1.3 gene expression

Question 1

Name the 2 main processes involved in gene expression

Answer 1

Transcription (making mRNA)
Translation (making protien)

Question 2

State three structural differences between DNA and RNA molecules

Answer 2

-RNA nucleotides have ribose sugar and DNA has deoxyribose sugar.
- RNA bases are similar, however RNA has the base uracil instead of thymine
- RNA and DNA structure resemble one another in they both are composed of nucleotides

Question 3

State the complementary base pairs that form between DNA and RNA

Answer 3

DNA- AT, GC
RNA- A and uracil, GC

Question 4

Identify the four different types of nucleic acid molecules found in cells

Answer 4

DNA : deoxyribose nucleic acid

mRNA : messenger ribose nucleic acid

tRNA : transfer ribose nucleic acid
rRNA : ribosomal ribose nucleic acid

Question 5

State the role of mRNA during the process of gene expression

Answer 5

mRNA (messenger RNA)- Transports a copy of the genetic code from DNA in the nucleus to the ribosome.

Question 6

State the role of tRNA during the process of gene expression

Answer 6

tRNA (transfer RNA)- Carries specific amino acids to the ribosome where they are assembled to make polypeptides

Question 7

State the role of rRNA during the process of gene expression

Answer 7

rRNA (ribosomal RNA)- Combines with protein to make up structure of a ribosome

Question 8

State the differences in structure between mRNA and tRNA molecules

Answer 8

mRNA has a linear structure and carries genetic information copied from DNA. tRNA has an L shaped 3D structure

Question 9

State the location of transcription in a cell

Answer 9

Nucleus

Question 10

Stage one of transcription

Answer 10

DNA strands become unwound

Question 11

Stage two of transcription

Answer 11

Weak hydrogen bonds between two bases are breaking causing the two DNA strands to separate

Question 12

Stage three of transcription

Answer 12

Free RNA nucleotides find their complimentary nucleotide on DNA

Question 13

Stage four of transcription

Answer 13

Weak hydrogen bonds are forming between two complimentary bases

Question 14

Stage five of transcription

Answer 14

Strong chemical bond is forming between the sugar of one RNA nucleotide and the phosphate of the next. The linking of nucleotides is brought about by RNA polymerase

Question 15

Stage six of transcription

Answer 15

Weak hydrogen bonds between DNA and RNA bases are breaking allowing the mRNA to become separated from DNA

Question 16

Stage seven of transcription

Answer 16

mRNA leaves the nucleus

Question 17

Stage eight of transcription

Answer 17

Weak hydrogen bonds form between 2 DNA strands again

Question 18

Identify the key enzyme required for transcription

Answer 18

RNA polymerase unwinds and unzips the double helix

Question 19

Identify the coding and non-coding riegons found in a primary mRNA transcript

Answer 19

Introns- Non-coding regions
Exons- Coding regions

Question 20

describe RNA splicing

Answer 20

Introns are cut out and removed from the primary transcript of mRNA and the exons are spliced together to form mRNA with a continuous sequence of nucleotides. This modified mRNA is called the mature transcript of mRNA and passes out of the nucleus to the cytoplasm and heads to the ribosome for translation to occur

Question 21

State the location of translation in a cell

Answer 21

Ribosome

Question 22

Define the process of translation

Answer 22

Translation is the process that turns nucleic acid language into amino acid language. This happens at a ribosome where tRNA’s are used to convert the genetic code carried by the mature mRNA strand into a polypeptide chain to form a specific protein molecule.

Question 23

State the term used to describe a triplet of bases on an mRNA molecule

Answer 23

Codon

Question 24

State the term used to describe a triplet of bases on a tRNA molecule

Answer 24

Anticodon

Question 25

Describe the complementary nature of codons and anticodons and explain the role that this plays in translating the genetic code

Answer 25

The nucleotide bases in the codons (mRNA) and anticodons (tRNA) form complementary base pairs held together by weak hydrogen bonds.

The complementary base pairs are : Adenine – Uracil (A-U)
Cytosine – Guanine (C-G)

Question 26

State the terms used to describe the mRNA codons that initiate and terminate the translation of a protein code

Answer 26

Start stop codons

Question 27

Describe the role of tRNA molecules in the process of translation

Answer 27

tRNAs carry amino acids to the ribosome and join with their complementary codons

Question 28

Describe the sequence of events involved in converting the genetic code into a sequence of amino acids

Answer 28

DNA to mRNA is transcription and mRNA into protein is translation

Question 29

Explain how the process of alternative RNA splicing can result in different proteins being expressed formed one gene code

Answer 29

After the primary mRNA transcript has undergone RNA splicing, the mature primary mRNA transcript is formed.

Question 30

State the type of chemical bonds formed between adjacent amino acids during translation

Answer 30

peptide bonds

Question 31

Identify the molecule that is formed from these linked amino acids

Answer 31

poly peptide chains

Question 32

Describe how the specific 3-dimensional shape of a protein molecule is achieved

Answer 32

The shape is achieved by chemical bonding to fold up and hold the protein in a specific 3-D structure using hydrogen bonds and other interactions between individual amino acids such as sulphur bridges.

Question 33

Give examples of proteins with specific shapes which determine their function

Answer 33

Enzymes, active site
Antibodies
Hormones

Question 34

Explain the role of gene expression in determining the phenotype of an organism

Answer 34

Gene codes for protein and a protein determines a phenotype