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B1 > Intro to Medical Genetics > Flashcards

Intro to Medical Genetics Flashcards

1
Q

A gene is a segment of DNA that encodes for a specific

a) protein
b) tRNA
c) rRNA
d) microRNA
e) all of the above

A

e

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2
Q

Define an allele

A

Alternative forms of a gene (DNA at a specific locus) that differ in sequence

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3
Q

Define a locus

A

A physical region of a chromosome; often used to refer to a segment of DNA that contains a specific gene

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4
Q

Homologous chromosomes are chromosomes that ______ during meiosis, ____ from each parent

A

pair, one

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5
Q

Are homologous chromosomes identical?

A

No, normally only a few base pair differences in each gene

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6
Q

Are sister chromatids identical?

A

Yes, two identical duplicated chromosomes joined by a single centromere

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7
Q

During which cell replication cycle would you find sister chromatids?

A

Metaphase

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8
Q

What are autosomes?

A

ANy chromosome that is not a sex chromosome

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9
Q

An organism with 4 copies of each chromosome would be ________

A

tetraploid

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10
Q

A human has 45 chromosomes in a cell. He is a _____________ (type of ploidy)

A

Aneuplod

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11
Q

A human has 69 chromosomes in a cell. He is a ____________ (type of ploidy)

A

Euploid - abnormal but still same number of each homologous chromosome

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12
Q

Germline cells are responsible for _____________________

A

production of gametes

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13
Q

What are gametes

A

haploid germ cells (sperm and ova)

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14
Q

What are zygotes

A

Two gametes fuse (during fertilization), diploid

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15
Q

Homologous chromosomes have _______ genes in ______ positions, but _______ alleles
(same/different)

A

same, same, different

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16
Q

Why is neonatal screening done?

A

To ID rare disorders that can cause brain damage or death if not treated early ie PKU

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17
Q

Describe prophase of mitosis

A

chromatin condenses (chromosomes with two chromatids) –> spindle forms –> nucleolus breaks down

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18
Q

Describe prometaphase of mitosis

A

spindle invades nuclear region, chromosomes move to equatorial plane

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19
Q

Describe metaphase of mitosis

A

Chromosomes at equatorial plane and centromeres divide

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20
Q

Describe anaphase of mitosis

A

poles move apart and chromosomes move towards destinations

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21
Q

Describe telophase of mitosis

A

Spindle breaks down –> chromatid uncoils –> nucleoli formed –> contractile ring causes cytokinesis

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22
Q

What is the product of cytokinesis in mitosis?

A

Two daughter cells, each genetically identical to parent cell

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23
Q

Describe prophase I of meiosis

A

Homologous chromosomes pair up and exchange fragments (cross over)

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24
Q

Describe metaphase I of meiosis

A

Homologous pairs line up at metaphase plate

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25
Q

Describe Anaphase I of meiosis

A

Homologues separate to opposite ends of cell, sister chromatids stay together

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26
Q

Describe Telophase I of meiosis

A

Newly formed cells are haploid, each chromosome has two (non-identical) sister chromatids

27
Q

Meiosis II is very similar to mitosis. What are the two differences?

A

1) Haploid (2n) cells at beginning rather than diploid (4n)

2) Creates 4 haploid cells, with chromosomes having one chromatid each

28
Q

What is the key difference between meiosis and mitosis?

A

During prophase homologous chromosomes synapse - pair up tightly and there is genetic exchange (evidenced by chiasmata)

29
Q

Describe synapsis

A

Pairs of sister chromatids align according to homologous sequences and are bound together –> crossing over occurs

30
Q

What is the product of crossing over? (type of chromosome)

A

recombinant!

31
Q

What are the 4 components of gene structure?

A

1) promoters
2) coding sequences (exons)
3) introns
4) structural regions (non-transcribed, 5’ and 3’ untranslated sequences)

32
Q

What causes genetic disorders

a) changes in DNA
b) changes in RNA
c) changes in protein level/activity

A

c

33
Q

What type of mutation in Hgb causes sickle cell anemia?

A

single base pair change

34
Q

Function of promoter sequence

A

controls levels of mRNA expression –> controls protein expression

35
Q

Function of introns

A

“intervening sequences”
interrupt coding sequences
spliced out

36
Q

Function of exons

A

Coding sequences

Specific sequence of AA in proteins

37
Q

Function of structural regions

A

Untranscribed regions

5’ and 3’ untranslated regions in mRNA

38
Q

The TATA box is a promoter sequence that specifies to other molecules ____________________

A

where transcription begins

39
Q

The CCAAT box is a distinct pattern of nucleotides with consensus sequence that occur upstream by ___________ bases to _______________

A

60-100, initial transcription site

40
Q

The core basal promoter determines ______ site for transcription and ____________

A

start, whether transcription occurs

41
Q

Describe the function of an enhancer

A

Short region of DNA that can be bound by activator proteins to increase the likelihood that transcription of a particular gene will occur

42
Q

Tissue specific elements say _____ and _____ a gene is transcribed

A

when and where

43
Q

Describe the function of regulatory elements

A

Determine when, where and how much transcription occurs

44
Q

Intron mutations are usually harmful, true or false

A

False, only mess things up when located in splice zone

45
Q

What percentage of a gene is not transcribed?

A

70%

46
Q

What percentage of a transcript is structural?

A

70%

47
Q

All combos beginning with CG will produce ______

A

ARGININE

48
Q

A point mutation that does not change the amino acid is called a

A

silent mutation

49
Q

A point mutation that does change the amino acid, but only to another with similar biochemical properties is called a

A

missense mutation

50
Q

A point mutation that introduces a premature stop codon

A

nonsense mutation –> truncated protein

51
Q

Does the addition of 3 nucleotides qualify as a frame shift mutation?

A

no. Can still be harmful examp: delta f508

52
Q

A promoter mutation would affect _______

A

levels of protein expression

53
Q

Tertiary post translational processing involves

A

Interdomain interactions

54
Q

Quartanery post translational processing involves

A

multiple polypeptide complexes

55
Q

Loss of function mutations lead to (2)

A

inactive protein products OR loss of expression

56
Q

PKU and Cystic Fibrosis are examples of haplosufficiency diseases. What does this mean?

A

One normal allele is enough to not have disease

DOMINANT

57
Q

Familial hypercholesteremia is a haploinsufficiency disease. What does this mean?

A

One bad allele and you’re f**ked

RECESSIVE

58
Q

Gain of function mutations lead to (2)

A

new protein product OR overexpression/misexpression (in wrong tissue of a normal protein

59
Q

Huntington’s Disease and the trisomies are caused by what type of mutation?

A

gain of function

60
Q

Osteogenesis Imperfect II is an example of a dominant negative disease. What does this entail?

A

Mutant protein inhibit activity of normal protein

61
Q

What does it mean to be reproductively lethal?

A

Organism can have mutation and live with it but cannot pass it on to next generation

62
Q

Reproductively lethal mutations are always ______

A

spontaneous and new

63
Q

Recessive disorders are always spontaneous new mutations, true or false

A

FALSE - rarely, X linked disorders present a special case

64
Q

What are the three ways a silent mutation can occur

A

1) in non essential sequences (introns, untranslated structural regions)
2) occur in redundant base (no AA change)
3) result in a conservative substitution that does not change protein structure or function

B1 (18 decks)

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