Biology Unit 6

Pyrimidine

(C, T, and U) single-ring nitrogenous base

Explain the use of genetic engineering techniques in analyzing or manipulating DNA.

Genetic engineering techniques can be used to analyze and manipulate DNA and RNA

Describe the mechanisms by which genetic information flows from the DNA to RNA protein.

Genetic information flows from a sequence of nucleotides in DNA to a sequence of bases in an mRNA molecule to a sequence of amino acids in a protein. RNA polymerase uses a single template strand to direct the inclusion of bases in the newly formed RNA molecule. The enzyme RNA polymerase synthesizes mRNA in the 5' to 3' direction by reading the template DNA strand in the 3' to 5' direction.

Describe the structures involved in passing hereditary information from one generation to the next.

Genetic information is stored in and passed on to subsequent generations through DNA molecules.

Describe Replication

Helicase unwinds the DNA strand. Topoisomerase relaxes supercoiling in front of the replication fork. RNA primers to initiate DNA synthesis. One strand of DNA is used as the template for a new strand of complementary DNA. DNA is synthesized in the 5' to 3' direction. DNA polymerase synthesizes DNA continuously on the leading strand and discontinuously on the lagging strand. Ligase joins the fragment on the lagging strand.

Explain how the location of regulatory sequences relates to their function.

In prokaryotes, groups of genes called operons are transcribed into a single mRNA molecule. In eukaryotes, groups of genes may be influenced by the same transcription factors to coordinately regulate transcription.

Purine

(G and A) double-ring nitrogenous base

Plasmid

A small, extrachromosomal, double stranded, circular, DNA molecule

Epinegenic Changes

Affect gene expression through reversible modifications on DNA histones

Describe the various mutations.

Alterations in a DNA sequence can lead to changes in the type or amount of the protein produced and the consequent phenotype. DNA mutations can be positive, negative, or neutral based on the effect or the lack of effect they have on the resulting nucleic acid or protein and the phenotypes that are conferred by the protein.

Explain how alterations in DNA sequences contribute to variations that can be subject to natural selection.

Changes in genotype may affect phenotypes that are subject to natural selection. Genetic changes that enhance survival and reproduction can be selected for by environmental conditions

Describe the characteristics which allows DNA to be used as the hereditary material.

DNA exhibits specific nucleotide pairings that are conserved through evolution.

Explain how changes in the genotype may result in changes in the phenotype.

Errors in DNA replication or DNA repair mechanisms, and external factors, including radiation and reactive chemicals, can cause random mutations in the DNA. Errors in mitosis or meiosis can also result in changes in phenotype.

Explain the connection between the regulation of gene expression and phenotypic differences in cells and organisms.

Gene regulation results in differential gene expression and influences cell products and function. Certain small RNA molecules have roles in regulating gene expression.

Explain how the binding of transcription factors to the promoter region affects gene expression and/ or the phenotype of the organism

Promoters are DNA sequences upstream of the transcription site where RNA polymerase and transcription factors bind to initiate transcription. Negative regulatory molecules inhibit gene expression by binding to DNA and blocking transcription.

What are the types of interactions that regulate gene expression?

Regulatory Sequences and Epigenetic Changes

Regulatory Sequences

Stretches of DNA that interact with regulatory proteins to control transcription.

Replication

The mechanism by which genetic information is copied for transmission between generations.

Describe Translation

Translation is initiated when the rRNA in the ribosome interacts with the mRNA at the start of the codon. tRNA brings the correct amino acids to the correct place specified by the codon on the mRNA. The amino acid is transferred to the growing polypeptide chain. The process continues along the mRNA until a stop codon is reached. The process terminates by the release of the newly synthesized polypeptide/ protein.

How is the phenotype of an organism is determined by its genotype?

Translation of mRNA to produce a polypeptide occurs on the ribosomes that are present in both prokaryotic and eukaryotic cells, and on the rough endoplasmic reticulum of eukaryotic cells.