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Medical Genetics > Lab 2 - Human genome > Flashcards

Lab 2 - Human genome Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

DNA molecule basic components

A

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

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2
Q

Pyrimidines

A

Cytosine and thymine

Single carbon-nitrogen rings

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3
Q

Purines

A

Adenine and guanine

Double-carbon nitrogen rings

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4
Q

How many hydrogen bonds between cytosine-guanine pairs?

A

Three

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5
Q

How many hydrogen bonds between adenine-thymine pairs?

A

Two

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6
Q

DNA coiling

A

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

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7
Q

Each nucleotide subunit consist of

A

One deoxyribose, one phosphate group and one base

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8
Q

Gene definition

A

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

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9
Q

Protein-coding gene

A

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

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10
Q

Within the genomic DNA, a gene is defined by

A

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

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11
Q

Sense strand

A

The DNA strand which corresponds to the RNA sequence

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12
Q

Antisense strand

A

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

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13
Q

UTR - Untranslated regions

A

The sequence before the start codon and after the stop codon

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14
Q

AAUAAA

A

Polyadenylation signal where transcription terminates

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15
Q

Introns

A

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

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16
Q

Exons

A

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

17
Q

Tandem repeats

A

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

18
Q

Satellite DNA

A

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

19
Q

Dispersed repetitive DNA

A

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

20
Q

Satellite DNA can easily be separated by

A

Centrifugation in a cesium chloride density gradient

21
Q

Alpha satellite DNA:

A

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

22
Q

Minisatelites

A

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

23
Q

Microsatellites

A

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

24
Q

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

A

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

25
Q

Transposons

A

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

26
Q

Retrotransposons

A

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

27
Q

Long terminal repeat (LTR)

A

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

28
Q

Long interspersed elements (LINEs)

A

Up to 7 kb

29
Q

Short interspersed elements (SINEs)

A

Up to 300 bp, incl. Alu

30
Q

Alu

A

Can mediate an asymmetric recombination and cause genomic deletions and duplications

31
Q

DNA molecules of mitochondria

A

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

32
Q

Mutation rate of mtDNA

A

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

33
Q

Threshold effect

A

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

34
Q

Organs that are most affected by mitochondrial diseases

A

CNS, heart, kidney

35
Q

Symptoms of mitochondrial diseases

A 
Encephalopathy
Myopathy
Cardiomyopathy
External ophthalmoplegia
Retinal degenaration
Renal dysfunction.
36
Q

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

A

Childhood

37
Q

What does myoclonus progress into?

A

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

38
Q

Leber herditary optic neuropathy

A

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

39
Q

Kearns-Sayre syndrome

A

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

Medical Genetics (10 decks)

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