Chapter 9

Question 1

how is genetic info

Answer 1

1. stored
2. replicated
3. translated

Question 2

DNA characteristics

Answer 2

1. carries a large amount of info
2. it can be accurately copied
3. is stable under a range of environmental conditions
4. the info it carries is used code for amino acid sequences

Question 3

structure of dna

Answer 3

DNA is a type of nucleic acid
polymers made from nucleotides 
nucelotide are conposed of three parts:
1. 5 carbon sugar
2. phosphate group
3. nitrogen base 
(variable structure)

Question 4

sugars

Answer 4

the sugar of one nucleotide bond to the phosphate of another nucleotide
the sugar and phosphate always have the same chemical structure

Question 5

in DNA there are 4 possibel nitrogen bases

Answer 5

Adenine (A)
thymine (T)
cytosine (C)
guanine (G) 
the sequence of nitrogen babes is a source of info

Question 6

DNA normally exists

Answer 6

as two separate strands

each strand runs in opposite directions

Question 7

hydrogen bond form

Answer 7

between the nitrogen bases of the strands
cytosine only bonds with guanine
adenine only bonds with thymine -complimentary pairing

Question 8

double strands of DNA are

Answer 8

twisted around one another into double helix

Question 9

DNA replication

Answer 9

one strand of DNA acts as a template for the construction of a new strand

1. double strands of DNA are pulled apart
2. complimentry nucleotides are synthesized into new DNA strands
3. hydrogen bonds re-form between nitrogen bases

Question 10

semi conservation replication

Answer 10

each new set of double DNA strands contains an old strand

Question 11

enzymes are responsible for

Answer 11

the 1st two stages of replication

responsible for each phase of replication

Question 12

DNA helicase

Answer 12

breaks hydrogen bonds between double strands

moves in one direction only

Question 13

DNA ploymerse

Answer 13

joins nucleotides together in their proper sequence by reading the sequence of the original strand
can only snythesize new strands in one direction
requires a primer (short sequence of nucleotides) to start a new DNA strand
one strand is made continuously, the othe ris made in sections

Question 14

DNA ligase

Answer 14

join strands of DNA together

the new strands run in opposite direction to the old strands

Question 15

another type of nuclecic acid

Answer 15

RNA (ribonucleic acid)

Question 16

structure

Answer 16

similar to DNA except:
1. the 5 carbon sugar is different
2. thymine is not present, it is replaced by uricil (U) it goes with adenine
3. does not necessarily form a double strand
it can also act as an enzyme

Question 17

protien synthesis (how genetic info is used)

Answer 17

DNA codes for amino acid sequences
4 different nitrogen babes in DNA code for 20 different amino acids in protiens
groups of three babes (codons) code for a single amino acid

Question 18

how many different combinations are there

Answer 18

64 different possible combinations of 3 nucleotide bases

some base combinations code for the same amino acid

Question 19

2 stages of protien synthesis

Answer 19

transcription

translation

Question 20

transscription

Answer 20

copying of one DNA strand into an RNA strand

Question 21

translation

Answer 21

coverting RNA sequence into an amino acid sequence

Question 22

invloved in transciption

Answer 22

takes places in the the nucleus
promotor: DNA sequence where transcription starts
terminator: DNA seqeuence where transciption ends
RNA polymerase: emzyme that carries out transsciption

Question 23

steps in transciption

Answer 23

1. initation- RNA polymerase attaches to DNA at the promoter
2. DNA strands are pulled apart
3. elongation- RNA nucleotides are bonded together based on the DNA sequence
4. termination- transciption occurs until a terminator sequence occurs until a terminator sequence is encountered
   at the terminator the RNA polymerse detaches from the DNA and releases the RNA strand
   the resulting RNA strand is known as messenger RNA or mRNA

Question 24

involved in translation

Answer 24

occurs in the cytoplasm on ribosomes
aligns mRNA and transfer RNA
have two binding sites for tRNA molecules

Question 25

transfer RNA (tRNA)

Answer 25

two attachment sites: 1. amino acid attachment site 2. aticodon- a set of three nucleotides complimentry to mRNA the type of amnio acid attached to a tRNA depends on its anticodon sequence

Question 26

steps in translation

Answer 26

1. ribosome and tRNA bind together. This always occurs at the nucleotide sequence (the start codon) 2. a 2nd tRNA molecule binds to the 2nd binding site of the ribosome 3. the amino acid from the first tRNA is removed from the tRNA and bonded to the amino acid on the second tRNA 5. the first tRNA is released from the ribosome 6. the second tRNA is shifted from the second to the first binding site 8. the process is repeated until a stop codon seqeunce is reached 9. thr amino acid sequence is released from the final tRNA

Question 27

genes

Answer 27

can be considered sections of DNA they are always located int he same region of a chromosome genes arent necessarily a easily defined sections of DNA

Question 28

alleles

Answer 28

make protiens that preform the same function but have different DNA code

Question 29

in ekaryotes there are additional steps in transciption

Answer 29

not all DNA codes for protiens- exons do, introns do not initially all sections are copied before mRNA leaves the nucleus introns are removed and the remaining sections joined more than one protien can be made from a section of DNA by splicing different sections of mRNA together