DNA Structure and Replication SC.912.L.16.9 Explain why the genetic code is universal. Explain why there are similarities in the genetic code of different organisms. SC.912.L.16.3 Describe the basic process of DNA replication. Explain why DNA replication has a role in the transmission and conservation of the genetic material. Demonstrate the process of DNA replication given a DNA strand. SC.912.L.16.4 Analyze the causes of gene and chromosomal mutations to predict the possible effect in a DNA sequence. Explain how mutations in a DNA sequence may or may not result in a phenotypic change. Explain how mutations in gametes may result in phenotypic changes in offspring.

Why is the genetic code universal? All organisms have DNA made of the same molecules. – DNA in every organism has the bases: A,T,C,G

Why are there similarities in the genetic code of similar organisms? Most organisms share a common ancestry and the process of inheritance carries traits from generation to generation.

How does the process of DNA replication enable genetic information to be transmitted and used to build proteins? DNA  RNA  Protein DNA Replication= making an identical copy of a DNA strand

DNA Replication DNA replication begins with the unwinding of the DNA double helix by several enzymes. The exposed strands are then used as a template, or model, to build the new strand according to base pairing rules (A to T, C to G). At the end of the process, there are two, identical strands of DNA, each with part of the original strand and a newly created strand.

Replication –

Transcription is catalyzed by RNA polymerase. –RNA polymerase and other proteins form a transcription complex. –The transcription complex recognizes the start of a gene and unwinds a segment of it. start site nucleotides transcription complex

–RNA polymerase reads one side of the DNA template and strings together a complementary strand of RNA nucleotides. –The DNA helix winds again as the gene is transcribed. DNA RNA polymerase moves along the DNA

– The RNA strand detaches from the DNA once the gene is transcribed. RNA

RNA differs from DNA in three major ways. –RNA has a ribose sugar. –RNA has uracil instead of thymine. –RNA is a single-stranded structure.

Transcription – Translation – Codon – A sequence of three non-overlapping nucleotides that code for a specific amino acid. Anticodon – Nucleotides on the tRNA molecule that help the molecule match up with the correct codon. - complementary pairing.

Amino acids are coded by mRNA base sequences. Translation converts mRNA messages into polypeptides. A codon is a sequence of three nucleotides that codes for an amino acid. codon for methionine (Met) codon for leucine (Leu)

Reading frame: series of non-overlapping nucleotides read in order. A change in the order in which codons are read changes the resulting protein. Regardless of the organism, codons code for the same amino acid (common language).

Mutations are changes in DNA that may or may not affect phenotype. Some mutations affect a single gene, while others affect an entire chromosome.

A mutation is a change in an organism’s DNA. Many kinds of mutations can occur, especially during replication. A point mutation substitutes one nucleotide for another. Mutated base

Many kinds of mutations can occur, especially during replication. –A FRAME SHIFT MUTATION inserts or deletes a nucleotide in the DNA sequence.

How can DNA mutate? Mutation = a mistake or change in the DNA sequence. – Causes: mistake during replication,exposure to x- rays, ultraviolet light, radioactive substances or certain chemicals.

Why don't all mutations result in visible change? Not all mutations are harmful, some may be beneficial, and may not be visible (silent mutation). – Silent mutations occur because the same amino acid is created despite the error.

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1. Which of the following statements describes processes that occur during DNA replication? a.a DNA sequence is read by RNA polymerase, which produces another RNA strand complementary to the first strand. b.Two free-floating single strands of DNA are joined by polymerase. The polymerase finds the point at which the two strands will match up into a double strand. c.Messenger RNA are decoded by a ribosome to produce an amino acid chain. In the cell's cytoplasm, transfer RNA join the messenger RNA, forming a polypeptide. d.A double-stranded DNA molecule is unwound into single strands. Polymerase matches the right nucleotides to the single strand so that each forms a double strand of DNA.

2. The genetic code is nearly universal, meaning that almost all organisms use the same genetic code. Which statement does NOT help explain why the genetic code is nearly universal? a.all organisms encode their genes using DNA or RNA b.All organisms can grow, respond to stimuli, and reproduce c.All organisms use the same codon for the same amino acid. d.All organisms are genetically related to all other organisms.

3. DNA mutations can be present in a gene for many reasons. Which of the following does NOT describe a reason genetic mutations may exist in a gene? a.When a cell dies, the DNA in the cell's nucleus can mutate. b.Exposure to chemicals or radiation can cause mutation in DNA. c.Mutations in DNA can be passed down from a parent to a child. d.Polymerase can make a mistake in matching nucleotides during replication.

4. Mutations in an organism's DNA may be either beneficial or harmful. Which of the following statements best describes the concept of DNA mutation? a.DNA mutation is an alteration in DNA replication that always results in phenotypic change. Mutations are usually due to radiation or other environmental factors b.DNA mutation is a change in the way that genes reproduce themselves, which may or may not affect phenotypic characteristics. Mutations are usually due to environmental factors or heredity. c.DNA mutation is a change in the gene sequence, which sometimes results in phenotypic change. Mutations can be due to environmental factors, heredity, or a mistake in DNA replication d.DNA mutation is an alteration in the nucleus of a cell that makes certain genes unable to be copied, and they result in phenotypic change. Mutations are usually due to viruses and environmental factors