Chat with AIExam 2: Fundamentals of Gene Structure, Gene Expression, and Human Genome Organization
Exam 1: Fundamentals of Dna, Chromosomes, and Cells17 Questions
Exam 2: Fundamentals of Gene Structure, Gene Expression, and Human Genome Organization41 Questions
Exam 3: Principles Underlying Core Dna Technologies20 Questions
Exam 4: Principles of Genetic Variation39 Questions
Exam 5: Single-Gene Disorders: Inheritance Patterns, Phenotype Variability, and Allele Frequencies27 Questions
Exam 6: Principles of Gene Regulation and Epigenetics39 Questions
Exam 7: Genetic Variation Producing Diseasecausing Abnormalities in Dna and Chromosomes47 Questions
Exam 8: Identifying Disease Genes and Genetic Susceptibility to Complex Disease40 Questions
Exam 9: Genetic Approaches to Treating Disease40 Questions
Exam 10: Cancer Genetics and Genomics38 Questions
Exam 11: Genetic Testing From Genes to Genomes, and the Ethics of Genetic Testing and Therapy32 Questions
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The endosymbiont hypothesis can explain why we have two very different genomes in our cells. What does it propose?
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Verified
VerifiedIt proposes that our two genomes originated when a type of aerobic prokaryotic cell was endocytosed by an anaerobic eukaryotic precursor cell, at a time when oxygen started to accumulate in significant quantities in the Earth's atmosphere. Over a long period, much of the original prokaryote genome was excised, causing a large decrease in its size, and the excised DNA was transferred to the genome of the engulfing cell. The latter genome increased in size and went on to undergo further changes in both size and form during evolution, developing into our nuclear genome; the much reduced prokaryotic genome gave rise to the mitochondrial genome.
The theory explains why mitochondria have their own ribosomes and their own protein-synthesizing machinery and why our mitochondrial DNA closely resembles in form a reduced (stripped-down) bacterial genome. Our current nuclear genome is much larger than that of the ancestral eukaryotic precursor cell because of mechanisms that copied existing DNA sequences and added them to the genome. After some considerable time, the copies acquired mutations to make them different from the parent sequences and led to the formation of new genes, new exons, and so on.
What is the purpose of RNA splicing? Why do some of our genes not undergo RNA splicing?
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VerifiedRNA splicing is important in eukaryotic cells, but especially prevalent in complex multicellular organisms. A major justification is an evolutionary argument. By splitting the genetic information within genes into different little exons, it becomes possible to create new genes by recombining exons from one gene with exons from another. Thus, for example, various genetic mechanisms allow individual exons to be duplicated or swapped from one gene to another on an evolutionary timescale. See Figure 2.15 for an example. An additional source of complexity comes from using different combinations of exons to make alternative transcripts from the same gene (alternative splicing).
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When a gene is expressed, the two DNA strands are locally unwound to allow access by the ____1_____ machinery. One of the DNA strands serves as a ____2____ for an RNA polymerase to synthesize a complementary RNA. The initial transcript, often called the ____3____ transcript, is identical in base sequence (except that U replaces T) to the sequence of the other DNA strand, which is known as the ____4____ strand (and so the opposing strand that serves as the ___2____ is also known as the ____5____ strand). The segment of genomic DNA that corresponds to the ____3____ transcript is known as the ___6___ ___7____.
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(29) Correct Answer:Verified
Verified1. transcriptional.
2. template.
3. primary.
4. sense.
5. anti-sense.
6. transcription.
7. unit.
What is the approximate ratio between the DNA content of our nuclear genome and our mitochondrial genome?
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(45) Fill in the blanks below.
Our genome has numerous identical or similar copies of certain DNA sequences. Some of these are ____1____ ____2______, neighboring duplicated segments that are more than 1 kb in length (and often much larger), and that show more than 90% sequence identity, having duplicated very recently during evolution. Many of our genes are present in multiple copies that are collectively known as ____3_____ ____4_____ (and often contain both functional gene copies and ____5______ ). They arose by a slow process of intermittent gene duplication over sometimes long periods of evolutionary time. Extremely similar gene copies, such as the two human ___6____ - globin genes that make identical proteins, arose by evolutionarily recent gene duplications. More distantly related gene copies generally arose from comparatively ___7___ gene duplications.
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(35) Fill in the blanks below.
Retrotransposon repeats account for just over ___1___ % of our genome and are classified into three broad families. One family resembles a class of RNA virus, known as a ___2____. Like a ___2____, they contain direct repeats at their ends, known as ___3____ ____4____ repeats, and full-length family members have the same gene structure as a simple ____2____. A second family of retrotransposon repeats, known as ____5____ , has some full-length copies with sizes of 6-8 kb, and like the retrovirus-like family some of them are able to make a specialized DNA polymerase known as _____6____ ____7_____. A third family of retrotransposon repeats, known as ___8____, have short full-length sequences of between 100 and 300 bp, and are exemplified by ___9____ repeats, the most prolific DNA sequence in the human genome, with a copy number of more than ____10____ ____11_____ repeats. Only a small fraction of the retrotransposon repeats can actively transpose (most are truncated copies or have ____11_____ mutations). ___8____ repeats and other _____8_____ are unable to make a ____6____ ____7_____ but very occasionally do transpose using a ____6____ ____7_____ produced by another retrotransposon.
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(33) Illustrate, with examples, how noncoding RNAs are more than ubiquitous general regulators of transcription or protein synthesis.
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(27) Which, if any, of the following statements are false?
a) Constitutive heterochromatin remains highly condensed throughout the cell cycle.
b) Unlike constitutive heterochromatin, facultative heterochromatin describes chromatin that can de-condense and behave as euchromatin under certain circumstances.
c) Most of the long arm of the Y chromatin is made up of constitutive heterochromatin.
d) In women one of the two X chromosomes in each diploid cell is heterochromatinised.
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(33) Fill in the blanks below.
During gene expression, the initial RNA transcript needs to undergo processing to make a mature RNA, either a ____1____ RNA or a ____2___ RNA. For many of our genes, the initial RNA transcript needs to be cleaved into pieces. Some of the pieces, called ____3____, are discarded, but other alternating pieces called ___4____ are retained and fused in the same linear order as their order when transcribed. The junctions between ___4____ and ____3____ contain some highly conserved nucleotides, notably a ____5____ dinucleotide at the beginning of ___3____ and an ___6____ dinucleotide at the ends of ____3____. For ____4_____ and _____3_____ the original definitions have been broadened to include the corresponding segments of _____7_____ ____8______
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(38) Regarding protein structure, which, if any, of the following statements is incorrect?
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(31) Roughly what percentage of our genome is made up of coding sequence?
(Multiple Choice)
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(36) Sequence conservation analyses often use computer-based alignment of the nucleotide sequences of equivalent genes in different organisms, or of the amino acid sequences of the corresponding proteins. The alignment below shows a BLAST alignment of the first 100 amino acids of the human CFTR (cystic fibrosis transmembrane receptor) protein (shown as the Query) and the equivalent sequence in the corresponding mouse protein (shown as Sbjct, an abbreviation of subject). The intervening middle line shows whether at the same position in the two sequences the amino acids are identical or chemically similar.
Query 1 MQRSPLEKASVVSKLFFSWTRPILRKGYRQRLELSDIYQIPSVDSADNLSEKLEREWDRE 60
MQ+SPLEKAS +SKLFFSWT PILRKGYR LELSDIYQ PS DSAD+LSEKLEREWDRE
Sbjct 1 MQKSPLEKASFISKLFFSWTTPILRKGYRHHLELSDIYQAPSADSADHLSEKLEREWDRE 60
Query 61 LASKKNPKLINALRRCFFWRFMFYGIFLYLGEVTKAVQPL 100
ASKKNP+LI+ALRRCFFWRF+FYGI LYLGEVTKAVQP+
Sbjct 61 QASKKNPQLIHALRRCFFWRFLFYGILLYLGEVTKAVQPV 100
Calculate (a) the degree of sequence identity for the aligned sequences (b) the degree of sequence similarity.
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(33) In some gene families the genes are clustered in defined chromosomal regions as a result of ___1____ gene duplication. That often occurs as a result of misalignment of chromatids: over a limited chromosomal region, the DNA sequences are paired but out of register. Subsequent ___2_____ in the mispaired region can generate chromatids with two copies of a gene. Successive gene duplications results in a cluster of highly related genes. Not all the gene copies are functional: some acquire inactivating mutations to become a type of ____3_____ known as a _____4_____ ____3____. In other gene families there may be up to many hundreds of more members scattered across the genome. They often have large numbers of ____5____ ____3______ , also known as ____6_____ that arose by copying the RNA transcripts of a functional gene using a ____7____ _____8_____ to make cDNA copies that integrated into the genome at other locations but subsequently acquired deleterious mutations.
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(32) What is the total DNA content of (a) our genome; (b) an average human chromosome; (c) the human mitochondrial genome?
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(38) Describe the DNA composition of the centromeres of our chromosomes. To what extent are these DNA sequences conserved between different chromosomes, and to what extent do they resemble the sequences of centromeres in other organisms?
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(32) Four different levels of protein structure are recognized. What are they? Illustrate your answer with examples, wherever possible.
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(24) What is the type of natural selection that is responsible for strong evolutionary conservation of functionally important DNA sequences, and how does it work?
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