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Medical Genetics > Exam 1 > Flashcards

Exam 1 Flashcards

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1
Q

What are the 3 classic divisions of genetics?

What does each deal with it?

A
  • Transmission genetics: inheritance
  • Molecular genetics: biochemical genetics
  • Population genetics: evolution and adaption
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2
Q

List the contributions to medical genetics of each model organism

  • Drosophila melanogaster
  • Escherichia coli
  • Caenorhabditis elegans
  • Arabidopsis thaliana
  • Mus musculus
  • Saccharomyces cerevisiae (yeast)
A
  • Drosophila melanogaster: sex linked traits
  • Escherichia coli: genetic code
  • Caenorhabditis elegans: Apoptosis
  • Arabidopsis thaliana: Plant genomics
  • Mus musculus: cancer
  • Saccharomyces cerevisiae (yeast): control mechanisms of the cell cycle and mitochondrial genetics
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3
Q

What are the 4 major types of genetic disorders?

A
  • Chromosome disorders
  • Multifactorial disorders (more prevalent)
  • Single-gene disoders
  • Mitochondrial disorders
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4
Q

____ and ____ are are pyrimidines where as ____ and _____ are purines

A
  • Cytosine/Thymine
  • Adenine/Guanine
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5
Q

How many hydrogen bonds does A and T/U have? G and C?

A

2, 3

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6
Q

Chromosomes contains…?

A

Genes

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7
Q

Somatic cells contain ____ pairs of chromosomes, for a total of ____. One pair is the sex chromosomes while the other ____ pairs are called _____.

A

23, 46, 22, autosomes

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8
Q

Autosomes are ____ of each other

A

Homologs

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9
Q

Somatic cells work in pairs. This makes them ____ whereas gametes are _____ and have ____ total chromosomes

A

Diploid, Haploid, 23

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10
Q

T/F: Bacteria lack histones

A

True

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11
Q

What does DNA Polymerase do?

A

Synthesizes DNA by assembling nucleotides and proofreads them to ensure that the added nucleotide is complementary

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12
Q

Where does transcription take place? Translation?

A

Nucleus, Cytoplasm

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13
Q

What are transcription and translation both mediated by?

A

RNA

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14
Q

____ initiates mRNA transcription by binding to the promoter region

A

RNA Polymerase II

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15
Q

The template strand is the ____ strand and is ____ to the RNA transcript.

The nontemplate strand is the ____ strand and is ____ to the RNA transcript.

A
  • Antisense, Complementary/Anti-parallel
  • Sense, Identical/Parallel
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16
Q

What is the purpose of the 5’ guanosine cap?

A

Helps the RNA molecule from being degraded and marks the starting position for translation

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17
Q

What is the purpose of the 3’ poly-A tail?

A

Adenine bases are added to the 3’ end of the RNA molecule to prevent the mRNA from degrading when it reaches the cytoplasm

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18
Q

_____ contains most genes, is loosely organized, and transcription is more active. In comparision, _____ contains less genes, is more compact, and transcription is less active

A

Euchromatin, Heterochromatin

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19
Q

In eukaryotes, what happens before the mature transcript is formed?

A

Exons are spliced out of primary mRNA

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20
Q

What are the 3 stop codons?

A

UAA, UGA, UAG

21
Q

What 3 letter code signifies the start codon? What AA does this specify?

A

AUG, Methionine

22
Q

Name the 3 phases of Interphase

What occurs during this process?

A
  • G1 –> S –> G2
  • DNA replication and protein synthesis
23
Q

Chromosomes reach their most highly condensed state and arrange at the middle of the spindle during what phase?

A

Methaphase

24
Q

Crossing over in meiosis ocurs during what phase?

A

Prophase 1

25
Q

During what phase does the nuclear envelope disappear?

A

Prophase

26
Q

What is the major difference between Interphase 1 and Interphase 2?

A

No DNA replication ocurrs during Interphase 2

27
Q

How many mature sperm are produced during spermatogenesis?

A

4

28
Q

Describe oogenesis

A
29
Q

Define:

  • Alleles
  • Locus
  • Genotype
A
  • Alleles: Different versions of the same gene (ex. eye color)
  • Locus: Location of a gene
  • Genotype: The combination of alleles that is present at a given locus (ex. HH, Hh, hh)
30
Q

T/F: A person with different alleles on a gene is said to be a homozygote

A

False: heterozygote

31
Q

What are the 3 types of point/single base pair substitutions?

A
  1. Silent mutation
  2. Missense mutation
  3. Nonsense mutation
32
Q

Base pair substitution that does not change the genetic code

A

Silent mutation

33
Q

Base pair substitution that alters one amino acid

A

Missense mutation

34
Q

Base pair substitution that produces a stop codon in the mRNA

A

Nonsense mutation

35
Q

What are the 3 types of DNA segments (multiple base pairs) mutations?

A
  1. Deletions or Insertions
  2. Duplications of whole genes
  3. Mobile DNA elements - Transposons
36
Q

A Frameshift mutation consists of _____. It is especially harpmful because it shifts the _____.

A

Deletions/Insertions, Reading frame

37
Q

Explain the mechanism behind cystic fibrosis

A
  • Changes one AA (CFTR) by deleting 3 bps
  • Most common deletion is a 3-bp deletions that deletes phenylalanine (missense mutation)
  • Chloride ion channels are effected which creates a salt/water imbalance and effects breathing
38
Q

Charcot-Marie-Tooth Disease is an example of a ____. This ocurrs on chromosome 17. This gene is said to display ____.

A

Duplication, Gene dosage/Dosage sensitivity

39
Q
  • Involved in some cases of Duchenne muscular dystrophy, B-thalassemia, and familal breast cancer
  • Can self-replicate without DNA polymerase
A

Transposons

40
Q

Describe promoter mutations

A

Decreases the affinity of RNA polymerase for a promoter site –> Decrases production of mRNA –> Decreases protein production

41
Q

Splice-site mutations can occur at ____ or ____ sites within mRNA introns. If these mutations occur on these sites it results in _____ which can be partial or complete. However, if these mutations occur near these sites it results in _____ which can also be partial or complete.

A
  • Acceptor/Donor
  • Intron inclusion
  • Exon exlusion
42
Q

The donor site occurs at what sequence and at what end of the splice site? Acceptor site?

A
  • Donor: GT sequence, 5’
  • Acceptor: AG sequence, 3’
43
Q

Tandem repeats usually repeat the 3-bp sequence ____. A normal amount or repeats is ____ but when _____ of repeats occur, this can cause genetic disease. This usually occurs during ____ and is passed on from _____

A
  • CAG
  • 10-30
  • Hundreds to thousands
  • Meiosis
  • Mother to son
44
Q

What are the 4 classifications of mutations?

A
  1. Substitution/Single base pair mutation
  2. DNA segements (multiple base pairs)
  3. Within regulatory sequences
  4. Tandem repeat sequences-expanded repeats
45
Q

3 molecular consequences of mutations (protein-coding genes)

A
  1. Gain of function
  2. Loss of function
  3. Dominant negative mutation
46
Q

Describe Gain of function, Loss of function, and Dominant negative mutations

A
  • Gain of function:
    • Dominant
    • Over expression/Inappropriate expression of (gene dosage)
    • Rately produces novel protein function
47
Q

Describe Loss of function

A
  • Loss of function:
    • Recessive
    • 1 allele mutated –> 50% loss of protein –> Heterozygote ok
    • Haploinsufficiency: The 1 copy is not enough which results in dominance –> 1 allele mutated –> disease state
      • Ex. Familial Hypercholesterolemia
48
Q

Describe Dominant negative mutations

A
  • Dominant negative mutations
    • Abnormal protein will manifest as dominant and inhibit the function of the normal protein product
    • Commonly seen in multi-protein complexes
49
Q

Describe induced mutations

A
  • Attributed to environmental causes
  • Can casue base substitutions, deletions, and frameshifts
  • Mutagens:
    • Radiation: Ionizing = dsDNA breaks, Nonionizing = pyrimidine dimers and kinks
    • Base analogs

Medical Genetics (4 decks)

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