Bio 121 Sheet #11

7.What is the cause of Hereditary Nonpolyposis Colorectal Cancer?

-Defective repair of mismatch mutations

24.What are the 4 main differences between DNA replication and transcription?

4 differences between DNA replication and transcription 1. Difference substrates: nucleotides differ -used RNA nucleotiides to build RNA; these contain the sugar ribose, and AUCG -Use DNA nucleotides to build DNA; these contain the sugar deoxyribose and ATCG (replication) 2. - transcribe one strand of DNA -replicate both strands of DNA 3. -must be told when and where to start and stop transcription 4. -Transcription starts form scratch and starts in a region that is not important ( the promoter) -DNA polymerase does not start from scratch because you need to replicate ALL of the DNA REMINDER: DNA replication requires DNA polymerase RNA transcription uses...

10.Why did Garrod conclude that some diseases have a genetic basis?

Garrod first to document that disease "runs in the family" inherited

2.What is photolyase?

Photolyase- enzyme that repairs DNA damage caused by US radiation; uses visiible light as an energy source to break the bonds between adjacent thymines (t)

23.What is a transcription factor?

Transcription factors; proteins that bind to regulatory sequences and tell RNA polymerase where to start transcription

1.How does UV damage DNA, and how is this damage repaired?

-UV causes the formation of thymine dimers in DNA - Adjacent R bases link together, causing a kink in the backbone. -Photo-repair enzyme called photolyase -photolyase absorbs visible light and uses the energy to cut the bond between the thymines, restoring DNA to its natural condition. NOTE: UV in sunlight causes the damage; visible light is used to repair the damage

20.What are the 3 roles of RNA in protein synthesis?

-rRNA: ribosomal RNA- component of the Ribosome; rRNA is structural -mRNA: messenger RNA; "xeroxed copy" of a gene; mRNA will go to ribosome and then ribosome reads the sequence of nucleotides in mRNA; this message is used to determine the order of amino acids in the protein "message"= order of amino acids in the protein -tRNA- Transfer RNA; transport amino acids to the ribosome each transfer ONE AND ONLY ONE type of amino acid

9.Why do defective BRCA1 or BRCA2 genes increase the risk of cancer?

BRCA1 and BRCA2 work with the protein RAD51 to repair double stranded breaks. If the genes are defective, then the proteins will be defective, and DNA damage will not be corrected.

12.How did Beadle and Tatum show that genes are instructions for making enzymes?

Beadle and Tatum: one gene- one enzyme hypothesis -deliberately destroyed genes, then looked for heritable defects in the enzymes -mutants (DNA was destroyed) were unable to grow in minimal media -identified the missing nutrient by adding specific chemicals, one at a time. -found that each gene coded for a different enzyme in pathway used to produce arginine -genes store for the production proteins. information is stored in the sequence of nucleotides in the genes

21.What are the sequences of the DNA and mRNA strands made from the template 5'-AGCTTGACTA-3'?

DNA 5'-TAGTCAAGCT--3' RNA 5'UAGUCAAGGU-3' DURING transcription, there is no T in RNA; use U instead

16.What is the central dogma?

DNA--------> RNA---------------> protein -trasncription in the nucleus -translation- in ribosome

13.How do we know that DNA specifies the primary structure of a protein?

Defective genes cause insertion of wrong amino acids in protein that the gene codes for

6.What is mismatch repair?

Mismatch pair -mechanism will repair DNA sequences where bases are not paired correctly Process: 1. find mistakes 2. replace the base on the new strand using the old strand as the template old strand is methlated

25.What are 3 post-transcriptional modifications to eukaryotic mRNA?

Post transcriptional modification (modification after transcription); EUKARKYOTIC CELLS ONLY 1. cap 5' end with 7 methyl G -identifies this molecule as mRNA 2. Splice; remove introns and splice together exons 3. Polyadenylation: 3' end replaced with approx. 250 adenines ( identifies this molecule as RNA)

22.What is a promoter, and what is a terminator?

Promoter: segment of DNA before (5') to the structural gene; forms a recognition and binding site for RNA polymerase; the binding of RNA polymerase to promoter is the first step of transcription Terminator: signal to RNA polymerase to end transcription

18.What are transcription and translation?

TRANSCRIPTION: using DNA to make RNA TRANSLATION: using RNA to make protein

17.What is gene expression and what are the two stages of gene expression?

The use of genetic information to produce a protein involves transcription THEN translation PRODUCT OF A GENE IS A PROTEIN

8.How do X-rays damage DNA?

X rays damage DNA by causing double stranded breaks

4.What causes Xeroderma pigmentosum?

Xeroderma pigmotisum: -disorder resulting from inability of cells to correct DNA damage due to UV -8 genes are involved in DNA repair caused by UV -individual is ultra-sensitive to UV

5.What is base excision repair?

base pair repair -repair of a few nucleotides 1. find mistake and remove defective bases 2. DNA polymerase replaces missing base(s) 3. DNA ligase will seal the backbone - nucleotides excision repairs- approximately 30 nucleotides -base excision repair -1-3 nucleotides

15.Why do we know there must be an intermediate between DNA and protein synthesis?

can make protein in a test tube without DNA

11.What evidence supports the hypothesis that each gene encodes a protein?

destroy a gene, cell does not make the corresponding protein gene: sequence of DNA nucleotides that codes for a certain protein

14.What is "in vitro translation," and why is it useful?

in vitro translation: in lab production; technique was used to 'crack' the genetic code - this technique tells us which codon codes for wich amino acid ex: AUG codon for methionine

3.What is nucleotide excision repair?

nucleotide excision repair -identify a region of DNA that is damaged (nucleotides are out of sequence) -remove that sequence -replace those nucleotides witht eh correct nucleotides using the undamaged stand as the template

19. What are ribosomes and what do they do?

organelles that make proteins out of amino acids Protein: large chain of amino acids ASSEMBLEDD IN A CERTAIN ORDER