DNA and Genetics

Question 1

Gene

Answer 1

A section of DNA nucleotides that codes for a specific protein.

Question 2

Where is DNA found?

Answer 2

Nucleus of eukaryotic cells

Question 3

Where are proteins made?

Answer 3

ribosomes within the cytoplasm of eukaryotic cells.

Question 4

RNA structure and function

Answer 4

ribonucleic acid; single-stranded nucleic acid that contains the pentose sugar ribose. It is a polynucleotide (made up of mononucleotides which contain phosphate groups) and is involved in protein synthesis (making proteins via translation). Contains bases (G,C,A,U (uracil)). There are three versions of it (MRNA,TRNA,rRNA)

Question 5

Genetic code

Answer 5

collection of codons of mRNA, each of which directs the incorporation of a particular amino acid into a protein during protein synthesis. (Adenine, uracil, guanine, cytosine).

Question 6

Number of amino combinations

Answer 6

20 (2 bases)

Question 7

Number of triplet combinations

Answer 7

64 (3 bases)

Question 8

Protein synthesis

Answer 8

the formation of proteins by using information contained in DNA and carried by mRNA. (Translation and transcription)

Question 9

Transcription definition

Answer 9

Process by which information on a DNA strand is transferred to an mRNA molecule. Occurs in the nucleus and is controlled by the enzyme RNA polymerase.

Question 10

Transcription process

Answer 10

• occurs in the nucleus (controlled by RNA polymerase)
  -DNA helicase unzips the double helix and breaks the hydrogen bonds between the base pairs.
  -free nucleotides that are complementary to the exposed DNA bases on the template are joined by phosphodiester bonds.
  -once made, the mRNA leaves the nucleus, through the nuclear pores, into the cytoplasm, onto a ribosome.

Question 11

Translation definition

Answer 11

The process of converting mRNA into amino acids that form proteins. Happens in ribosomes in the cytoplasm.

Question 12

Translation process

Answer 12

• amino acids in the cytoplasm are activated for protein synthesis
• ribosomes bind to the mRNA (messenger)
• in the cytoplasm there are free molecules of tRNA (transport) which have a triplet of unpaired bases at one end (anticodon) and a specific amino acid binding site at the other.
  -There are at least 20 different tRNA molecules, each with a specific anti codon and specific amino acid binding site
• tRNA transfers the amino acid to the ribosome
• the mRNA reads 3 bases at a time as each triplet is read a tRNA delivers the corresponding amino acid, which is added to a chain of amino acids, that once complete folds into a complex shape to form the protein’s secondary, tertiary (and quaternary) structure.

Question 13

Allele

Answer 13

Alternative forms of the gene on the same position (loci) on a chromosome.

Question 14

Phenotype

Answer 14

An organism’s physical appearance, or visible traits.

Question 15

Genotype

Answer 15

genetic makeup of an organism/an organism’s combination of alleles.

Question 16

Dominant

Answer 16

Alleles that can be express their phenotypic character with only one example in a body cell.

Question 17

Recessive

Answer 17

Alleles which will be expressed only if homozygous in a body cell and dominant allele not present.

Question 18

Where does transcription occur?

Answer 18

Nucleus

Question 19

What does degenerate mean?

Answer 19

redundant code (codons that encode the same amino acid).

Question 20

Describe the role of mRNA in protein synthesis

Answer 20

mRNA carries amino acids from the DNA in a cell’s nucleus to a ribosome in the cytoplasm, where the mRNA sequence is read three bases at a time and each codon is translated into its corresponding amino acid in a growing protein chain.

Question 21

Compare and contrast the structure of a DNA double helix with the structure of tRNA

Answer 21

DNA contains a deoxyribose sugar, whereas tRNA contains a ribose sugar. DNA is a double stranded helix, whereas tRNA is a is single stranded and folded into a clover leaf structure. Both structure contain complementary base pairings but tRNA also contains an anticodon of 3 bases that codes for a specific amino acid. tRNA also contains an amino acid attachment site and DNA does not.

Question 22

Sex linked trait

Answer 22

characteristics (or traits) that are influenced by genes carried on the sex chromosomes

Question 23

Epigenetic

Answer 23

Nature vs nurture (how environment can affect genome)

Question 24

Polygenic

Answer 24

Trait controlled by multiple genes (e.g height, eye colour)

Question 25

Monogenic

Answer 25

Traits controlled by one gene (e.g dwarfism)

Question 26

Lac operon stages

Answer 26

1. Repressor attached to operator section of DNA stopping RNA polymerase from binding to the DNA.
2. Lactose binds to the repressor (changing its shape) so it comes off the operator.
3. This allows RNA to bind to the promoter region of DNA and so transcription can occur.
4. mRNA will be translated and the enzyme to break down lactose will be made.

Question 27

Lac operon definition

Answer 27

Prokarytoic example of controlled gene expression. When bacteria feed on lactose they will make an enzyme to break down the lactose. When they don’t feed on lactose the enzyme is not made.