Pre-AP Biology Tuesday March 13

Transcription and Translation

If you were absent:

1. Review the diagram model on slide 32. Record the summary notes from slide 4 in your packet (lined notebook

paper)3. See the questions on slide 5 and answer them verbally 4. Click on the video link on slide 6 to see an animation of translation5. Study slides 7 – 116. Verbally answer the questions on slide 12 by referring to your chart on P.

2 of your packet7. Answer the questions on slide 14 verbally, by connecting it to the model

on slide 138. Practice transcription and translation on slides 15 - 16

Transcription

• Occurs in the nucleus

• The enzyme RNA polymerase uses base-pairing rules to add complementary RNA nucleotides to the templatestrand of DNA

• The resulting mRNA is a copy of a gene

• This represents the instructions to build a protein (such as hemoglobin)

http://www.dnalc.org/resources/3d/13-transcription-advanced.html

Transcription Model

1. Where in the cell is the DNA found?

2. Where in the cell does transcription take place?

3. What polymer is synthesized during transcription?

4. What monomers are used to construct this polymer and where are they found?

5. According to Model 1, what enzyme is required for transcription?

6. Describe the base-pair rules that are used to match the DNA strand to the RNA strand:

7. What is the difference in base-pairing from how the two DNA strands pair?

8. What is the name for the strand of DNA that contains the “blueprint” for the pre-mRNA?

9. Before printing presses were available, books had to be transcribed in order to share the information in them. Consider the definition of transcription and explain why the process in Model 1 is described using that word.

• Translation of the mRNA occurs in the cytoplasm on the ribosome

• The ribosome may be free in the cytoplasm or attached to the rough ER

• The mRNA code is used to build a specific protein (polypeptide)

Translation

https://www.dnalc.org/resources/3d/16-translation-advanced.html

What is the structure of the ribosome?Large & small subunits, made of rRNA & proteinWhat is the function of the ribosome?The ribosome is the site of protein synthesisName 2 locations in the cell where ribosomes are found:Loose: in the cytoplasmBound: to the rough endoplasmic reticulum

Amino Acids (a.a.)

• a.a. are the monomers of proteins

• 20 different a.a.

• Proteins have a unique 3-D shape

How many unique 3-letter combinations of A, U, C, & G are possible?

A

U

C

G

A

UC

G

AUC

G

ThirdSecondFirst Letter

4 x 4 = 16

4 x 4 = 16

4 x 4 = 16

4 x 4 = 16

4 x 4 x 4 = 64 or 43

1. How many codons (3-letter mRNA combinations) are there?

2. How many amino acids (monomers of protein) are there? And how are the amino acids abbreviated?

3. What three mRNA nucleotides signal start?

4. Which amino acid will be at the start of each protein?

5. Which codons signal transcription to stop?

6. The codons (in your chart) are the same for all species on Earth. What is this evidence for?

7. How many codons are for the amino acid Pro? How are they similar and different?

8. Why do you think this redundancy exists?

Translation Model

1. Refer to Model 2. Name the three stages of translation:

2. Define each of the three stages using the terms in your answer and using everdaylanguage:

3. According to Model 2, when the mRNA leaves the nucleus, to which cellular organelle does it attach?

4. The mRNA attaches to the organelle at the sequence AUG. What is the significance of this sequence of nucleotides?

5. Describe the movement of the ribosome as translation occurs:

6. The tRNA molecues in a cell are short sequences of nucleotides (about 80 bases) that contain an anticodon and carry a specific amino acid. Find the tRNA in Model 2 that is carrying the Histidine (His). What sequence of nucleotides makes the anticodon on this tRNA molecule?

7. What codon on mRNA would match this anticodon?

8. Verify that the codon you wrote in part b codes for Histidine by looking as your decoding table.

9. What anticodon would be found on a tRNA molecule carrying Glycine (Gly)/

10.The “t” in tRNA is short for transfer. Explain why this molecule is called transfer RNA:

Practice & Self-Check: Transcription & Translation

Transcribe (copy) only the template strand (circled) into mRNA

Practice & Self-Check: Transcription & Translation