The Human Genome (MCB L3)

Question 1

Euchromatin

Answer 1

Makes up most of the chromatin in a nucleus and thus makes up most of the human genome. Comprises the most active portion of the human genome within the nucleus

Question 2

Heterochromatin

Answer 2

Very tightly packed chromatin which is usually not transcribed into RNA. Not active, activity of genes is suppressed.

Question 3

Nucleolus function

Answer 3

transcribes ribosomal RNA

Question 4

Give 3 functions of DNA

Answer 4

Encode all info required to make an organism. Must replicate itself accurately. Must allow beneficial mutations to be selected

Question 5

Gene

Answer 5

A unit of biological information that encodes a specific protein or regulatory molecule

Question 6

Regulatory molecule

Answer 6

Something that controls a protein

Question 7

Precision Medicine

Answer 7

An emerging data-driven approach for disease treatment and prevention that takes into account individual variability in genes, environment and lifestyle for each person

Question 8

Sometimes a gene will code for an RNA molecule that is not translated into a protein. What is this RNA?

Answer 8

A regulatory molecule. It controls a protein.

Question 9

What proportion of our DNA bases code do not for something? What do we call the bases that code for nothing?

Answer 9

50% code for nothing; these are called high-copy repetitive elements. We do not know the significance of these repeats

Question 10

SNP

Answer 10

Single Nucleotide Polymorphism is when a single base pair is changed.

Question 11

SNP helps to increase human………..

Answer 11

Genetic Variation

Question 12

SNP doesn’t always lead to disease. Why?

Answer 12

Either because there is no change in the protein or because we are diploid so have 2 copies of gene, one faulty and one functional.

Question 13

Disease is due to a mixture of ……..

Answer 13

Genetic factors and environmental factors

Question 14

Disease susceptibility is affected by…….

Answer 14

The human genome e.g. a single mutation in a single gene means you are more susceptible to a disease

Question 15

Clinical relevance of genomics

Answer 15

Understand mechanisms of disease. Targeted therapeutics and gene therapy, allows you to predict illnesses, pharmacogenetics

Question 16

Pharmacogenetics

Answer 16

Concerned with the effect of genetic factors on reaction to drugs

Question 17

Give an example of a disease that ca be predicted using genomics

Answer 17

Huntington’s disease

Question 18

You can tell the ……. of foetus by looking at the ……….

Answer 18

Genotype, maternal blood

Question 19

People respond to drugs differently. This is down to…….

Answer 19

How the drugs are metabolised in body by e.g. enzymes

Question 20

What does it mean that DNA molecules are ‘polar’

Answer 20

It means they have direction i.e. 5’ to 3’

Question 21

In which direction is DNA read?

Answer 21

5’ to 3’

Question 22

Purines

Answer 22

Double ringed. Adenine and Guanine

Question 23

Pyrimidines

Answer 23

Single ringed. Cytosine and Thymine

Question 24

How to fit all the DNA in to one nucleus?

Answer 24

Supercoiling

Question 25

Supercoiling

Answer 25

DNA sequence is highly condensed around histone proteins with multiple levels of folding

Question 26

Nucleosomes

Answer 26

A structural unit of a eukaryotic chromosome, consisting of a length of double helix DNA coiled around a histone octamer

Question 27

Why does DNA wind so easily around Histones?

Answer 27

Because Histones are +ve and DNA is -ve so they attract.

Question 28

Nucleosome has how many histones?

Answer 28

8 histones (histone octamer)

Question 29

What is the 1st level of folding in supercoiling?

Answer 29

Nucleosomes: DNA wound around two lots of each of the following histones: H2A, H2B, H3, H4

Question 30

Second level of folding in supercoiling requires how many additional histones than first level? After second level of folding, how is the DNA structured in nuclei?

Answer 30

One extra. After second level of folding, DNA is structured as we find it most of the time in most cells.

Question 31

Outline two methods used in nuclei to allow enzymes full access to the full DNA strand, wound around histones, for DNA replication and gene expression

Answer 31

Chromatin-remodelling complexes: these complexes grab onto DNA and histone barrel and pull thus unwinding the barrel and pulling the DNA out. Allows for transcription. Histone-modifying enzymes: Chemically change the histones by adding/removing acetyl, phosphate or methyl groups. Change how histones fold onto each other

Question 32

Explain how supercoiling can affect gene expression through histone modification patterns and give the effects. Is this a problem for the individual only?

Answer 32

Genes are coiled up too tightly into heterochromatin, so gene may not be expressed, leading to a disease. These histone modification patterns can be inherited.

Question 33

Give 2 examples of diseases that arise due to switched off genes

Answer 33

Severe anaemia arises due to beta-globin gene being switched off and cancer arises due to tumour suppressor genes not being expressed.

Question 34

Give an example of a disease that arises due to abnormalities in the chromatin?

Answer 34

Rubinstein-Taybi syndrome

Question 35

Karyotype

Answer 35

The number and appearance of the chromosomes in cell nuclei of cells of an organism

Question 36

Human Karyotype can be used to diagnose……

Answer 36

Gross genetic changes e.g. Down’s Syndrome