Question

OLU Ucues Assignment 4c. In eukaryotes, genes are composed of exons and introns, with only exons included in the mRNA. Each gene also has its own adjacent promoter, to which the transcribing enzyme RNA polymerase binds. Related genes may be clustered together on the same chromosome as a “gene family." Answer each of the following questions in the answer box of the assignment. You may also write the answers directly into the assignment document and then upload your answers. Number the answers to correspond to the questions, 1. How many protein coding genes are there in the beta globin cluster? In your own words, describe the function of each of the genes in the beta globin cluster. 2. The human beta globin gene contains both exons and introns. How many exons does it have? How many introns? 3. Genes always begin and end with an exon. If you had a gene with 22 exons, how many introns would you predict that it has? 4. Make a diagram of the organization of the beta globin cluster of genes. Use "E" to represent the enhancer region, "P" to represent each promoter, and B-1 through B-5 to represent the five active genes of the cluster. Use hyphens to separate the different regions of the gene cluster, e.g. ---A--B---C-- 5. Craig Venter was the CEO of Celera Genomics, one of the two groups that first sequenced the human genome. In his report on the human genome, Venter defined a gene as "a series of cotranscribed exons." Explain in your own words what this definition means. Include in your explanation a description of what an exon is. Hint: what does "catranscribed" mean?

Answer 1

1. The beta globin cluster has five genes, namely: epsilon HBE, gamma G HBG2 gamma A HBG1 delta HBD and beta HBB.

The HBB encodes for the beta chain of the hemoglobin.

The HBE gene is a mutant form of the HBB gene that encodes lysine instead of glutamate at position 26

The HBD encodes the δ-globin chain of the minor adult hemoglobin.

The HBG1 and HBG2 are gamma globin genes which are expressed in fetal liver, spleen and bone marrow. The HBG1 has alanine at 136 and HBG2 has glycine at 136.

2.The human beta globin gene has three exons and two introns.

3.There might be around 19.5 introns

4. the order will be like: Enhancer-Promoter-Epsilon- GammaG-GammaA-Delta-Beta

5. Cotranscribed means transcription of two or more exons simultaneously. According to Venter a gene is a series of simultaneouly transcribed series of exon, exon is the coding sequence of a gene. Therefore for a whole gene to be expressed into a meaningful protein all the exons in a gene needs to be transcribed in the same time.