chapter 16: the molecular basis of inheritance

What is the components of a nucleotide

Phosphate and deoxyribose backbone and a nitrogenous base

What are the purines?

Adenine and Guanine

What are the pyrimidines?

cytosine, thymine, uracil

What is the orientation of the strands of DNA

antiparallel

What kind of bonds do nitrogenous bases have?

Hydrogen bonds

When does DNA replication happen?

S phase

What is semiconservative replication?

Each new helix contains a strand from the parent DNA molecule and a newly synthesized strand.

What is the template strand in DNA replication?

strand being copied

What is the complementary strand?

A newly synthesized strand of DNA that has a base sequence complementary to that of the template strand.

Where does replication start?

origin of replication

How many origins of replication to prokaryotes and eukaryotes have.

prokaryotes have one and eukaryotes have several

In what direction is DNA synthesized?

5' to 3'

What enzyme opens up the DNA molecule?

helicase

What enzyme relieves the strain of twisting?

topoisomerase

What does primase do?

synthesize a short sequence of RNA that complements a short

sequence of the strand, creating a primer

How long is the RNA primer?

5-10 nucleotides

What does DNA polymerase III do?

bind to the primer to

initiate the replication

What end of the primer will the new strand start?

5'

What does DNA polymerase do

add nucleotides to the new strand

What end of the new DNA strand are nucleotides added to?

3'

What is a nucleotide triphosphate?

high energy compound adding the nucleotide

What type of reaction adds the new nucleotide.

Dehydration

What is released from the dehydration reaction?

2 pyrophosphates

Why is elongation antiparallel?

Because the strands are antiparallel.

Which strand is synthesized toward the fork?

Leading strand

Which strand is synthesized away from the fork?

the lagging strand

What are the series of fragments in the lagging strand called?

Okazaki fragments

What does DNA polymerase I do?

removes the RNA primer and replaces it with DNA

What does ligase do

Join the okazaki fragments

What does DNA polymerase do once the strands are synthesized?

Proofreads the newly made strand?

What does nuclease do?

Removes the persistently mispaired fragment, DNA polymerase replaces it.

How can an error become permanent?

If it gets passed to the next generation?

How often do errors happen?

Not often

Why can eukaryotic cells not synthesize the 5' of liner DNA

The machinery cant synthesize the 5' end without the 3' end being available

What happens to DNA at each replication?

It gets a little bit shorter.

Do prokaryotes or eukaryotes have telomeres?

Eukaryotes

What is a telomere?

the ends of linear chromosomes

What does a telomere do?

it gets shortened instead of the coding gene sequences.

What cells have telomerase?

germ cells and cancer cells

What does telomerase do?

It catalyzes telomeres so they become longer and aren't affected too much by telomere erosion.

What is a bacterial chromosome?

double-strand circular molecule associated with a few proteins

What is bacterial DNA and where is it found?

supercoiled and found in a region called the nucleoid

What are eukaryotic chromosomes like compared to prokaryotic chromosomes?

chromosomes have linear DNA molecules associated with a large

amount of proteins

What is chromatin?

DNA and protein complex

What are histones?

proteins responsible of the main level of DNA packing during interphase

How many times does a DNA wrap around a histone?

twice

What is a histone with DNA wound around it called?

nucleosome

What does a nucleosome do?

involved in the regulation of gene expression

What is euchromatin?

Loosely packed chromatin, gene expressible

What is heterochromatin?

highly condensed chromatin, transcriptionally inactive

Where is heterochromatin found?

Centromeres and telomeres

What happens to chromatin in mitosis?

chromatin is organized into loops and coils, eventually

condensing into short, thick metaphase chromosomes