y4.2 molecular genetics 🧬

Question 1

what is the relationship between DNA, genes and chromosomes?

Answer 1

Each chromosome contains one long DNA molecule, usually carrying several hundred or more genes.

Question 2

characteristics of genes

Answer 2

a sequence of nucleotides
specific for its function
used in protein synthesis, contributes to the development of the body

Question 3

structure of dna

Answer 3

double helix of two, anti-parallel, polynucleotide chains

Question 4

what makes a nucleotide

Answer 4

phosphate group
deoxyribose sugar
nitrogenous base

Question 5

now remember how the dna looks

Answer 5

ok the picture is on pg 5

Question 6

rule of complementary base pairing (aka chargaff’s rule)

Answer 6

(Adenine) A-T (Thymine)
(Cytosine) C-G (Guanine)
hydrogen bonds form between nucleotide bases

Question 7

process of DNA replication

Answer 7

semi-conservative replication
each strand of original DNA acts as as a template for the synthesis of new complementary DNA strand
double helix separated by enzymes, nucleotides within the cell are bound to separated parent DNA strand (rule of complementary base pairing)
formation of double stranded DNA molecule - half of original parent strand, half newly synthesized daughter strand

Question 8

what is a gene

Answer 8

A sequence of nucleotides as part of a DNA molecule that contains the information to make a polypeptide (folded into protein in rough er)
can be expressed or not expressed

Question 9

function of DNA

Answer 9

used to carry genetic code used to synthesize specific proteins

Question 10

central dogma of molecular biology

Answer 10

DNA => RNA => protein
(DNA directs NRA synthesis, through RNA, DNA controls protein synthesis
RNA is an intermediate in protein synthesis)

Question 11

structure of DNA and RNA (similarities)

Answer 11

both have a sugar-phosphate backbone joined by phosphodiester bonds
both contain 3 common nitrogenous bases (adenine, cytosine, guanine)

Question 12

Structure of DNA and RNA (differences)

Answer 12

DNA vs RNA
Number of polynucleotide chains: two vs one
Monomers: deoxyribonucleotides vs ribonucleotides
pentose suger (see pic on pg 8 prolly not that impt though idk)
Nitrogenous bases: adenine, guanine, cytosine, thymine vs adenine, guanine, cytosine, uracil
Ratio of bases: A:T = G:C = 1:1 (chargaff’s rule) vs no fixed ratio
bonds between bases: hydrogen bonding present between bases vsno hydrogen bonds if NRA is a straight chain

Question 13

how is the information in DNA used to synthesize polypeptides in eukaryotes (transcription)

Answer 13

Transcription: DNA→mRNA
transfer of genetic information from DNA to mRNA
formation of specific mRNA sequence complementary to a specific DNA sequence on the template strand by complementary bae pairing

Question 14

how is the information in DNA used to synthesize polypeptides in eukaryotes (translation)

Answer 14

Translation: mRNA→DNA
mRNA contains a series of codons that interact via complementary base pairing with tRNA, which is attached to specific amino acids in ribosome
ribosome behaves like a small factory that travels along the mRNA, forming peptide bond between the corresponding amino acids to assemble to polypeptide

Question 15

“fate of polypeptide chains” basically what happens aft translation

Answer 15

polypeptide chains are folded at the rough endoplasmic reticulum (ER) to form proteins
transport vesicles containing substances made by the endoplasmic reticulum (ER) are pinched off the ER
transport vesicles fuse with and release their substances into the Golgi apparatus
substances are chemically modified and packaged inside the Golgi apparatus
secretory vesicles containing these substances and pinched off the Golgi apparatus, move towards and fuse with the cell membrane, releasing the substances outside the cell by exocytosis

Question 16

what is a mutation

Answer 16

a sudden or spontaneous change in the structure of a gene, chromosomes (sickle cell anaemia) or in the chromosome number (down syndrome)

Question 17

they will probably give a case study for mutation but read the sickle cell anaemia and down syndrome notes on

Answer 17

pg 12-13

Question 18

factors that may increase the rate of mutation

Answer 18

environmental forces (atomic radiation)
mutagens:
- ionizing radiation (gamma rays and x-rays)
- chemical mutagens

Question 19

why do we use bacteria to produce insulin?

Answer 19

• relatively easy to transfer the genes into the bacterium, as bacteria contain plasmids which have a small number of genes, and an insulin gene can be inserted easily into a plasmid
• bacteria take a short time to replicate, and its plasmid is replicated along with it. a single cell reproduced through cell division to create repeated cell divisions to form clones of itself, transcribing and translating the insulin gene into the plasmid to produce large quantities of insulin

Question 20

steps for inserting human insulin gene into bacterial DNA

Answer 20

obtain the DNA segment in human chromosome containing insulin gene
cut the gene using a restriction enzyme, producing ‘sticky ends’
obtain a plasmid from a bacterium
cut the plasmid with the same restriction enzyme to produced ‘sticky ends’ complementary to the ends of the insulin gene
mix the plasmid with the DNA fragment containing the insulin gene, allowing the insulin gene to bind with the plasmid through complementary base pairing between their ‘sticky ends’
add DNA ligase to seal the DNA fragment to the plasmid to form a recombinant plasmid
mix the plasmid with (x) bacterium, applying temporary heat or electric shock to open the cell wall and membrane to enter
transgenic bacterium with insulin gene will be isolated and grown in large scale under optimum conditions
transgenic bacterium will synthesize insulin together with other proteins from the plasmid
insulin must be extracted and purified before use