Fergus - Introduction to the Human Genome

Question 1

What are the three components of DNA/RNA?
(3)

Answer 1

Nucleotide made from a five carbon sugar (deoxyribose/ribose)

A phosphate

A nitrogenous base

Question 2

How does deoxyribose differ from ribose?

Answer 2

In deoxyribose the 2nd carbon on the sugar is a hydrogen

In ribose the 2nd carbon in the sugar is an OH group

Question 3

In what direction are new nucleotides added onto DNA?

Answer 3

From the 5’ to the 3’ end

Question 4

What does the 5’ of DNA/RNA contain?

Answer 4

A phosphate group

Question 5

What are the four bases of DNA?

Answer 5

Adenine
Guanine
Cytosine
Thymine

Question 6

What are the four bases in RNA?

Answer 6

Adenine
Guanine
Cytosine
Uracil

Question 7

How does uracil differ to thymine?

Answer 7

Uracil is closely related to thymine
Uracil has a H as its variable group while thymine has a CH3

Question 8

How does G bind to C?

Answer 8

By three hydrogen bonds

Question 9

How does A bind to T

Answer 9

By two hydrogen bonds

Question 10

How many bases are needed for a complete turn of a DNA sequence?

Answer 10

10 bases

Question 11

Classify nitrogenous bases

Answer 11

Purines

Pyrimidines

Question 12

How many chromosomes do we have?

Answer 12

46

Question 13

How are our chromosomes classified?

Answer 13

Autosomes

Sex chromosomes

Question 14

How does a female karyotype occur?

Answer 14

One X chromosme from father

One X chromosome from mother

Question 15

How does a male keryotype occur?

Answer 15

One Y chromosome from father

One X chromosome from mother

Question 16

How does a male keryotype occur?

Answer 16

One Y chromosome from father

One X chromosome from mother

Question 17

How does a male keryotype occur?

Answer 17

One Y chromosome from father

One X chromosome from mother

Question 18

What is different about the karyotype in someone who has Down’s Syndrome?

Answer 18

There is an extra copy of the 21st chromosome

Question 19

What is mosaic downs?

Answer 19

There isn’t an extra copy of chromosome 21 in every single cell

Question 20

What percentage of the human genome codes are genes (protein coding sequences)?

Answer 20

15%

Question 21

What percentage of the human genome is heterochromatin?

Answer 21

8%

Question 22

What is heterochromatin?

Answer 22

Densely packed chromatin found in the nucleus

Question 23

What percentage of the human genome is segmental duplications?

Answer 23

5%

Question 24

What are segmental duplications?

Answer 24

Duplications that may have developed due to replication errors, chromosomes that have been replicated, same sequences replicated twice

Question 25

What percentage of the human genome are single sequence repeats

Answer 25

3 % -> usually errors in replications

Question 26

What percentage of the human genome are retrovirus-like elements?

Answer 26

8% RNA viruses that have left their genome in our genome

Question 27

What percentage of the human genome are DNA transposon 'fossils' and what are they?

Answer 27

7% they allow bacteria to transfer genetic material around to other cells

Question 28

What percentage of the human genome are SINEs and LINEs and what are they?

Answer 28

About 34% of the genome Short and long interspersed retrotransposable elements Don't really know their function yet

Question 29

Write a note on a promoter sequence (4)

Answer 29

No more than about 200 bp long Determines wether a gene will be active or not Determines wether a gene will produce RNA or not At least one of the following is always found in a promoter: - TATAA, CAAT, GC and Oct sequences

Question 30

Write a note on an enhancer (2)

Answer 30

Can be thousands of bp long Determine how much RNA can be produced

Question 31

Write a note on exons (2)

Answer 31

They code for proteins These end up in mRNA and are then translated into protein

Question 32

Write a note on introns

Answer 32

These do not code for proteins They are made into RNA but are then spliced out to make mRNA

Question 33

How many exons does the biggest human gene have?

Answer 33

300

Question 34

How many bps does the dystrophin gene have?

Answer 34

It has 2.5 million base pairs but it has only 12,000 after splicing has occurred to form mRNA

Question 35

What often happens to the first exon?

Answer 35

It is often untranslated It arrives in mRNA but does not get translated or at least not all of it does

Question 36

Give an example of a promoter

Answer 36

The methionine codon -> indicates the start point of translation

Question 37

There is part of the 5' region (promoter) that is not translated, what happens at the 3' region?

Answer 37

There is also a 3' untranslated region

Question 38

Briefly describe the formation of a protein

Answer 38

Nucleus -> DNA transcription -> hnRNA -> post transcriptional processing -> mRNA -> moves out to cytoplasm through nuclear pores -> ribosome - translation -> post translational modification -> protein

Question 39

Give some examples of post transcriptional processing (3)

Answer 39

Capping Splicing Polyadenylation

Question 40

How many genes do we have?

Answer 40

20,000 approximately

Question 41

What are polymorphisms? (2)

Answer 41

Natural variations in our genome (not associated with disease) Allows us to differentiate from each other - they are why we look different

Question 42

What does hnRNA stand for?

Answer 42

Heterogenous nuclear RNA This is the RNA transcribed straight from DNA - there has been no modifications e.g. splicing

Question 43

Give two examples of post translational modifications

Answer 43

Phosphorylation - addition of a phosphate groups Cleavage - chopping off a part of the protein e.g. insulin

Question 44

Is cystic fibrosis recessive or dominant?

Answer 44

Recessive

Question 45

Where is the mutation for cystic fibrosis found? (3)

Answer 45

Found in chromosome 7 CFTR gene Exon 10

Question 46

List the different parts of the human genome - What makes up the human genome (8)

Answer 46

SINEs and LINEs = 34% Introns = 25% Heterochromatin = 8% retrovirus-like elements = 8% DNA transposon 'fossils' = 7% segmental duplications = 5% single sequence repeats = 3% Exons = 1.5%