1.2- structure and replication of DNA

Question 1

flow of control in DNA

Answer 1

order of bases decides;

order of amino acids decides;

type of protein + function

Question 2

structure of a protein

Answer 2

composed of amino acids joined together by peptide bonds into a unique sequence

Question 3

what decides a proteins characteristics?

Answer 3

type and order of amino acids

Question 4

what determines the order of amino acids and specifically what?

Answer 4

DNA of the gene which codes for the protein

specifically the sequence of the bases in the DNA which stores the genetic information (the genotype and the genome) of the organism

Question 5

what forms the genetic code?

Answer 5

the base sequences of DNA

Question 6

structure of a chromosome

Answer 6

thread-like structures found in the nucleus of the cell

contain DNA that is tightly wound around proteins called histones

Question 7

what are the strands of the double helix made up from?

Answer 7

nucleotides

Question 8

3 things that make up one nucleotide

Answer 8

base
phosphate
deoxyribose sugar

Question 9

what bond is formed between nucleotides?

Answer 9

strong chemical bond between phosphate group of one nucleotide and the carbon 3 of the deoxyribose on another nucleotide

Question 10

how is a strand of nucleotides formed?

Answer 10

in a long, permanent strand in which sugar molecules alternate with phosphate groups

this forms the DNA molecules sugar-phosphate backbone

Question 11

what joins together the DNA strands and where?

Answer 11

weak hydrogen bonds

between the bases

Question 12

what can happen to hydrogen bonds?

Answer 12

can be broken when necessary for the 2 strands to separate

Question 13

what are anti-parallel strands?

Answer 13

strands that are parallel but moving in opposite directions

Question 14

where is the 3’ end located on DNA?

Answer 14

deoxyribose sugar

Question 15

where is the 5’ end located on DNA?

Answer 15

phosphate group

Question 16

what is the only way a chain can grow?

Answer 16

adding nucleotides to its 3’ end

Question 17

6 requirements for DNA replication

Answer 17

DNA template

supply of free DNA nucleotides

supply of energy (ATP)

DNA polymerase

Ligase

Primers for DNA polymerase

Question 18

function of DNA template

Answer 18

provide the initial genetic code

Question 19

function of supply of free DNA nucleotides

Answer 19

DNA nucleotides will be added together to form the strand

Question 20

function of supply of energy (ATP)

Answer 20

provide energy to allow this process to take place

Question 21

function of DNA polymerase

Answer 21

adds DNA nucleotides using complementary base pairing to the deoxyribose 3’ end

Question 22

function of ligase

Answer 22

joins together fragments of DNA

Question 23

function of primers for DNA polymerase

Answer 23

short strand of nucleotides which binds to the 3’ end of the template DNA strand

Question 24

function of helicase

Answer 24

unzipping strands of DNA

Question 25

function of **primase**

Answer 25

makes primers

Question 26

what is **supercoiling**?

Answer 26

over winding of DNA

Question 27

what is DNA replicated by **prior** to cell division?

Answer 27

by DNA polymerase enzyme

Question 28

**where** can DNA polymerase add nucleotides?

Answer 28

3' end of the primer

Question 29

**process of DNA replication**

Answer 29

double helix of the DNA molecule is unwound by an enzyme and the hydrogen bonds between the bases are broken to form two template strands due to the antiparallel arrangement of the strands, one of the separated strands ends with an exposed 3' end which is called the leading strand **process** the other ends with the 5' end called the lagging strand **process**

Question 30

**process of the replication of the leading strand of DNA**

Answer 30

after hydrogen bonds break, the DNA strands separate forming two template strands DNA primer attaches to the start of the piece of DNA being copied DNA polymerase attaches free nucleotides to the 3' end of the primer and the formation of the sugar-phosphate backbone is also a result of this enzyme process is continuous and forms the leading strand

Question 31

**process of the replication of the lagging strand of DNA**

Answer 31

lagging strand replicated in fragments as DNA polymerase can only add onto 3' end of a primer many primers attach along the strand and are extended by DNA polymerase DNA fragments are the joined by the enzyme ligase process is discontinuous and forms the lagging strand

Question 32

what does polymerase chain reaction **do**?

Answer 32

amplifies DNA using complementary primers for specific target sequences

Question 33

what are **primers** in **PCR**?

Answer 33

short strands of nucleotides complementary to specific target sequences at the two ends of the region of DNA to be amplified

Question 34

4 **requirements** of PCR

Answer 34

DNA template free DNA molecule heat tolerant DNA polymerase primers

Question 35

**why** is heat tolerant DNA polymerase used in PCR?

Answer 35

PCR requires high temperatures in order to replicate the DNA enzymes generally denature at high temperatures

Question 36

**process of PCR**

Answer 36

DNA heated to between 92 and 98 to separate the strands then cooled to between 50 and 65 to allow primers to bind to target sequences the heated to between 70 and 80 for heat tolerant DNA polymerase

Question 37

what does **repeated cycles** of heating and cooling do?

Answer 37

amplifies the target region of DNA

Question 38

3 **practical applications** of PCR

Answer 38

solve crimes settle paternity suits diagnose genetic disorders