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Genetics > L11-14: Eukaryotic genes and transcripts & Inheritance > Flashcards

L11-14: Eukaryotic genes and transcripts & Inheritance Flashcards

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1
Q

What does polycistronic mean?

A

It is when clustered genes are often transcribed as a single molecule or mRNA

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2
Q

What parts of the transcription unit are not encoded in the genome?

A

The cap and the poly A tail

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3
Q

How do differences in gene organisation impact geneticsin eukaryotes and prokaryotes?

A

In prokaryotes if there is a mutation it effects the recognition of all genes but in eukaryotes its only impacts one

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4
Q

What are transcription promotors?

A

Region of DNA upstream that contains specific nucleotide sequences that transcription factors associate with which allows the recruitment of RNA polymerase

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5
Q

What are the key features of prokaryotic promotors?

A

Conserved sequences upstream
Conserved sequences recognised by sigma factor which positions the polymerase:
RNA pol + sigma factor = holoenzyme

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6
Q

What are the RNA polymerases in eukaryotes?

A

RNA pol I - rRNA
RNA pol II - all protein coding genes
RNA pol III - tRNA, 5S rRNA and other small ‘non-coding RNAs’

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7
Q

What are features of RNA polymerase II in eukaryotes?

A

TATA-box that is bound by the transcription factor IID complex
TFIID recruits other TFs and RNA polymerase II
5’ cap is added while mRNA is transcribed

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8
Q

When is the poly A tail added?

A

At a specific signal AAUAA when RNA is cut releasing it from the DNA then the poly A tail is added

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9
Q

What is a microarray?

A

DNA corresponding to each gene in the organisms genome spotted onto a slide

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10
Q

How does splicing take place?

A

Spliceosome removes introns from RNA

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11
Q

What are the functions of the small and large subunits of the ribosome?

A

Small: reading mRNA, finding ORF and interpreting the codon
Large: synthetic peptidyl transferase centre

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12
Q

How does bacterial translation take place?

A

Using the Shine-Dalgarno sequence which is recognised by the small subunit by base pairing
Large and small subunit bind which initiates translation

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13
Q

How is translation initiated in eukaryotes?

A

Small subunit binds to cap and moves along to the first AUG

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14
Q

How are genes polygenic?

A

When multiple genes interact

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15
Q

What is the difference between linked and unlinked genes?

A

Linked genes cannot assort independently whereas unlinked can

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16
Q

What phenotypic and genotypic ratios are typically used to work out allele frequency?

A

1:2:1 and 3:1

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17
Q

What is the Hardy-Weinburg equation?

A

p^2+2pq+q^2=(p+q)^2=1

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18
Q

How do populations retain genetic variability?

A

Due to the genotypic ratios in a randomly-breeding population remaining constant from generation to generation

19
Q

When does Hardy-Weinburg not apply?

A

Gene flow
Genetic drift
Nonrandom mating
Natural selection

20
Q

What does Hardy-Weinburg assume?

A

Large population, random mating and no evolutionary forces acting

21
Q

What are examples of human autosomal recessive conditions?

A

Albinism
Phenylketoneuria
Tay-Sachs
CF
Sickle-cell anemia
Haemochromatosis

22
Q

What are examples of autosomal dominant conditions?

A

Huntington’s
Polycystic kidney disease
Achondroplastic dwarfism
Polydactyly
Hypercholesterolemia
FASPS

23
Q

What are characteristics of sex linkage?

A

X and Y share little homology
X has more genes than Y
Many genes on Y are for male sex determination
Many genes on X that are not involved in determination
The presence of a gene on X or Y leads to distinct patterns of inheritance

24
Q

What are examples of X-linked recessive disorders in humans?

A

Haemophilia
Duchenne & Becker muscular dystrophies
Fragile-X syndrome
Deuteranopia (colourblindness)

25
Q

What is haemophilia?

A

Failure of the blood to clot which is caused by the absence of Factor VIII (ran in royal family)

26
Q

What is an example of a Y-linked disorder?

A

Retinitis pigmentosa

27
Q

What is Leri-Weill dyschondrosteosis?

A

Disorder of bone growth, caused by mutation/lack of one copy of SHOX gene, SHOX is found on X and Y

28
Q

What terms are used in the relationship of genotype to phenotype?

A

Penetrance & expressivity
Pleiotrophy
Epistasis
Environmental effects
Complementation

29
Q

What types of dominance relationships?

A

Complete, Incomplete and Codominant

30
Q

What is codominance?

A

Both alleles are expressed in the phenotype so traits show equally in F1

31
Q

What is pleiotrophy?

A

Some genes/alleles of them affect more than one unrelated characteristic, like in manx cats has recessive lethal phenotype

32
Q

What is epistasis?

A

Where one mutation hides/modifies the phenotype of another gene that is epistatic to another modifies/masks its phenotype

33
Q

What does hypostatic mean?

A

The gene whose phenotype is modified/masked in epistasis

34
Q

What is penetrance?

A

It describes how many members of a population with a particular genotype show the expected phenotype

35
Q

What is variable expressivity?

A

The range of signs and symptoms that can occur in different people with the same genetic condition

36
Q

What is an example of incomplete penetrance and variable expressivity?

A

Polydactyly

37
Q

How do environmental effects impact phenotype?

A

Temperature is one element
e.g. Siamese cats for a thermosensitive allele which encodes an enzyme catalysing melanin production

38
Q

What is a complementation group?

A

A set of mutations mapping to the same chromosomal locus that fail to complement each other when crossed

39
Q

What is a key feature of complementation analysis?

A

Can only be done with recessive alleles

40
Q

What is intragenic complementation?

A

A protein has multiple functions or which forms multimers

41
Q

How are non-parental genotypes formed?

A

Independent assortment of genes on different chromosomes
Breakage and rejoining of homologous chromosomes during meiosis

42
Q

What is recombination frequency?

A

RF= (No. of recombinants/ total progeny) x100

43
Q

What is the centimorgan?

A

It is a map unit, 2 loci are one centimorgan apart if recombination is observed between them in 1% of meiosises

44
Q

How are genetic and physical maps used?

A

Not co-linear
Recombination is not random along chromosomes ‘hot spots’
More of an approximation to the physical map from genetic data

Genetics (11 decks)

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