1. Cystic fibrosis is the most common serious genetic disease in the USA. If the
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Question
1. Cystic fibrosis is the most common serious genetic disease in the USA. If the frequency, q, of the recessive cystic fibrosis allele, c, in the USA is 0.04, what is the frequency of people with cystic fibrosis? Remember that if C is the normal allele with a frequency p, then p + q = 1 and and the frequencies of the homozygous dominant, heterozygous and homozygous recessive genotypes are p2, 2pq and q2 respectively.2. Explain the difference between homologous and analogous structures in animals or plants and describe what each tells us about the relatedness of the species involved.
3. Explain how the impact of a large meteor or asteroid colliding with the earth could have caused the Cretaceous extinction 65 million years ago. What is the evidence for such a collision?
4. Describe the four stages in the in the four stage hypothesis for the origin of life. Why is RNA a likely candidate for the original self-replicating molecule?
Explanation / Answer
1) Given that q^2 = 0.04
q = 0.2
p+q = 1
p = 1-0.2 = 0.8
p^2 = 0.64
2pq= 0.32
q^2 = 0.04
2) Difference between homologous and analogous structures in animals or plants and relatedness of the species involved is that if widely separated groups of organisms are originated from a common ancestry, they are expected to have certain basic features in common. The degree of resemblance between two organisms should indicate how closely related they are in evolution.
Groups with little in common are assumed to have diverged from a common ancestory much earlier in geological history than groups which have a lot in common.
3) Probably the most convincing evidence for a worldwide catastrophe was the discovery of the crater which has since been named chicxulub crater. This crater is centered on the Yucatán Peninsula of Mexico and was discovered by Tony Camargo and Glen Pentfield while working as geophysicsts for the Mexican oil company PEMEX. What they reported as a circular feature later turned out to be a crater estimated to be 180 km (110 mi) in diameter. Other researchers would later find that the end-Cretaceous extinction event that wiped out the dinosaurs had lasted for thousands of years instead of millions of years as had previously been thought. This convinced the vast majority of scientists that this extinction resulted from a point event that is most probably an extraterrestrial impact and not from increased volcanism and climate change (which would spread its main effect over a much longer time period).
4). The four stages of origin of life are
Stage 1: Abiotic Synthesis of Organic Monomers
Stage 2: Abiotic Synthesis of Polymers
Stage 3: Formation of Pre-Cells
Stage 4: Origin of Self-Replicating Molecule
In RNA world hypothesis proposes that a world filled with life based on RNA predates the current world of life based on DNA and protein. RNA, which can both store information like DNA and act as an enzyme like proteins, may have supported cellular or pre-cellular life. Some hypotheses as to the origin of life present RNA-based catalysis and information storage as the first step in the evolution of cellular life.
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