Describe the two ways in which meiosis produces new combinations of genes. What will be an ideal response?
ANSWER: Random assortment of maternal and paternal chromosomes during cell division is the first
way that meiosis produces new combinations of genes. In each pair of chromosomes, one
copy was inherited from each parent. Random combinations of parental chromosomes arise
in metaphase I when the maternal and paternal members of each pair line up at random with
respect to all the other pairs. In other words, the arrangement of any chromosomal pair can bematernal:paternal
or paternal:maternal. As a result, cells produced in meiosis I are much
more likely to receive a combination of maternal and paternal chromosomes than they are to
receive a complete set of maternal chromosomes or a complete set of paternal chromosomes.
Crossing over is the second way meiosis generates new combinations of genes. This process
involves the physical exchange of parts between non-sister chromatids. Members of a
chromosome pair carry identical genes but may carry different versions of those genes
(alleles). For example, a chromosome may carry a gene for eye color. One copy of the
chromosome may carry an allele for blue eyes, while the other carries an allele for brown
eyes. The exchange of chromosome parts during crossing over creates new combinations of
alleles inherited from each parent.
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Which of the following relationships about nucleotide composition in DNA is TRUE?
A. C G=A T. B. C A=G T. C. C=A. D. G=T. E. C=T.
An agent that causes genetic mutations is called __________
a. a carcinogen b. cancer c. a virus d. a malignant tumor
In flatworms and sea anemones, circulation of
solutes and gases is by way of
a. interstitial fluid diffusion. b. an open circulatory system. c. a closed circulatory system. d. cell to cell transport. e. intracellular diffusion.
If the wild type DNA sequence reads THE CAT ATE THE BIG RAT, what type of mutation would change the sequence to THE CAT ATA ETH EBI GRA T?
A. insertion B. missense C. nonsense D. silent E. deletion