Chapter 6

Question 1

DNA structure

Answer 1

• A polymer of nucleotides
• Each nucleotide consists of
  1) Deoxyribose sugar
  2) Phosphate group
  3) Nitrogenous bases

Question 2

Nitrogenous bases

Answer 2

Pyrimidines= Adenine and thymine (single ring) (2-hydrogen bonds)

Purines= Guanine and cytosine (double ring) (3- hydrogen bonds)

Question 3

Structure of nucleotides

Answer 3

Nitrogenous base is attached to the 1’ carbon of the surge by a glycosyl bond

The phosphate is attached to the 5’ carbon by an ester bond

Question 4

The double helix

Answer 4

Two anti parallel strands

Double helix turns in a clockwise direction every 10 nucleotides (3.4nm)

Sugar phosphate backbone forms sides of the molecule

Question 5

DNA helicase

Answer 5

Unwinds the double helix by breaking hydrogen bonds between bases- replication form

Question 6

Single strand binding proteins (SSB’s)

Answer 6

Prevents DNA derom annealing

Question 7

DNA gyrase

Answer 7

(topoisomerase) releives any tension to the unwinding of DNA

Question 8

DNA polymerase III

Answer 8

Builds complementary DNA to the 5’ to 3’ direction (bonds 3’ end on RNA primer)

Question 9

Primase

Answer 9

Makes RNA primers, sequence of 10-60 RNA bases which first binds to template

Question 10

DNA polymerase I

Answer 10

Removes RNA primers, replacing them with DNA

Question 11

DNTP’s (deoxyribonucleoside triphosphate)

Answer 11

Provide energy and new nucleotides (ATP, GTP, CTP, TTP)

Question 12

Leading strand

Answer 12

Build towards replication fork (new DNA in 5’ to 3’ direction)

Question 13

Lagging strand

Answer 13

Synthesized in short fragments opposite to replication fork (new DNA still in 5’ to 3’)

Question 14

DNA ligase

Answer 14

Joins okazaki fragments

Question 15

Replication bubble

Answer 15

When two replication forks are quite near each other they from a replication bubble

Question 16

Meselson and stahl

Answer 16

Listed the three possible models of gene replication (conservative, disperse and semiconservative)

Question 17

Watson and Crick

Answer 17

Proposed the idea of the double helix

Question 18

Miescher

Answer 18

Proteins were thought to carry genetic information

He collected pus from bandages of his patients and extracted an acidic substance with a high level of phosphorus

He called in nuclein because it was found in the nucleus of white blood cells

Question 19

Hershey and Chase

Answer 19

Used bacteriophage and ecoli

Labeled DNA with P32 and proteins with S35

Radioactivity was in the DNA, radioactive protein coates had remained outside the bacteria cells while the radioactive DNA had entered the cells

Question 20

Avery, McLeod and McCarty

Answer 20

DNA is the transforming substance

Question 21

Chargaff

Answer 21

Determined the A:T G:C ratio

Humans have 30.9% A, 29.4%T, 19.9%G and 19.8%C

Question 22

Wilkins and Franklin

Answer 22

Used X- ray crystallography to determine the shape of DNA

The atoms in a compound deflected the X- rays creating a pattern

Wilkins had discovered helical structure

Franklin suggested the sugar phosphate backbone faced the outside of the molecule, DNA was a double helix which rotated in a clockwise direction with a diameter of 2nm and that one turn of the helix was 3.4 nm in length

Question 23

Beadle and Tatum

Answer 23

Studied mutations

Question 24

McClintock

Answer 24

Discovered transpoons

Question 25

Ingram

Answer 25

Blood relates diseases. Sickle cell anemia

Question 26

Craig Venter

Answer 26

Synthesized genomes and DNA in an attempt to synthesize life

Question 27

Histone

Answer 27

A special protein molecule that is the core around which the DNA strands wrap Positively charged

Question 28

Genome

Answer 28

The complete set of an organisms hereditary information

Question 29

Plasmid

Answer 29

Small circular section of DNA found in the cytosol of bacteria, replicates independently of the chromosomal DNA

Question 30

Nucleosome

Answer 30

Contains 8 histones

Question 31

Solenoid

Answer 31

A group of 6 nucleosomes

Question 32

How does DNA in prokaryotes conserve space

Answer 32

Uses a coiling technique (super coiling)

Question 33

Telomers repeating sequences of nucleotides

Answer 33

repeating sequences of nucleotides

Question 34

Telomerase

Answer 34

An enzyme that adds new teller sequences to the ends of chromosomes

Question 35

Cell senescence

Answer 35

the period in a cell's lifespan when it looses the ability to divide and grow, often referred to as the cell's aging

Question 36

Hayflick limit

Answer 36

The total number of times that a normal cell can divide

Question 37

Nucleotides

Answer 37

Monomers of DNA

Question 38

Telomere

Answer 38

A repeating sequence of DNA at the end of a chromosome that protects coding regions from being lost during replication

Question 39

Bacteriophage

Answer 39

Bacteria that targets bacteria, the one they used had both a DNA and a protein coat No one knew much about virus because they could not be seen

Question 40

Purines

Answer 40

Adenine and guanine, double ring structure

Question 41

Pyrmidines

Answer 41

Thymine and cytosine, single ring structure