Genetics 1 and 2 Flashcards
What was the hershey-chase experiment?
labelled protein capsule or DNA of virus with radioactive phosphorus - looked at which one passed on the radioactivity during multiplication = DNA
Describe the work of Mendel
worked on pea plants, bred them to be pure with different characteristics, then crossed them,
Discovered dominant and recessive alleles
What are Mendel’s 4 rules
- There are alternative forms of genes - alleles
- For each heritable trait an organism has 2 genes, one from each parent
- A sperm or egg only carries one allele for each trait
- When the two genes of a pair are different alleles, one is fully expressed whilst the other has no noticeable effect
What is the ratio in a double dom to double rec cross
All dom.
What is the ratio in a second gen cross of double dom to double rec?
3:1
What is the ratio for crossing heterozygotes with 2 phenotypes?
9:3:3:1
What are some examples of mendelian disease?
Phenylketonia Huntington's Achondroplasia Cystic Fibrosis Sickle Cell disease
What is the basis that all Mendelian genetics work on?
Random assortment of genes into the gametes
What did Thomas Morgan Hunts discover
the effect of non-independent assortment of alleles i.e. genes that are linked and so not sorted randomly into alleles
(discovered in flies with red eyes and grey bodies - WT, and mutants with white eyes and black bodies)
What is the distance between genes called
recombination frequency
How is linkage analysis done?
Lod (logarithm of the odds) score with tests to compare the likelihood that 2 loci are linked vs the likelihoood that they are unlinked
What is incomplete dominance? Give and example.
Where the alleles share dominance e.g. blood groups
Describe the molecular makeup of DNA.
DNA = base (purine or pyramidine) + sugar + phosphate
purines - adenine and guanine
Pyrimidines - cytosine, uracil and thymine
Sugars - ribose (OH) or deoxyribose (H)
Which base pair is strongest?
GC - has 3 H bonds instead of the 2 that AT has
Briefly describe the makeup of chromosomes
DNA double helix –> nucleosome, chromatin, looped into heterochromatin which forms the compacted chromosome
What is chromosome aneuploidy
having the wrong number of chromosomes
what are the 3 trisomies that are compatible with life?
21 (downs), 13 (pataus), 18 (edwards)
What is the most common monosomy?
X because one copy of female X chromosome is silenced
What can cause chromosome aneuploidies?
non- disjunction of meiosis or mitosis
What is a possible cause of apparent genetic defect that actually isn’t genetic?
disfunction of splicing
What are the 5 basic types of mutation?
missense (base substitution leading to swapping of amino acid)
silent (base substiution but still get same protien due to triplet code/wobble base pair)
Frameshift insertion (base insertion leads to reading of triplet code one base out of sync)
deletion (base or amino acid deletion)
Chain termination mutation (addition of stop codon)
What is the average gene length?
3000 bases
How long is the dystrophin gene?
2.4 mill bases
how much of the genome is protein coding?
1.5 %
What is a gene?
any interval along the chromosomal DNA that is transcribed into a function RNA molecule or that is then transcribed into a functional protein
lnc RNA genes?
transcribed but not translated
antisense RNA?
transcribed from the mRNA
pseudogenes
RNA gone back into DNA
What are examples of autosomal dominant genetic disorders?
Huntingtons, Marfans, achondroplasia
What are examples of autosomal recessive disorders?
cycstic fibrosis, sickle cell anaemia, alkaptonuria
Why are recessive disorders not wiped out?
Because they tend themselves to advantages in other areas e.g. CF carriers are more cholera tolerant and SC anaemia carriers are resistant to malaria
What is cytogenetic analysis?
looking for changes in karyotype to determine what is causing the disease e.g. balanced translocations, duplications, deletions, inversions, non-disjunctions, aneuplodies
What is mitochondrial inheritance?
looking into the mitochondrial DNA
What does mtDNA tell you?
maternal line - mtDNA degraded in sperm
What is the problem with mtDNA
variability within cells
varibility between cells - best obsevered in post-mitotic cells such as muscles and neurons
What does methylation if DNA do?
represses transcription
What does cytosination of DNA do?
promotes transcription
What does acetylation of histones do?
Unravells the chromosome for reading
What can adenosine deaminase do?
edit RNA
What are restriction endonucleases?
Cut DNA to form palindromic sticky ends
What does DNA ligase do?
Stick DNA back together
What is reFLP?
Creating libraries of DNA, then southern blot to detect which one is a mutant protein (which one is lost)
Northern blot for RNA to supplement
Use a probe to find the mutation on the chromosome by putting back in situ
What are cDNA libraries
Using reverse transcriptase to create libraries of DNA
What are vectors?
things to splice DNA into
plasmids, yeast artificial chromosomes
Sange sequencing?
DNA polymerase adds tagged terminal nucleotides onto a DNA primer
Use capillary sequencing to work out order up to 600bp
PCR?
Amplification of DNA using known primers to create complimentary strands
Hybridisation microarray assay?
look for hybridisation between different fluorescent probes on microarrays, find which sequences are present
Genome wide association studies?
looking at population level to find SNPs and tell if they are disease causing or just natural variance
Next gen sequencing
short reads but intensive depth
can read whole genome
Which trinucleotide repeat causes huntingtons?
CAG - as numbers increase the classification and disease status alter
