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GCD 8917 > General Review > Flashcards

General Review Flashcards

1
Q

How is DNA read?

A

5’->3’

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2
Q

How is RNA different from DNA?

A

1) RNA is single stranded
2) Uracil instead of thymine
3) DNA is more stable because doesn’t have oxygen group (deoxy)

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3
Q

How many genes in each G-band?

A

~50 genes

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4
Q

Why no trisomy 22 if Ch22 is smaller than chromosome 21?

A

Ch 22 is gene rich, so no living trisomies despite being even smaller than Ch 21

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5
Q

Why is redundancy between mRNA codons and Amino Acids important?

A

Redundancy = Resilience b/c Mutation has a smaller effect -> more likely to be a silent mutation

BUT NOT ALWAYS -> because splice sites can be different

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6
Q

How to make cDNA?

A

take mRNA with 3’ poly A tail and add an oligo dT primer (12-20 thymine nucleotides that hybridize to poly-A tail) to prime or start cDNA synthesis. Then you introduce reverse transcriptase, which generates complementary DNA strand resulting in heterogenous mRNA/cDNA. The mRNA stand is broken down and DNA polymerase replaces it with DNA. Finally DNA ligase rejoins phosphodiester bonds to make the new strand connected. This results in doubt stranded cDNA.

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7
Q

Does cDNA contain introns?

A

No, only exons because it is generated form mRNA

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8
Q

2 main reasons for cDNA? ->

A

1) Transcriptomics ->convert mRNA to cDNA and this way indirectly measure how much mRNA there was (qPCR) or by microarray analysis.
2) gene cloning -> cDNA is inserted into a plasmid and produced by e. coli

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9
Q

What gene is mutated in sickle cell?

A

Beta-globing gene (A->T results in glutamic acid->valine)

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10
Q

How many rounds of cell replication and division in Mitosis vs Meiosis

A

1 of each in identical mother/daughter cells (diploid) vs 1 round of replication/recombination over and 2 rounds of division in gametes (haploid)

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11
Q

What is Interphase?

A

Resting phase between mitotic divisions of a cell, or between the first and second divisions of meiosis.

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12
Q

What phases constitute Interphase

A

G1, S, G2

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13
Q

What is G1 phase?

A

No DNA synthesis for hours, days, years. Cell functions normally and grows into mature cell

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14
Q

If a neuron or RBC stops dividing in G1 permanently, what is it called?

A

G0 (permanent)

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15
Q

S phase

A

DNA replication into sister chromatids, involves telomerase/telomeres

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16
Q

G2 Phase

A

organelles replicate to prepare for division

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17
Q

What happens in G2 to M-phase checkpoint?

A

check for errors in DNA replication (mutations)

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18
Q

Errors in mitosis lead to ?

A

apoptosis, cancer, somatic disease

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19
Q

How does meiosis generate diversity in life?

A

Through crossing over (recombination) and extra division -> random assortment of each type of chromosome

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20
Q

Do homologous chromosomes have the same alleles?

A

They have the same genes but not the same alleles

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21
Q

What happens if crossing over is misaligned?

A

duplications or deletions

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22
Q

What phase is Egg arrested in?

A

In prophase 1in early fetal life of female

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23
Q

When do later stages of meiosis take place?

A

During ovulation

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24
Q

How many oocytes produced by female in lifetime?

A

400 oocytes mature and are ovulated (33 years if 1/month)

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25
Q

When does meiosis happen in males

A

many times after puberty

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26
Q

How many sperm produced in male’s life?

A

1 trillion

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27
Q

Alternative Splicing

A

splicing process during gene expression that allows a single gene to code for multiple proteins

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28
Q

Are introns coding or non-coding?

A

Introns non-coding, exons exit the nucleus, therefore coding

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29
Q

Promoter

A

A promoter is a sequence of DNA needed to turn a gene on or off. The process of transcription is initiated at the promoter.

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30
Q

What is on the 3’ end?

A

OH group

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31
Q

What is on 5’ end?

A

Phosphate group

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32
Q

What is a TATA Box?

A

It is a part of the promotor region upstream of the gene that tells RNA polymerase where to bind

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33
Q

Upstream is towards

A

3’ end

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34
Q

Downstream is towards

A

5’ end

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35
Q

What is a 5’ cap?

A

special guanine added to 5’ end of mRNA

36
Q

What is poly-A tail?

A

added to 3’ end 250 Andenines

37
Q

What is the start codon on mRNA for almost every protein?

A

AUG -> Methionine

38
Q

Where is TATA box located?

A

25-30 bp upstream of transcription site

39
Q

CCAAT location

A

further upstream than TATA box

40
Q

What types of Regulatory Elements exist?

A

Enhancers, insulators

41
Q

Locus of Control definition?

A

enhances expression of linked genes at distant chromatin sites

42
Q

What are pseudogenes?

A

Pseudogenes are nonfunctional segments of DNA that resemble functional genes. Most arise as superfluous copies of functional genes, either directly by DNA duplication or indirectly by reverse transcription of an mRNA transcript.

43
Q

Adrenal Hyperplasia characteristics?

A

Cortisol deficiency, Aldosterone deficiency, Androgen excess

44
Q

non-coding RNA

A

an RNA molecule that is not translated into a protein. The gene product is the RNA itself

45
Q

types of non-coding RNA

A

t-RNA, r-RNA, snoRNA, microRNA’s

46
Q

What are snoRNA’s?

A

Small nucleolar RNAs (snoRNAs) are a class of small RNA molecules that primarily guide chemical modifications of rRNAs

47
Q

What do microRNA’s do?

A

~22 bp in length they suppress translation by binding to their own mRNA’s by base-pairing with complementary sequences within mRNA molecules

48
Q

How does DNA methylation work?

A

Methyl group added to Cytosine, leading chromatin modeling enzyme to suppress transcription

49
Q

Is methylation passed on in somatic cells?

A

Yes

50
Q

Where does demetheylation occur?

A

in germ cells to create pluripotent stem cells

51
Q

Glucocorticoid Receptor gene and rat pups?

A

GR gene gradually demethylates, making the gene more active. These pups will be more relaxed in response to stress

52
Q

Monoallelic Gene expression

A

only one of the two gene copies is actively expressed, while the other is silent

53
Q

Parent of origin imprinting

A

epigenetic phenomenon that causes genes to be expressed in a parent-of-origin-specific manner

54
Q

X chromosome inactivation

A

one chromosome inactivated

55
Q

pseudoautosomal regions?

A

Essentially identical regions of an X and Y chromosome undergo rearranagement. short regions of homology between the mammalian X and Y chromosomes. The pair behave like an autosome and recombine during meiosis. Thus genes in this region are inherited in an autosomal rather than a strictly sex-linked fashion

56
Q

Prader will and angelman’s Syndrome

A

Deletion in Chromosome 15. If Some genes at a location are expressed from the maternal chromosome, and some from the paternal chromosome.If the expressed allele is deleted, disease occurs. If the methylated copy has a deletion, no problem. Usually both maternal and paternal copies are expressed. IN imprinting however only 1 copy is expressed. One is expressed and the other is silenced. If paternal allele expressed but has deletion on section of CH 15-> Prader-willi and the opposite is true with Angelman’s syndrome. For genes that should be paternally expresssed, but deletion took place, and mother’s copy is turned off -> prader-willy

57
Q

Uniparental disomy

A

2 methylated (silent alleles are present at the locus because both donated from the same parent )-> genes are silenced

58
Q

TO be a genetic polymorphism how common must allele frequency be?

A

> 1% of the population

59
Q

single-nucleotide polymorphism

A

a germline substitution of a single nucleotide at a specific position in the genome

60
Q

Would you expect more SNPs in coding or non-coding areas of the genome?

A

non-coding

61
Q

Types of genetic polymorphisms?

A

SNPs, insertion-deletion polymorphisms, Copy number variants, inversions

62
Q

Copy number variants

A

duplication or deletion of 1000bp or more

63
Q

microsatellite

A

a tract of repetitive DNA in which certain DNA sequences repeats again typically 5–50 times. Microsatellites occur at thousands of locations within an organism’s genome.

64
Q

LINE sequences

A

repetitive elements throughout the genome that can insert themselves into other locations and cause problems

65
Q

Nonsense mutations introduce

A

premature stop codon

66
Q

missence mutations

A

point mutations

67
Q

splice site mutations

A

mutations where splice site happens

68
Q

Nonsense mutation is notated as

A

p.W40T->p.W40X or p.W40*

69
Q

penetrance

A

the extent to which a particular gene is expressed in the phenotypes of individuals carrying it

# of individuals with symptoms
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
# of individuals with genotype
70
Q

homozygous

A

patient has 2 same gene variants from both parents

71
Q

hemizygous

A

pt.only has 1 member of chromosome pair - males with x chromosome OR also caused by deletion of other copy of a gene on non-sex chromosome

72
Q

variable expression

A

patient has a phenotype but not everyone has the same severity of symptoms - some symptoms present in some pts. but other sx not

73
Q

Mosaicism examples

A

Duschenne muscular dystrophy and tubular sclerosis

74
Q

Codominance

A

neither allele is recessive and the phenotypes of both alleles are expressed

Think blood type - AB Type

75
Q

incomplete dominance

A

each parental contribution is genetically unique and gives rise to progeny whose phenotype is intermediate - pink

76
Q

Uniparental disomy

A

when both copies of a chromosome, or of part of a chromosome, are derived from a single parent

77
Q

pseudoutosomal regions

A

short regions of homology between the mammalian X and Y chromosomes

78
Q

Fragile X syndrome

A

Trinucleotide repeats - CGG (*check for giant gonads)

79
Q

Fragile X expansion more likely in

A

females

80
Q

Huntingtons expansion more likely in

A

males

81
Q

How many mitochondrial genes?

A

37 genes, maternal inheritance, reduced penetrance, variable expression

82
Q

Hetrosplasmy

A

presence of more than one mtDNA type in an individual , but it is 2% by blood

83
Q

tRNAVal is specific to mitochondrial tRNA

A

need pretty high level of this mutation to see symptoms

84
Q

Sex-limited phenotype

A

unrelated to the chromosomes, but based on sex of a child, notmutation of X and Y chromosome. Example of this is hemochromatosis - males tendto show earlier because females menstruate, and men were more like to destroy their liverwith alcohol, making phenotype more obvious

85
Q

Locus of heterogeneity

A

3 different mutations can cause the same phenotype

86
Q

What are microsatellites?

A

Repeat sequences of non-coding DNA. Anywhere from 2 to 25 base pair sequence repeats (e.g. CACACACACA would be 2 bp sequence repeat)

87
Q

Why are Microsatellites are useful genetic markers?

A

they tend to be highly polymorphic. Some people might have 3 bp repeats while another person might have 5 bp repeat sequence. It is not uncommon to have human microsatellites with 20 or more alleles and heterozygosities

GCD 8917 (5 decks)

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