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Med School > Genetics > Flashcards

Genetics Flashcards

0
Q

Aneuploidy

A

Organisms that do not have an exact multiple of their chromosomes, - ie a person with 47 chromosomes.

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1
Q

Euploidy

A

Having an exact multiple of chromosomes, - ie humans have 23 chromosomes, we are diploid, so we have 46 chromosome.

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2
Q

What is aneuploidy and its cause?

A

Loss or gain of an entire chromosome. Caused by nondisjunction.

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3
Q

Euploidy

A

Multiple of haploid number

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4
Q

During what phase do chromosomes have two sister chromatids?

A

Metaphase.

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5
Q

Chromatids are held together by what?

A

Centromere.

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6
Q

What is the short arm of a chromosome called? The long arm?

A 
Short = p
Long = q
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7
Q

What are the dark and light bands in chromosomes? What is the difference?

A 
Dark = heterochromatin, tightly wound, not being actively transcribed. 
Light = euchromatin, loosely wound, usually being actively transcribed.
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8
Q

What is an autosome?

A

A chromosome that is not a sex chromosome.

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9
Q

What is the difference between genotype and phenotype?

A

Genotype: alleles at a locus.

Phenotype: an observable train.

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10
Q

What is “penetrance”?

A

The number of people with the disorder divided by the number of people with the genotype of the disorder.

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11
Q

What is genetic fitness?

A

Reproductive success of a genotype; inversely proportional to mutation rate.

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12
Q

What is cytogenics?

A

The study of chromosomes, their structure and their inheritance.

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13
Q

What is Mitosis? What is Meiosis?

A

The process of cell division in ordinary somatic cells. Meiosis occurs only in germ cells and make gametes (reproductive cells). Gametes only have 23 chromosomes, so that when they are fertilized they again attain the 46 chromosomes necessary.

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14
Q

Do numerical abnormalities of autosomes result in clinical abnormalities? How about numerical abnormalities of sex chromosomes?

A

Numeric abnormalities of autosomes always result in pathological states. Numeric abnormalities of sex chromosomes cause minor effects in structure or function.

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15
Q

What are the biggest causes of chromosome malfunction?

A

Non-disjunction metaphase (mom’s of advanced maternal age) and rearrangements (“unbalanced”) of chromosomes such as deletions or duplications.

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16
Q

What are some examples of “balanced” rearrangements of chromosomes?

A

inversions and translocations

17
Q

Are gametes haploid or diploid?

A

Haploid. Sperm and eggs only have 23 chromosomes each.

18
Q

What are the four things about Meiosis that make it different from Mitosis?

A
  1. Chromosomes go from 2n to n.
  2. Crossing over happens.
  3. Segregation of alleles at Meiosis I or Meiosis II
  4. Shuffling of genes by random assortment of homologs.
19
Q

What is FISH Chromosome Analysis?

A

Make a DNA tag that is specific, and add some fluorescence. If the gene of interest is present, then the tag binds and we can see the fluorescence.

20
Q

What is a locus specific FISH probe?

A

When the disease causing sequence is known, this tag can look for that sequence.

21
Q

What are centromeric FISH probes?

A

Each chromosome has a unique centromere, and each centromere can be tagged separately. This is a quick way to look for trisomies, for example.

22
Q

What is Array Comparative Genomic Hybridization (aCGH)?

A

Digest patient and reference DNA into little bits, mix them in a bunch of little jars with the matching bits together. If the reference DNA is greater (the patient is missing some DNA), then the color of the reference DNA will predominate.

23
Q

What is a downside to aCGH?

A

The specificity exceeds our understanding. Are these minute deletions pathological or natural? An analysis of the parent’s DNA is often needed to confirm whether or not it is a natural variant.

24
Q

What is genetic heterogeneity?

A

Same phenotype is produced by different genotypes.

25
Q

What is allelic heterogeneity?

A

When different alleles at the same site cause the same abnormal phenotype.

26
Q

What is locus, or non-allelic heterogeneity?

A

When a particular phenotype can be the result of mutations at 2 or more loci.

27
Q

What is a Robertsonian translocation?

A

That is when a parent is a translocation carrier. It is confined to acrocentric chromosomes.

28
Q

What is “mosaicism”?

A

That is when there are two or more cell lines in an individual.

29
Q

What are the primary structural abnormalities?

A
  1. Deletion
  2. Duplication
  3. Inversions
  4. Translocations
30
Q

How many base pairs in the genome?

A

3.1 billion

31
Q

How many genes in a person?

A

25,000

32
Q

What percent is our genome the same?

A

99.9%

33
Q

What are some trains of x-linked dominant?

A

Affected fathers have unaffected sons and no normal daughters. All female offspring have a 50/50 chance of having the disease. Although it can present more mildly in women because they only use one X chromosome.

34
Q

What are some traits of x-linked recessive genes?

A

It affects boys more than girls. Boys have a 50% chance of being affected, and girls have a 50% chance of being carriers. An affected man gives the gene to all of his daughters, but to none of his sons. An affected mother gives the gene and phenotype to all of her sons.

35
Q

What is Allelic Heterogeneity?

A

Different alleles at the same locus create the same phenotype.

36
Q

What is variable expressivity?

A

Different people with the same genotype can have different phenotypes.

37
Q

What is locus heterogeneity?

A

Different genotype, same phenotype.

38
Q

What is mosaicism?

A

Two or more populations of cells with different genotypes in the same individual or organism.

39
Q

What is pleiotropy?

A

When one gene influences multiple, seemingly unrelated phenotypic traits.

Med School (24 decks)

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