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Eukaryotic Genetics
Inheritance, diversity and genome evolution
133
Biochemistry
Undergraduate 1
01/11/2013

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Term
What is polycistronic mRNA?
Definition
An mRNA that has similar clustered genes
Term
What is monocistronic mRNA?
Definition
An mRNA that has only one gene
Term
What type of mRNA is present in prokaryotes?
Definition
Polycistronic mRNA
Term
What type of mRNA is present in eukaryotes?
Definition
Monocistronic mRNA
Term
What is the general sequence of an mRNA?
Definition
Cap, Start codon, Coding sequence, Stop codon, Poly A tail
Term
What is the advantage of having a polycistronic mRNA?
Definition
Similar proteins can be transcribed together
Term
What is the disadvantage of having a polycistronic mRNA?
Definition
If a malfunction occurs in the transcription promoter then all proteins are not transcribed
Term
What is the advantage of having a monocistronic mRNA?
Definition
If a malfunction occurs in the transcription promoter then one only one protein is not transcribed
Term
What is the disadvantage of having a monocistronic mRNA?
Definition
Proteins have to each be transcribed seperately
Term
How many different RNA polymerases do eukaryotes have?
Definition
Three
Term
What does RNA polymerase I transcribe?
Definition
Ribosomal RNA
Term
What does RNA polymerase II transcribe?
Definition
All proteins
Term
What does RNA polymerase III transcribe?
Definition
tRNA, 5s rRNA and other smaller RNA's
Term
What is the TATA-box?
Definition
A promoter sequence
Term
What does the TATA-box bind?
Definition
TFIID
Term
What does TFIID do?
Definition
Recruit RNA polymerase II and other transcription factors
Term
Where is the TATA-box?
Definition
-25bp before start codon
Term
Where does transcription end?
Definition
10-35nt downstream of the AAUAAA seqeunce
Term
How do endonucleases relate to transcription?
Definition
They can release the DNA from RNA polymerase
Term
What is the equivalent of the TATA-box in prokaryotes?
Definition
The sigma factor
Term
Give three examples of changing gene expression patterns?
Definition
Cancer, Tissue differentiation and development
Term
What is the name of the machinery that removed introns?
Definition
Spliceosome
Term
What is the purpose of the splice sites of introns?
Definition
Recruits the spilcesosome so the introns can be spliced out
Term
What is the effect of an intron mutation?
Definition
Does not affect coding sequence but may effect splicing
Term
What is the effect of an exon mutation?
Definition
Affects the coding sequence
Term
What two things are added to mRNA after cplicing?
Definition
The cap and the poly a tail
Term
What is capping?
Definition
The addition of the cap to the mRNA
Term
What is polyadenylation?
Definition
The addition of the poly A tail
Term
What does the small ribosomal subunit do?
Definition
Finds the reading frame of the DNA
Term
What does the large ribosomal subunit do?
Definition
Houses the protein synthetic peptidyl transferase centre
Term
How is the open reading frame in bacterial translation identified?
Definition
By the Shine-Dalgarno sequence
Term
What is the advantage of using the Shine-Dalgarno sequence to translated bacterial mRNA?
Definition
All the polycistronic proteins can be transcribed seperately but also at the same time
Term
When the small ribosomal subunit has recognised the open reading frame it does what?
Definition
Binds the CAP protein to the first AUG
Term
What is the Kozak consensus?
Definition
The most frequently found sequence before the AUG
Term
What does coupled mean in reference to transcription and translation?
Definition
Translation can affect transcription
Term
What does uncoupled mean in reference to transcription and translation?
Definition
Translation can not affect transcription
Term
Prokaryotes undergo _______ translation and transcription?
Definition
Coupled
Term
Eukaryotes undergo _______ translation and transcription?
Definition
Uncoupled
Term
What is the limiting factor in the trp operon?
Definition
The presence of tryptophan
Term
Which amino acid does the code AUG code for?
Definition
Methionine
Term
Who conducted many experiments into inheritance?
Definition
Mendel
Term
How did Mendel carry out his inheritance studies?
Definition
By crossing peas
Term
What is a monohybrid cross?
Definition
A genetic cross between two individuals that differ in one trait
Term
What is Mendels first law?
Definition
The principle of segregation
Term
Why is it unlikely that we have many single-gene traits in the human body?
Definition
Large number of genes and environmental influence
Term
What are the four single-gene traits?
Definition
PTC tasting, albinism, white cats and wet/dry earwax
Term
Which allele controls PTC tasting?
Definition
TAS8R38
Term
Is albinism dominant, recessive or codominant?
Definition
Recessive
Term
How common is the dominant 'W' allele in white cats?
Definition
Very rare
Term
Is wet ear wax dominant or recessive?
Definition
Dominant
Term
The cross of a homozygous dom and a homozygous rec will always yield what?
Definition
A heterozygous
Term
Te cross of a heterzygous and a homozygous rec will yeild what?
Definition
50% Heterzygous
50% Homozygous rec
Term
What is Mendels second law?
Definition
The principle of independent assortment
Term
What are the two approaches to working out genotypic ratios?
Definition
Forked Line and Punnet Square
Term
How do you work out the probability of each allele?
Definition
Multipliying all the probability's of each parents together
Term
What is continuous variation>
Definition
Phenotypes showing a large range of variation rather than discrete phenotypes
Term
What are polygenic phenotypes?
Definition
Characteristics that are influenced by more than one gene
Term
Give two examples of polygenic phenotypes?
Definition
Height and shoe size
Term
What is a complementation group?
Definition
A set of mutations on the same chromosome that fail to compliment each other when crossed
Term
What are the two types of drosophila wing?
Definition
Wrinkled and normal
Term
Give an example of a complimentaton group?
Definition
Drosophila wings
Term
WHat are the four alleles for Drosophila wings?
Definition
a, b, c and x
Term
What two alleles create wrinkled wings?
Definition
Ra/Ra and Rb/Rb
Term
Why do the c and x alleles not affect Drosophila wings?
Definition
The enzymes they code for do not affetc protein too much and so the wings are the same
Term
Why do the a and b alleles affect Drosophila wings?
Definition
The enzymes they code for do affect the proteins to the extent that the wings become wrinkled
Term
What is the classical geneticist definition of a gene?
Definition
Sequence required for a biological function/charcteristic
Term
What is the molecular geneticist definition of a gene?
Definition
Nucleic acid sequence necessary to produce and mRNA transcript and ultimately a polypeptide
Term
Name the five human autosomal recessive conditions?
Definition
Albinism, Phenylketoneuria, Tay-Sachs, Cystic Fibrosis and Sickle Cell Anemia
Term
What is albinism?
Definition
Lack of melanin
Term
What is penylketoneuria?
Definition
Inability to metabolise phenylalanine
Term
What is Tay-Sachs?
Definition
Neurodegeneration due to lack of NAH
Term
What is cysytic fibrosis?
Definition
Thick mucus due to lack of CFTR
Term
What is sickle-cell anemia?
Definition
Mutation in the beta-chain of hemoglobin
Term
Name the five human autosomal dominant conditions?
Definition
Huntington's disease, Achondroplastic dwarfism, Polydactyly, Hypercholerterolemia and FASPS
Term
What is Huntington's disease?
Definition
Progressive brain disease
Term
What is Achondroplastic dwarfism?
Definition
Failure to convert cartlidge to bone
Term
What is polydactyly?
Definition
Extra finger/s
Term
What is hypoercholesterolemia?
Definition
Removal of cholesterol from the blood, causes heart attacks
Term
What is FASPS
Definition
Waking up very early
Term
What is a family pedigree?
Definition
A family tree of genetic disease
Term
What are the features of an autosomal recessive pedigree?
Definition
Unaffected parents with affected offspring and effecting both males and females
Term
What are the features of an autosomal dominant predigree?
Definition
Appear in each generation affecting 5-% of offspring, affecting both males and females
Term
What is sex linkage?
Definition
Inherited diseases from the X chromosome
Term
Why are sex related illnesses more prominent in men?
Definition
They only have one X chromosome so a mutation will always affect them
Term
What are the four sex linked recessive disorders?
Definition
Haemophillia, Muscular dystophies, Fragile-X-Syndrome and Deuteranopia
Term
What is haemophilia?
Definition
Unable to form clotting blood (Absence of factor VIII)
Term
What is Muscular Dustrophie?
Definition
Muscle wastage
Term
What is Fragile-X-Synedrome?
Definition
Mental retardation
Term
What is Deuteranopia?
Definition
Red/Green colour blindness
Term
What is an example of an X-Linked dominant disorder?
Definition
Hypophosphatemia (Vitamin D-resistance rickets)
Term
Who do affected males pass on the dominant sex linked traits to?
Definition
All daughters
Term
What is co-dominance?
Definition
Traits that show up equally due to both alleles being equally domianant
Term
Give an example of a co-dominant trait?
Definition
Blood groups
Term
What is incomplete dominance?
Definition
Where the offspring resemble neither parent
Term
Give an example of incomplete dominance?
Definition
Petal colour in snapdragons
Term
What is pleiotrophy?
Definition
The alleles affect unrelated characteristics
Term
Give two examples of pleiotrophy?
Definition
Manx phenotype in cats and Sickle-cell syndrome
Term
What happens in heterozygotic Manx cats?
Definition
No tail development
Term
What happens in homozygous Manx cats?
Definition
Death
Term
What is epistasis?
Definition
Where one allele modifies/masks another
Term
Give two examples of epistasis?
Definition
Bombay phenotypes and adenine bosynthesis in yeast
Term
What happens in homozygous recessive bombay pheotypes
Definition
They can't produce substance H so can't add sugars A or B so always have O blood group
Term
What is penetrance?
Definition
How not all expected phenotypic ratios are always met
Term
What is expressivity?
Definition
How not all genes are expressed due to lack of environmental influence
Term
Name a disorder that is affected by penetrance and expressivity?
Definition
Polydactyly
Term
What is the main environmental influence factor?
Definition
Temperature
Term
What is linkage?
Definition
The inheritance of two genes due to them being situated at close loci
Term
What prevents sex linkage?
Definition
The formation of chiasmata between the two genes during meiosis
Term
What are the two ways we can track linkage and recombination?
Definition
Using SNP's and RFLP's or doing genetic crosses
Term
What is a backcross?
Definition
Cross and homozygous wild type with a homzygous recessive. Then test the heterozygous with each of the traits
Term
How would one go about using genetic crosses to test for 2 linked genes?
Definition
Doing a backcross
Term
What is the equation for recombination frequency?
Definition
Recombinance frequency = ( Number of recombinants/total progeny )X100
Term
How many centimorgans apart are two loci?
Definition
One centimorgan
Term
In humans how many base pars is one centimorgan?
Definition
1x10 to the power of 6
Term
WHta can we do with genetic and physical chromosome maps?
Definition
Combine them to find out more information about chromosome biology
Term
What is synteny?
Definition
Genes that are grouped on chromosomes in the same way across many species
Term
How can we define chromosomal rearrangements?
Definition
By looking at different synteny blocks across organisms
Term
What is reciprocal translocation?
Definition
Where two non-homologous chromosomes break and exchange information
Term
What causes Acute Myelogenous Leukaemia?
Definition
Translocations between chromsomes (8 and 21) and (15 and 17)
Term
What is chromosome fusion?
Definition
Where two telocentric chromosomes fuse to create of chromosome
Term
What is Robertsonian translocation?
Definition
Removal of the short arms of chromosomes and the recombination of the longer arms to form one chromosome
Term
how do translocations and fusions occur?
Definition
By mistake/accidentally
Term
How does a genome become more complex?
Definition
Number of duplications
Term
What is unequal sister chromosome crossover?
Definition
Where the sister chromosomes do not line up correctly and so one recieves more genetic information over the crossover
Term
Name an organism that has recently undergone a genome duplication?
Definition
S. cerevisae
Term
What can occur during whole genome duplication?
Definition
Recombination that results in mass loss of genes
Term
What are hox genes?
Definition
Transcription factors that influence the development patterns of development genes
Term
If hox genes are not expressed in humans what is usually affected?
Definition
The spine
Term
How do hox genes affect hemoglobin development?
Definition
Originally creates fetal hemoglobin with a high affinity for oxygen which then changes into adult hemoglobin with a normal affinity for oxygen
Term
What is Thalassemia?
Definition
production of abnormal hemoglobin due to unbalanced production of globins
Term
What are the two types of Thalassemia?
Definition
Aplha and Beta
Term
What are the results from alpha thalassemia?
Definition
1 or 2 affected -> No effect
3 affeted -> Unstable oxygen dissociation
4 affected -> Still birth
Term
What are the results from beta thalassemia?
Definition
1 affected -> No symptons
2 affected -> Death at 20 years due to heart failure
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