The Human Genome Flashcards
A guide to the human genome for clincians
What 2 elements lead to disease?
Genetics and environment
What is the concept of precision medicine?
Identify and treat people who will benefit from treatment. Those who the treatment isn’t suitable for either have to get a different treatment or for some there is no suitable alternative.
How is DNA organised?
Double stranded, antiparallel, when replicated read in 5’-3’ direction. Sugar backbone is 2-deoxyribose. Bases ATGC
Where is the information in DNA held?
The sequence of bases held on a sugar-phosphate background
How are DNA bases paired?
Adenine with thymine, cytosine with guanine
What does the DNA strand associate with and form?
Wrapped around proteins (histone) and wound into chromosomes
How much of your genome is genes?
2-3%
What are the 4(/5) stages of the cell cycle?
G1, (sometimes G0), S(ynthesis), G2 and M(itosis)
During what phases of the cell cycle does DNA replication occur?
S phase
What is the DNA damage and repair mechanism?
Damage can occur during replication of DNA, and there are repair mechanisms however if the mechanisms are defected disease can be caused.
What significance does only 2% of the genome being genes have in mutations?
When mutations occur during mitosis it has a very high chance of occurring in an area that isn’t genes so won’t affect the genotype
What are the key parts of meiosis?
One diploid parent cell = 4 haploid daughter cells. Crossing over occurs
When does meiosis happen?
During gamete formation
How does RNA differ in comparison to DNA?
Single stranded, ribose sugar in backbone not deoxyribose, and uracil instead of thymine
Which one is more stable, RNA or DNA?
DNA as if RNA was more stable it would stay making proteins for too long and it is only required for a short time to code
What binds to the promotors in DNA?
Transcription factors
Are introns coding or non-coding?
Non-coding and so cut from DNA during transcription
Are exons coding or non-coding?
Coding and so spliced together after introns cut during transcription
What factors determine the amount of protein produced?
Rate of transcription, rate of splicing to mRNA, half life of mRNA and rate of processing of polypeptide.
What is DNA transcribed to?
Pre mRNA
What is pre mRNA spliced to?
mRNA
What is mRNA translated to?
A protein (remember 3 bases encode an amino acid or a stop codon)
Why do some point mutations have no affect on the protein created?
As sometimes a different triplet of bases code for the same amino acid
How do sequences vary in a gene?
Changes in the promotor sequence and changes in the exon sequence
What is the promotor sequence?
The region of the DNA sequence where transcription of a gene by RNA polymerase begins
What causes sequence changes in the DNA between genes?
Single nucleotide polymorphisms (SNPs) or larger deletions/duplications
What is polymorphism?
Any variation in the human genome that has a population frequency of >1% OR any variation in the human genome that doesn’t cause a disease but may be a predisposition to one.
What is a mutation?
A gene change that causes a genetic disorder OR any heritable change in the human genome
How does variation in the human genome occur?
Crossing over at meiosis cause variants to segregate independently of each other (unless they were close together on the chromosome)
Why do people have genetic variants their parents don’t have?
As DNA replication isn’t perfect and so every cell in your body has mutations acquired during mitosis
