PLEASE i NEED THE ANSWERS 1.The two reasons for the large differences in genome

Question

PLEASE i NEED THE ANSWERS

1.The two reasons for the large differences in genome size among species  are BLANK and  BLANK

2.What highly repetitive sequence of DNA is essential for the attachment of spindle fibers to the centromeres during cell division? MULTIPLE CHOICE

LTR elements

LINEs

Alpha satellite DNA

SINEs

3.Major evolutionary changes can be accomplished only by the acquisition of whole new genes.

True

False

4.Any number of sequences of sequence arrangements that indicate the likely function of a segment of DNA is called what?MULTIPLE CHOICE

Sequence motif

Sequence assembly

Genome annotation

Shotgun sequencing

5.What DNA sequencing method is it when the sequenced fragments do not originate from a particular gene or region, but from sites scattered randomly across the molecules? MULTIPLE CHOICE

Shotgun sequencing

Sequence motif

Sequence assembly

Genome annotation

6.Describe one example of a sequence motif.(SHORT ANSWER)

LTR elements

LINEs

Alpha satellite DNA

SINEs

Explanation / Answer

1. Two major reasons for large differences in genome size are presence of Transposable element (repeated sequences) and non-coding DNA( telomeres, introns,etc.)

2. C. Alpha satellite DNA. Alpha satellite deoxyribonucleic acid (DNA) is based on 171 bp tandem repeats located in the centromeric and pericentromeric regions of all primate chromosomes. A variation in its sequence has been recently shown to alter centromere function. CENP-A, was identified as an unusual variant of histone H3 that replaces H3 in nucleosomes found exclusively at the centromere . The activity of CENP-A appears to be fundamental to centromeres, as cells that lack CENP-A fail to divide properly. CENP-B as a protein that binds to a simple sequence repeated many times in centromeric DNA. CENP-A and CENP-B might interact with alpha satellite DNA. A single unit of alpha satellite DNA is 171 base pairs in length, each of which contains a 17-base-pair binding site for CENP-B, referred to as the CENP-B box. Because centromeres vary in length, an individual chromosome can contain anywhere from hundreds to thousands of potential CENP-B boxes. CENP-B works as a dimer, so it may be able to cross-link two nearby satellite sequences, thereby contributing to the higher-order structure of the chromosome.

3. False. Major evolutionary changes are not subject to acquisition of whole new genes. Mutations or changes in the genetic sequence are the main cause of diversity among organisms. Mutations are the primary forces driving the process of evolution through natural selection. Therefore, acquisition of whole gene is not required for accomplishing major evolutionary changes. Infact fewer mutations implementing a drastic effect on the phenotype are enough to result in major evolutionary changes.

4. A. Sequence motif. Sequence motifs are short, recurring patterns
in DNA that are presumed to have a biological
function. It is a nucleotide or amino-acid sequence pattern that is widespread and has been proven or assumed to have a biological significance.

5. A. Shotgun sequencing. Shotgun sequencing is used to decode a genome by shredding ("shotgunning") it into smaller fragments of DNA which can then be individually sequenced. The sequences of these fragments are then ordered, based on overlaps in the genetic code, and finally reassembled into the complete sequence. Therefore, the sequences ibtained are not from a particular gene or region but from the whole genome.

6. Sequence motifs are conserved sequences of similar or identical patterns that occur within nucleic acids (DNA, RNA) or proteins either within different molecules produced by the same organism or within molecules from multiple species of organisms. One example includes the TATA box motif which was the first eukaryotic core promoter motif to be identified. The TATA box is considered a non-coding DNA sequence (also known as a cis-regulatory element) found in the core promoter region of genes in archea and eukaryotes."TATA box" contains a consensus sequence characterized by repeating T and A base pairs. The prokaryotic homolog of the TATA box is called the Pribnow box which has a shorter consensus sequence.  In Drosophila, less than 40% of 205 core promoters contain a TATA box while 30% of 1031 potential promoter regions contain a putative TATA box motif in humans.

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