Genetics Chapter on Repetitive Sequences

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Questions and Answers

What defines tandem repeats in the genome?

Repeats are directly next to each other. (correct)

Repeats are characterized by their banding patterns.

Repeats are located far apart from each other.

Repeats only occur within genes.

Which element is NOT a characteristic used to identify chromosomes in a karyotype?

Size relative to other chromosomes.

Shape based on centromere position.

Staining method.

Gene sequence information. (correct)

In which order are chromosomes categorized based on centromere placement?

Telocentric, metacentric, acrocentric.

Telocentric, acrocentric, submetacentric.

Metacentric, submetacentric, acrocentric. (correct)

Submetacentric, metacentric, telocentric.

What is the haploid number of chromosomes typically found in humans?

23 Signup and view all the answers

What causes the dark and light banding patterns visible in stained chromosomes?

Staining of tightly and loosely packed DNA. Signup and view all the answers

Homologous chromosomes can be distinguished by which of the following characteristics?

Same size, shape, and genes in the same order. Signup and view all the answers

Which feature is characteristic of all chromosomes?

Presence of telomeres and centromeres. Signup and view all the answers

What is the function of telomeres in chromosomes?

They protect the ends of chromosomes from degradation. Signup and view all the answers

What is the primary composition of the majority of genomes found in organisms?

Double-stranded DNA Signup and view all the answers

In what way do prokaryotic genomes primarily differ from eukaryotic genomes?

Prokaryotic genomes are typically circular. Signup and view all the answers

What is the role of noncoding DNA within chromosomes?

They may have important functions and can include origins of replication. Signup and view all the answers

Which of the following correctly characterizes the eukaryotic genome?

It is contained within a nucleus and can be much larger than prokaryotic genomes. Signup and view all the answers

What sequence marks the beginning of DNA replication in a genome?

Origin of replication sequence Signup and view all the answers

What is the expected relationship between genome size and the number of genes in prokaryotic organisms?

Genome size is linearly related to the number of genes. Signup and view all the answers

Which characteristic is least associated with eukaryotic chromosomes?

Single circular chromosome. Signup and view all the answers

What is true about the structure of chromosomes during cell division?

Chromosomes undergo replication before cell division. Signup and view all the answers

What is the most commonly found secondary structure in DNA?

B form (B-DNA) Signup and view all the answers

What type of helix does A-DNA represent?

Right-handed helix Signup and view all the answers

What occurs when dsDNA is dehydrated?

Formation of A form Signup and view all the answers

What structural feature is essential for the formation of nucleosomes?

Binding of DNA to histone proteins Signup and view all the answers

What is heterochromatin?

Tightly packed nucleosomes Signup and view all the answers

What is the primary role of topoisomerase in DNA structure?

To introduce additional turns into the nucleic acid Signup and view all the answers

How does acetylation of histone tails affect chromatin structure?

It neutralizes the tails and loosens packing Signup and view all the answers

What is the function of functional repeats in DNA?

To facilitate high expression of certain proteins Signup and view all the answers

What is the definition of a diploid genome?

A genome that contains two haploid sets of chromosomes. Signup and view all the answers

Which of the following components is NOT part of a nucleotide?

Carboxylic acid Signup and view all the answers

What type of sugar is found in RNA?

Ribose Signup and view all the answers

Which base is found in DNA but not in RNA?

Thymine Signup and view all the answers

How many copies of each gene are present in a diploid organism?

Two Signup and view all the answers

Which of the following statements about SNPs is true?

SNPs can result in different alleles affecting gene function. Signup and view all the answers

What is the typical relationship between haploid (n) and diploid (2n) numbers in species?

Diploid number is twice the haploid number. Signup and view all the answers

What causes chromosomal variation within species?

Chromosomal sex and chromosomal disorders. Signup and view all the answers

What does Chargaff's rules state about the quantities of nitrogenous bases in DNA?

Adenine amounts are equal to thymine amounts. Signup and view all the answers

What role did X-ray chromatography play in the discovery of DNA's structure?

It provided measurements that fit the double helix dimensions. Signup and view all the answers

What is the significance of the 5’ and 3’ ends of a DNA strand?

They provide the directionality of the antiparallel strands. Signup and view all the answers

How are hydrogen bonds involved in the pairing of DNA nitrogenous bases?

Adenine and thymine form 2 hydrogen bonds. Signup and view all the answers

What is a characteristic of regions enriched with guanine and cytosine in DNA?

They are more stable due to increased hydrogen bonds. Signup and view all the answers

What defines the primary structure of DNA?

The sequence of nucleotides and their modifications. Signup and view all the answers

What does the term 'antiparallel strands' refer to in DNA structure?

One strand runs 5’ to 3’ and the other runs 3’ to 5’. Signup and view all the answers

What is the purpose of phosphodiester bonds in DNA?

They connect sugar and phosphate groups along the backbone. Signup and view all the answers

Study Notes

Homologous Chromosomes and Genomes

Homologous chromosomes differ at the sequence level due to small variations, known as SNPs (single nucleotide polymorphisms).
SNPs can result in alleles, which are different versions of a gene that can affect gene function.
Diploid genomes contain two haploid sets of chromosomes, with each species exhibiting a typical haploid number (n) and corresponding diploid number (2n).
Diploid organisms inherit one haploid set from each parent, while haploid sets consist of one chromosome from each homologous pair.
Chromosomal variations can occur within species, including chromosomal sex differences and disorders like trisomy.

Molecular Properties of the Genome

Genetic information is stored in nucleic acids, polymers made of nucleotide units.
Nucleotides consist of three components: a pentose sugar (deoxyribose in DNA, ribose in RNA), a nitrogenous base (purines: adenine, guanine; pyrimidines: cytosine, thymine in DNA, uracil in RNA), and a phosphate group.
Phosphate groups impart a negative charge to nucleic acids.

Genome Structure and Cell Cycle

The genome includes the complete set of species-specific genes, typically found in most cells.
Both prokaryotic and eukaryotic genomes generally consist of double-stranded DNA (dsDNA).
Prokaryotic genomes are primarily one circular chromosome, while eukaryotic organisms have multiple linear chromosomes.
Eukaryotic genomes are generally much larger and contain more non-coding DNA compared to prokaryotic genomes.

Chromosomal Characteristics

Eukaryotic chromosomes are identified by their characteristics visible in karyotypes, including centromere position, size, and banding patterns.
Chromosomes are named in descending order of size, with sex chromosomes typically placed last.
Homologous chromosomes are pairs that are similar in size, shape, and genetic content, with one chromosome inherited from each parent.

DNA Structure and Function

The double helix of DNA consists of two antiparallel strands with complementary nucleotide pairing (A-T, G-C) held together by hydrogen bonds.
The structure of DNA is stabilized by the sugar-phosphate backbone and forms major and minor grooves.
DNA structure can be categorized into three levels:
- Primary: Linear sequence of nucleotides
- Secondary: Formation of helices (B-DNA, A-DNA, Z-DNA)
- Tertiary: Further folding and compacting through supercoiling and nucleosome formation.

Nucleosomes and Chromatin

In eukaryotes, DNA wraps around histones to form nucleosomes, which are further organized into chromatin.
Heterochromatin (tightly packed) and euchromatin (loosely packed) represent different compaction levels of chromatin.
Acetylation of histone tails can influence chromatin structure, promoting a less condensed form allowing for transcriptional activity.

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Description

This quiz focuses on the characteristics of repetitive sequences in genomes, including the distinction between tandem and dispersed repeats. It also covers the structure of linear chromosomes in eukaryotic organisms and their origins of replication. Test your understanding of these fundamental genetics concepts.