Storing and Using Genetic Information

Question 1

define phenotype

Answer 1

physical manifestation of an organism ( physical appearance)

Question 2

define genotype

Answer 2

full hereditary information of an organism (even if not expressed physically)

Question 3

what are components of a nucleotide?

Answer 3

• sugar (5-carbon sugar)
• base
• phosphate group

Question 4

what are components of a nucleoside?

Answer 4

-sugar (5-carbon sugar)
- base
(NO phosphate group)

Question 5

how many bases are there for every turn of the helix?

Answer 5

10 bases

Question 6

what are 2 most common sugars used in DNA?

Answer 6

• deoxyribose (lacking oxygen)

- ribose

Question 7

is deoxyribose or ribose less resistant to enzymes?

Answer 7

deoxyribose

Question 8

does DNA or RNA break down quicker?

Answer 8

RNA

Question 9

how do polynucleotide chains run against each other? (in what way)

Answer 9

anti-parallel (from 5’ to 3’ which makes it stable)

Question 10

what structures are present for interactions of proteins with the DNA molecule?

Answer 10

major and minor grooves (many binding sites found on major groove)

Question 11

what volume of nucleus is the nucleolus?

Answer 11

approx. 25%

Question 12

what is the function of the nucleolus?

Answer 12

site of transcription and assembly of rRNA and creates ribosomes

Question 13

when are chromosomes visible?

Answer 13

when the cell is dividing

Question 14

what structures does DNA coil around?

Answer 14

histones

Question 15

how many proteins make up a histone?

Answer 15

9 proteins

Question 16

What is DNA around a histone called?

Answer 16

a nucleosome

Question 17

what part of mitosis, does coiling of DNA occur?

Answer 17

metaphase

Question 18

what is chromatin?

Answer 18

mixture of DNA, proteins and RNA that packages DNA within the nucleus

Question 19

what 2 types of chromatin are there?

Answer 19

• heterochromatin

- euchromatin

Question 20

what is heterochromatin?

Answer 20

condensed, non-functional part of the DNA

Question 21

what is euchromatin?

Answer 21

extended form, functional part of the DNA

Question 22

what are 2 major mechanisms which make chromatin more accessible?

Answer 22

1. histones can be enzymatically modified

2. histones can be displaced by chromatin remodelling complexes

Question 23

is DNA folding and unfolding reversible?

Answer 23

yes

Question 24

what does structure of chromatin/DNA depend on?

Answer 24

varies depending on the access required to the DNA

Question 25

what are 2 main characteristics of DNA replication?

Answer 25

1. semi-conservative | 2. bi-directional

Question 26

what is meant by DNA being semi-conservative?

Answer 26

one half of each new molecule of DNA is old and one half is new

Question 27

what bonds are broken when DNA is "unzipped"?

Answer 27

hydrogen bonds

Question 28

DNA polymerase can only add new nucleotides to which end of the growing strand?

Answer 28

3' end of growing strand

Question 29

what does DNA ligase do?

Answer 29

joins DNA strands together by catalysing the formation of double bonds.

Question 30

what are Okazaki fragments?

Answer 30

formed on the lagging strand (small newly synthesised segments DNA) which join together by DNA ligase to form a continuous strand (Okazaki fragments form short double-stranded DNA sections which are complementary to lagging template strand)

Question 31

In what direction does DNA polymerase work in?

Answer 31

(5'--> 3') and adds to the 3' end

Question 32

does new strand grow in the opposite direction to the old strand?

Answer 32

yes

Question 33

what are exons?

Answer 33

part of the code for a particular gene (CODING regions)

Question 34

what are introns?

Answer 34

doesn't code for anything, "junk" of the DNA strand (NON-CODING regions)

Question 35

how many bases make up a codon?

Answer 35

3 bases

Question 36

how many amino acids are there?

Answer 36

20 amino acids

Question 37

what is the degeneracy/ redundancy of the genetic code?

Answer 37

Many (more than one) codons can code for the same amino acid (exceptions; methionine and tryptophan)

Question 38

what is the name given to codons which refer to the same amino acid?

Answer 38

synonyms

Question 39

where is the most common location for variations between synonyms to occur?

Answer 39

at third base of the codon(wobble position)

Question 40

what is the point of degeneracy in a genetic code?

Answer 40

- minimises the effect of genetic mutations - alterations to the base sequences are less likely to alter the protein being coded for - prevent alteration to protein structure and hence function

Question 41

what is the initiation codon?

Answer 41

methionine

Question 42

what is a common example of a single point mutation?

Answer 42

sickle cell anaemia

Question 43

what is mRNA?

Answer 43

transcribed from DNA in nucleus during transcription, carries information for protein synthesis

Question 44

what is alternative splicing?

Answer 44

- process by which exons of the RNA produced by transcription of a gene (primary gene transcript of pre-mRNA) are reconnected in multiple ways. - resulting different mRNAs can be translated into different protein forms - therefore a single gene may code for multiple proteins

Question 45

what is tRNA?

Answer 45

- acts as an adapter molecule between coded amino acid and mRNA - anti-codon on tRNA will bind to the codon on mRNA

Question 46

what is rRNA?

Answer 46

- component of ribosomes (produced in nucleus) - transported to cytoplasm where they combine with proteins to form ribosomes - susceptible to enzyme degradation