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GCD 8917 > General Review > Flashcards

General Review Flashcards

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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
When does meiosis happen in males
many times after puberty
26
How many sperm produced in male’s life?
1 trillion
27
Alternative Splicing
splicing process during gene expression that allows a single gene to code for multiple proteins
28
Are introns coding or non-coding?
Introns non-coding, exons exit the nucleus, therefore coding
29
Promoter
A promoter is a sequence of DNA needed to turn a gene on or off. The process of transcription is initiated at the promoter.
30
What is on the 3’ end?
OH group
31
What is on 5’ end?
Phosphate group
32
What is a TATA Box?
It is a part of the promotor region upstream of the gene that tells RNA polymerase where to bind
33
Upstream is towards
3’ end
34
Downstream is towards
5’ end
35
What is a 5’ cap?
special guanine added to 5’ end of mRNA
36
What is poly-A tail?
added to 3’ end 250 Andenines
37
What is the start codon on mRNA for almost every protein?
AUG -> Methionine
38
Where is TATA box located?
25-30 bp upstream of transcription site
39
CCAAT location
further upstream than TATA box
40
What types of Regulatory Elements exist?
Enhancers, insulators
41
Locus of Control definition?
enhances expression of linked genes at distant chromatin sites
42
What are pseudogenes?
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
Adrenal Hyperplasia characteristics?
Cortisol deficiency, Aldosterone deficiency, Androgen excess
44
non-coding RNA
an RNA molecule that is not translated into a protein. The gene product is the RNA itself
45
types of non-coding RNA
t-RNA, r-RNA, snoRNA, microRNA’s
46
What are snoRNA’s?
Small nucleolar RNAs (snoRNAs) are a class of small RNA molecules that primarily guide chemical modifications of rRNAs
47
What do microRNA’s do?
~22 bp in length they suppress translation by binding to their own mRNA’s by base-pairing with complementary sequences within mRNA molecules
48
How does DNA methylation work?
Methyl group added to Cytosine, leading chromatin modeling enzyme to suppress transcription
49
Is methylation passed on in somatic cells?
Yes
50
Where does demetheylation occur?
in germ cells to create pluripotent stem cells
51
Glucocorticoid Receptor gene and rat pups?
GR gene gradually demethylates, making the gene more active. These pups will be more relaxed in response to stress
52
Monoallelic Gene expression
only one of the two gene copies is actively expressed, while the other is silent
53
Parent of origin imprinting
epigenetic phenomenon that causes genes to be expressed in a parent-of-origin-specific manner
54
X chromosome inactivation
one chromosome inactivated
55
pseudoautosomal regions?
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
Prader will and angelman’s Syndrome
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
Uniparental disomy
2 methylated (silent alleles are present at the locus because both donated from the same parent )-> genes are silenced
58
TO be a genetic polymorphism how common must allele frequency be?
>1% of the population
59
single-nucleotide polymorphism
a germline substitution of a single nucleotide at a specific position in the genome
60
Would you expect more SNPs in coding or non-coding areas of the genome?
non-coding
61
Types of genetic polymorphisms?
SNPs, insertion-deletion polymorphisms, Copy number variants, inversions
62
Copy number variants
duplication or deletion of 1000bp or more
63
microsatellite
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
LINE sequences
repetitive elements throughout the genome that can insert themselves into other locations and cause problems
65
Nonsense mutations introduce
premature stop codon
66
missence mutations
point mutations
67
splice site mutations
mutations where splice site happens
68
Nonsense mutation is notated as
p.W40T->p.W40X or p.W40*
69
penetrance
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
homozygous
patient has 2 same gene variants from both parents
71
hemizygous
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
variable expression
patient has a phenotype but not everyone has the same severity of symptoms - some symptoms present in some pts. but other sx not
73
Mosaicism examples
Duschenne muscular dystrophy and tubular sclerosis
74
Codominance
neither allele is recessive and the phenotypes of both alleles are expressed Think blood type - AB Type
75
incomplete dominance
each parental contribution is genetically unique and gives rise to progeny whose phenotype is intermediate - pink
76
Uniparental disomy
when both copies of a chromosome, or of part of a chromosome, are derived from a single parent
77
pseudoutosomal regions
short regions of homology between the mammalian X and Y chromosomes
78
Fragile X syndrome
Trinucleotide repeats - CGG (*check for giant gonads)
79
Fragile X expansion more likely in
females
80
Huntingtons expansion more likely in
males
81
How many mitochondrial genes?
37 genes, maternal inheritance, reduced penetrance, variable expression
82
Hetrosplasmy
presence of more than one mtDNA type in an individual , but it is 2% by blood
83
tRNAVal is specific to mitochondrial tRNA
need pretty high level of this mutation to see symptoms
84
Sex-limited phenotype
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
Locus of heterogeneity
3 different mutations can cause the same phenotype
86
What are microsatellites?
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
Why are Microsatellites are useful genetic markers?
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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