8 DNA genes and protein synthesis

Question 1

what is a gene?

Answer 1

a section of DNA that codes for amino acid sequences

Question 2

the genetic code is:

Answer 2

• non overlapping
• degenerate
• universal

Question 3

what does degenerate mean?

Answer 3

more than one codon codes for an amino acid

Question 4

what does non-overlapping mean?

Answer 4

each base belongs to only one codon or triplet

Question 5

wha does universal mean?

Answer 5

the same 3 bases code for the same amino acid in all organisms

Question 6

what are the non coding sequences called in DNA?

Answer 6

introns

Question 7

what are the coding sequences called in DNA?

Answer 7

exons

Question 8

state 3 differences between prokaryotic and eukaryotic DNA

Answer 8

prokaryotic:
- not associated with histones
- circular
- shorter
eukaryotic:
- associated with histones
- linear
- longer

Question 9

describe mitochondrial and chloroplast DNA

Answer 9

• circular
• short
• not associated with histones

Question 10

when are chromosomes visible?

Answer 10

when a cell is dividing (start of cell division)

Question 11

what are the 2 threads of chromosomes called?

Answer 11

chromatids

Question 12

what is the difference between an allele and a gene?

Answer 12

genes are particular characteristics that can exist in 2 or more different forms called alleles

Question 13

what are 3 bases called in DNA?

Answer 13

triplet

Question 14

what are 3 bases called in mRNA?

Answer 14

codon

Question 15

what are 3 bases called in tRNA?

Answer 15

anti-codon

Question 16

define genome

Answer 16

the complete set of genes in a cell including those from the mitochondria or chloroplast

Question 17

define proteome

Answer 17

the complete set of proteins produced by the genome

Question 18

what does RNA stand for?

Answer 18

ribonucleic acid

Question 19

what is the structure of RNA?

Answer 19

• pentose ribose sugar
• phosphate group
• adenine, uracil, thymine or guanine

Question 20

what are the two types of RNA important in protein synthesis?

Answer 20

tRNA and mRNA

Question 21

describe the structure of a tRNa molecule

Answer 21

• amino acid binding site
• cloverleaf shape

Question 22

what are 4 differences between mRNA and tRNA?

Answer 22

tRNA
- amino acid binding site
- anti-codon
- cloverleaf shape
- smaller molecule
mRNA
- no amino acid binding site
- codon
- linear
- larger molecule

Question 23

what are the 2 stages of protein synthesis called?

Answer 23

transcription and translation

Question 24

explain transcription

Answer 24

1. DNA helicase unwinds DNA by breaking H bonds
2. one strand of DNA acts as a template strand
3. free RNA nucleotides join on the template strand by RNA polymerase (adenine to uracil and cytosine to guanine) and stops once it reaches the ‘stop triplet code’
4. pre-MRNA spliced to remove introns
5. mRNA leaves nucleus via nuclear pores

Question 25

describe translation

Answer 25

1. mRNA binds to ribosome
2. ribosome finds start codon
3. two tRNA molecules with complementary anticodons bind to two codons
4. peptide bond forms between 2 amino acids that tRNA holds using energy from ATP
5. tRNA released as ribosome moves
6. ribosome releases polypeptide when stop codon reached