Chap 25

Question 1

Chromosomes and histones

Answer 1

• Chromosome – complex of protein and DNA.

- Histone – organizing protein that DNA is twisted around.

Question 2

Composition of Nucleic Acids

Answer 2

Ribose or deoxyribose, A, T, G, C, and U.

- Purines – AG, Pyrimidines - GCU

Question 3

Difference between nucleotide and nucleoside

Answer 3

• Nucleoside – sugar + base

- Nucleotide – Sugar + base + phosphate

Question 4

How are nucleotides put together? Phosphodiester linkages

Answer 4

• Phosphate bonds with the 3’ sugar

Question 5

Know about base-pairing

Answer 5

G-C, and A-T in DNA or G-C and A-U in RNA.

- G-C has 3 bonds, A-T has 2

Question 6

DNA replication

Answer 6

Replication forks, DNA polymerase, nucleoside triphosphates are used.
Always in 5’ to 3’ direction so you get Okazaki fragments on one side.
Note poor labeling of leading/lagging strands

Question 7

Transcription

Answer 7

Initiation site marked by a promoter (TATA binding protein)
RNA polymerase transcribes a copy of the information into RNA
Termination (in bacteria) is caused by a hairpin that forms in the new RNA.
Eukaryotes more complicated…

Question 8

Know the three types of RNA, and what they are used for

Answer 8

mRNA—codes for the amino acid sequence in a protein
make sure you know about splicing: introns are cut out, exons expressed.
tRNA—brings amino acids, and ‘reads’ the mRNA to ensure correct protein sequence
rRNA—makes up most of the ribosome structure (~2/3 is RNA by weight)

Question 9

What are the stop and start codons

Answer 9

methionine(AUG) always starts a protein chain on the ribosome, and there are stop-codons to terminate a protein chain (TAG, TAA, TGA).