Warm-up: answer the questions on your paper

Transcription

1 Warm-up: answer the questions on your paper 1. What type of bonds hold DNA molecules together? Are they weak or strong, and why? 2. During protein synthesis, an mrna sequence is produced from a DNA sequence, what process is occurring? 3. Transcribe the following DNA sequence: TTAAG 4. Describe the process of translation.

2 Warm-up: Check your Answers 1. What type of bonds hold DNA molecules together? Are they weak or strong, and why? Hydrogen weak so that the strands can separate for replication 2. During protein synthesis, an mrna sequence is produced from a DNA sequence, what process is occurring? Transcription 3. Transcribe the following DNA sequence: TTAAG AAUUC 4. Describe the process of translation. Using codons in mrna to produce amino acids

3 Use the following pages to help you complete the guided note portion of your paper.

4 GENETIC CODE The language that translates the sequence of nitrogen bases in DNA (mrna) into the amino acids of a protein. Codon = three nucleotides on DNA or mrna One codon specifies one amino acid Some codons are redundant (that means they code for the same amino acid) The genetic code is universal to all organisms

5 What can we conclude? 64 codons to make 20 amino acids So several codons code for the same amino acids This means we can make the same proteins even if the codons get changed a little (substitution mutation).

6 Cells make mistakes, these are called mutations! Mutations changes in the genetic material A change in the genetic code, even though DNA polymerase proofreads Mutations can be positive, negative, or neutral. Positive: Rarely, a mutation will give an organism benefits that its parents did not have. This trait might make the organism able to survive better, more attractive to the opposite sex, or be able to adapt to different conditions. Mutations are also the source of genetic variability in a species. Neutral: cause no big changes to the DNA Negative: cause big changes in the DNA and have very negative effects Many genetic disorders and types of cancer are caused by genetic mutations.

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8 3 Types of Mutations: 1. Substitutions 1 nucleotide is exchanged for another Only affect 1 nucleotide E.g. TAC GCA TGG TAC GTA TGG Results in a change in 1 amino acid

9 3 Types of Mutations: 2. Additions adding nucleotides into a sequence E.g. TAC GCA TGG TAC GCCA TGG 3. Deletions deleting nucleotides from a sequence E.g. TAC GCA TGG TAC GA TGG **Additions and Deletions have more serious consequences because it shifts the sequence and changes more than 1 codon and therefore the amino acid changes**

10 What causes mutations? DNA does not copy correctly Environmental factors: Chemicals Radiation Sunlight (UV radiation, temperature) Smoking

11 Effect of Mutations Most have little or no effect on gene expression Ones that do have an effect- it is usually dramatic Could cause genetic disorders Could benefit the organism

12 Gene Regulation Only a fraction of genes in a cell are expressed at a given time Expressed gene one that is transcribed into RNA

13 Gene Regulation Gene = a group of bases (ATCG) that code for 1 protein Every cell in an organism has the SAME DNA Think of it this way Every piano has the same set of keys (just like every cell has the same DNA). However, different songs sound different because of the specific keys that the player chooses to play (just like different cells are able to perform different functions based on the genes that are chosen to be expressed.) How can we have cells that do different jobs? All thanks to gene regulation

14 Genes can be turned on and off when they are needed If we don t need the gene to make the protein for eye color, we just don t turn it on If we need a certain protein, the genes get a signal to turn on and make the protein Can be hormones or environmental factors that tell cells what to do/become

15 How does a cell determine which genes will be expressed and which will be silent? Cells must communicate in order to coordinate the activity of each cell (usually involves proteins)

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17 1. Environmental influences Different genes are expressed depending on the environment of the cell. (A musician would not chose to play rap in a jazz club) Ex. E. coli bacteria in the human stomach -E. coli feed on lactose (a sugar found in milk) - When lactose is present in your stomach, certain genes (lac genes) get turned on to digest it -When all of the lactose has been digested,, those genes turn off and no proteins are created (because the proteins are not needed)

18 2. Cell Specialization -Different genes are expressed depending on the specific job of the cell Ex. Liver cells will turn on different genes than muscle cells, because they have completely different jobs

19 Timing is everything! Just like the wrong beat can ruin a song, the production of the wrong proteins or the production of the right proteins at the wrong time can ruin your body, and even your life. 1. Injury repair: Sometimes, it is beneficial for your body to produce A TON of new proteins, such as when you break a bone or cut your skin: new proteins aid in the healing process

20 2. Cancer: Other times, proteins are created at the wrong time, which causes uncontrolled cell reproduction leading to tumors that may cause cancer

21 Last Steps: Flip your paper over and complete the Snorks activity If you have time: Finish the online textbook (Chapter 12) reading and practice Complete the extra credit questions and activities on the class weebly