Biology 2581B Lecture Notes - Lecture 13: Centromere, Dosage Compensation, Zygosity

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24 Apr 2017

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Mutations can occur on a large scale and impact parts of chromosomes and whole genomes. Before genome sequences, genes were analyzed from different organisms to find out their sequence and function. At the sequence level many similarities. Before it was sequenced, they found this out by staining and observing banding patterns. After both genomes were sequenced, they were aligned and similar sequences between the human and mouse genome were found: found many of the genes and large fragments with the same order and type of genes. Each mouse chromosome was (cid:498)pieced together(cid:499) from different human chromosomes. Same information was there in the human genome and mouse but it wasn"t localized to a: but they were on different chromosomes single chromosome, it was on different chromosomes in human chromosomes. There were rearrangements over evolutionary time to account for the differences between mice and human chromosomes: things moved and got pieced together in different ways.

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13. The arms of a human and the wing of a bat are _________________ structures, composed of the same bones that have been modified for different functions.

analogous

vestigial

c.	homologous

d.	convergent

14. Xeroderma pigmentosum is an autosomal recessive genetic disorder. People who are homozygous for the disease-causing allele have skin that is damaged by exposure to ultraviolet radiation; this can lead to skin cancer at an early age. The mutation that causes this disorder is in a gene that functions:

a.	to repair DNA by excising (removing) nucleotides damaged by UV light.

b.	in lysosomes, to break down lipids that otherwise accumulate in the nervous system.

c.	to produce the UV blocking pigment melanin in the skin cells

d.	in red blood cells to carry oxygen to the skin.

15. The Amish are a religious sect descended from a small group of colonists who came to the United States over 200 years ago. Their religious beliefs have kept them isolated from society. The Amish have a much higher than average incidence of both polydactyly (extra fingers and toes) and dwarfism in their communities. This is most likely explained by:

a.	inheritance of acquired characters.

b.	the founder effect.

c.	disruptive selection.

d.	natural selection.

16. In the structure of DNA that Watson and Crick proposed, the sides of the "ladder" of the DNA molecule are always the same distance apart, making the molecule a constant width. This occurs because when the bases hydrogen bond to form the rungs of the "ladder", a:

a.	purine always pairs with a pyrimidine.

b.	purine always pairs with a purine.

c.	pyrimidine always pairs with a pyrmidine.

d.	The structure of the double helix is not determined by how the bases pair.

17. The RNA transcript of DNA that travels to the cytoplasm, carrying the instructions to make a protein, is called:

rRNA.

tRNA.

mRNA.

d.	RNA polymerase.

18. When DNA is replicated, the error rate is approximately one error for every 10,000 nucleotides copied. However, that error rate is reduced to only 1 error for every 1 billion nucleotides. The DNA sequence is "corrected" by:

a.	repeating S phase to see if the error rate is lower the second time around.

b.	enzymes that proofread the DNA and repair errors.

c.	messenger RNA during the process of transcription.

d.	Any errors made during DNA replication cannot be corrected. If errors are detected after S phase, the cell is destroyed.

19. Mendel's principle of segregation says that:

a.	when gametes are formed, each gamete receives only one allele for a particular gene.

b.	some genes are dominant to others.

c.	a testcross must be used to determine the genotype of an organism with a dominant phenotype.

d.	all of the above

20. Tay-Sachs disease is lethal before reproductive age, but the allele persists in Louisiana French Canadians because:

a.	it is a dominant allele.

b.	new mutations causing this disease are common in that population.

c.	it is not expressed in the phenotype of heterozygous individuals.

d.	the disease is contagious and can be transmitted by nonheritable means.

21. Physical features that are similar in organisms which are not closely related to each other are most likely a result of ____________. A good example of this is the similarities seen between some marsupial and placental mammals.

a.	natural selection.

b.	adaptation to similar environments

c.	convergent evolution

d.	All of the above phrases can be used to correctly fill this blank.

22. In humans, which of the following sex chromosome compliments could be found in males?

23. The proteins that are associated with eukaryotic chromosomes:

a.	help to package the DNA within the nucleus.

b.	are involved in gene expression, through binding with the DNA.

c.	may be replicating or transcribing the DNA.

d.	All of these are true of proteins that are associated with eukaryotic chromosomes.

24. A sequence of DNA nucleotides that contains the information to produce a single protein is a(n):

codon.

gene.

c.	polypeptide.

d.	anticodon.

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Biology 2581B Lecture Notes - Lecture 13: Centromere, Dosage Compensation, Zygosity

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