DNA

Question 1

What is the structure of DNA

Answer 1

DNA is arranged in a double helix structure with complementary base pairing
The DNA is coiled around his tone proteins

Question 2

Where is DNA located

Answer 2

In the nucleus and mitochondria

Question 3

How many chromosomes do each cell have

Answer 3

46 chromosomes - 22 pairs and a pair of sex chromosomes

Question 4

What is a karyotype

Answer 4

Karyotype is an individuals complete set of chromosomes

Question 5

How does DNA become chromosomes

Answer 5

DNA wraps around his tone proteins and form a nucleosome which supercoils to become chromosomes

Question 6

How is DNA stored in a prokaryote

Answer 6

In a prokaryotes there is no nuclear envelope/membrane and the DNA is organised in a single chromosome/loop known as a nucleoid

Question 7

How is DNA stored in a eukaryotes

Answer 7

DNA is stored in the nucleus, with chromatid wrapped round his tone proteins

Question 8

What is maternal DNA

Answer 8

The DNA found in the mitochondria is maternal DNA (only from the mother)

Question 9

Explain how DNA folds into a chromosome

Answer 9

DNA starts as a double helix which winds around core particles (histone proteins) to form nucleosomes. These fold into a zig-zag fibre which folds into irregular to form a thick fibre.
In dividing cells the looped chromatin coils further to from each chromatid. 4 chromatid make up a chromosome which is joined by a centromere in the centre which forms a chromosome

Question 10

What are the overall functions of DNA

Answer 10

• stores genetic information
• transfers genetic information
• acts as a template and regulator for transcription and protein synthesis
• DNA is the structural basis for hereditary and genetic disease

Question 11

What are the different types of mutations in DNA

Answer 11

Duplications
Deletions
Mutations of regulatory sequence
DNA damage
DNA repair issue
Non-sense
Mis-sense
Splice site mutation
Expansion of tri-nucleotide
Anticipation

Question 12

What is a duplication

Answer 12

Sections within DNA that are repeating so the incorrect protein is generated

Question 13

What are the types of deletions and what do each cause

Answer 13

There are 2 types of deletions
Our of frame deletions which means the sequence shifts meaning the reading frame of the gene is changed
In frame deletions is where one codon is removed meaning one amino acid is lost but the reading frame remains the same

Question 14

What occurs in a mutation of regulatory sequence

Answer 14

The coding sequence is still in tack but the gene itself is either switched on or switched off

Question 15

How can DNA become damaged

Answer 15

Chemicals
UV rays
Radiation

Question 16

What are non-sense mutations

Answer 16

Non-sense mutations are point mutations that produce a stop codon resulting in an incomplete, usually a non-functional protein

Question 17

What can a non-sense mutation cause

Answer 17

Duchenne’s muscular dystrophy

Question 18

What is a mis-sense mutation

Answer 18

A mis-sense mutation is a point mutation where a single results in a codon that codes for a different amino acid which can result in silent mutation and a non-functional protein been made

Question 19

What can be an example disease caused by mis-sense mutation

Answer 19

Sickle cell disease where CAG is replaced with CTG

Question 20

What is a splice site mutation

Answer 20

A splice site mutation affects the accurate removal of an intron

Question 21

What disease can be caused by an expansion of tri-nucleotide repeat

Answer 21

Huntingtons disease
CAG triplet code is repeated several times in the first part of the coding sequence- if CAG repeats more than 36 times huntingtons will develop

Question 22

What does anticipation mean

Answer 22

In terms of Huntington’s disease repeats of the CAG in the coding sequence gets bigger when they are transmitted to the next generation which means the symptoms will occur earlier and of greater severity