Lab 2 - Human genome

Question 1

DNA molecule basic components

Answer 1

The pentose sugar, deoxyribose, a phosphate group and four types of nitrogenous bases

Question 2

Pyrimidines

Answer 2

Cytosine and thymine

Single carbon-nitrogen rings

Question 3

Purines

Answer 3

Adenine and guanine

Double-carbon nitrogen rings

Question 4

How many hydrogen bonds between cytosine-guanine pairs?

Answer 4

Three

Question 5

How many hydrogen bonds between adenine-thymine pairs?

Answer 5

Two

Question 6

DNA coiling

Answer 6

First DNA is wound around a histone proteins core to form nucleosome –> nucleosome form a helical solenoid, each turn including six nucleosomes –> solenoid are organized into chromatin loops

Question 7

Each nucleotide subunit consist of

Answer 7

One deoxyribose, one phosphate group and one base

Question 8

Gene definition

Answer 8

A functional unit in the genome that contains the genetic information for one or more gene products

Question 9

Protein-coding gene

Answer 9

Three components: the coding sequence, regulatory sequence, and seemingly useless sequences

Question 10

Within the genomic DNA, a gene is defined by

Answer 10

The direction of transcription in the 5’ to 3’ direction

Question 11

Sense strand

Answer 11

The DNA strand which corresponds to the RNA sequence

Question 12

Antisense strand

Answer 12

Complement of the sense strand (which serve as a template for RNA biosynthesis)

Question 13

UTR - Untranslated regions

Answer 13

The sequence before the start codon and after the stop codon

Question 14

AAUAAA

Answer 14

Polyadenylation signal where transcription terminates

Question 15

Introns

Answer 15

Noncoding sequence in a gene that are positioned between coding sequences (exons) and removed by splicing from the pre-mRNA transcript

Question 16

Exons

Answer 16

Coding sequences in the pre-mRNA that are separated by noncoding introns

Question 17

Tandem repeats

Answer 17

occur in DNA when a pattern of one or more nucleotides is repeated and the repetitions are directly adjacent to each other

Question 18

Satellite DNA

Answer 18

Repeats are clustered together in certain chromosome locations, where they occur as tandem repeats

Question 19

Dispersed repetitive DNA

Answer 19

tend to be scattered singly throughout the genome; they do not occur in tandem

Question 20

Satellite DNA can easily be separated by

Answer 20

Centrifugation in a cesium chloride density gradient

Question 21

Alpha satellite DNA:

Answer 21

Tandem repeats of 171-bp sequence. Found near the centromeres of chromosomes. Several million base pairs

Question 22

Minisatelites

Answer 22

Block of tandem repeats (14 to 500-bp), whose total length is much smaller, usually a few thousand base pairs

Question 23

Microsatellites

Answer 23

Smaller, repeat units are 1 to 13-bp, and the total length of the array is usually less than a few hundred base pairs

Question 24

Why are minisatellites and microsatellites of special interest in human genetics?

Answer 24

Because they vary in length among individuals, making them highly useful for gene mapping

Question 25

Transposons

Answer 25

"Jumping genes", mobile DNA elements. DNA sequences are able to leave a chromosome and to reenter the genome at nonhomologous points of the DNA

Question 26

Retrotransposons

Answer 26

The DNA sequence is multiplied through reverse transcription of mRNA into cDNA, which is integrated into a different location

Question 27

Long terminal repeat (LTR)

Answer 27

5-10 kb. Central protein-encoding region is flanked by LTR or non LTR

Question 28

Long interspersed elements (LINEs)

Answer 28

Up to 7 kb

Question 29

Short interspersed elements (SINEs)

Answer 29

Up to 300 bp, incl. Alu

Question 30

Alu

Answer 30

Can mediate an asymmetric recombination and cause genomic deletions and duplications

Question 31

DNA molecules of mitochondria

Answer 31

Base pairs arranged on a double stranded circular molecule. Encodes 2 rRNAs and 22 tRNAs. Contain no introns. Males do not transmit mtDNA

Question 32

Mutation rate of mtDNA

Answer 32

10 times higher than nuclear DNA. (lack of RNA repair mechanism + damage from free oxygen radicals

Question 33

Threshold effect

Answer 33

Whether a heteropasmic mitochondrial is expressed phenotypically depends on the proportion of the cell’s normal mtDNA to mutated mtDNA

Question 34

Organs that are most affected by mitochondrial diseases

Answer 34

CNS, heart, kidney

Question 35

Symptoms of mitochondrial diseases

Answer 35

``` Encephalopathy Myopathy Cardiomyopathy External ophthalmoplegia Retinal degenaration Renal dysfunction. ```

Question 36

When does MERRF syndrom (myoclonic epilepsy with Ragged Red Fibers) typically presents symptoms?

Answer 36

Childhood

Question 37

What does myoclonus progress into?

Answer 37

Generilized epilepsy, ataxia, weakness, finally dementia. Short stature, hearing loss, optic atrophy, cardiomyopathy

Question 38

Leber herditary optic neuropathy

Answer 38

Affect optic nerve, acute painless loss of vision, progress to severe optic atrophy, males>females. Many carriers remain asymptomatic

Question 39

Kearns-Sayre syndrome

Answer 39

CPEO (chronic progressive external ophthalmoplegia), retinopathy, ptosis, deafness, cardiac arrhythmias, ataxia