Human Genome

Question 1

What is Chromatin, and its function

Answer 1

Chromatin is a substance found within a chromosome consisting of DNA and proteins.

It’s function is to tightly package DNA in compact and dense structure.

Question 2

Draw and label a nucleus (5)

Answer 2

Allocate

1. Eurochromatin
2. Heterochromatin
3. Nucleolus
4. Nuclear Envelope
5. Nuclear Pores

Question 3

What are the functions DNA has to fufil? (3)

Answer 3

1. Encodes all the information required to make an organism (DNA to RNA to Protein)
2. It must replicate itself accurately
3. It must allow beneficial mutations to be selected.

Question 4

What are the central dogma of Molecular biology? (3)

Answer 4

1. DNA Synthesis (replication)
2. RNA synthesis (transcription)
3. Protein synthesis (translation)

Question 5

What is Genetics? (1)

Answer 5

A study of the process by which characteristics are passed from parent to offspring (hereditary)

Question 6

What is a Gene?

Answer 6

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

Question 7

What is the human genome?

Answer 7

A complete set of nucleic acid sequences for humans, encoded as DNA within the 23 chromosome pairs in cell nuclei and in a small DNA molecule found within individual mitochondria.

Question 8

Give a brief history of the human genome discovery (4)

Answer 8

1990-2003 - 20 countries in 6 countries work together, first analysis in 2001, then published further sequence in 2003.

2001 - Celera (Craig Venter) also published sequence in 2001. Also published first diploid genome of an individual in 2007.

2008: 1000 Genomes Project; 2010: 10,000 Genomes Project; 2013: 100,000 Genomes Project and NHS: linking clinical data to sequence
2016: 1m+ US ‘All of us’ program

Now: Private and public enterprises

Question 9

What are the cost and timeline changes associated with human genome sequencing, future?

Answer 9

First Genome - 13 years, $13 billion
Now - Few days, $5000
Next Few Years - 15 mins, $500

Question 10

Important stats.
How many bases of DNA?
How many Genes?
What is the proportion of repeating elements?
What is the proportion of Genome that actually codes for proteins?

Answer 10

1. 3.2 x 10^9
2. 20,000 Genes
3. 50% repeating
4. 1.5% codes for proteins

Question 11

What is the extent of human genetic variation? (3)

Answer 11

1. All genes are 99.99% identical.
2. Each have around 3 million single nucleotide polymorphisms (SNP)
3. Each have around 50-100 SNPs associated with an inherited disease. Two copies of gene means we’re healthy.

Question 12

Rank from what is caused by genetic factors alone to Multifactorial to environment:

1. Diabetes
2. Sickle Cell Anaemia
3. Tuberculosis
4. Scurvy
5. Heart Disease

Answer 12

1. Sickle Cell Anaemia

Multifactorial:

2. Tuberculosis
3. Diabetes
4. Heart Disease

Environment alone:

5. Scurvy

Question 13

What is the impact of genomics on Medicine (what we can learn/research) Part 1. (3)

Answer 13

Functional Genomics (what we learn):
1. Mechanisms of disease (rare diseases)

2. Targeted theraperutics and gene therapy (cancer biology)
3. Human Evolution

Question 14

What is the impact of genomics on Medicine (how we apply to treatment) Part 2. (3)

Answer 14

Personalised Medicine:
1. Prediction of disease (Huntington’s)

2. Pharmacogenetics (40% of drugs prescribed have no effect due to genetics)
3. Ethics (Foetal DNA from maternal blood)

Question 15

What is the structure of DNA? (3)

Answer 15

1. Double helix of nucleic Acid
2. Complementary strands of nucleotides. A-T, C-G
3. Sequence of bases code for different proteins

Question 16

Describe the molecules involved in DNA and the bonds they make. (4)

Answer 16

1. Phosphate-sugar and nitrogenous base make up a nucleotide.
2. The DNA strand has 5 prime end and 3 prime end.
3. Hydrogen bond between base pairs in double strand
4. Strong ‘phosphodiester’ Covalent bonds within each linear strand

Question 17

How is DNA arranged in chromosome? (4)

Answer 17

1. DNA is tightly wound around a ‘bead’ of histones.
2. Chromatin fibre is tightly packed into nucleosome
3. Chromatin fiber folds into loops.
4. This makes up mitotic chromosome.

Question 18

What is Nucelosome made of? (2)

Answer 18

Core Particles

1. 8 histones (octomer) (2x H2A, H2B, H3, and H4)
2. Histones +ve, DNA -ve charged.

Question 19

How is DNA condensation Regulated? (2)

Answer 19

1. Chromatin-remodelling complexes using ATP.

2. Histone modifying enzyme (using ATP). (Adds/removes, acetyle, phosphate or methyl groups)

Question 20

How can supercoiling affect gene expression? (2)

Answer 20

Supercoiling can affect gene expression by causing it to be switch off.

(B-globin: Severe Anaemia
Tumour suppressor genes: Cancer)

• Histone pattern can be inherited

Question 21

What is Epigenetics? (2)

Answer 21

Heritable changes in gene function that cannot be explained by changes in DNA sequence (e.g methylation).

Question 22

One example of Chromatin Diseases?

Answer 22

Rubinstein-Taybu Syndrome (RSTS). Mutation in histone acetyl-transferases.

1/100,000.

Non-specific symptoms, Intellectual disability, Facial abnormalities, big thumbs and toes.

Question 23

How many pairs of chromosomes do we have? (2)

Answer 23

1. Normal Cells (Diploid) - 22 homologous autosomal chromosomes and a pair of sex chromosomes (XX/XY)
2. Except Haploid gametes (22 single chromosomes + X or Y = 23)

Question 24

What is Cytogenetics?

Answer 24

The study of inheritance in relation to the structure and function of chromosomes.