Later research demonstrated that many proteins are composed of several polypeptides, each of which has its own gene. Therefore, Beadle and Tatum’s idea has been restated as the one gene - one polypeptide hypothesis.
Fig. 17.10 (1) Pre-mRNA combines with snRNPs and other proteins to form a spliceosome. (2) Within the spliceosome, snRNA base-pairs with nucleotides at the ends of the intron. (3) The RNA transcript is cut to release the intron, and the exons are spliced together; the spliceosome then comes apart, releasing mRNA, which now contains only exons.
The anticodon base-pairs with a complementary codon on mRNA. –If the codon on mRNA is UUU, a tRNA with an AAA anticodon and carrying phenyalanine will bind to it. Codon by codon, tRNAs deposit amino acids in the prescribed order and the ribosome joins them into a polypeptide chain.
Practice ’90/’94 In DNA replication, DNA polymerase catalyzes the reaction in which A.The double helix unwinds B.The sugar-phosphate bonds of each strand are broken C.A phosphate group is added to the 3’-carbon or 5’- carbon of ribose D.A nucleotide with a base complementary of the base on the template stand is added to the new DNA strand E.The two nucleotide strands come together and intertwine to form a double helix
Practice The relative location of four genes on a chromosome can be mapped from the following data on crossover frequencies. GenesFrequency of crossover B and D 5% C and A 15% A and B 30% C and B 45% C and D 50% Which of the following represents the relative positions of these four genes on the chromosome? A.ABCD B.ADCB C.CABD D.CBAD E.DBCA
The illustrations above represent homologous pairs of chromosomes as they appear in various stages of mitosis and meiosis (2n=2). 1. At which stage do the chromosomes have the LEAST amount of DNA per cell? 2. Which diagram represents anaphase of meiosis I?
Shading indicates the presence of sickle cell anemia. The phenotype of individual C is best explained by the fact that this individual received an allele for sickle cell anemia from A.an autosomal chromosome of each parent B.the Y chromosome contributed by the father C.the X chromosome contributed by the mother D.the X chromosome contributed by the father E.the Y chromosome contributed by the mother
What is the probability that the next child of parents A and B would have had sickle cell anemia? A.0% B.25% C.60% D.75% E.100%
The most reasonable explanation for the fact that the offspring of C and D do not have sickle cell anemia is that each received a A.sickle allele from the mother B.normal allele from the father C.sickle allele from each parent D.normal allele from each parent E.pair of normal alleles from the father
Which of the following statements is correct about the four offspring of C an D? A.Only the females are carriers of the sickle cell trait. B.Only the males are carriers of the sickle cell trait. C.Only the females are heterozygous for the sickle cell trait. D.All are homozygous for the sickle cell trait. E.All are carriers of the sickle cell trait.
Achondroplastic dwarfism is a dominant genetic trait that causes severe malformation of the skeleton. Homozygotes for this condition are spontaneously aborted (hence, the homozygous condition is lethal) but heterozygotes will develop to be dwarfed. Matthew has a family history of the condition, although he does not express the trait. Jane is an achondroplastic dwarf. Matthew and Jane are planning a family of several children and want to know the chances of producing a child with achondroplastic dwarfism.
The genotypes of Matthew and Jane are best represented as MatthewJane (A)AAAa (B)Aaaa (C)aaaa (D)aaAa (E)AaAa
The probability that Matthew and Jane’s first child will be an achondroplastic dwarf is (A)0% (B)25% (C)50% (D)75% (E)100%
If three children are born to Matthew and Jane, what are the chances that the first two children will not express the trait but that the third child will be an achondroplastic dwarf? (A)5/8 (B)4/8 (C)3/8 (D)1/8 (E)1/16