Unit 1 Do You Know

Question 1

Give an account of the structure of a single DNA nucleotide

Answer 1

Phosphate group
Nitrogenous base ( A, T, C, G)
Deoxyribose sugar
Phosphate joined to the 5 carbon end of the deoxyribose

Question 2

Give an account of the structure of DNA molecule

Answer 2

Double helix 
Chains of composed nucleotides
Nucleotide is a deoxyribose, phosphate group and a sugar- phosphate backbone
Has complementary base pairing A&T G&C
Anti parallel 5’-3’ 3’-5’

Question 3

Describe the difference between prokaryotic and eukaryotic cells

Answer 3

Prokaryotic
-have circular chromosomes: in the main chromosome and the plasmids

Eukaryotic

• have linear chromosomes in the nucleus and circular chromosomes in the mitochondria and chloroplasts
• year is a special eukaryote as it has plasmids which contain circular chromosomes

Question 4

Describe the steps in DNA replication

Answer 4

DNA double helix unwinds and hydrogen bonds break
Primers bund to start replication
DNA polymerase adds DNA nucleotides to the 3’ end of the leading strand
The leading strand is replicated continuously
The lagging strands are replicated in fragments and these fragments are joined together by ligase

Question 5

Describe the steps in PCR

Answer 5

DNA is heated to 92-98°C to separate strands
Then cooled to between 50-65°C to allow primers to bind to the target sequence
Primers are complementary to the target sequence at the two end of the region to be amplified
Heat tolerant DNA polymerase then replicated the primed sequence of DNA at 70-80°C
Repeated cycles of heating and cooling amplify this region of DNA

Question 6

Give an account of transcription of DNA

Answer 6

RNA polymerase unwinds and unzips DNA
RNA polymerase adds complementary RNA nucleotides to make a primary transcript, primary mRNA
Introns are removed
Exon’ are spliced to make mature mRNA transcript
Order of Exxon’s remains unchanged
Occurs in the nucleus

Question 7

Describe the events leading to the formation of a mature mRNA transcript following transcription

Answer 7

RNA splicing forms mature mRNA transcript
The introns of the primary transcript are non coding
Introns are removed
Exxon’s or the primary transcript are coding regions
Exxon’s are joined together to form a mature mRNA
transcript
Order of Exxon’s remains unchanged
Different mRNA transcript can be made depending on which Exxon’s are retained

Question 8

Give an account of translation of mature mRNA

Answer 8

mRNA goes to the ribosome
tRNA carries specific amino acids
Anti coding on the tRNA align with codons on the mRNA
Amino acids align in the correct sequence
Amino acids are joking by peptide bonds

Question 9

Describe the structure of proteins

Answer 9

Aiming and acid group
Amino acids are joined together by peptide bonds to for proteins/ polypeptides
Protein/ polypeptide chains fold to form a 3 dimensional shape of the protein
Folds are held together by hydrogen bonds and other interactions between the individual amino acids
Proteins have a large variety of shapes which determine their function

Question 10

Give an account of cellular differentiation

Answer 10

Cellular differentiation is the process by which a cell expresses certain genes or some genes are witches on while others remain off
Genes code for a proteins characteristics for that type of cell
This allows for cells to carry out specialised functions
Meristems are regions of unspecialised cells in plants that can self renew and differentiate
Stem cells are cells in animals the are unspecialised that can self renew and differentiate

Question 11

Describe the differences between embryonic stem cells and tissue stem cells

Answer 11

Embryonic
Found in developing embryo
Have the potential to become all types of cells as they are pluripotent
All genes have the potential to be switched on
Can self renew in laboratory

Tissue
Found in body tissue
Can only differentiate into narrow ranges of cell types as they are multi potent
Developers into cells of the tissue where they are found

Question 12

Describe the structure of the genome

Answer 12

The genome of an organism is its entire hereditary information coded in DNA
There are coding and non coding sequences
DNA sequences that code from protein are called genes
Non coding sequences are called intron
Those that are transcribed in RNA but are not translated
Forms of RNA which are translated include tRNA rRNA