trait.

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ENCODE project

A project aiming to identify all functional elements in the human genome, including non-coding regions.

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Epistasis

When one gene masks the effect of another gene, influencing phenotypic expression.

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Gene expression

The process of how genes are activated to produce a protein, which ultimately determines a trait.

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Inheritance patterns

Patterns of how traits are passed from parents to offspring.

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Epigenetic modifications

Modifications to DNA that do not change the sequence but can influence gene expression.

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Human genome organization

The arrangement of DNA within the nucleus, including chromosomes, genes, and non-coding regions.

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Genotype

The combination of alleles an individual possesses for a specific gene.

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Study Notes

Basic Concepts and Terminology

  • Genes: Units of heredity on chromosomes.
  • Alleles: Different forms of a gene.
  • Chromosomes: Carry genetic material, organized in pairs.
  • Traits: Characteristics determined by genes.

Chromatin Structure and Gene Expression

  • Chromatin structure: How DNA is packaged in the nucleus, impacting gene expression.
  • Open chromatin: Allows for active gene expression.
  • Closed chromatin: Restricts access to DNA.
  • Epigenetic modifications: Alter chromatin structure, affecting gene accessibility.
  • Histone modifications: Crucial in regulating chromatin and gene expression.
  • Transcription factors: Bind to DNA sequences to initiate gene expression.
  • Chromatin remodeling complexes: Alter chromatin structure to regulate transcription.

Chromosome Structure and Organization

  • Chromosome structure: Arrangement of DNA and proteins within the nucleus.
  • Chromatin: Thread-like structures that chromosomes are organized into.
  • Chromosome condensation: Occurs during cell division for distribution of genetic material.
  • Chromosome number: Specific to each species.
  • Chromosome pairs: One inherited from each parent.
  • Centromere, telomeres: Parts of chromosome structure.
  • Genetic disorders: Can arise from errors in chromosome structure or organization.

DNA Replication and Cell Cycle

  • DNA replication: Making identical copies of DNA before cell division to ensure accurate genetic information transfer.
  • S phase: DNA replication takes place during the cell cycle's S phase.
  • Mutations: Errors in replication that can lead to genetic diseases or cell abnormalities.
  • Cell cycle regulation: Checkpoints monitor DNA integrity and ensure correct progression through cell cycle phases.
  • Cyclin-dependent kinases (CDKs): Regulatory proteins controlling cell cycle transitions.

Gene Expression and Inheritance Patterns

  • Gene expression: Activation of genes to produce a trait.
  • Inheritance patterns: How traits are passed from parents to offspring.
  • Epigenetic modifications: Influence gene expression without changing DNA sequence.
  • Mendelian inheritance: Organisms inherit genes following specific patterns.
  • Gene expression regulation: Influenced by environmental conditions and signaling molecules.

Human Genome Organization

  • Human genome: Arrangement of DNA within the nucleus (chromosomes, genes).
  • Genes: Functional units coding for proteins.
  • Regulatory regions: Control gene expression.
  • Non-coding DNA: Includes introns and other sequences without protein-coding genes.

Key Terms

  • Alleles: Alternative forms of a gene that can result in different traits; inherited one from each parent; can be dominant or recessive.
  • Genotypes: Combinations of alleles an individual possesses.
  • Autosomes: Chromosomes that determine traits excluding sex determination.
  • Chromatid: Half of a duplicated chromosome.
  • Chromatin: DNA and proteins in the nucleus; condenses into chromosomes during division.
  • Chromosome: Thread-like structure containing DNA, carrying genetic information.
  • Codominance: Both alleles are expressed in the offspring.
  • Diploid: Cells with two sets of chromosomes (one from each parent).
  • Dominant mutations: Expressed with only one copy, masking the normal allele.
  • ENCODE project: Identify functional elements in the human genome.
  • Epistasis: One gene masking the effect of another gene.
  • Euchromatin: Loosely packed chromatin, allowing gene expression.
  • Eukaryote: Organism with complex cells; contains a nucleus.
  • Expressivity: Variation in the extent or severity of a genetic trait.
  • Gene: Segment of DNA with instructions for making a protein.
  • Genome: An organism's complete set of genetic material.
  • Genotype: Genetic information of an organism.
  • Haploid: Cell with one set of chromosomes.
  • Haplotype: Group of genes inherited from a single parent.
  • Heterochromatin: Tightly packed, transcriptionally inactive chromatin.
  • Heterozygote: Individual with different alleles for a gene.
  • Histone modifications: Chemical changes to histone proteins, influencing gene expression.
  • Homologues: Similar structures/genes in different organisms, indicating evolutionary link.
  • Homozygote: Individual with two identical alleles for a gene.
  • Human Genome Project: Project to map the human genome.
  • Incomplete dominance: Heterozygous phenotype is a blend of homozygous phenotypes.
  • Karyotype: Visual representation of an individual's chromosomes.
  • Nucleosome: Structural unit of DNA wrapped around histone proteins.
  • Penetrance: Likelihood of a genetic mutation leading to a trait or disorder.
  • Phenotype: Observable physical characteristics resulting from gene and environmental interaction.
  • Sex chromosomes: Determine biological sex.

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