chapter 16 & 17

Question 1

what is the molecule of heredity?

Answer 1

DNA

Question 2

when does DNA replication occurs?

Answer 2

During S-phase of the cell cycle

Question 3

what enzymes are involved in DNA replication?

Answer 3

DNA polymerase, Helicase

Question 4

where in the cell does DNA replication occur?

Answer 4

in the nucleus

Question 5

what is RNA splicing?

Answer 5

introns removed; exons spliced together

Question 6

What is an intron?

Answer 6

non coding regions

Question 7

what is an exon?

Answer 7

coding regions

Question 8

what is a mutation?

Answer 8

a change in the DNA

Question 9

what is a point mutation?

Answer 9

change in single nucleotide pair in a gene

Question 10

how are mutations caused?

Answer 10

spontaneously or by radiation / chemical substances (mutagens)

Question 11

silent mutation

Answer 11

the amino acid that the wild type coded for is the same amino acid that resulted from the mutation, therefore the mutation is silent

Question 12

missense mutation

Answer 12

a mutation that causes an amino acid to be changed to a different amino acid
ex: Met-Ser-Lys-His
Met-Leu-Lys-His

Question 13

nonsense mutation

Answer 13

a mutation in DNA that replaces a codon that codes for an amino acid with a codon that codes for a stop codon

Question 14

insertion mutation

Answer 14

this mutation adds a nucleotide in the genetic sequence changed the genetic code for all the triplets following after that

Question 15

deletion mutation

Answer 15

this mutation causes the deletion of a nucleotide in the genetic sequence therefore changed the genetic code for all the triplets following after that

Question 16

frameshift mutation

Answer 16

the addition or deletion of one or more bases(nucleotides) that changes the genetic code for all triplets following after that

Question 17

what type of mutation causes sickle-cell disease?

Answer 17

Point mutation: Missense mutation

Question 18

Describe transcription in eukaryotic cells

Answer 18

-transcription is taking DNA to make RNA
transcription steps
1. Initiation:
- Transcription factors and an RNA polymerase binds to the TATA box AKA the promoter

• RNA transcript starts at the template strand (3’ to 5’ AKA bottom strand of DNA)
• the RNA polymerase reads the DNA and makes mRNA

2. Elongation:
   -The two DNA starts separating due to the RNA polymerase
   - As the RNA polymerase starts reading the DNA strand it starts adding nucleotides to the template strand making an RNA strand (makes a copy of the non-template strand)
3. Termination:
   - Polyadenylation signal (row of adenine signal sequence) causes the RNA transcripted to be cut free from RNA polymerase

Question 19

How do eukaryotic cells process RNAs after transcription?

Answer 19

By RNA splicing:
-meaning introns are removed (non-coding regions) and exons (coding regions) are spliced together
-and the end result is a RNA with a 5’ cap (sequence of guanine added to the start), the coding segments (exons), and the poly-A tail (50-250 adenines added to the end)

Question 20

What are some characteristics of the genetic code?

Answer 20

1. its redundant AKA repetitive
2. no ambiguity; two or more codons could code for the same thing. alone 4 codons are truly unique (start and stop codons)
3. nearly universal; almost every organism uses the same code

Question 21

What are the three types of RNA?

Answer 21

-mRNA: Messenger RNA
-tRNA:
-rRNA:

Question 22

What are the steps of Initiation in translation?

Answer 22

Initiation:
-translation occurs in ribosomes on the cytoplasm
-the mRNA the ribosome at the binding site, and then later attaches an initiator tRNA codon to the small subunit that scans for the start codon (AUG)
-Large subunit then binds forming translation initiation complex
- GTP hydrolysis provides the energy for assembly

Question 23

what are the steps of elongation in translation?

Answer 23

-There’re 3 steps cycle
1. Codon recognition:
- we start with a polypeptide already attached to the tRNA on the P site of the enzyme complex
- Anticodon of incoming tRNA binds with mRNA codon in A site
2. Peptide bond formation:
-Amino acids connected by peptide bond- catalyzed by tRNA of large subunit
- polypeptide chain moves from P sit to A site
3. Translocation:
-ribosome moves:
-A site: becomes empty
-P site: growing chain
-E site: used tRNA exits and reloaded

Question 24

What are the steps of termination in translation?

Answer 24

1. ribosome reaches a stop codon on mRNA. A site accepts release factor
2. Release factor promotes hydrolysis, freeing polypeptide
3. ribosomal subunits and other components dissociate