Fergus - Introduction to the Human Genome Flashcards
What are the three components of DNA/RNA?
(3)
Nucleotide made from a five carbon sugar (deoxyribose/ribose)
A phosphate
A nitrogenous base
How does deoxyribose differ from ribose?
In deoxyribose the 2nd carbon on the sugar is a hydrogen
In ribose the 2nd carbon in the sugar is an OH group
In what direction are new nucleotides added onto DNA?
From the 5’ to the 3’ end
What does the 5’ of DNA/RNA contain?
A phosphate group
What are the four bases of DNA?
Adenine
Guanine
Cytosine
Thymine
What are the four bases in RNA?
Adenine
Guanine
Cytosine
Uracil
How does uracil differ to thymine?
Uracil is closely related to thymine
Uracil has a H as its variable group while thymine has a CH3
How does G bind to C?
By three hydrogen bonds
How does A bind to T
By two hydrogen bonds
How many bases are needed for a complete turn of a DNA sequence?
10 bases
Classify nitrogenous bases
Purines
Pyrimidines
How many chromosomes do we have?
46
How are our chromosomes classified?
Autosomes
Sex chromosomes
How does a female karyotype occur?
One X chromosme from father
One X chromosome from mother
How does a male keryotype occur?
One Y chromosome from father
One X chromosome from mother
How does a male keryotype occur?
One Y chromosome from father
One X chromosome from mother
How does a male keryotype occur?
One Y chromosome from father
One X chromosome from mother
What is different about the karyotype in someone who has Down’s Syndrome?
There is an extra copy of the 21st chromosome
What is mosaic downs?
There isn’t an extra copy of chromosome 21 in every single cell
What percentage of the human genome codes are genes (protein coding sequences)?
15%
What percentage of the human genome is heterochromatin?
8%
What is heterochromatin?
Densely packed chromatin found in the nucleus
What percentage of the human genome is segmental duplications?
5%
What are segmental duplications?
Duplications that may have developed due to replication errors, chromosomes that have been replicated, same sequences replicated twice
What percentage of the human genome are single sequence repeats
3 % -> usually errors in replications
What percentage of the human genome are retrovirus-like elements?
8%
RNA viruses that have left their genome in our genome
What percentage of the human genome are DNA transposon ‘fossils’ and what are they?
7% they allow bacteria to transfer genetic material around to other cells
What percentage of the human genome are SINEs and LINEs and what are they?
About 34% of the genome
Short and long interspersed retrotransposable elements
Don’t really know their function yet
Write a note on a promoter sequence
(4)
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
Write a note on an enhancer
(2)
Can be thousands of bp long
Determine how much RNA can be produced
Write a note on exons
(2)
They code for proteins
These end up in mRNA and are then translated into protein
Write a note on introns
These do not code for proteins
They are made into RNA but are then spliced out to make mRNA
How many exons does the biggest human gene have?
300
How many bps does the dystrophin gene have?
It has 2.5 million base pairs but it has only 12,000 after splicing has occurred to form mRNA
What often happens to the first exon?
It is often untranslated
It arrives in mRNA but does not get translated or at least not all of it does
Give an example of a promoter
The methionine codon -> indicates the start point of translation
There is part of the 5’ region (promoter) that is not translated, what happens at the 3’ region?
There is also a 3’ untranslated region
Briefly describe the formation of a protein
Nucleus -> DNA transcription -> hnRNA -> post transcriptional processing -> mRNA -> moves out to cytoplasm through nuclear pores -> ribosome - translation -> post translational modification -> protein
Give some examples of post transcriptional processing
(3)
Capping
Splicing
Polyadenylation
How many genes do we have?
20,000 approximately
What are polymorphisms?
(2)
Natural variations in our genome (not associated with disease)
Allows us to differentiate from each other - they are why we look different
What does hnRNA stand for?
Heterogenous nuclear RNA
This is the RNA transcribed straight from DNA - there has been no modifications e.g. splicing
Give two examples of post translational modifications
Phosphorylation - addition of a phosphate groups
Cleavage - chopping off a part of the protein e.g. insulin
Is cystic fibrosis recessive or dominant?
Recessive
Where is the mutation for cystic fibrosis found?
(3)
Found in chromosome 7
CFTR gene
Exon 10
List the different parts of the human genome
- What makes up the human genome
(8)
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%
