Gene expression

Question 1

What does every cell in a multicellular organism contain?

Answer 1

A complete set of chromosomes with every gene needed to make every protein the body will ever make

Question 2

How many genes in the chromosomes will be expressed?

Answer 2

A very small fraction in any particular cell

Question 3

What is each cell?

Answer 3

Specialised to perform a certain task, only needing to express certain genes

Question 4

What is gene expression?

Answer 4

Gene expression is the process by which specific genes are activated to produce a required protein

Question 5

What is a phenotype?

Answer 5

An organisms phenotype is determined based on protein produced, depending on environmental factors

Question 6

What is the gene expression process made up of and what does it involve?

Answer 6

The gene expression is made up of translation and transcription processes, it involves RNA

Question 7

What is RNA?

Answer 7

RNA is a type of nucleic acid called ribonucleic acid

Question 8

What do RNA nucleotides come together to form?

Answer 8

RNA nucleotides come together to form a single strand

Question 9

How are RNA nucleotides held together?

Answer 9

With strong covalent bonds between the sugar of one nucleotide to the phosphate of another

Question 10

In what ways to DNA and RNA differ?

Answer 10

RNA is single stranded whilst DNA is double stranded
RNA has a sugar called ribose whilst DNA has a sugar called deoxyribose
RNA has the base uracil while DNA has base thymine

Question 11

How many types of RNA are involved and gene expression and what are they?

Answer 11

mRNA, tRNA, rRNA

Question 12

What is mRNA?

Answer 12

Messenger RNA (mRNA) is a linear molecule that carries a copy of the gene to be expressed from the nucleus to the ribosomes in the cytoplasm.

Question 13

What is tRNA?

Answer 13

Transfer RNA (tRNA) has a cloverleaf shape. It is made from a single strand of RNA which folds due to base pairing, forming its odd shape. It has a triplet anti codon site and an attachment site for a specific amino acid. It carries specific amino acids to ribosomes where they can be assembled to form polypeptide chains

Question 14

What is rRNA?

Answer 14

Ribosomal RNA (rRNA) and proteins form the ribosome. The ribosome is the structure where protein synthesis takes place

Question 15

What is a gene?

Answer 15

Genes are DNA sequences that code for a protein

Question 16

What is an unusual feature of most genes?

Answer 16

That the sequence of nucleotides that code for a protein is regularly interrupted by none coding stretches of DNA

Question 17

What are the coding regions of a gene called?

Answer 17

Exons

Question 18

What are the non coding regions of a gene called?

Answer 18

Introns

Question 19

What is RNA splicing?

Answer 19

When genes are to be expressed by a cell, the non coding sequences of DNA must be edited out before they can be turned into a protein

Question 20

What is a protein molecule?

Answer 20

Polypeptide chain

Question 21

What is a poly peptide chain?

Answer 21

A sequence of amino acids held together by peptide bonds

Question 22

How proteins vary in shape? what is the importance of this?

Answer 22

A polypeptide chain is folded into a three-dimensional shape held in place by hydrogen bonds and other interactions between induvial amino acids. The shape of a protein is linked to its function

Question 23

What are the stages of gene expression?

Answer 23

Two main stages, transcription and translation

Question 24

What happens in transcription?

Answer 24

A copy of the gene in the form of mRNA is created

Question 25

What happens in translation?

Answer 25

A specific sequence of amino acids are built up using the mRNA code

Question 26

What bases does RNA consist of?

Answer 26

Adenine, Uracil (instead of Thymine), Guanine and Cytosine

Question 27

What is a codon?

Answer 27

Every group of three bases is described as a codon as each one codes for an amino acid

Question 28

What is the first step of the transcription process?

Answer 28

The enzyme RNA polymerase unwinds and unzips the double helix of the gene to be expressed and aligns free RNA nucleotides against the exposed DNA nucleotides of the template strand. Complementary base pairing ensure correct positioning of RNA nucleotides, which are then joined to form a primary transcript.

Question 29

What is a primary transcript?

Answer 29

A primary transcript is a complementary copy of the gene made up of groups of three bases called codons. Primary transcripts start with start codons and finish with stop codons

Question 30

What is removed from the primary transcript?

Answer 30

Introns

Question 31

What happens to exons after introns are removed?

Answer 31

They are spliced together to form mature mRNA transcripts

Question 32

What is alternative splicing?

Answer 32

Alternative splicing is where certain exons are removed along with introns to allow the same sequence to be expressed in different ways, as it allows a primary transcript to be formed into different mature mRNA sequences

Question 33

What does mature mRNA do once it is formed?

Answer 33

Binds onto a ribosome

Question 34

What does mRNA carry to start and stop translation?

Answer 34

Start codon and a stop codon

Question 35

What is an anti codon?

Answer 35

tRNA has an anti codon which is a triplet of three base pairs

Question 36

What tRNA have to transport specific amino acid to mRNA on the ribosomes?

Answer 36

An attatchment site

Question 37

How to tRNA and mRNA align?

Answer 37

According to their anti codons which are complimentary to the codons of the mRNA