1.1 DNA and the genome

Question 1

What is DNA?

Answer 1

Genetic material that is inherited (passed down from generation to generation) which can be located within the nucleus of all cells {apart from red blood cells.}

Question 2

Why is DNA important?

Answer 2

DNA is a long chemical sequence containing the info for that living thing to develop, survive and pass on its genetic info to the next generation

Question 3

What is a genotype?

Answer 3

The DNA chemical sequence differs between individuals. The pattern of this sequence is called its genotype.

Question 4

What is a genome?

Answer 4

The sum total of all genetic info of an individual is the genome.

Question 5

Function of DNA?

Answer 5

DNA contains genetic info to make the specific proteins required by a cell
The proteins determine a cell’s structure allowing it to perform it’s function - allowing the cells to differentiate
Copies of the cells genetic info are passed onto the daughters cells during cell division (mitosis)
Copies of the cells genetic info are passed onto the next generation when gametes fuse during fertilisation - the genetic code is inherited

Question 6

How does DNA package in Human chromosomes?

Answer 6

1. DNA double helix is wrapped around histone proteins forming nucleosomes
2. The chain of nucleosomes then folds into a thicker chromatin fibre
3. The thick chromatin fibre then folds again, on a non histone protein scaffold to form looped fibres
4. the folded chromatin then folds further to produce a condensed chromosome

Question 7

What do proteins contain?

Answer 7

the elements carbon, hydrogen, oxygen and nitrogen

Question 8

What are proteins?

Answer 8

Proteins are large insoluble molecules made up of a chain of smaller molecules called amino acids of which there are 20 types

Question 9

What are structural proteins?

Answer 9

Building proteins forming hair and cell membranes

Question 10

What are enzymes?

Answer 10

Speed up the rate of reactions such as photosynthesis and respiration that are essential for life

Question 11

What are hormones?

Answer 11

Chemical messengers e.g. insulin

Question 12

What are antibodies?

Answer 12

defence against antigens

Question 13

What is the shape of DNA?

Answer 13

DNA has two strands coiled into a double helix.

Each strand of DNA is made up of nucleotides

Question 14

What is a nucleotide?

Answer 14

A nucleotide consists of a phosphate group, a deoxyribose sugar and a nitrogenous base

Question 15

How is the carbons on the deoxyribose sugars numbered?

Answer 15

C1 is on the right and the carbons are numbered in a clockwise direction
C5 is situated between C4 and the phosphate

Question 16

How does it form a strand?

Answer 16

Nucleotides are linked by their deoxyribose sugars and phosphates to form a strand with a sugar phosphate back bone.
Strong chemical bond link nucleotides in one strand.
* free nucleotides can join onto DNA at 3’ end only *

Question 17

What is the complementary base pairing rule?

Answer 17

adenine and thymine

guanine and cytosine

Question 18

What direction do the strands run in?

Answer 18

The two DNA strands connect running in opposite directions.
The strands are said to be anti parallel
One strand runs 3’ - 5’ the other 3’ - 5’

Question 19

Features to remember of a DNA molecule for the exam?

Answer 19

• double helix shape
• Sugar phosphate backbone
• Anti parallel strands
• Hydrogen bonds linking strands
• complementary base pairing rules applied to nucleotide

Question 20

Organisms fall into what two categories?

Answer 20

Prokaryotes and Eukaryotes

Question 21

Prokaryotes Vs Eukaryotes

Answer 21

in both prokaryotic and eukaryotic cells, DNA is organised into structures called chromosomes 
In prokaryotes (bacteria) chromosomes are circular
In eukaryotes (animals and plants) chromosomes are linear

Question 22

What is a prokaryotic cell?

Answer 22

A prokaryotic cell does not have a membrane bound nucleus
DNA is found in the cytoplasm in the form of a large circular chromosome or smaller rings called plasmids
Prokaryotic cells also do not have a membrane bound organelles (chloroplasts or mitochondria)

Question 23

How is bacterial plasmids used in genetic engineering?

Answer 23

They are extracted from the bacteria, cut open with endonucleas enzyme leaving sticky ends
A gene from another organism is placed between the sticky ends and the plasmid is sealed with the ligase enzyme
the bacterial cell now has a gene that can code for a foreign protein

Question 24

What is a eukaryotic cell?

Answer 24

they have a membrane bound organelle and organelles

Question 25

Features of Prokaryotes

Answer 25

dna packaged into chromosomes
dna not found within a nucleus
plasmids can be present
dna usually found as a double stranded circular molecule
dna is the genetic material
dna is double stranded
organisms have a different sequence of bases along dna

Question 26

Features of Eukaryotes

Answer 26

Genetic material contained within the nucleus
dna packaged into a set of linear chromosomes
chloroplasts dna in some species
dna can be a mix of circular and linear chromosomes
mitochondrial dna located within the cytoplasm
dna is the genetic material
dna is double stranded
organisms have different sequence of bases along dna

Question 27

When do chromosomes condense?

Answer 27

they condense in eukaryotic cells during mitosis when they become visible with a microscope

Question 28

Because the dna molecule is very long, what must it do?

Answer 28

coil around bundles of histone proteins to form chromatin fibres, which loop, fold and condense to form chromosomes

Question 29

where are mitochondria found?

Answer 29

in the cytoplasm of cells including ova

Question 30

where is mitochondrial dna inherited exclusively from?

Answer 30

our mother

Question 31

what do mitochondria genes code for?

Answer 31

enzymes of aerobic respiration so mutations can be lethal

Question 32

What are yeast cells?

Answer 32

eukaryotic, unicellular fungi

Question 33

What do yeast cells contain?

Answer 33

linear chromosomes within a membrane bound nucleus.

they also contain some circular plasmids in their similar to those found in prokaryotes

Question 34

which of the following are eukaryotes or prokaryotes
bacteria
yeast cell
palisade mesophyll cell
cheek cell?

Answer 34

bacteria - prokaryote

the rest are eukaryotes

Question 35

which of the following have a nucleus present
bacteria
yeast cell
palisade mesophyll cell
cheek cell?

Answer 35

yeast
palisade mesophyll cell
cheek cell

Question 36

which of the following have a chloroplast present
bacteria
yeast cell
palisade mesophyll cell
cheek cell?

Answer 36

palisade mesophyll cell

Question 37

which of the following have a plasmid present
bacteria
yeast cell
palisade mesophyll cell
cheek cell?

Answer 37

bacteria AND yeast

Question 38

which of the following have a mitochondria present
bacteria
yeast cell
palisade mesophyll cell
cheek cell?

Answer 38

yeast
palisade mesophyll cell
cheek cell

Question 39

Why are yeast cells unusual in the organism of DNA?

Answer 39

They contain plasmids but have a nucleus with linear chromosomes and nuclear bound organelles in their cytoplasm

Question 40

What is a DNA fingerprint or profile?

Answer 40

the unique pattern of fragments a persons DNA base sequence produces when their DNA is ‘digested’ with restriction endonuclease (enzymes)

Question 41

What is gel electrophoresis?

Answer 41

DNA profiling makes use of the technique gel electrophoresis where the fragments of DNA in a sample can be separated by size on the …. of an electrical voltage

Question 42

Describe the gel in gel electrophoresis and the effect it ahs on the size of molecules?

Answer 42

the gel is porous and small molecules move faster through the gels than larger molecules and so travel further in …. time

molecules of the same size travel the same distance and, when strained form a bond on the gel