Lab 7 - From Genes to Proteins

Question 1

Promoter

Answer 1

Region of DNA that initiates transcription of a particular gene.

RNA polymerase binds to a promoter site on the DNA to initiate mRNA trancription

Question 2

Enhancer

Answer 2

a short (50–1500 bp) region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur.

Activators bind to a second class called co-activators, which in turn bind to the general transcription factor complex.

Question 3

Silencer

Answer 3

a DNA sequence capable of binding transcription regulation factors, called repressors.

When a repressor protein binds to the silencer region of DNA, RNA polymerase is prevented from transcribing the DNA sequence into RNA.

Question 4

Primary transcript

Answer 4

A primary transcript is the single-stranded ribonucleic acid (RNA) product synthesized by transcription of DNA, and processed to yield various mature RNA products such as mRNAs, tRNAs, and rRNAs.

Question 5

Gene splicing

Answer 5

Nuclear enzymes remove sections of RNA, and the remaining sections are spliced together to form the functional mRNA that will migrate to the cytoplasm

Question 6

Introns

Answer 6

Any nucleotide sequence within a gene that is removed by RNA splicing during maturation of the final RNA product.

Question 7

Exons

Answer 7

Any part of a gene that will encode a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing.

Question 8

What can errors in gene splicing cause?

Answer 8

Genetic disease

Question 9

Mature transcript

Answer 9

Introns are spliced out of the primary mRNA transcript before the mature transcript leaves the nucleus

Question 10

Alternative splice sites

Answer 10

a regulated process during gene expression that results in a single gene coding for multiple proteins.

Some genes contain alternative splice sites, which allow the same primary transcript to be spliced in different ways. Produces different protein products from the same gene

Question 11

Transcription factors

Answer 11

Required for the transcription of DNA to mRNA. General transcription factors are used by all genes, and specific transcription factors help to initiate the transcription of genes in specific cell types at specific points in time

Question 12

DNA-binding motifs

Answer 12

Is how the transcription factors locate specific DNA sequences. DNA-binding motifs are configurations in the transcription-factor protein that allow it to fit snugly and stably into a unique portion of the DNA double helix. Each major motif contains many variations that allow specificity in DNA binding. In some cases, they bend DNA so that distant enhancer sequences can interact with target genes

Dna binding proteins recognize and bind to specific sequences. This binding is supported by the presence of DNA binding motifs which help in positioning the DNA binding sequences in a way that gives easy and stable binding.

Question 13

Housekeeping genes

Answer 13

Genes that are transcribed in all cells of the body that encode products required for a cell’s maintenance and metabolism

Question 14

Genetic code

Answer 14

The genetic code is the set of rules used by living cells to translate information encoded within genetic material (DNA or mRNA sequences) into proteins.

Question 15

Codon

Answer 15

Triplets of bases that specify amino acids.

Question 16

Stop codons

Answer 16

UAA, UGA, UAG

Question 17

Anticodon

Answer 17

An anticodon is a unit made up of three nucleotides that correspond to the three bases of the codon on the mRNA.

The anticodon is on the tRNA.

Question 18

Collagen fibril formation (Simple)

Answer 18

1. Synthesis of pro a-chain
2. Hydroxylation of selected prolines and lysines
3. Glycosylation of selected hydroxylysines
4. Triple helix formation (secreted out of the cell)
5. Procollagen molecule
6. Cleavage of portions of procollagen
7. Mature collagen molecule
8. Assembly into collagen fibril

Question 19

What causes OI ?

Answer 19

Mutations in either of the two genes that encode type 1 collagen (COL1A1, COL1A2)

Question 20

Symptoms of OI

Answer 20

Bone fractures, short stature, hearing loss, abnormal tooth development, bluish sclerae, various bone deformaties incl scoliosis

Question 21

Subunits of type 1 procollagen

Answer 21

two proalpha 1 chains, one proalpha 2 chain

Question 22

Which chromosomes are pro-alpha1 and pro-alpha2 chains encoded by?

Answer 22

Pro-alpha1 chains: 18-kb gene on chromosome 17

Pro-alpha2 chain: 38-kb gene on chromsome 7

Question 23

Most common type of mutation that cause OI

Answer 23

Missense mutation. Replacement of glycine with another amino acid. Seen in severe forms.

Question 24

Posttranslational modifications in collagen fibril formation:

Answer 24

Hydroxylation and Glycosylation

Question 25

What is hydroxylated during the process of collagen fibril formation?

Answer 25

Proline and lysine to form hydroxyproline and hydroxylysine

Question 26

Where is the polypeptides associated with one another, and how are they stabilized?

Answer 26

They associate with one another at their COOH termini, and are stabilized by sulphide bonds

Question 27

Some of the hydroxylysines and glycosylates occurs where?

Answer 27

In the rough-ER

Question 28

Germline mosaicism

Answer 28

Mutations that occur de novo in a family may have arisen relatively early in germ cell development, resulting in a significant number of gametes that carry the mutation

Question 29

Can the parent with gerline mosaicism transmit the mutation to the offspring?

Answer 29

Since the parent carries the mutation in the germline (but does not express the disease because the mutation is absent in the cells) the parent can transmit the mutation to offspring

Question 30

What technique is used to amplify DNA from the sperm of a father of two children with type II OI?

Answer 30

Polymerase chain reaction (PCR) technique

Question 31

Other diseases where germaine mosaicism have been shown

Answer 31

Achondroplasia, neurofibromatosis type 1, Duchenne muscular dystrophy, hemophilia A

Question 32

Pleiotropy

Answer 32

Describes genes that have multiple phenotypic effects on the body.

Question 33

What are the observed features of Marfan syndrome caused by?

Answer 33

Unusually stretchable connective tissue

Question 34

Other single-gene diseases in which pleiotropy is seen

Answer 34

Cystic fibrosis: sweat glands, lungs, pancreas affected
OI: bones, teeth, sclerae affected
Albinism: pigmentation and optic fiber development affected

Question 35

Marfan syndrom- symptoms

Answer 35

Defects in ocular, skeletal and cardiovascular system.
Ocular: myopia, displaced lens
Skeletal: unusually long and slender limbs, hallow chest, scoliosis, arachnodactyly, hypermobility in joints
Cardiovascular: prolapse of mitral valve, dilation of ascending aorta which may lead to congestive heart failure

Question 36

What is Marfan syndrome caused by?

Answer 36

FBN1 mutations that are expressed in the aorta, periosteum and the suspensor ligaments of the lens
FBN1 encodes a connective tissue protein, fibrillin, so mutations alter the structure of connective tissue.

Question 37

What kind of mutations are FBN1 mutations? And what kind of mutation produces a more severe disease phenotype?

Answer 37

Most are missense, some are frameshift and nonsense mutations
Missense mutations causes more severe disease phenotype because of dominant negative effect

Question 38

What can specific mutations in FBN1 cause?

Answer 38

Familial archnodactyly (with no other symptoms), familial ectopic lentis.

Question 39

Mutation of FBN2 causes which disease? What is the features of this disease?

Answer 39

Congenital contractural arachnodactyly.

Exhibits many of the skeletal features of Marfan syndrome but does not involve cardiac or ocular defects.

Question 40

Marfan syndrome can be caused of mutation on other genes except for FBN1 or FBN2. Which gene?

Answer 40

Mutations in the gene that encodes transforming growth factor B receptor 2 (TGFBR2)

Question 41

Mutations in the gene that encodes transforming growth factor B receptor 2 (TGFBR2) leads to what?

Answer 41

Increases signaling activity of TGF-b, contributing to aortic dilation and abnormal bone growth

Question 42

Phenotype

Answer 42

The phenotype is what is actually observed physically or clinically

Question 43

Cystic fibrosis type of disorder

Answer 43

Autosomal recessive

Question 44

Can the same genotype produce different phenotypes in different environment?

Answer 44

Yes, an example is recessive disease phenylketonuria

Question 45

Cystic fibrosis caused by

Answer 45

mutations in a gene, CFTR, that encodes the cystic fibrosis transmembrane conductance regulator

Question 46

Class 1 CFTR gene mutation

Answer 46

result in no synthesis of the gene product

Question 47

Class 2 CFTR gene mutation

Answer 47

produce a defective protein product that is destroyed in proteasomes.

Question 48

Class 3 CFTR gene mutation

Answer 48

produce a protein that gets to the cell surface but is abnormally regulated

Question 49

Class 4 CFTR gene mutation

Answer 49

result in defective chloride ion conductance.

Question 50

Class 5 CFTR gene mutation

Answer 50

typically promoter or intron–exon splicing mutations that reduce the number of mRNA transcripts, allowing some normal protein products.

Question 51

Class 6 CFTR gene mutation

Answer 51

mutations result in increased rates of turnover of the chloride channel at the cell surface.

Question 52

Mutations in which gene causes achondroplasia?

Answer 52

FGFR3 gene (Fibroblast growth factor receptor 3)

Question 53

Age dependent penetrance in Huntingtons disease

Answer 53

HD is caused by a CAG expanded tandem repeats. Inheritance of 36 or more copied of the repeat can produce disease.
Larger number of repeats is correlated with earlier age of onset of the disorder.
Greater repeat expansion when the father, rather than the mother, transmits the disease-causing mutation.

Question 54

Mild expression of neurofibromatosis 1 symptoms

Answer 54

Café-au-lait spots (French for “coffee with milk,” describing the color of the hyperpigmented skin patches)
Lisch nodules (benign growths on the iris)
Neurofibromas (nonmalignant peripheral nerve tumors).

Question 55

Severe expression of neurofibromatosis 1

Answer 55

Hundreds to thousands of neurofibromas
Plexiform neurofibromas
Optic pathway gliomas (benign tumors of the optic nerve)
Learning disabilities
Hypertension
Scoliosis (lateral curvature of the spine)
Malignancies

Question 56

Which gene has one of the highest known locus-specific mutation rates, about 1 in 10,000 per generation

Answer 56

NF1 gene, because of its large size (approximately 350 kb)

Question 57

NF1 mutation occurring during embryonic development results in

Answer 57

Somatic mosaicism. It will only effect some cells of the individual

Question 58

Neurofibromatosis 2 is characterized by

Answer 58

vestibular schwannomas (tumors that arise in Schwann cells and affect the eighth cranial nerve) and, occasionally, café-au-lait spots.

Question 59

NF2 gene encodes a tumor suppressor protein called

Answer 59

Merlin or schwannomin